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Effect of Soil Management Practices and Slope on Soil Fertility of Cultivated Lands in Mawula Watershed, Loma District, Southern Ethiopia

Effect of Soil Management Practices and Slope on Soil Fertility of Cultivated Lands in Mawula... Hindawi Advances in Agriculture Volume 2020, Article ID 8866230, 13 pages https://doi.org/10.1155/2020/8866230 Research Article Effect of Soil Management Practices and Slope on Soil Fertility of Cultivated Lands in Mawula Watershed, Loma District, Southern Ethiopia Damte Balcha Gadana, Parshotam Datt Sharma , and Dereje Tsegaye Selfeko Department of Plant Science, College of Agricultural Sciences, Arba Minch University, Arba Minch, Ethiopia Correspondence should be addressed to Parshotam Datt Sharma; sharmaparshotamdatt@gmail.com Received 13 May 2020; Accepted 20 August 2020; Published 1 September 2020 Academic Editor: Jiban Shrestha Copyright © 2020 Damte Balcha Gadana et al. (is is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Soil degradation is a serious problem challenging food security in Ethiopia. To halt degradation and restore impoverished soils, the government has initiated soil management practices in the affected areas. Still, there is little information on the impact of these practices in terms of improvement in soil fertility of cultivated lands under different soil and climatic conditions. Accordingly, the study was carried out to study the effect of soil management practices, viz, soil bund (SB), application of farm yard manure (FYM), soil bund integrated with FYM (SBFYM), and vis-a-vis no management practice (NM), on soil fertility under upper (20%–30%) and lower (2%–10%) slope ranges at Mawula watershed, Loma district, Southern Ethiopia. Twenty-four composite soil samples (4 practices × 2 slope ranges × 3 sites) drawn from the surface layer (0–20 cm) were analysed for different physical and chemical properties indicative of soil fertility. (e data were analysed statistically in a randomized complete block design. All the soil management practices improved significantly the different aspects of physical and chemical fertility (soil texture, bulk density, total porosity, moisture content, organic carbon, and contents of macro and micronutrients, viz, N, P, K, Na, Ca, Mg, Fe, Mn, Zn, and Cu). (e practice SBFYM was significantly superior to FYM and SB. (e order of performance was SBFYM> FYM> SB> NM. (e usefulness of soil management practices was further corroborated by the farmers’ response (based on semistructured questionnaires), as 83% of them perceived the practices well and opted for their adoption. As such, the soil management practices, notably SBFYM, merit their implementation on a large scale to improve fertility and productivity of degraded lands. agricultural productivity, continued food insecurity, and 1. Introduction rural poverty in Ethiopia [4–6]. Every year, the country is Land degradation, implying deterioration of soil in terms of losing billions of birrs in the form of soil, nutrient, water, and its quality and productivity due to improper use, is a major agrobiodiversity losses [7]. As a result, poverty and food global issue and will remain high on the international agenda insecurity are concentrated in rural areas [8]. Although in the 21st century due to its effects on agronomic pro- estimates vary considerably, the direct losses of productivity ductivity, the environment, and food security [1]. Various from land degradation in Ethiopia may be put minimally at sources suggest that 5-6 million hectares of arable land 3% of agriculture GDP [9]. (e Ethiopian highlands cov- worldwide are being lost annually to severe degradation [2]. ering a sizeable landmass are particularly more severely Due to severity of land degradation, Africa as a whole has degraded, eroding the valuable soil resource base and ag- become a net food importer since Saharan Africa because gravating drought and repeated food shortages [10, 11]. 65% of the population is rural, and the main livelihood of Among various biophysical, socioeconomic, and polit- about 90% of the population is agriculture [3]. Land deg- ical factors of soil degradation, poor land management is radation is one of the major causes of low and declining thought to be playing an overriding role in the overall 2 Advances in Agriculture usefulness of the practices was also assessed by conducting a degradation process in many regions [12]. (e increased anthropogenic influence on land resources evident in in- questionnaire-based survey on perception and adoption of soil management practices by farmers in the watershed. creased cultivation of marginal land with steep gradients and low-input or fertility-mining methods of subsistence agri- culture accelerates soil erosion and cause sharp decline in 2. Materials and Methods soil fertility [13]. (e MoARD and WB [14] reported that cultivation on steep and fragile lands with inadequate in- 2.1. General Description of Study Area vestments in soil conservation or vegetation cover, erratic and erosive rainfall patterns, declining use of fallow, and 2.1.1. Location and Physiography. (e study was conducted limited recycling of dung and crop residues to the soils are at the Mawula watershed (Figure 1), which is located in largely responsible for continued soil degradation in Loma district of Dawro Zone in the Southern Nations and Ethiopia. (e cultivated lands in Ethiopia, particularly in Nationality Regional State (SNNPRS). It is located between steeply sloping areas, are reported to have very high rates of ° ° ° ° 6 57′0″N–6 59′30″N latitude and 37 11′0″E–37 17′0″E −1 −1 soil erosion ranging from 20 to 237 t·ha ·year [15–18]. longitude, with an altitude ranging from 1779 to 2361 meters Majority of Ethiopian soils are, therefore, poor in soil fer- above sea level. It is at about 365 km from Hawassa city in the tility [19–21]. As a consequence of declining soil fertility, the southern direction and at about 546 km southwest of Addis crop productivity has been low, and average cereal yield at Ababa. It is one of the 108 watersheds in Loma district and −1 the national level is still less than 2 t·ha . covered 937 ha out of the total area of 117,043 ha in the To cope up with the soil erosion problem, Ethiopian district. (e area is marked by 15.9% gentle slope, 43.4% Government had launched massive soil conservation pro- moderate slope, 26.5% moderately steep slope, 10.5% steep grams throughout the country in the middle of 1970s [22], slope, and 3.7% mountainous terrain [28]. About 54% of involving different nongovernmental organizations (NGOs) total area in the watershed was managed under different and mobilizing local people. (e different programs under conservation practices. food-for-work program comprised land leveling programme (LLP), sustainable land management (SLM), United Nations Development Program (UNDP), and Productive Safety Net 2.1.2. Land Use and Farming System. (e cultivated, forest, Program (PSNP). (e programs aimed at transforming and grazing lands covered 78.3%, 11.4%, and 3.8% of area in agriculture through conservation of soils, reducing soil the watershed. Agriculture is characterized by the subsistent erosion, and restoring soil fertility. One of the programs was mixed crop-livestock farming system. (e important cereal in steeply sloping areas for rehabilitation of degraded lands crops were maize (Zea mays), sorghum (sorghum bicolor), by introducing mechanical conservation measures, use of barley (Hordeum vulgare), and wheat (Triticum aestivum). perennial crops, plantation of forest areas, and use of organic (e vegetables grown were potato (Solanum tuberosum L.), manures. (e commonly followed soil management prac- tomato (Solanum lycopersicum), cabbage (B. oleracea var. tices included (a) use of a soil bund, (b) use of only manure, capitata), onion (Allium cepa), carrot (Daucus carota), green and (c) use of integrated bund and manure. (e manage- pepper (Capsicum spp.), faba bean (Vicia faba L.), pea ment practices ought to influence differentially the soil (Arachis hypogea), and haricot bean (Phaseolus vulgaris). characteristics and attendant soil fertility regimes. Most of the area around the homestead was covered with Recent studies [23, 24] have indicated usefulness of these perennial enset (Enset ventricosum), which is a staple food conservation practices in improvement of soil fertility. Such and income source. Coffee (Coffee arabica) and fruit trees studies need to be taken up under different soil and climatic such as false banana (Musa species), avocado (Persea conditions influencing the performance of soil conservation americana), and mango (Mangifera indica) were also among measures. Monitoring and evaluation of soil management the widely cultivated crops [28]. programs is essential to have their continuity, reinforce- ment, and corrections to make them compatible with so- cioeconomic environment imperatives. It becomes all the most important in Ethiopia, as about 18% of the rainfed 2.1.3. Climate and Agroecology. (e district is divided into three climatic zones on the basis of altitudinal and annual croplands have so far been treated with soil and water rainfall variations, as “Dega,” “Woyna Dega,” and “Wet conservation measures, and 60%, i.e., nearly 12 million ha, still need to be treated [25]. Kola.” (e study site belonged to “Woyna Dega.” (e mean monthly rainfall and maximum and minimum temperatures Management-induced changes in soil can be evaluated by assessing soil’s physical and chemical properties, such as for eleven years (2000–2010) are presented in Figure 2. (e mean annual rainfall was 1720 mm, and mean minimum and texture, water holding capacity, bulk density, porosity, soil organic carbon, total nitrogen, available phosphorus, ex- maximum temperatures were 11.7 and 23.5 C, respectively. (e rainfall distribution was bimodal. (e medium rainy changeable potassium, soil pH, and electrical conductivity [23, 24, 26, 27]. Accordingly, this study was envisaged to season (Belg) occurs from March to May, while the main rainy season (Kremt) occurs from June to September. Also, evaluate the effect of three soil management practices under two slope ranges on the improvement of soil fertility (re- there is small rain in October and November. (e Mawula watershed is drained into the Manstha River, which is a part flected in indicative soil properties) of cultivated lands in Mawula watershed, Loma district, Southern Ethiopia. (e of the Omo Gibe River basin. Advances in Agriculture 3 Loma woreda Ethio regions Mawula watershed SouthR kebeFF Dawuro zone SouthR kebeFF Dawuro zone Loma woreda Mawula watershed 0 1.75 3.5 7 Kilometers Figure 1: Map of study area. 25 300 0 0 Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec min T RF monthly max T Figure 2: Monthly rainfall and maximum and minimum temperatures of the study area (11 years average). 2.1.4. Soil Type. (e soil of the area is grouped as Orthic management, soil bund, manure application, and soil bund Acrisols [29]. (ese soils have a distinct argillic B horizon integrated with manure) at two slope ranges (20–30% slope and a low base saturation. (e soils are chemically poor. (e as upper range and 2–10% slope as lower range). content of weatherable minerals is generally low, the pH is About 15 subsamples each for the different soil man- less than 5.5, and available P is low. (e rooting depth might agement practices were drawn from 0–20 cm depth at a be limited by the argillic B horizon or by rock at shallow particular site for two slope ranges from the cultivated depth. (e moisture storage capacity of soil is moderate to fields. (e subsamples for each practice were composited. good. (us, a total of 24 composite samples (four practices∗ two slope ranges∗ three sites as replications) were obtained for 2.2. Soil Sampling. (e soil sampling was performed at three laboratory analyses. Soil core samples from the 0–20 cm sites of the watershed (Table 1) for four soil management depths were taken with a sharp-edged steel cylinder forced practices being followed by farmers for about 8 years (no manually into the soil for bulk density determination. T (°C) 6°57′0″N 6°58′0″N 6°59′0″N 37°11′0″E 37°11′30″E 37°12′0″E 37°12′30″E 37°13′0″E 37°13′30″E 37°14′0″E 37°14′30″E 37°15′0″E 37°15′30″E 37°16′0″E 37°16′30″E 37°17′0″E RF (mm) 4 Advances in Agriculture Table 1: Sample site characteristics. Site name Slope range Coordinate point Altitude (masl) Slope (%) Aspect ° ° 6 58′01″–6 57′21″ Upper 2153–2156 20–30 Southern ° ° 37 14′21″–7 15′38″ Borthe ° ° 37 15′11″–37 16′31″ Lower 1658–1855 2–10 Southern ° ° 6 58′81″–6 58′82″ ° ° 6 57′66″–6 57′88″ Upper 2153–2156 20–30 Southern ° ° 37 13′57″–37 14′67″ Fulasa ° ° 6 58′56″–6 58′78″ Lower 1658–1952 2–10 Southern ° ° 37 15′28″–37 16′61″ ° ° 6 58′60″–6 58′80″ Upper 2153–2156 20–30 Southern ° ° 37 13′88″–37 14′42″ Xossa wora ° ° 6 57′45″–6 57′65″ Lower 1658–1952 2–10 Southern ° ° 37 15′22″–37 16′42″ Global positioning system (GPS) and clinometers were people in watershed according to the sampling formula of used to know the geographical location and slope of the Glenn [38]: sampling sites, respectively. n � , (1) 1 + N(e) 2.3. Soil Analyses. (e analyses for physical fertility pa- where n � sample size, N � total population, and e is the rameters (soil texture, bulk density, and moisture content) precision level chosen (10% confidence level). and chemical fertility parameters (pH, organic carbon, total Accordingly, n � 362/1 + 362(0.1) � 362/1 + 3.62 � nitrogen, cation exchange capacity, and available phos- 362/4.62 � 362/5 � 72. phorus) were performed at SNNPR State Agricultural Bu- (e respondents belonged to community elder groups, reau Sodo Soil Laboratory. (e analyses for macro and development/extension agents, watershed management plan- micronutrients (Ca, Mg, K, Na, Fe, Mn, Cu, and Zn) were ning committee, male and female household heads, and water performed at Arba Minch University, Abaya Campus En- development committee. vironmental and Soil Laboratory. (e particle size distribution was determined by the Boycouos hydrometric method [30]. Soil bulk density was 2.5. Statistical Analysis. (e soil physical and chemical properties were subjected to analysis of variance using the determined using undisturbed core samples as described by Black [31]. Total porosity was calculated using general general linear model procedure of the statistical analysis system version 9.1 [39]. (e least significance difference equation relating bulk density and particle density. Soil moisture content was expressed on mass basis (M ). (e pH (LSD) was used to separate significantly differing treatment means after main effects were found significant at P< 0.05. of the soils was measured in soil-water suspension (1 : 2.5 : soil : water) using a glass-calomel electrode [32]. Soil organic Simple correlation analyses were executed to reveal the carbon content was determined by the Walkley and Black [33] magnitudes and directions of relationships between selected wet digestion method. (e Kjeldhal digestion and distillation soil physicochemical parameters. (e farmers’ perception method was used to measure total nitrogen [34]. Cation and the adoption of soil management practices were ana- exchange capacity (CEC) was determined after extracting the lysed using IBM SPSS statistics software version 20. soil samples with 1N NH OAc at pH 7.0 and distilling am- monium displaced by leaching with NaCl solution [35]. 3. Results and Discussion Available soil P was analysed following procedure of Olsen et al. [36]. Available/exchangeable potassium and sodium 3.1. Effect of Soil Management Practices on Soil were determined by the flame photometry [35]. Calcium, Physical Properties magnesium, and micronutrients (Fe, Zn, Mn, and Cu) were 3.1.1. Soil Texture. (e soil texture was significantly affected analysed by the atomic absorption spectrophotometer [37]. (P< 0.05) by soil management practices and slope range. (e proportion of sand in soil under no management practice (NM) was significantly higher compared to soil management 2.4. Farmers’ Survey. Semistructured questionnaires were practices (Table 2). It decreased progressively under SB (soil used to gather information from watershed people about soil bund), FYM (farm yard manure application), and SBFYM management practices and their adoption. (e general (soil bund coupled with farm yard manure application). discussions and interviews were made with 72 randomly Conversely, the clay fraction was significantly higher under sampled respondents taken from a total of 362 household SB, FYM, and SBFYM compared to NM by 7%, 14%, and Advances in Agriculture 5 Table 2: Effect of soil management practices and slope range on physical properties of soils in Mawula watershed. −3 −3 SMP Sand (%) Silt (%) Clay (%) STC BD (Mg·m ) PD (Mg·m ) MC (%) TP (%) a b d a c d c NM 50.7 21.5 27.7 SCL 1.165 2.58 12.2 56.2 b b c b b c cb SB 47.2 23 29.7 CL 1.08 2.61 22.47 57.4 c a b b b b b FYM 41.7 26.5 31.7 CL 1.08 2.62 27.65 58.8 d a a c a a a SBFYM 38.5 27 34.5 CL 0.99 2.64 32.57 62.3 LSD (0.05) 1.25 1.86 1.67 0.06 0.014 4.39 2.26 SEM (±) 0.50 0.07 0.57 0.014 0.004 1.30 0.60 CV% 2.34 6.19 4.01 4.79 2.85 16.52 3.74 Slope range a b a a a a b US 45.7 23.92 30.42 Loam 1.11 2.62 22.67 57.64 b a a b a a a LS 43.3 25.25 31.33 Loam 1.05 2.61 24.78 59.68 LSD (0.05) 0.89 1.32 1.18 0.04 0.06 3.11 1.60 SEM (±) 0.89 1.32 1.18 0.045 0.06 3.1058 1.60 CV% 0.36 0.49 0.010 0.003 0.92 0.42 Means within a column followed by the same letter are not significantly different from each other at P≤ 0.05; SMP, soil management practices; STC, soil texture class; SCL, sandy clay loam; CL, clay loam; BD, bulk density; PD, particle density; MC, moisture content; TP, total porosity; US, upper slope; LS, lower slope. −3 24.5%, respectively. (e proportion of silt was significantly manure (1.08 Mg·m ), and soil bund combined with farm −3 higher under FYM and SBFYM practices compared to NM yard manure (0.99 Mg·m ) (Table 2). (e total porosity, and SB. From the foregoing, it is clear that soil with any of having negative relationship with bulk density, was signif- the management practices is having higher amounts of finer icantly lower in soil with no conservation practice (56.2%) fractions, viz., clay and silt, and lower of coarse sand fraction. compared to soils with conservation practices. (e highest Such a situation is desirable from the soil fertility point of value of porosity (62.3%) was obtained with the practice of view, as it is the finer soil fraction that retains nutrients soil bund + farm yard manure. Such a trend of bulk density and water. (e soil with no management practice is and total porosity values under different management subject to soil erosion and removal of finer soil fraction practices could be explained to their level of protection with runoff water. Accordingly, the texture of soil with against the processes of soil erosion, viz., dispersion, conservation practices was better (clay loam) compared to transportation, and deposition of soil particles. (e practice no conservation practice (sandy clay loam). Although, soil with no conservation practice will have removed the finer texture being a basic soil property is not subject to change soil fraction, raising the value of bulk density. Conversely, with management, such a situation may be warranted on the soils having conservation practices will have less erosion the removal of finer fraction with soil erosion and al- and more proportion of clay and silt, lowering the value of teration in the mass proportion of textural separates. (e bulk density. A similar decrease in the bulk density of soil results are corroborated by the findings of Wolka et al. treated with management practice of SB + FYM compared to [13] who reported increase in clay and silt contents in soils no management has been reported by Selassie et al. [23] in provided with soil bund and stone bund on cultivated Zikre watershed, northwestern Ethiopia. Also, Agele et al. lands in Southern Ethiopia. Also, Dagnachew et al. [24] [40] found soil amended with FYM to be having lower bulk reported significantly improved silt and clay fractions density and higher total porosity, possibly due to increases in with soil and water conservation measures (SWC) com- the proportion of macroaggregates and soil organic matter. pared to no SWC on farm lands. Texturally, the perfor- Husen et al. [41] indicated that soil bund had a significant mance of soil management practices was in the order of effect on soil bulk density. SBFYM> FYM> SB> NM. (e interaction effect of soil management and slope (e slope range did not show a change in the soil texture range (Table 3) indicated better textural composition of soil as it was loam under both the categories of the upper slope provided with management practices of SBFYM at both and lower slope. However, proportion of sand was signifi- slope ranges. cantly higher under the upper slope (45.7%) than the lower (e slope condition was found to affect bulk density and slope (43.3%) and proportion of silt higher under the lower total porosity significantly. (e upper slope had significantly −3 slope (25.2%) than the upper slope (23.9%). (e higher silt higher bulk density (1.11 Mg·m ) compared to the lower −3 content in the lower slope might be due to reduced soil slope (1.05 Mg·m ). (e total porosity was significantly erosion and more deposition of fine fractions of soil. higher for the lower slope (59.7%) compared to the upper slope (57.6%). Actually, when soil erosion takes place, finer particles get suspended in the accumulating water and are 3.1.2. Bulk Density and Total Porosity. (e bulk density of transported down the slope, leaving coarser material at the soil was significantly higher under soil with no conservation top slope positions that raise bulk density and lower pore −3 practice (1.17 Mg·m ) compared to soils with soil conser- spaces. On the other hand, the suspended finer particles −3 vation practices, viz., soil bund (1.08 Mg·m ), farm yard transported down the slope get accumulated at the bottom 6 Advances in Agriculture Table 3: Interaction effect of soil management practices and slope range on physical properties of the soils in Mawula watershed. −3 −3 Sand (%) Silt (%) Clay (%) BD (Mg·m ) PD (Mg·m ) MC (%) TP (%) SMP US LS US LS US LS US LS US LS US LS US LS a b e bdec d d a b e de d d d c NM 54.7 52.3 22.3 24 22.67 23.67 1.21 1.12 2.58 2.59 14.4 15.37 53.2 56.7 c c de dec c cb b cb bc bc c c c c SB 49 47 22.67 23.3 29 30.3 1.12 1.07 2.61 2.62 21.7 23.17 57.1 59.2 d e bdac a b b b cd bc ba bc ba c ba FYM 44 41.3 25.33 27.67 31.67 31.67 1.11 1.04 2.62 2.63 26.4 28.83 57.3 60.2 fe f ba bac a a cd d a a ba a ba a SBFM 40 39 26.33 26.2 34.3 35 1.04 1.01 2.64 2.65 31.1 34.07 60.7 62.03 LSD 2.16 2.95 2.45 0.06 0.019 5.582 2.588 SEM (±) 5.2 6.22 12.3 0.55 2.33 13.5 20.5 Means for specific soil parameter followed by the same letter(s) are not significantly different from each other at P≤ 0.05; SMP, soil management practices; NM, no management; SB, soil bund; FYM, farm yard manure; SBFYM, soil bund integrated with farm yard manure; BD, bulk density; PD, particle density; MC, moisture content; TP, total porosity; US, upper slope; LS, lower slope. slope positions, thus, lowering bulk density and raising total the lower slopes. (e runoff generation and soil erosion become more as degree of slope increases. Dagnachew et al. porosity of lower slopes. Similar results were reported by Selassie et al. [23] who found a significant reduction in bulk [24] also found significantly higher volumetric water content at the bottom slope classes than the upper slope due to erosion density from the upper slope (28%) to the lower slope (8%). Likewise, Khan et al. [42] found bulk density to be decreased reduction and the deposition effect of SWC measures. with decrease in the slope. Based on soil volume functions, (ere was a significant effect of interaction between soil the performance of land management practices could be in management practices and slope range on soil moisture the order of SBFYM> FYM � SB> NM. (Table 3). (e highest water content (34.1%) was obtained (e interaction between soil management practices and with SBFYM at the lower slope range and minimum with slope (Table 3) indicated BD to be highest with NM at the NM at the upper slope. −3 upper slope (1.21 Mg·m ) and lowest with SBFYM at the −3 lower slope (1.01 Mg·m ). (e porosity was highest (62%) with SBFYM at the lower slope and lowest with NM at the 3.2. Effect of Soil Management Practices on Soil upper slope (53.2%). (e interaction effect, therefore, further Chemical Properties established the superiority of management practice of 3.2.1. Soil pH. (e pH was significantly lower with no SBFYM in maintaining physical soil environment. management practice (5.2) compared to soils having management practices such as soil bund (5.9), farm yard manure (6.2), and combination of soil bund and farmyard 3.1.3. Soil Moisture Content. (ere was a significant effect (P< 0.05) of soil management practices on soil moisture manure (6.5) (Table 4). (e depression in soil pH in soils without any conservation practice was probably due to content. (e soil with no conservation practice contained significantly lower amount of moisture (12.2%) compared removal of basic cations along with the eroding fine soil fractions. To the contrary, the soils protected with certain to soils having soil conservation practices (22.5–32.6%) (Table 2). (e highest moisture content was obtained with conservation practice would retain the basic cations along with fine fraction, raising the soil pH. the practice of SBFYM followed by FYM and SB. (e percentage increases in moisture content were 84, 126, Similar increases in soil pH with provision of soil and water conservation measures have also been reported else- and 167 under SB, FYM, and SBFYM, respectively, over NM. Such a marked increase in soil moisture by the where. For instance, Wolka et al. [13] reported increase in conservation practices could be ascribed to their influ- soil pH with the construction of level stone and soil bunds in Bokole watershed, Ethiopia. Likewise, Tugizimana [44] in- ence on water storage in soil profile. (e practices offering mechanical barriers to the flow of water reduce the runoff dicated increase in soil pH with the adoption of soil and water conservation measures in Rwanda. velocity and offer more opportunity for water to infiltrate into the soil. Also, the conservation practices reducing (e upper slope range indicated significantly lower pH (5.8) than the lower slope range (6.1) (Table 4). (is is loss of fine fractions of soil, including humus, would enhance the water holding capacity of the soils. Similar obvious as upper slopes have more loss of basic cations that causes lowering of pH, while lower slopes have gain of basic increase in soil water content with SWC measures over no SWC has been reported by Dagnachew et al. [24]. An cations raising the soil pH. increase in water retention as a result of enhanced (e interaction effect of soil management practices and structure stability in coarse textured soils amended with the slope range was significantly different (P< 0.05). (e composted manure and sewage sludge has been reported three soil management practices at both upper and lower slope ranges showed significantly higher soil pH compared by Mamedov et al. [43]. (e soil moisture percentage was significantly higher to no practice. (e highest mean value of 6.6 was at the lower slope under SBFYM and lowest of 5.1 was under NM at the under the lower slope (24.8%) than the upper slope (22.7%). (e effect was obvious with loss of fine fraction of soil, upper slope (Table 5). (e practices of FYM and SBFYM had similar pH, but significantly higher than rest of the treatment retaining water, from the upper slopes and its deposition in Advances in Agriculture 7 Table 4: Effect of soil management practices and slope range on soil chemical properties in Mawula watershed. SMP pH OC (%) TN (%) C : N AP (mg/kg) d d d c d NM 5.20 0.51 0.09 5.89 7.50 c c c a c SB 5.91 2.08 0.15 13.59 13.30 b b b b b FYM 6.17 2.62 0.21 12.54 17.83 a a a b a SBFYM 6.52 2.97 0.26 11.6 21.16 LSD (0.05) 0.16 2.87 0.02 1.02 1.02 SEM (±) 0.02 0.02 0.01 0.68 76.70 CV% 2.18 6.95 9.64 7.57 6.29 Slope range b b b b Upper 5.80 1.93 0.17 10.76 14.00 a a a a Lower 6.10 2.17 0.19 11.04 15.92 LSD (0.05) 0.11 0.12 0.01 0.72 0.82 SEM (±) 0.02 0.02 0.001 0.68 0.54 Means within a column followed by the same letter are not significantly different from each other at P≤ 0.05; SMP, soil management practices; NM, no management; SB, soil bund; FYM, farm yard manure; SBFYM, soil bund integrated with farm yard manure; OC, soil organic carbon; TN, total nitrogen; C : N, carbon to nitrogen ratio; AP, available phosphorus; US, upper slope; LS, lower slope. Table 5: Interaction effect of soil management practices and slope ranges on chemical properties of soils in Mawula watershed. pH OC (%) TN (%) C : N AP (mg/kg) SMP US LS US LS US LS US LS US LS f f d d e e d d g f NM 5.1 5.3 0.44 0.59 0.07 0.10 6.0 5.78 6.0 9.0 e d c b d d cd a e e SB 5.6 6.03 1.75 2.42 0.14 0.16 12.4 14.71 12.67 14.0 dc c b b c cb cb cb d c FYM 6.2 6.36 2.59 2.67 0.21 0.21 12.5 12.56 17.0 18.6 ba a a a b a cb c b a SBFYM 6.4 6.6 2.93 3.02 0.24 0.27 12.1 11.11 20.3 22.0 LSD 0.227 0.249 0.029 1.445 1.650 SEM (±) 0.075 0.082 0.009 0.476 0.543 Means for specific soil parameter followed by the same letter(s) are not significantly different from each other at P≤ 0.05; SMP, soil management practices; NM, no management; SB, soil bund; FYM, farm yard manure management; SBFYM, soil bund integrated with farm yard manure; SEM, standard error of mean; US, upper slope; LS, lower slope. combinations. As per rating of Tekalign [45], the non- It is interesting to note that physical soil conservation measure managed soil in upper and the lower slope was strongly SB complemented with organic manure application could acidic (pH of 5.1–5.3). (e soil with practice of SB in the raise soil SOC content better than soil bund alone. Similar upper slope was moderately acidic (pH of 5.6) and in the increase in organic carbon content (over 120 percent) under lower slope was slightly acidic (pH of 6.0). (e soil with FYM SBFYM compared to NM has been reported by Selassie et al. alone and with SB + FYM was also slightly acidic (pH of 6.4 [23] in Zikre watershed, Ethiopia. Likewise, farm land with and 6.6). SWC measure significantly improved soil organic carbon compared to farm land without SWC [24, 48]. As organic matter is the main supplier of nutrients in low input farming 3.2.2. Organic Carbon (OC). (e organic carbon content was systems, a continuous decline in the soil OC content of the significantly (P≤ 0.05) affected by soil management practices. soils is likely to affect the soil productivity and sustainability. It was significantly lower under no management practice (0.51%) compared to soil bund (2.08%), farm yard manure Considering the main effect of two slope ranges (Table 4), application (2.62%), and soil bund combined with farm yard the OC content was significantly higher under the lower slope manure application (2.97%) (Table 4). (e percentage in- (2.17%) than the upper slope (1.93%). (e increase in former creases in OC content for SB, FYM, and SBFYM over NM was due to deposition of eroded sediments and organic fraction were 308, 414, and 482 percent, respectively. A very low from the upper slope and less intense soil erosion due to re- content of OC under NM was due to the fact that soils are duction in degree of the slope. (e similar results on the effect subject to inexorable processes of soil erosion, leaving soils of the slope range on OC content in soils have been reported by devoid of organic fraction. On the other hand, the lands with Wolka et al. [13], Tadele et al. [49], and Selassie et al. [23]. management practices that provide mechanical barriers to the As for the interaction effect of soil management practices runoff water would have reduced the loss of fine soil fractions and slope range (Table 5), the practice SBFYM at both upper and organic carbon. (e clay particles have substantial ex- and lower slopes gave significantly higher content of OC change surface areas and, therefore, adsorb and stabilize OC compared to rest of the combinations of practice and slope. in soils [46, 47]. (e soil management practices such as FYM (e no management recorded significantly lowest OC at and SBFYM would also add organic matter to the soils both the slope ranges. It was noticed that by employing soil through manure application besides controlling soil erosion. 8 Advances in Agriculture management practices such as FYM and SBFYM, the same water from the higher slope and build up at the lower slope level of OC could be maintained at upper and lower slopes. position. (e soil erosion might have decreased major plant (e amount of OC in soils rated according to Tekalign [45] nutrient (TN) at the higher slope and increased at the lower was found to be low under nonmanaged land and medium slope. under three management practices. (e C : N ratio was also significantly (P < 0.05) higher under soil management practices, viz., SB (13.57), FYM (12.54), and SBFYM (11.6) compared to NM (5.89). How- 3.2.3. Total Nitrogen (TN) and C : N Ratio. Total nitrogen ever, the difference was nonsignificant between the practices (TN) amount was significantly affected (P< 0.05) by dif- having incorporation of FYM (Table 4). (e effect of slope ferent soil management practices and slope conditions. It percentage was not significant. (e C : N ratio is indication was significantly lower with no management (0.086%) of soil mineralization rate. Generally, the C : N ratio of 10–15 compared to soil bund (0.153%), farmyard manure ap- is normal, 15–25 may indicate slowing of decomposition plication (0.210%), and soil bund integrated with FYM process, and >25 may show organic matter to be raw and (0.258%) (Table 4). (e increase in N under SB, FYM, and unlikely to breakdown quickly. Accordingly, all the soil SBFYM over NM was 58%, 144%, and 200%, respectively. management practices were having C : N ratios as normal. (e increases in N content under soil management prac- (e interaction effect (Table 5) showed higher ratio for FYM tices were due to less loss of fertility bearing soil fractions practice than NM. such as clay and silt and addition of farm yard manure. (e N enrichment was more marked under management practices adding farm yard manure. (e soil management 3.2.4. Soil Available Phosphorus (AP). (e soil available practices reducing runoff and soil loss and enhancing phosphorus was significantly (P< 0.01) affected by soil profile water storage would enhance crop growth and management practices, slope range, and the interaction contribute to OM and N input in the soil. (e significance between soil management practices and the slope (Tables 4 of soil management in enhancing soil fertility has been and 5). All the soil management practices indicated sig- highlighted by some studies. For instance, nonconserved nificantly higher contents of AP than no management. (e land had the smallest mean value of TN compared to the practice of soil bund integrated with farm yard manure conserved land [26]. In another study [13], soil and water appeared to be significantly superior to the practices of soil conservation increased the total soil N in Bokole watershed bund and farm yard manure alone. Accordingly, AP fol- in Ethiopia. Similarly, the soil management practices of lowed an order SBFYM (21.16 mg/kg)> FYM (17.83 mg/ farm yard manure complemented with soil bund increased kg)> SB (13.3 mg/kg)> NM (7.5 mg/kg). Generally, varia- the total nitrogen content by 107% over nonconserved land tions in available P contents in soils should be related to the [23]. level of soil management, i.e., mechanical and cultural (e mean N content decreased considerably from practices retaining/adding mineral and organic fractions in 0.188% in the bottom slope to 0.166% in the upper slope soil soil, besides intensity of soil weathering and P fixation. (e (Table 4), revealing a reduction of about 12%. (e difference practice of soil bund would retain more fertility bearing soil in N content may be due to deposition of eroded sediments particles as a result of decreased soil erosion. Whereas the from the upper to the lower slope. A similar decrease in total soil bund integrated with farm yard manure incorporation N on the upper slope compared to the bottom slope has been would also have addition of phosphorus through manure reported by Dagnachew et al. [24]. application besides decreased soil erosion. More buildup of Considering the interaction of soil management prac- available phosphorus in soil with soil bund and continuous tices by the slope range (Table 5), the significantly highest N application of farm yard manure has also been indicated by (0.27%) compared to other treatment combinations was Selassie et al. [23]. Also, Mulugeta and Stahr [26] have recorded with the practice of soil bund integrated with farm reported significantly higher contents of available phos- yard manure at the lower slope, followed by the same phorus in conserved compared to nonconserved fields. (e practice at the upper slope (0.24%). (e significantly lowest main effect of slope range also revealed that available P was concentration of N compared to other treatment combi- significantly higher (15.92 mg/kg) in the lower slope than in nations was shown by NM practice both at upper (0.07%) the upper slope (14.00 mg/kg) because of its removal from and lower (0.10%) slope ranges. the upper slope and deposition in the lower slope. Following the rating of total N [45], the soil under no According to Cottenie [50], the available soil P level of management was low in N, the soil under management <5 mg/kg is rated as very low, 5–9 mg/kg as low, practices, viz., soil bund alone and farm yard manure alone 10–17 mg/kg as medium, 18–25 mg/kg as high, and was moderate in N status, and the soil under integrated soil >25 mg/kg as very high. (us, the available P of the soils management of soil bund + farm yard manure was high in N was high under SBFYM and FYM, medium under SB, and status. As the OC and total N contents showed strong as- low under NM. ∗∗ sociation (r═ 0.811 ), the reduction in the total N contents (e interaction between soil management practices and of the soils both with nonmanagement practice and the slope range indicated significantly highest available P con- tent (22 mg/kg) in SBFYM at the lower slope compared to upper slope was possibly due to reduction of soil OM content. (e increase of total N at the lower slope might be other treatment combinations, followed by the same practice at the upper slope (20.3 mg/kg). due to the downward movement of nutrient with runoff Advances in Agriculture 9 Table 6: Effect of soil management practices and slope ranges on exchangeable cations in soils of Mawula watershed. −1 Exchangeable cations (cmol kg ) −1 SMP CEC (cmol kg ) K Ca Mg Na d d d b d NM 0.53 4.89 3.05 0.18 22.66 c c c c SB 0.87 7.18 4.58 0.19b 26.53 b b b a b FYM 1.13 9.41 5.43 0.29 30.85 a a a a a SBFYM 1.22 11.05 6.72 0.35 34.56 LSD (0.05) 0.070 0.359 0.168 0.056 0.925 SEM (±) 0.023 0.118 0.0555 0.0183 0.305 CV (%) 9.3 3.95 4.17 17.9 2.35 Slope range b b b b b US 0.89 7.65 4.65 0.23 27.81 a a a a a LS 0.97 8.61 5.24 0.28 29.49 LSD (0.05) 0.049 0.254 0.119 0.039 0.6543 SEM (±) 0.164 0.0838 0.0392 0.0129 0.2157 Means within a column followed by the same letter are not significantly different from each other at P≤ 0.05; SMP, soil management practices; NM, no management; SB, soil bund; FYM, farm yard manure; SBFYM, soil bund integrated with farm yard manure; CEC, cation exchange capacity; US, upper slope; LS, lower slope. Table 7: Interaction effect of soil management practices and slope ranges on exchangeable cations in soils of Mawula watershed. −1 cmol·kg SMP K Ca Mg Na CEC US LS US LS US LS US LS US LS d d g f f f d dc h g NM 0.51 0.55 4.51 5.21 2.9 3.17 0.15 0.19 21.8 23.5 c c e d e d d dc f e SB 0.82 0.91 6.81 7.54 4.23 4.93 0.16 0.22 25.8 27.2 b a c b d c bc ba d c FYM 1.07 1.18 8.85 9.97 5.1 5.76 0.22 0.33 29.9 31.78 a a b a b a ba a b a SBFYM 1.18 1.25 10.4 11.66 6.3 7.1 0.33 0.34 33.7 35.7 LSD 0.099 0.508 0.238 0.078 1.31 SEM (±) 0.62 2.12 3.12 0.23 21.5 Means for specific soil parameter followed by the same letter(s) are not significantly different from each other at P≤ 0.05; SMP, soil management practices; NM, no management; SB, soil bund; FYM, farm yard manure management; SBFYM, soil bund integrated with farm yard manure; SEM, standard error of mean; US, upper slope; LS, lower slope. −1 3.2.5. Exchangeable Cations (Macro and Micronutrients) and compared to no management, NM (22.66 cmol (+) kg ). Cation Exchange Capacity (CEC). (e exchangeable cations (e practice of soil bund integrated with farm yard manure (K, Ca, Mg, Na, Fe, Zn, Mn, and Cu) were significantly application was significantly superior to application of farm (P≤ 0.05) affected by soil management practices, slope range, yard manure alone, which, in turn, was significantly superior and interaction between practices and the slope (Tables 6–9). to the practice of soil bund alone. (e CEC values were in the In general, the mean values of all cations were significantly order of SBFYM> FYM> SB> NM. It is a general fact that higher under soil management practices of SB, FYM, and both clay and colloidal OM have the ability to adsorb and SBFYM compared to no management NM (Tables 6 and 8). hold positively charged ions. (us, soils containing high clay Among soil management practices, SBFYM was signifi- and organic matter contents have high CEC. (is is very well cantly superior to FYM and SB alone. (e slope range also corroborated by the highly significant and positive corre- ∗∗ ∗∗ affected significantly the contents of macronutrients; the lations of CEC with clay (r � 0.885 ) and OM (0.913 ) in mean values were significantly higher at the lower slope this study. An increase in CEC of soils with high organic than the upper slope. Such a significant difference for matter and clay contents has also been reported by Selassie micronutrients was, however, only for Fe and Cu. et al. [23] and Selassie and Ayanna [51]. Similarly, Mulugeta Likewise, the CEC values of the soils were significantly and Stahr [26] have supported the idea that high clay soils (P≤ 0.05) affected by soil management practices, slope can hold more exchangeable cations than low clay con- range, and the interaction between management practices taining soils. (e practice SBFYM was capable of retaining and slope range (Tables 6 and 7). Considering the main more clay due to less erosion besides having addition of OM effects, the CEC values were significantly higher under soil through FYM application. (e practices of FYM and SB −1 management practices, viz., SB (26.53 cmol (+) kg ), FYM alone were not as promising as SBFYM because of absence of −1 −1 (30.85 cmol (+) kg ), and SBFYM (34.56 cmol (+) kg ) either mechanical protection or addition of manure in them. 10 Advances in Agriculture Table 8: Effect of soil management practices and slope ranges on micronutrient cations in soils of Mawula watershed. −1 −1 −1 −1 SMP Fe (mg·kg ) Zn (mg·kg ) Mn (mg·kg ) Cu (mg·kg ) d d d d NM 5.24 2.82 2.06 4.59 c c c c SB 5.53 3.38 2.81 5.19 b b b b FYM 5.84 3.95 3.46 5.86 a a a a SBFYM 6.30 5.06 4.09 6.26 LSD (0.05) 0.166 0.353 0.531 0.162 SEM (±) 0.056 0.116 0.178 0.053 CV (%) 8.46 26.2 13.12 58.4 Slope range b a a b US 5.64 3.69 2.95 5.32 a a a a LS 5.82 3. 91 3.26 5.63 LSD (0.05) 0.112 0.249 0.382 0.114 SEM (±) 0.037 0.822 0.125 0.037 Means within a column followed by the same letter are not significantly different from each other at P≤ 0.05; SMP, soil management practices; NM, no management; SB, soil bund; FYM, farm yard manure; SBFYM, soil bund integrated with farm yard manure; US, upper slope; LS, lower slope. Table 9: (e interaction effect of soil management practices and slope ranges on micronutrient cations in soils of Mawula watershed −1 (mg·kg ). Fe Zn Mn Cu SMP US LS US LS US LS US LS e d ff ef f ef g f NM 5.1 5.38 2.74 2.9 1.69 2.43 4.45 4.74 d cd cd cd ed edc e d SB 5.45 5.6 3.26 3.49 2.74 2.87 4.98 5.41 cb b cb b bdc bac c cb FYM 5.77 5.9 3.86 4.03 3.34 3.58 5.78 5.93 a a a a ba a b a SBFYM 6.23 6.37 4.9 5.19 4.02 4.15 6.06 6.45 LSD 0.226 0.498 0.764 0.228 SEM (±) 3.2 2.4 3.1 3.8 Means for specific soil parameter followed by the same letter(s) are not significantly different from each other at P≤ 0.05; SMP, soil management practices; NM, no management; SB, soil bund; FYM, farm yard manure management; SBFYM, soil bund integrated with farm yard manure; SEM, standard error of mean; US, upper slope; LS, lower slope. Table 10: Types of soil management practices on Mabula Zikre watershed, northwestern Ethiopia. (e higher con- watershed. tents of micronutrients in managed soils could be linked to higher amounts of organic matter in them, as organic matter Soil management practices Frequency Percentage retards the oxidation and precipitation of micronutrients Soil bund alone 16 22.2 into unavailable forms and enhances their availability Farm yard manure 24 33.3 through chelating action. (e enhancement of available Zn Soil bund + farm yard manure 31 43.1 in soil with the use of farm yard manure and soil conser- Stone bund + farm yard manure 1 1.4 vation measure has been reported by Kumar and Babel [52]. (e higher values of CEC at lower slope range Table 11: Adoption of soil management practices by farmers and −1 (29.49 cmol (+) kg ) than the upper slope (27.81 cmol their supporters. −1 (+) kg ) are, obviously, due to more accumulation of clay Adoption Frequency Percentage and organic matter moved from the upper slope. Considering the interaction effect of land management Farmers No 12 16.7 practices and slope range, the significantly highest value of CEC −1 Yes 60 83.3 (35.4 cmol (+) kg ) compared to other treatment combina- Supporters tions was recorded with SBFYM at the lower slope and lowest −1 None 10 16.7 (21.8 cmol (+) kg ) with NM at the upper slope (Table 7). NGO 27 45.0 Based on the ratings given by Hazelton and Murphy [53] Government 23 38.3 for CEC, the soils under three soil management practices and no management could be rated as high and medium, (erefore, more enrichment of cations was obtained in the respectively. (erefore, proper use of land by providing soils where there was mechanical protection in the form of appropriate soil conservation practices would maintain soil soil bund coupled with incorporation of farm yard manure. fertility, while keeping it unmanaged would make it poor. (e favorable effect of soil management practices on soil (e integrated use of soil bund and farm yard manure is the exchangeable K has been indicated by Selassie et al. [23] in best option for vis-a-vis soil bund or FYM alone. Advances in Agriculture 11 Table 12: Farmers’ suggestions on adoption of soil management physical and chemical aspects of soil fertility. (e results practices. from farmers’ survey indicated that majority of farmers (83.3%) perceived well and adopted the soil conservation Suggestion Frequency Percentage practices. Farmers’ sensitization on SMP 19 26.4 From the foregoing information on soil and farmers’ Technical support for SMP 21 29.2 adoption of soil management practices, it could be con- Farmers’ trainings and experiences 26 36.1 cluded that soil management practices had a positive in- sharing fluence on enhancement of soil fertility of degraded lands. Provision of incentive to the farmers 6 8.3 (e management practice of soil bund combined with farm yard manure was most promising in improving soil fertility 3.3. Soil Management Practices and 8eir Adoption. Based on both at upper and lower slopes and could be recommended information gathered from sampled households of the for wider adoption by the farmers in Mawula watershed. watershed, the soil management practices followed for prevention of soil erosion and enhancement of soil fertility Data Availability were soil bund alone, farm yard manure alone, soil bund + farm yard manure, and stone bund + farm yard (e data used to support this study are available from the manure. (e soil bund integrated with farm yard manure corresponding author upon request. was the most preferred (43 %) followed by farm yard manure (33%) and soil bund alone (22%) (Table 10). In all, 83.3% of Conflicts of Interest farmers of Mabula watershed perceived well the conserva- tion practices and adopted them (Table 11) for soil fertility (e authors declare that they have no conflicts of interest gains and productivity enhancement. (e conservation regarding publication of this paper. practices were supported largely by NGOs (45%) and government (38.3%). (e greater role of NGOs in adoption Acknowledgments of soil and water conservation technology has been high- (e authors are thankful to Loma Administration and Fi- lighted by Wolka and Negash [54] in Bokole and Toni nances and Economy Development Offices for their fi- subwatersheds, Southern Ethiopia. (e respondents sug- nancial support. gested farmers’ training and experiences sharing (36.1%), technical support (29.2%), and farmers’ sensitization (26.4%) as important determinants of adoption of soil References management practices (Table 12). [1] T. 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Negash, “Farmers’ adoption of soil and water conservation technology: a case study of Bokole and Toni sub-watersheds, southern Ethiopia,” Journal of Science & Development, vol. 2, no. 1, pp. 35–48, 2014. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Advances in Agriculture Hindawi Publishing Corporation

Effect of Soil Management Practices and Slope on Soil Fertility of Cultivated Lands in Mawula Watershed, Loma District, Southern Ethiopia

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Copyright © 2020 Damte Balcha Gadana et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
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Hindawi Advances in Agriculture Volume 2020, Article ID 8866230, 13 pages https://doi.org/10.1155/2020/8866230 Research Article Effect of Soil Management Practices and Slope on Soil Fertility of Cultivated Lands in Mawula Watershed, Loma District, Southern Ethiopia Damte Balcha Gadana, Parshotam Datt Sharma , and Dereje Tsegaye Selfeko Department of Plant Science, College of Agricultural Sciences, Arba Minch University, Arba Minch, Ethiopia Correspondence should be addressed to Parshotam Datt Sharma; sharmaparshotamdatt@gmail.com Received 13 May 2020; Accepted 20 August 2020; Published 1 September 2020 Academic Editor: Jiban Shrestha Copyright © 2020 Damte Balcha Gadana et al. (is is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Soil degradation is a serious problem challenging food security in Ethiopia. To halt degradation and restore impoverished soils, the government has initiated soil management practices in the affected areas. Still, there is little information on the impact of these practices in terms of improvement in soil fertility of cultivated lands under different soil and climatic conditions. Accordingly, the study was carried out to study the effect of soil management practices, viz, soil bund (SB), application of farm yard manure (FYM), soil bund integrated with FYM (SBFYM), and vis-a-vis no management practice (NM), on soil fertility under upper (20%–30%) and lower (2%–10%) slope ranges at Mawula watershed, Loma district, Southern Ethiopia. Twenty-four composite soil samples (4 practices × 2 slope ranges × 3 sites) drawn from the surface layer (0–20 cm) were analysed for different physical and chemical properties indicative of soil fertility. (e data were analysed statistically in a randomized complete block design. All the soil management practices improved significantly the different aspects of physical and chemical fertility (soil texture, bulk density, total porosity, moisture content, organic carbon, and contents of macro and micronutrients, viz, N, P, K, Na, Ca, Mg, Fe, Mn, Zn, and Cu). (e practice SBFYM was significantly superior to FYM and SB. (e order of performance was SBFYM> FYM> SB> NM. (e usefulness of soil management practices was further corroborated by the farmers’ response (based on semistructured questionnaires), as 83% of them perceived the practices well and opted for their adoption. As such, the soil management practices, notably SBFYM, merit their implementation on a large scale to improve fertility and productivity of degraded lands. agricultural productivity, continued food insecurity, and 1. Introduction rural poverty in Ethiopia [4–6]. Every year, the country is Land degradation, implying deterioration of soil in terms of losing billions of birrs in the form of soil, nutrient, water, and its quality and productivity due to improper use, is a major agrobiodiversity losses [7]. As a result, poverty and food global issue and will remain high on the international agenda insecurity are concentrated in rural areas [8]. Although in the 21st century due to its effects on agronomic pro- estimates vary considerably, the direct losses of productivity ductivity, the environment, and food security [1]. Various from land degradation in Ethiopia may be put minimally at sources suggest that 5-6 million hectares of arable land 3% of agriculture GDP [9]. (e Ethiopian highlands cov- worldwide are being lost annually to severe degradation [2]. ering a sizeable landmass are particularly more severely Due to severity of land degradation, Africa as a whole has degraded, eroding the valuable soil resource base and ag- become a net food importer since Saharan Africa because gravating drought and repeated food shortages [10, 11]. 65% of the population is rural, and the main livelihood of Among various biophysical, socioeconomic, and polit- about 90% of the population is agriculture [3]. Land deg- ical factors of soil degradation, poor land management is radation is one of the major causes of low and declining thought to be playing an overriding role in the overall 2 Advances in Agriculture usefulness of the practices was also assessed by conducting a degradation process in many regions [12]. (e increased anthropogenic influence on land resources evident in in- questionnaire-based survey on perception and adoption of soil management practices by farmers in the watershed. creased cultivation of marginal land with steep gradients and low-input or fertility-mining methods of subsistence agri- culture accelerates soil erosion and cause sharp decline in 2. Materials and Methods soil fertility [13]. (e MoARD and WB [14] reported that cultivation on steep and fragile lands with inadequate in- 2.1. General Description of Study Area vestments in soil conservation or vegetation cover, erratic and erosive rainfall patterns, declining use of fallow, and 2.1.1. Location and Physiography. (e study was conducted limited recycling of dung and crop residues to the soils are at the Mawula watershed (Figure 1), which is located in largely responsible for continued soil degradation in Loma district of Dawro Zone in the Southern Nations and Ethiopia. (e cultivated lands in Ethiopia, particularly in Nationality Regional State (SNNPRS). It is located between steeply sloping areas, are reported to have very high rates of ° ° ° ° 6 57′0″N–6 59′30″N latitude and 37 11′0″E–37 17′0″E −1 −1 soil erosion ranging from 20 to 237 t·ha ·year [15–18]. longitude, with an altitude ranging from 1779 to 2361 meters Majority of Ethiopian soils are, therefore, poor in soil fer- above sea level. It is at about 365 km from Hawassa city in the tility [19–21]. As a consequence of declining soil fertility, the southern direction and at about 546 km southwest of Addis crop productivity has been low, and average cereal yield at Ababa. It is one of the 108 watersheds in Loma district and −1 the national level is still less than 2 t·ha . covered 937 ha out of the total area of 117,043 ha in the To cope up with the soil erosion problem, Ethiopian district. (e area is marked by 15.9% gentle slope, 43.4% Government had launched massive soil conservation pro- moderate slope, 26.5% moderately steep slope, 10.5% steep grams throughout the country in the middle of 1970s [22], slope, and 3.7% mountainous terrain [28]. About 54% of involving different nongovernmental organizations (NGOs) total area in the watershed was managed under different and mobilizing local people. (e different programs under conservation practices. food-for-work program comprised land leveling programme (LLP), sustainable land management (SLM), United Nations Development Program (UNDP), and Productive Safety Net 2.1.2. Land Use and Farming System. (e cultivated, forest, Program (PSNP). (e programs aimed at transforming and grazing lands covered 78.3%, 11.4%, and 3.8% of area in agriculture through conservation of soils, reducing soil the watershed. Agriculture is characterized by the subsistent erosion, and restoring soil fertility. One of the programs was mixed crop-livestock farming system. (e important cereal in steeply sloping areas for rehabilitation of degraded lands crops were maize (Zea mays), sorghum (sorghum bicolor), by introducing mechanical conservation measures, use of barley (Hordeum vulgare), and wheat (Triticum aestivum). perennial crops, plantation of forest areas, and use of organic (e vegetables grown were potato (Solanum tuberosum L.), manures. (e commonly followed soil management prac- tomato (Solanum lycopersicum), cabbage (B. oleracea var. tices included (a) use of a soil bund, (b) use of only manure, capitata), onion (Allium cepa), carrot (Daucus carota), green and (c) use of integrated bund and manure. (e manage- pepper (Capsicum spp.), faba bean (Vicia faba L.), pea ment practices ought to influence differentially the soil (Arachis hypogea), and haricot bean (Phaseolus vulgaris). characteristics and attendant soil fertility regimes. Most of the area around the homestead was covered with Recent studies [23, 24] have indicated usefulness of these perennial enset (Enset ventricosum), which is a staple food conservation practices in improvement of soil fertility. Such and income source. Coffee (Coffee arabica) and fruit trees studies need to be taken up under different soil and climatic such as false banana (Musa species), avocado (Persea conditions influencing the performance of soil conservation americana), and mango (Mangifera indica) were also among measures. Monitoring and evaluation of soil management the widely cultivated crops [28]. programs is essential to have their continuity, reinforce- ment, and corrections to make them compatible with so- cioeconomic environment imperatives. It becomes all the most important in Ethiopia, as about 18% of the rainfed 2.1.3. Climate and Agroecology. (e district is divided into three climatic zones on the basis of altitudinal and annual croplands have so far been treated with soil and water rainfall variations, as “Dega,” “Woyna Dega,” and “Wet conservation measures, and 60%, i.e., nearly 12 million ha, still need to be treated [25]. Kola.” (e study site belonged to “Woyna Dega.” (e mean monthly rainfall and maximum and minimum temperatures Management-induced changes in soil can be evaluated by assessing soil’s physical and chemical properties, such as for eleven years (2000–2010) are presented in Figure 2. (e mean annual rainfall was 1720 mm, and mean minimum and texture, water holding capacity, bulk density, porosity, soil organic carbon, total nitrogen, available phosphorus, ex- maximum temperatures were 11.7 and 23.5 C, respectively. (e rainfall distribution was bimodal. (e medium rainy changeable potassium, soil pH, and electrical conductivity [23, 24, 26, 27]. Accordingly, this study was envisaged to season (Belg) occurs from March to May, while the main rainy season (Kremt) occurs from June to September. Also, evaluate the effect of three soil management practices under two slope ranges on the improvement of soil fertility (re- there is small rain in October and November. (e Mawula watershed is drained into the Manstha River, which is a part flected in indicative soil properties) of cultivated lands in Mawula watershed, Loma district, Southern Ethiopia. (e of the Omo Gibe River basin. Advances in Agriculture 3 Loma woreda Ethio regions Mawula watershed SouthR kebeFF Dawuro zone SouthR kebeFF Dawuro zone Loma woreda Mawula watershed 0 1.75 3.5 7 Kilometers Figure 1: Map of study area. 25 300 0 0 Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec min T RF monthly max T Figure 2: Monthly rainfall and maximum and minimum temperatures of the study area (11 years average). 2.1.4. Soil Type. (e soil of the area is grouped as Orthic management, soil bund, manure application, and soil bund Acrisols [29]. (ese soils have a distinct argillic B horizon integrated with manure) at two slope ranges (20–30% slope and a low base saturation. (e soils are chemically poor. (e as upper range and 2–10% slope as lower range). content of weatherable minerals is generally low, the pH is About 15 subsamples each for the different soil man- less than 5.5, and available P is low. (e rooting depth might agement practices were drawn from 0–20 cm depth at a be limited by the argillic B horizon or by rock at shallow particular site for two slope ranges from the cultivated depth. (e moisture storage capacity of soil is moderate to fields. (e subsamples for each practice were composited. good. (us, a total of 24 composite samples (four practices∗ two slope ranges∗ three sites as replications) were obtained for 2.2. Soil Sampling. (e soil sampling was performed at three laboratory analyses. Soil core samples from the 0–20 cm sites of the watershed (Table 1) for four soil management depths were taken with a sharp-edged steel cylinder forced practices being followed by farmers for about 8 years (no manually into the soil for bulk density determination. T (°C) 6°57′0″N 6°58′0″N 6°59′0″N 37°11′0″E 37°11′30″E 37°12′0″E 37°12′30″E 37°13′0″E 37°13′30″E 37°14′0″E 37°14′30″E 37°15′0″E 37°15′30″E 37°16′0″E 37°16′30″E 37°17′0″E RF (mm) 4 Advances in Agriculture Table 1: Sample site characteristics. Site name Slope range Coordinate point Altitude (masl) Slope (%) Aspect ° ° 6 58′01″–6 57′21″ Upper 2153–2156 20–30 Southern ° ° 37 14′21″–7 15′38″ Borthe ° ° 37 15′11″–37 16′31″ Lower 1658–1855 2–10 Southern ° ° 6 58′81″–6 58′82″ ° ° 6 57′66″–6 57′88″ Upper 2153–2156 20–30 Southern ° ° 37 13′57″–37 14′67″ Fulasa ° ° 6 58′56″–6 58′78″ Lower 1658–1952 2–10 Southern ° ° 37 15′28″–37 16′61″ ° ° 6 58′60″–6 58′80″ Upper 2153–2156 20–30 Southern ° ° 37 13′88″–37 14′42″ Xossa wora ° ° 6 57′45″–6 57′65″ Lower 1658–1952 2–10 Southern ° ° 37 15′22″–37 16′42″ Global positioning system (GPS) and clinometers were people in watershed according to the sampling formula of used to know the geographical location and slope of the Glenn [38]: sampling sites, respectively. n � , (1) 1 + N(e) 2.3. Soil Analyses. (e analyses for physical fertility pa- where n � sample size, N � total population, and e is the rameters (soil texture, bulk density, and moisture content) precision level chosen (10% confidence level). and chemical fertility parameters (pH, organic carbon, total Accordingly, n � 362/1 + 362(0.1) � 362/1 + 3.62 � nitrogen, cation exchange capacity, and available phos- 362/4.62 � 362/5 � 72. phorus) were performed at SNNPR State Agricultural Bu- (e respondents belonged to community elder groups, reau Sodo Soil Laboratory. (e analyses for macro and development/extension agents, watershed management plan- micronutrients (Ca, Mg, K, Na, Fe, Mn, Cu, and Zn) were ning committee, male and female household heads, and water performed at Arba Minch University, Abaya Campus En- development committee. vironmental and Soil Laboratory. (e particle size distribution was determined by the Boycouos hydrometric method [30]. Soil bulk density was 2.5. Statistical Analysis. (e soil physical and chemical properties were subjected to analysis of variance using the determined using undisturbed core samples as described by Black [31]. Total porosity was calculated using general general linear model procedure of the statistical analysis system version 9.1 [39]. (e least significance difference equation relating bulk density and particle density. Soil moisture content was expressed on mass basis (M ). (e pH (LSD) was used to separate significantly differing treatment means after main effects were found significant at P< 0.05. of the soils was measured in soil-water suspension (1 : 2.5 : soil : water) using a glass-calomel electrode [32]. Soil organic Simple correlation analyses were executed to reveal the carbon content was determined by the Walkley and Black [33] magnitudes and directions of relationships between selected wet digestion method. (e Kjeldhal digestion and distillation soil physicochemical parameters. (e farmers’ perception method was used to measure total nitrogen [34]. Cation and the adoption of soil management practices were ana- exchange capacity (CEC) was determined after extracting the lysed using IBM SPSS statistics software version 20. soil samples with 1N NH OAc at pH 7.0 and distilling am- monium displaced by leaching with NaCl solution [35]. 3. Results and Discussion Available soil P was analysed following procedure of Olsen et al. [36]. Available/exchangeable potassium and sodium 3.1. Effect of Soil Management Practices on Soil were determined by the flame photometry [35]. Calcium, Physical Properties magnesium, and micronutrients (Fe, Zn, Mn, and Cu) were 3.1.1. Soil Texture. (e soil texture was significantly affected analysed by the atomic absorption spectrophotometer [37]. (P< 0.05) by soil management practices and slope range. (e proportion of sand in soil under no management practice (NM) was significantly higher compared to soil management 2.4. Farmers’ Survey. Semistructured questionnaires were practices (Table 2). It decreased progressively under SB (soil used to gather information from watershed people about soil bund), FYM (farm yard manure application), and SBFYM management practices and their adoption. (e general (soil bund coupled with farm yard manure application). discussions and interviews were made with 72 randomly Conversely, the clay fraction was significantly higher under sampled respondents taken from a total of 362 household SB, FYM, and SBFYM compared to NM by 7%, 14%, and Advances in Agriculture 5 Table 2: Effect of soil management practices and slope range on physical properties of soils in Mawula watershed. −3 −3 SMP Sand (%) Silt (%) Clay (%) STC BD (Mg·m ) PD (Mg·m ) MC (%) TP (%) a b d a c d c NM 50.7 21.5 27.7 SCL 1.165 2.58 12.2 56.2 b b c b b c cb SB 47.2 23 29.7 CL 1.08 2.61 22.47 57.4 c a b b b b b FYM 41.7 26.5 31.7 CL 1.08 2.62 27.65 58.8 d a a c a a a SBFYM 38.5 27 34.5 CL 0.99 2.64 32.57 62.3 LSD (0.05) 1.25 1.86 1.67 0.06 0.014 4.39 2.26 SEM (±) 0.50 0.07 0.57 0.014 0.004 1.30 0.60 CV% 2.34 6.19 4.01 4.79 2.85 16.52 3.74 Slope range a b a a a a b US 45.7 23.92 30.42 Loam 1.11 2.62 22.67 57.64 b a a b a a a LS 43.3 25.25 31.33 Loam 1.05 2.61 24.78 59.68 LSD (0.05) 0.89 1.32 1.18 0.04 0.06 3.11 1.60 SEM (±) 0.89 1.32 1.18 0.045 0.06 3.1058 1.60 CV% 0.36 0.49 0.010 0.003 0.92 0.42 Means within a column followed by the same letter are not significantly different from each other at P≤ 0.05; SMP, soil management practices; STC, soil texture class; SCL, sandy clay loam; CL, clay loam; BD, bulk density; PD, particle density; MC, moisture content; TP, total porosity; US, upper slope; LS, lower slope. −3 24.5%, respectively. (e proportion of silt was significantly manure (1.08 Mg·m ), and soil bund combined with farm −3 higher under FYM and SBFYM practices compared to NM yard manure (0.99 Mg·m ) (Table 2). (e total porosity, and SB. From the foregoing, it is clear that soil with any of having negative relationship with bulk density, was signif- the management practices is having higher amounts of finer icantly lower in soil with no conservation practice (56.2%) fractions, viz., clay and silt, and lower of coarse sand fraction. compared to soils with conservation practices. (e highest Such a situation is desirable from the soil fertility point of value of porosity (62.3%) was obtained with the practice of view, as it is the finer soil fraction that retains nutrients soil bund + farm yard manure. Such a trend of bulk density and water. (e soil with no management practice is and total porosity values under different management subject to soil erosion and removal of finer soil fraction practices could be explained to their level of protection with runoff water. Accordingly, the texture of soil with against the processes of soil erosion, viz., dispersion, conservation practices was better (clay loam) compared to transportation, and deposition of soil particles. (e practice no conservation practice (sandy clay loam). Although, soil with no conservation practice will have removed the finer texture being a basic soil property is not subject to change soil fraction, raising the value of bulk density. Conversely, with management, such a situation may be warranted on the soils having conservation practices will have less erosion the removal of finer fraction with soil erosion and al- and more proportion of clay and silt, lowering the value of teration in the mass proportion of textural separates. (e bulk density. A similar decrease in the bulk density of soil results are corroborated by the findings of Wolka et al. treated with management practice of SB + FYM compared to [13] who reported increase in clay and silt contents in soils no management has been reported by Selassie et al. [23] in provided with soil bund and stone bund on cultivated Zikre watershed, northwestern Ethiopia. Also, Agele et al. lands in Southern Ethiopia. Also, Dagnachew et al. [24] [40] found soil amended with FYM to be having lower bulk reported significantly improved silt and clay fractions density and higher total porosity, possibly due to increases in with soil and water conservation measures (SWC) com- the proportion of macroaggregates and soil organic matter. pared to no SWC on farm lands. Texturally, the perfor- Husen et al. [41] indicated that soil bund had a significant mance of soil management practices was in the order of effect on soil bulk density. SBFYM> FYM> SB> NM. (e interaction effect of soil management and slope (e slope range did not show a change in the soil texture range (Table 3) indicated better textural composition of soil as it was loam under both the categories of the upper slope provided with management practices of SBFYM at both and lower slope. However, proportion of sand was signifi- slope ranges. cantly higher under the upper slope (45.7%) than the lower (e slope condition was found to affect bulk density and slope (43.3%) and proportion of silt higher under the lower total porosity significantly. (e upper slope had significantly −3 slope (25.2%) than the upper slope (23.9%). (e higher silt higher bulk density (1.11 Mg·m ) compared to the lower −3 content in the lower slope might be due to reduced soil slope (1.05 Mg·m ). (e total porosity was significantly erosion and more deposition of fine fractions of soil. higher for the lower slope (59.7%) compared to the upper slope (57.6%). Actually, when soil erosion takes place, finer particles get suspended in the accumulating water and are 3.1.2. Bulk Density and Total Porosity. (e bulk density of transported down the slope, leaving coarser material at the soil was significantly higher under soil with no conservation top slope positions that raise bulk density and lower pore −3 practice (1.17 Mg·m ) compared to soils with soil conser- spaces. On the other hand, the suspended finer particles −3 vation practices, viz., soil bund (1.08 Mg·m ), farm yard transported down the slope get accumulated at the bottom 6 Advances in Agriculture Table 3: Interaction effect of soil management practices and slope range on physical properties of the soils in Mawula watershed. −3 −3 Sand (%) Silt (%) Clay (%) BD (Mg·m ) PD (Mg·m ) MC (%) TP (%) SMP US LS US LS US LS US LS US LS US LS US LS a b e bdec d d a b e de d d d c NM 54.7 52.3 22.3 24 22.67 23.67 1.21 1.12 2.58 2.59 14.4 15.37 53.2 56.7 c c de dec c cb b cb bc bc c c c c SB 49 47 22.67 23.3 29 30.3 1.12 1.07 2.61 2.62 21.7 23.17 57.1 59.2 d e bdac a b b b cd bc ba bc ba c ba FYM 44 41.3 25.33 27.67 31.67 31.67 1.11 1.04 2.62 2.63 26.4 28.83 57.3 60.2 fe f ba bac a a cd d a a ba a ba a SBFM 40 39 26.33 26.2 34.3 35 1.04 1.01 2.64 2.65 31.1 34.07 60.7 62.03 LSD 2.16 2.95 2.45 0.06 0.019 5.582 2.588 SEM (±) 5.2 6.22 12.3 0.55 2.33 13.5 20.5 Means for specific soil parameter followed by the same letter(s) are not significantly different from each other at P≤ 0.05; SMP, soil management practices; NM, no management; SB, soil bund; FYM, farm yard manure; SBFYM, soil bund integrated with farm yard manure; BD, bulk density; PD, particle density; MC, moisture content; TP, total porosity; US, upper slope; LS, lower slope. slope positions, thus, lowering bulk density and raising total the lower slopes. (e runoff generation and soil erosion become more as degree of slope increases. Dagnachew et al. porosity of lower slopes. Similar results were reported by Selassie et al. [23] who found a significant reduction in bulk [24] also found significantly higher volumetric water content at the bottom slope classes than the upper slope due to erosion density from the upper slope (28%) to the lower slope (8%). Likewise, Khan et al. [42] found bulk density to be decreased reduction and the deposition effect of SWC measures. with decrease in the slope. Based on soil volume functions, (ere was a significant effect of interaction between soil the performance of land management practices could be in management practices and slope range on soil moisture the order of SBFYM> FYM � SB> NM. (Table 3). (e highest water content (34.1%) was obtained (e interaction between soil management practices and with SBFYM at the lower slope range and minimum with slope (Table 3) indicated BD to be highest with NM at the NM at the upper slope. −3 upper slope (1.21 Mg·m ) and lowest with SBFYM at the −3 lower slope (1.01 Mg·m ). (e porosity was highest (62%) with SBFYM at the lower slope and lowest with NM at the 3.2. Effect of Soil Management Practices on Soil upper slope (53.2%). (e interaction effect, therefore, further Chemical Properties established the superiority of management practice of 3.2.1. Soil pH. (e pH was significantly lower with no SBFYM in maintaining physical soil environment. management practice (5.2) compared to soils having management practices such as soil bund (5.9), farm yard manure (6.2), and combination of soil bund and farmyard 3.1.3. Soil Moisture Content. (ere was a significant effect (P< 0.05) of soil management practices on soil moisture manure (6.5) (Table 4). (e depression in soil pH in soils without any conservation practice was probably due to content. (e soil with no conservation practice contained significantly lower amount of moisture (12.2%) compared removal of basic cations along with the eroding fine soil fractions. To the contrary, the soils protected with certain to soils having soil conservation practices (22.5–32.6%) (Table 2). (e highest moisture content was obtained with conservation practice would retain the basic cations along with fine fraction, raising the soil pH. the practice of SBFYM followed by FYM and SB. (e percentage increases in moisture content were 84, 126, Similar increases in soil pH with provision of soil and water conservation measures have also been reported else- and 167 under SB, FYM, and SBFYM, respectively, over NM. Such a marked increase in soil moisture by the where. For instance, Wolka et al. [13] reported increase in conservation practices could be ascribed to their influ- soil pH with the construction of level stone and soil bunds in Bokole watershed, Ethiopia. Likewise, Tugizimana [44] in- ence on water storage in soil profile. (e practices offering mechanical barriers to the flow of water reduce the runoff dicated increase in soil pH with the adoption of soil and water conservation measures in Rwanda. velocity and offer more opportunity for water to infiltrate into the soil. Also, the conservation practices reducing (e upper slope range indicated significantly lower pH (5.8) than the lower slope range (6.1) (Table 4). (is is loss of fine fractions of soil, including humus, would enhance the water holding capacity of the soils. Similar obvious as upper slopes have more loss of basic cations that causes lowering of pH, while lower slopes have gain of basic increase in soil water content with SWC measures over no SWC has been reported by Dagnachew et al. [24]. An cations raising the soil pH. increase in water retention as a result of enhanced (e interaction effect of soil management practices and structure stability in coarse textured soils amended with the slope range was significantly different (P< 0.05). (e composted manure and sewage sludge has been reported three soil management practices at both upper and lower slope ranges showed significantly higher soil pH compared by Mamedov et al. [43]. (e soil moisture percentage was significantly higher to no practice. (e highest mean value of 6.6 was at the lower slope under SBFYM and lowest of 5.1 was under NM at the under the lower slope (24.8%) than the upper slope (22.7%). (e effect was obvious with loss of fine fraction of soil, upper slope (Table 5). (e practices of FYM and SBFYM had similar pH, but significantly higher than rest of the treatment retaining water, from the upper slopes and its deposition in Advances in Agriculture 7 Table 4: Effect of soil management practices and slope range on soil chemical properties in Mawula watershed. SMP pH OC (%) TN (%) C : N AP (mg/kg) d d d c d NM 5.20 0.51 0.09 5.89 7.50 c c c a c SB 5.91 2.08 0.15 13.59 13.30 b b b b b FYM 6.17 2.62 0.21 12.54 17.83 a a a b a SBFYM 6.52 2.97 0.26 11.6 21.16 LSD (0.05) 0.16 2.87 0.02 1.02 1.02 SEM (±) 0.02 0.02 0.01 0.68 76.70 CV% 2.18 6.95 9.64 7.57 6.29 Slope range b b b b Upper 5.80 1.93 0.17 10.76 14.00 a a a a Lower 6.10 2.17 0.19 11.04 15.92 LSD (0.05) 0.11 0.12 0.01 0.72 0.82 SEM (±) 0.02 0.02 0.001 0.68 0.54 Means within a column followed by the same letter are not significantly different from each other at P≤ 0.05; SMP, soil management practices; NM, no management; SB, soil bund; FYM, farm yard manure; SBFYM, soil bund integrated with farm yard manure; OC, soil organic carbon; TN, total nitrogen; C : N, carbon to nitrogen ratio; AP, available phosphorus; US, upper slope; LS, lower slope. Table 5: Interaction effect of soil management practices and slope ranges on chemical properties of soils in Mawula watershed. pH OC (%) TN (%) C : N AP (mg/kg) SMP US LS US LS US LS US LS US LS f f d d e e d d g f NM 5.1 5.3 0.44 0.59 0.07 0.10 6.0 5.78 6.0 9.0 e d c b d d cd a e e SB 5.6 6.03 1.75 2.42 0.14 0.16 12.4 14.71 12.67 14.0 dc c b b c cb cb cb d c FYM 6.2 6.36 2.59 2.67 0.21 0.21 12.5 12.56 17.0 18.6 ba a a a b a cb c b a SBFYM 6.4 6.6 2.93 3.02 0.24 0.27 12.1 11.11 20.3 22.0 LSD 0.227 0.249 0.029 1.445 1.650 SEM (±) 0.075 0.082 0.009 0.476 0.543 Means for specific soil parameter followed by the same letter(s) are not significantly different from each other at P≤ 0.05; SMP, soil management practices; NM, no management; SB, soil bund; FYM, farm yard manure management; SBFYM, soil bund integrated with farm yard manure; SEM, standard error of mean; US, upper slope; LS, lower slope. combinations. As per rating of Tekalign [45], the non- It is interesting to note that physical soil conservation measure managed soil in upper and the lower slope was strongly SB complemented with organic manure application could acidic (pH of 5.1–5.3). (e soil with practice of SB in the raise soil SOC content better than soil bund alone. Similar upper slope was moderately acidic (pH of 5.6) and in the increase in organic carbon content (over 120 percent) under lower slope was slightly acidic (pH of 6.0). (e soil with FYM SBFYM compared to NM has been reported by Selassie et al. alone and with SB + FYM was also slightly acidic (pH of 6.4 [23] in Zikre watershed, Ethiopia. Likewise, farm land with and 6.6). SWC measure significantly improved soil organic carbon compared to farm land without SWC [24, 48]. As organic matter is the main supplier of nutrients in low input farming 3.2.2. Organic Carbon (OC). (e organic carbon content was systems, a continuous decline in the soil OC content of the significantly (P≤ 0.05) affected by soil management practices. soils is likely to affect the soil productivity and sustainability. It was significantly lower under no management practice (0.51%) compared to soil bund (2.08%), farm yard manure Considering the main effect of two slope ranges (Table 4), application (2.62%), and soil bund combined with farm yard the OC content was significantly higher under the lower slope manure application (2.97%) (Table 4). (e percentage in- (2.17%) than the upper slope (1.93%). (e increase in former creases in OC content for SB, FYM, and SBFYM over NM was due to deposition of eroded sediments and organic fraction were 308, 414, and 482 percent, respectively. A very low from the upper slope and less intense soil erosion due to re- content of OC under NM was due to the fact that soils are duction in degree of the slope. (e similar results on the effect subject to inexorable processes of soil erosion, leaving soils of the slope range on OC content in soils have been reported by devoid of organic fraction. On the other hand, the lands with Wolka et al. [13], Tadele et al. [49], and Selassie et al. [23]. management practices that provide mechanical barriers to the As for the interaction effect of soil management practices runoff water would have reduced the loss of fine soil fractions and slope range (Table 5), the practice SBFYM at both upper and organic carbon. (e clay particles have substantial ex- and lower slopes gave significantly higher content of OC change surface areas and, therefore, adsorb and stabilize OC compared to rest of the combinations of practice and slope. in soils [46, 47]. (e soil management practices such as FYM (e no management recorded significantly lowest OC at and SBFYM would also add organic matter to the soils both the slope ranges. It was noticed that by employing soil through manure application besides controlling soil erosion. 8 Advances in Agriculture management practices such as FYM and SBFYM, the same water from the higher slope and build up at the lower slope level of OC could be maintained at upper and lower slopes. position. (e soil erosion might have decreased major plant (e amount of OC in soils rated according to Tekalign [45] nutrient (TN) at the higher slope and increased at the lower was found to be low under nonmanaged land and medium slope. under three management practices. (e C : N ratio was also significantly (P < 0.05) higher under soil management practices, viz., SB (13.57), FYM (12.54), and SBFYM (11.6) compared to NM (5.89). How- 3.2.3. Total Nitrogen (TN) and C : N Ratio. Total nitrogen ever, the difference was nonsignificant between the practices (TN) amount was significantly affected (P< 0.05) by dif- having incorporation of FYM (Table 4). (e effect of slope ferent soil management practices and slope conditions. It percentage was not significant. (e C : N ratio is indication was significantly lower with no management (0.086%) of soil mineralization rate. Generally, the C : N ratio of 10–15 compared to soil bund (0.153%), farmyard manure ap- is normal, 15–25 may indicate slowing of decomposition plication (0.210%), and soil bund integrated with FYM process, and >25 may show organic matter to be raw and (0.258%) (Table 4). (e increase in N under SB, FYM, and unlikely to breakdown quickly. Accordingly, all the soil SBFYM over NM was 58%, 144%, and 200%, respectively. management practices were having C : N ratios as normal. (e increases in N content under soil management prac- (e interaction effect (Table 5) showed higher ratio for FYM tices were due to less loss of fertility bearing soil fractions practice than NM. such as clay and silt and addition of farm yard manure. (e N enrichment was more marked under management practices adding farm yard manure. (e soil management 3.2.4. Soil Available Phosphorus (AP). (e soil available practices reducing runoff and soil loss and enhancing phosphorus was significantly (P< 0.01) affected by soil profile water storage would enhance crop growth and management practices, slope range, and the interaction contribute to OM and N input in the soil. (e significance between soil management practices and the slope (Tables 4 of soil management in enhancing soil fertility has been and 5). All the soil management practices indicated sig- highlighted by some studies. For instance, nonconserved nificantly higher contents of AP than no management. (e land had the smallest mean value of TN compared to the practice of soil bund integrated with farm yard manure conserved land [26]. In another study [13], soil and water appeared to be significantly superior to the practices of soil conservation increased the total soil N in Bokole watershed bund and farm yard manure alone. Accordingly, AP fol- in Ethiopia. Similarly, the soil management practices of lowed an order SBFYM (21.16 mg/kg)> FYM (17.83 mg/ farm yard manure complemented with soil bund increased kg)> SB (13.3 mg/kg)> NM (7.5 mg/kg). Generally, varia- the total nitrogen content by 107% over nonconserved land tions in available P contents in soils should be related to the [23]. level of soil management, i.e., mechanical and cultural (e mean N content decreased considerably from practices retaining/adding mineral and organic fractions in 0.188% in the bottom slope to 0.166% in the upper slope soil soil, besides intensity of soil weathering and P fixation. (e (Table 4), revealing a reduction of about 12%. (e difference practice of soil bund would retain more fertility bearing soil in N content may be due to deposition of eroded sediments particles as a result of decreased soil erosion. Whereas the from the upper to the lower slope. A similar decrease in total soil bund integrated with farm yard manure incorporation N on the upper slope compared to the bottom slope has been would also have addition of phosphorus through manure reported by Dagnachew et al. [24]. application besides decreased soil erosion. More buildup of Considering the interaction of soil management prac- available phosphorus in soil with soil bund and continuous tices by the slope range (Table 5), the significantly highest N application of farm yard manure has also been indicated by (0.27%) compared to other treatment combinations was Selassie et al. [23]. Also, Mulugeta and Stahr [26] have recorded with the practice of soil bund integrated with farm reported significantly higher contents of available phos- yard manure at the lower slope, followed by the same phorus in conserved compared to nonconserved fields. (e practice at the upper slope (0.24%). (e significantly lowest main effect of slope range also revealed that available P was concentration of N compared to other treatment combi- significantly higher (15.92 mg/kg) in the lower slope than in nations was shown by NM practice both at upper (0.07%) the upper slope (14.00 mg/kg) because of its removal from and lower (0.10%) slope ranges. the upper slope and deposition in the lower slope. Following the rating of total N [45], the soil under no According to Cottenie [50], the available soil P level of management was low in N, the soil under management <5 mg/kg is rated as very low, 5–9 mg/kg as low, practices, viz., soil bund alone and farm yard manure alone 10–17 mg/kg as medium, 18–25 mg/kg as high, and was moderate in N status, and the soil under integrated soil >25 mg/kg as very high. (us, the available P of the soils management of soil bund + farm yard manure was high in N was high under SBFYM and FYM, medium under SB, and status. As the OC and total N contents showed strong as- low under NM. ∗∗ sociation (r═ 0.811 ), the reduction in the total N contents (e interaction between soil management practices and of the soils both with nonmanagement practice and the slope range indicated significantly highest available P con- tent (22 mg/kg) in SBFYM at the lower slope compared to upper slope was possibly due to reduction of soil OM content. (e increase of total N at the lower slope might be other treatment combinations, followed by the same practice at the upper slope (20.3 mg/kg). due to the downward movement of nutrient with runoff Advances in Agriculture 9 Table 6: Effect of soil management practices and slope ranges on exchangeable cations in soils of Mawula watershed. −1 Exchangeable cations (cmol kg ) −1 SMP CEC (cmol kg ) K Ca Mg Na d d d b d NM 0.53 4.89 3.05 0.18 22.66 c c c c SB 0.87 7.18 4.58 0.19b 26.53 b b b a b FYM 1.13 9.41 5.43 0.29 30.85 a a a a a SBFYM 1.22 11.05 6.72 0.35 34.56 LSD (0.05) 0.070 0.359 0.168 0.056 0.925 SEM (±) 0.023 0.118 0.0555 0.0183 0.305 CV (%) 9.3 3.95 4.17 17.9 2.35 Slope range b b b b b US 0.89 7.65 4.65 0.23 27.81 a a a a a LS 0.97 8.61 5.24 0.28 29.49 LSD (0.05) 0.049 0.254 0.119 0.039 0.6543 SEM (±) 0.164 0.0838 0.0392 0.0129 0.2157 Means within a column followed by the same letter are not significantly different from each other at P≤ 0.05; SMP, soil management practices; NM, no management; SB, soil bund; FYM, farm yard manure; SBFYM, soil bund integrated with farm yard manure; CEC, cation exchange capacity; US, upper slope; LS, lower slope. Table 7: Interaction effect of soil management practices and slope ranges on exchangeable cations in soils of Mawula watershed. −1 cmol·kg SMP K Ca Mg Na CEC US LS US LS US LS US LS US LS d d g f f f d dc h g NM 0.51 0.55 4.51 5.21 2.9 3.17 0.15 0.19 21.8 23.5 c c e d e d d dc f e SB 0.82 0.91 6.81 7.54 4.23 4.93 0.16 0.22 25.8 27.2 b a c b d c bc ba d c FYM 1.07 1.18 8.85 9.97 5.1 5.76 0.22 0.33 29.9 31.78 a a b a b a ba a b a SBFYM 1.18 1.25 10.4 11.66 6.3 7.1 0.33 0.34 33.7 35.7 LSD 0.099 0.508 0.238 0.078 1.31 SEM (±) 0.62 2.12 3.12 0.23 21.5 Means for specific soil parameter followed by the same letter(s) are not significantly different from each other at P≤ 0.05; SMP, soil management practices; NM, no management; SB, soil bund; FYM, farm yard manure management; SBFYM, soil bund integrated with farm yard manure; SEM, standard error of mean; US, upper slope; LS, lower slope. −1 3.2.5. Exchangeable Cations (Macro and Micronutrients) and compared to no management, NM (22.66 cmol (+) kg ). Cation Exchange Capacity (CEC). (e exchangeable cations (e practice of soil bund integrated with farm yard manure (K, Ca, Mg, Na, Fe, Zn, Mn, and Cu) were significantly application was significantly superior to application of farm (P≤ 0.05) affected by soil management practices, slope range, yard manure alone, which, in turn, was significantly superior and interaction between practices and the slope (Tables 6–9). to the practice of soil bund alone. (e CEC values were in the In general, the mean values of all cations were significantly order of SBFYM> FYM> SB> NM. It is a general fact that higher under soil management practices of SB, FYM, and both clay and colloidal OM have the ability to adsorb and SBFYM compared to no management NM (Tables 6 and 8). hold positively charged ions. (us, soils containing high clay Among soil management practices, SBFYM was signifi- and organic matter contents have high CEC. (is is very well cantly superior to FYM and SB alone. (e slope range also corroborated by the highly significant and positive corre- ∗∗ ∗∗ affected significantly the contents of macronutrients; the lations of CEC with clay (r � 0.885 ) and OM (0.913 ) in mean values were significantly higher at the lower slope this study. An increase in CEC of soils with high organic than the upper slope. Such a significant difference for matter and clay contents has also been reported by Selassie micronutrients was, however, only for Fe and Cu. et al. [23] and Selassie and Ayanna [51]. Similarly, Mulugeta Likewise, the CEC values of the soils were significantly and Stahr [26] have supported the idea that high clay soils (P≤ 0.05) affected by soil management practices, slope can hold more exchangeable cations than low clay con- range, and the interaction between management practices taining soils. (e practice SBFYM was capable of retaining and slope range (Tables 6 and 7). Considering the main more clay due to less erosion besides having addition of OM effects, the CEC values were significantly higher under soil through FYM application. (e practices of FYM and SB −1 management practices, viz., SB (26.53 cmol (+) kg ), FYM alone were not as promising as SBFYM because of absence of −1 −1 (30.85 cmol (+) kg ), and SBFYM (34.56 cmol (+) kg ) either mechanical protection or addition of manure in them. 10 Advances in Agriculture Table 8: Effect of soil management practices and slope ranges on micronutrient cations in soils of Mawula watershed. −1 −1 −1 −1 SMP Fe (mg·kg ) Zn (mg·kg ) Mn (mg·kg ) Cu (mg·kg ) d d d d NM 5.24 2.82 2.06 4.59 c c c c SB 5.53 3.38 2.81 5.19 b b b b FYM 5.84 3.95 3.46 5.86 a a a a SBFYM 6.30 5.06 4.09 6.26 LSD (0.05) 0.166 0.353 0.531 0.162 SEM (±) 0.056 0.116 0.178 0.053 CV (%) 8.46 26.2 13.12 58.4 Slope range b a a b US 5.64 3.69 2.95 5.32 a a a a LS 5.82 3. 91 3.26 5.63 LSD (0.05) 0.112 0.249 0.382 0.114 SEM (±) 0.037 0.822 0.125 0.037 Means within a column followed by the same letter are not significantly different from each other at P≤ 0.05; SMP, soil management practices; NM, no management; SB, soil bund; FYM, farm yard manure; SBFYM, soil bund integrated with farm yard manure; US, upper slope; LS, lower slope. Table 9: (e interaction effect of soil management practices and slope ranges on micronutrient cations in soils of Mawula watershed −1 (mg·kg ). Fe Zn Mn Cu SMP US LS US LS US LS US LS e d ff ef f ef g f NM 5.1 5.38 2.74 2.9 1.69 2.43 4.45 4.74 d cd cd cd ed edc e d SB 5.45 5.6 3.26 3.49 2.74 2.87 4.98 5.41 cb b cb b bdc bac c cb FYM 5.77 5.9 3.86 4.03 3.34 3.58 5.78 5.93 a a a a ba a b a SBFYM 6.23 6.37 4.9 5.19 4.02 4.15 6.06 6.45 LSD 0.226 0.498 0.764 0.228 SEM (±) 3.2 2.4 3.1 3.8 Means for specific soil parameter followed by the same letter(s) are not significantly different from each other at P≤ 0.05; SMP, soil management practices; NM, no management; SB, soil bund; FYM, farm yard manure management; SBFYM, soil bund integrated with farm yard manure; SEM, standard error of mean; US, upper slope; LS, lower slope. Table 10: Types of soil management practices on Mabula Zikre watershed, northwestern Ethiopia. (e higher con- watershed. tents of micronutrients in managed soils could be linked to higher amounts of organic matter in them, as organic matter Soil management practices Frequency Percentage retards the oxidation and precipitation of micronutrients Soil bund alone 16 22.2 into unavailable forms and enhances their availability Farm yard manure 24 33.3 through chelating action. (e enhancement of available Zn Soil bund + farm yard manure 31 43.1 in soil with the use of farm yard manure and soil conser- Stone bund + farm yard manure 1 1.4 vation measure has been reported by Kumar and Babel [52]. (e higher values of CEC at lower slope range Table 11: Adoption of soil management practices by farmers and −1 (29.49 cmol (+) kg ) than the upper slope (27.81 cmol their supporters. −1 (+) kg ) are, obviously, due to more accumulation of clay Adoption Frequency Percentage and organic matter moved from the upper slope. Considering the interaction effect of land management Farmers No 12 16.7 practices and slope range, the significantly highest value of CEC −1 Yes 60 83.3 (35.4 cmol (+) kg ) compared to other treatment combina- Supporters tions was recorded with SBFYM at the lower slope and lowest −1 None 10 16.7 (21.8 cmol (+) kg ) with NM at the upper slope (Table 7). NGO 27 45.0 Based on the ratings given by Hazelton and Murphy [53] Government 23 38.3 for CEC, the soils under three soil management practices and no management could be rated as high and medium, (erefore, more enrichment of cations was obtained in the respectively. (erefore, proper use of land by providing soils where there was mechanical protection in the form of appropriate soil conservation practices would maintain soil soil bund coupled with incorporation of farm yard manure. fertility, while keeping it unmanaged would make it poor. (e favorable effect of soil management practices on soil (e integrated use of soil bund and farm yard manure is the exchangeable K has been indicated by Selassie et al. [23] in best option for vis-a-vis soil bund or FYM alone. Advances in Agriculture 11 Table 12: Farmers’ suggestions on adoption of soil management physical and chemical aspects of soil fertility. (e results practices. from farmers’ survey indicated that majority of farmers (83.3%) perceived well and adopted the soil conservation Suggestion Frequency Percentage practices. Farmers’ sensitization on SMP 19 26.4 From the foregoing information on soil and farmers’ Technical support for SMP 21 29.2 adoption of soil management practices, it could be con- Farmers’ trainings and experiences 26 36.1 cluded that soil management practices had a positive in- sharing fluence on enhancement of soil fertility of degraded lands. Provision of incentive to the farmers 6 8.3 (e management practice of soil bund combined with farm yard manure was most promising in improving soil fertility 3.3. Soil Management Practices and 8eir Adoption. Based on both at upper and lower slopes and could be recommended information gathered from sampled households of the for wider adoption by the farmers in Mawula watershed. watershed, the soil management practices followed for prevention of soil erosion and enhancement of soil fertility Data Availability were soil bund alone, farm yard manure alone, soil bund + farm yard manure, and stone bund + farm yard (e data used to support this study are available from the manure. (e soil bund integrated with farm yard manure corresponding author upon request. was the most preferred (43 %) followed by farm yard manure (33%) and soil bund alone (22%) (Table 10). In all, 83.3% of Conflicts of Interest farmers of Mabula watershed perceived well the conserva- tion practices and adopted them (Table 11) for soil fertility (e authors declare that they have no conflicts of interest gains and productivity enhancement. (e conservation regarding publication of this paper. practices were supported largely by NGOs (45%) and government (38.3%). (e greater role of NGOs in adoption Acknowledgments of soil and water conservation technology has been high- (e authors are thankful to Loma Administration and Fi- lighted by Wolka and Negash [54] in Bokole and Toni nances and Economy Development Offices for their fi- subwatersheds, Southern Ethiopia. (e respondents sug- nancial support. gested farmers’ training and experiences sharing (36.1%), technical support (29.2%), and farmers’ sensitization (26.4%) as important determinants of adoption of soil References management practices (Table 12). [1] T. 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