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Variation of some chemical indicators in forage of annual winter pure and mixed crops cultivated in Central Balkan Mountains (Bulgaria)

Variation of some chemical indicators in forage of annual winter pure and mixed crops cultivated... The aim of this experiment was to determine the variations in some important chemical indicators of annual winter cereal and legume pure and mixed crops for green forage production under the conditions of the fore-mountain regions of the Central Northern Bulgaria (Troyan region). In pure crops the crude protein content had fewer values compared to mixed crops. The cereals accumulated less crude fat in comparison with legumes. In mixed crops the crude fat was from 1.99 to 2.82%, with a relatively lower coefficient of variation in comparison with pure crops. More crude fibre was indicated in winter barley, triticale and winter vetch. All pure crops displayed a low coefficient of variation (from 7.21% to 10.26%). The lowest values of crude fibre were in the mixed crops with winter pea and they had a lower coefficient of variation compared to pure crops. In regard to crude ash content the legumes exceeded the cereals. In the legume pure crops a low coefficient of variation was established, while in cereals it was a medial value. On the whole all mixed crops had a low coefficient of variation. In legumes the calcium content was higher but with a low coefficient of variation than cereals. In mixed crops irrespective of whether it had a cereal or legume component the calcium content in forage varied from 0.530 to 0.870%. In mixtures the calcium variation was mostly with a medial value. The phosphorus content had lower values in forage of pure and mixed crops. The least variation (as a medial value) was observed in winter vetch and winter barley. In mixed crops with winter barley this indicator had a low coefficient of variation. The most favorable proportion between calcium and phosphorus for pure crops was found in cereals (triticale and winter barley) ­ respectively 2.46 and 2.23 and for mixed crops ­ in Winter barley+winter pea and Winter barley+winter vetch ­ from 1.76 to 2.57. Key words: annual winter crop; variation; chemical indicator; Central Balkan Mountains (Bulgaria) Vladimir Lingorski, Research Institute of Mountain Stockbreeding and Agriculture (RIMSA), 281, Vasil Levski Street, 5600 Troyan, Bulgaria vilievl@yahoo.com INTRODUCTION In the last two decades, the climate of Central and Eastern Europe has begun to be characterized by arid conditions and that makes agricultural production in these areas very difficult. Therefore it is reasonable that agriculture should be 15 Journal of Agrobiology, 29(1): 15­21, 2012 placed in a closer dependence on environmental conditions. The objective is to seek biological and technological decisions for the most efficient use of soil water resources, and the growing of wintering forms of any forage crops serve this end well. These crops utilize more efficiently the moisture from winter and spring precipitation and ensure the production of green fodder at the end of May and June. After harvesting there is the possibility for growing second crops, which would achieve a compacted usage of the agricultural areas. In this respect in recent years several attempts have been conducted in Bulgaria and abroad. In various regions of Bulgaria a number of studies of the annual winter forage crops (cereals and legumes) have been conducted with regard to the conditions and factors forming their yields (Gramatikov 2002, Kertikov 2003, Kolev and Ivanova 2004), as well as estimating the nutritive value and quality parameters of the forage obtained (Zhelyazkova 2010). In this connection winter forage cereals (such as barley and triticale) and legumes (such as pea and vetch) and their mixed crops are of particular interest also abroad. The studies conducted are aimed at the development of the technology of cultivation as well as the establishment of quality indicators for the forage (Harper 1962, Buxton and Fales 1994, Orak 2000, Schulz et al. 2000, Annicchiarico and Iannucci 2007, Miller et al. 2011). At present such developments are incomplete and insufficient for the conditions of fore-mountain regions in Bulgaria and have been conducted up to now with a low priority in the region of the Central Balkan Mountains (Lingorski and Kertikov 2006). The objective of this experiment was to determine the variations of some important chemical indicators of annual winter cereal and legume pure and mixed crops for green forage production under the conditions of the fore-mountain regions of the Central Northern Bulgaria (Troyan region). measures were applied according to the biophysiological and technological requirements of the respective forage crop. The application of phosphorus fertilizer (as double superphosphate) was made once before basic soil cultivation (in September of the previous year) at 60 kg ha­1 active substance (a.s.). The nitrogen fertilizer (as ammonium nitrate) was applied only once in early spring (in March of the following year), as follows: 80 kg ha­1 a.s. for winter barley and triticale, 50 kg ha­1 a.s. for winter pea and winter vetch and 60 kg ha­1 a.s. for the mixed crops. The following species and cultivars of annual winter cereal and legume crops were studied: as pure crops: var. 1 ­ Winter barley cv. Kaskadyor 3 (Standard 1 ­ for cereals); var. 2 ­ Triticale cv. Rakita; var. 3 ­ Winter pea cv. Mir (No 12) (Standard 2 ­ for legumes); var. 4 ­ Winter vetch cv. Asko 1 and as mixed crops: var. 5 ­ Winter barley+winter pea (Standard 3 ­ for mixed crops); var. 6 ­ Winter barley+winter vetch; var. 7 ­ Triticale+winter pea; var. 8 ­ Triticale+winter vetch. Sowing was performed at an inter-row spacing of 12 cm and a depth of 3­5 cm for barley, triticale and vetch to 5­7 cm for pea with rolling before and after. In the experiment the sowing rates per 1 m2 of pure crops were: winter barley ­ 450 germinable seeds, triticale ­ 450 germinable seeds, winter pea ­ 120 germinable seeds and winter vetch ­ 260 germinable seeds. The components of the cereal-legume mixed crops were sown in a ratio of 1:3 depending on the sowing rates of pure crops. Every year the trial plots were harvested for green forage by cutting them at the following phenological stages: for pure crops ­ at the earing of winter barley and triticale and at the flowering of winter pea and winter vetch; for mixed crops ­ at the early flowering of the legume component (Lingorski and Kertikov 2006). The samples (100­200 g depending on the relevant forage crop) for chemical analyses were taken before harvesting of the trial plots for each variant and repetition. The chemical composition (in %) of absolutely dry matter included the following indicators: content of crude protein (by the Kjeldahl method), crude fibre (by the Heteron and Jensen method), nitrogen-free extract matters (NFEM) ­ by the Weende method (according to Hennenburg and Stohmann), crude ash (through dry incineration in a muffle oven at a temperature of 550 °C), crude fat (by the Soxlet method), calcium (by the Stotz method ­ complexmetrically) and phosphorus (by the vanadiummolybdenum method of Gericke and Kurmis). MATERIAL AND METHODS Treatment of the experiment The field experiment was carried out over the period 2003­05. Crops were sown every year in early autumn (in October) in the Experimental field of RIMSA in Troyan at 384 m above sea level. The block-method with four replications and a harvest plot of 6 m2 was used. The agricultural Journal of Agrobiology, 29(1): 15­21, 2012 The ratio between calcium and phosphorus was determined by mathematical calculation. The standard deviations (SD, %) and coefficient of variations (CV, %) in the dynamics of the chemical indicators studied for all pure and mixed crops, were determined mathematically by the computer program Microsoft Excel (AVERAGE, STDEV, COVAR). Ecological characteristics of the region The experiment was carried out on light grey pseudopodzolic soil without irrigation. This soil type has a low natural fertility, humus content 2.21% and 0.123% total nitrogen. Th soil resources for total and assimilable phosphorus (0.194% and 14.3 mg/100 g soil) were good, with assimilable potassium low (10.2%) and with soluble nitrogen, medium (29.4 mg/100 g soil). The soil reaction was slightly acidic (pHH20 5.2). The territory of the RIMSA in Troyan is a foremountain climate region and it is characterized by a temperate continental climate. The average annual air temperatures during the trial period ranged from 10.0 °C (in 2005) to 10.2 °C (in 2003) as against 10.0 °C for the 1967­2005 period. The average air temperatures during the vegetation period (April­October) ranged from 15.3 °C (in 2004) to 16.3 °C (in 2003) as against 15.4 °C for the 38-yearly period. It is obvious that air temperature conditions had allied values compared to the period 1967­2005. The sum of rainfall during the growing season varied from 557.7 mm (in 2003) to 1151.3 mm (in 2005), while for a longer period (30 years) it was 591.1 mm. It is obvious that the sum of rainfall was almost similar in comparison to the longer period and only in 2005 was it twice as high (Lingorski and Kertikov 2006). obvious that the crude protein content in the legumes (var. 3 and 4) was more than the cereals (var. 1 and var. 2): an average of 8.92% and 8.97%, respectively. In both legume crops the crude protein content had a very weak coefficient of variation ­ 2.17 and 3.14%, while the standard deviations reached 0.19 and 0.28%, respectively. Depending on the legume component, the same chemical indicator in the mixtures was more than in the pure crops only in two of the variants. For the mixed crop Winter barley+winter pea was distinguished with a maximum crude protein content of 10.77% (min) to 12.97% (max) at very weak coefficient of variation of 5.28%. For the mixed crop the minimum protein content indicator (in the Triticale+winter vetch mixture) varied from 8.60% (min) to 9.26% (max) at very weak coefficient of variation of 3.69%. In the both variants low standard deviations ­ 0.28 and 0.33%, were reported respectively. There was a reverse dependency between the crude protein and crude fibre contents during the vegetation period, i.e. in the different phenophases of plants (Kertikov 2003). In the pure crops more crude fibre was indicated in the winter barley and triticale of the cereals and in the winter vetch of the legumes. Their average values were respectively 25.19, 26.14 and 26.12%, as against to the winter pea ­ 22.38%. The standard deviations for cereals were 2.58% and for legumes (var. 3 and var. 4) ­ 1.61 and 2.65%. In all pure crops a low coefficient of variation ­ 7.21% (winter pea), 9.87% (triticale), 10.14% (winter vetch) and 10.26% (winter barley) was established. The lowest values of crude fibre were shown in the mixed crops with winter pea, and reached 23.58% (var. 5) and 24.67% (var. 7), while for the rest of the mixed crops (var. 6 and var. 8) higher values ­ 28.61 and 28.79% respectively ­ were shown. The standard deviations varied from 0.58% (var. 5) to 1.49% (var. 7). The mixed crops had a lower coefficient of variation of this indicator compared to the pure crops ­ from 2.41% (var. 8) to 6.06% (var. 7). It was established that among pure crops, the cereals accumulated less crude fat in comparison with legumes. So, in winter vetch and winter pea the mean values of this indicator reached 2.62 and 3.16% as against 2.25% (in triticale) and 2.45% (in winter barley), respectively, but, only for the winter pea, was fixed at a very weak coefficient of variation of 4.26%. The results from the presented study were in agreement with other findings by Harper (1962) as regard to Austrian winter peas and hairy vetch. For all the rest of the pure crops RESULTS AND DISCUSSION It is evident from Table 1 that between the cereals, triticale had more crude protein accumulation in forage compared to winter barley crop ­ average 8.39% as against 8.21%. The results presented in the current study related to crude protein content are in agreement with the results of lev and Ivanova (2004) with regard to some triticale cultivars and with the results of Zhelyazkova in relation to (2010) to winter pea pure crops. In the winter barley a very weak coefficient of variation ­ 3.10% was reported, while with the triticale it was a low 7.44%. The standard deviations amounted to 0.25 and 0.62%, respectively. It is Journal of Agrobiology, 29(1): 15­21, 2012 Table 1. Variation of some biochemical indicators in forage of annual winter pure and mixed (cereal and legume) crops average for the 2003­05 period Chemical composition of dry mass, % min max xaverage SD CV, % Var. 1 ­ Winter barley (Standard 1) Crude protein Crude fat Crude fibre NFEM1 Crude ash lcium hosphorus Ca:P 7.96 1.98 22.61 42.52 5.97 0.390 0.237 1.25 8.47 2.93 27.78 48.83 8.69 0.870 0.314 3.67 Var. 2 ­ Triticale Crude protein Crude fat Crude fibre NFEM Crude ash lcium hosphorus Ca:P 7.77 1.96 23.56 42.62 5.50 0.550 0.228 2.00 9.02 2.55 28.72 50.13 7.74 0.790 0.390 2.47 8.39 2.25 26.14 46.37 6.62 0.670 0.309 2.23 0.62 0.29 2.58 3.75 1.12 0.12 0.08 0.23 7.44 13.08 9.87 8.10 16.92 17.91 26.21 10.51 8.21 2.45 25.19 45.67 7.33 0.630 0.275 2.46 0.25 0.47 2.58 3.15 1.36 0.24 0.04 1.21 3.10 19.35 10.26 6.91 18.55 38.09 13.97 15.02 Var. 3 ­ Winter pea (Standard 2) Crude protein Crude fat Crude fibre NFEM Crude ash lcium hosphorus Ca:P 8.78 3.03 20.77 48.66 7.45 0.950 0.289 2.95 9.17 3.3 24.00 52.95 8.81 1.260 0.407 3.46 8.97 3.16 22.38 50.80 8.13 1.100 0.348 3.20 0.19 0.13 1.61 2.14 0.68 0.15 0.06 0.25 2.17 4.26 7.21 4.22 8.36 14.03 16.95 7.96 Var. 4 ­ Winter vetch Crude protein Crude fat Crude fibre NFEM Crude ash lcium hosphorus Ca:P 8.64 2.21 23.47 43.44 7.22 1.000 0.291 3.17 9.20 3.03 28.77 46.67 8.89 1.200 0.378 3.76 8.92 2.62 26.12 45.05 8.05 1.100 0.334 3.46 0.28 0.41 2.65 1.61 0.83 0.10 0.04 0.29 3.14 15.65 10.14 3.58 10.37 9.09 13.00 8.51 Var. 5 ­ Winter barley+winter pea (Standard 3) Crude protein Crude fat Crude fibre NFEM Crude ash lcium hosphorus Ca:P 10.77 2.59 23.00 46.90 7.77 0.470 0.275 1.51 11.97 3.05 24.16 50.00 8.62 0.600 0.350 2.01 11.37 2.82 23.58 48.45 8.19 0.530 0.312 1.76 0.60 0.23 0.58 1.55 0.42 0.06 0.04 0.25 5.28 8.16 2.46 3.19 5.19 12.15 12.00 14.20 Var. 6 ­ Winter barley+winter vetch Crude protein Crude fat Crude fibre NFEM Crude ash lcium hosphorus Ca:P 8.88 1.77 27.67 42.63 7.10 0.690 0.285 2.23 9.45 2.22 29.55 46.12 8.17 0.880 0.340 2.92 9.16 1.99 28.61 44.37 7.63 0.780 0.312 2.57 0.28 0.22 0.94 1.74 0.53 0.09 0.03 0.34 3.11 11.28 3.28 3.93 7.01 12.10 8.80 13.40 Journal of Agrobiology, 29(1): 15­21, 2012 Chemical composition of dry mass, % min max xaverage SD CV, % Var. 7 ­ Triticale+winter pea Crude protein Crude fat Crude fibre NFEM Crude ash lcium hosphorus Ca:P 8.88 2.15 23.18 47.50 6.04 0.770 0.225 2.88 9.39 2.34 26.17 52.51 6.83 0.970 0.286 3.78 9.13 2.24 24.67 50.00 6.43 0.870 0.255 3.33 0.25 0.09 1.49 2.50 0.39 0.10 0.03 0.45 2.79 4.23 6.06 5.01 6.14 11.49 11.94 13.51 Var. 8 ­ Triticale+winter vetch Crude protein Crude fat Crude fibre NFEM Crude ash lcium hosphorus Ca:P = nitrogen-free extract matters medial coefficients of variation were established ­ from 13.08% (triticale) to 19.35% (winter barley). The standard deviations had very low values: for cereals 0.29% (triticale) ­ 0.47% (winter barley) and for legumes 0.13% (winter pea) ­ 0.41% (winter vetch). Similar results were reported by Kertikov (2003). after experiments with winter pea pure crop. In the study of mixed crops the same chemical indicator was average from 1.99% (var. 6) to 2.82% (var. 5). The rest of the mixed crops occupied medial positions. In two of the mixed crops (var. 7 and 8) very small coefficients of variation were established ­ 4.23 and 4.43%, but in others (var. 5 and 6) ­ low coefficients of variation ­ 8.16 and 11.28%, respectively. With regard to the nitrogen-free extract matters (NFEM) there were no significant differences between pure and mixed crops. Among the pure crops winter pea had a larger mean value, 50.80%, than the other crops (var. 1, 2 and 4) ­ 45.67, 46.37 and 45.05%, respectively. The cereals displayed higher values of NFEM: standard deviations of 3.15 and 3.75% while the legumes had lower values ­ 1.61% (var. 4) and 2.14% (var. 3). Therefore in legumes there was a lower coefficient of variation compared to cereals ­ 4.22 and 3.38% as against 6.91 and 8.10%. In mixed crops the highest mean value (50.00%) of this indicator was displayed by Triticale+winter pea (var. 7) followed by Winter barley+winter pea (48.45%), Triticale+winter vetch (46.56%) and Winter barley+winter vetch (44.37%). The highest deviation of this indicator was obtained in var. 7 ­ 2.50%, while in the rest of the mixed crops it was the lowest ­ from 1.54% (var. 8) to 1.74% (var. 6). Iin var. 7 a higher coefficient of variation ­ 5.01% as against of 3.19% (var. 5) ­ 3.93% (var. 6) was established. On the whole, all mixed crops had a very weak coefficient of variation with regard to this indicator. The same table shows that in regard to crude ash content the legumes exceeded the cereals. Thus, in legume pure crops this indicator had values of 8.05% (var. 4) and 8.13% (var. 3), while in the cereals it was less ­ 6.62% (var. 2) and 7.33% (var. 1). In comparison with the legumes the highest values of deviation were reported in the cereals ­ 1.12% (triticale) and 1.36% (winter barley) as against 0.68% (winter pea) and 0.83% (winter vetch). In legumes also a less coefficient of variation ­ 8.36 and 10.37% (a low value), was established while in the cereals it was a medial rate ­ of 16.92% (var. 2) and 18.55% (var. 1). The mixed crops had a higher mean ash content ­ in winter barley (var. 5 and 6) ­ a 8.19% (min 7.77%, max 8.62%) and 7.63% (min 7.10%, max 8.17%). The triticale mixed crops (var. 7 and var. 8) had a lower ash content (6.43 and 5.89%). In mixtures with winter barley (var. 4 and var. 5) the standard deviation showed higher values compared with triticale mixtures ­ 0.42 and 0.53% as against 0.39 and 0.44%. In three of the mixed crops (var. 5, 6 and 7) very little variation of this chemical indicator (5.19, 7.01 and 6.14%) was observed but Journal of Agrobiology, 29(1): 15­21, 2012 only one of them (var. 8) had a low coefficient of variation ­ 7.47%. It is evident that among the pure crops the calcium content was higher in the legume than the cereals. So, in winter pea and winter vetch values of 1.100% were established while in the cereals (var. 1 and 2) were reported at 0.630 and 0.670%, respectively. The variation of the above-mentioned values was as follows: in winter barley ­ from 0.390% (min) to 0.870% (max) with a deviation rate of 0.24%, while in triticale the calcium content varied from 0.550% (min) to 0.790% (max), but with a lower deviation ­ 0.120%. In winter pea the calcium variation was in the limits: 0.950% (min) and 1.260% (max) and the standard deviation was 0.15%, while in winter vetch 1.000, 1.200 and 0.10%, respectively. In cereals the greatest variation was observed in winter barley (38.09% ­ a high value) following by triticale (17.91% ­ a medial value). In legumes of winter pea there was found also a medial coefficient of variation (14.03%) higher than the winter vetch (9.09% ­ a low value). In mixed crops irrespective of cereal and legume component the highest calcium content in forage was found in var. 7 and var. 6 ­ 0.870 and 0.780% following by var. 8 and var. 5 ­ 0.630 and 0.530%. The lowest deviations (0.06 and 0.09%) were established in the mixed crops with winter barley (var. 5 and var. 6), while in those with triticale (var. 7 and 8) were slightly more ­ 0.10 and 0.12%. In mixtures with winter barley the calcium variation was almost similar and with medial values (12.15 and 12.10%), while in the triticale crops ­ with a low value (11.49%) and with a medial value (19.68%). Compared to calcium content, phosphorus showed lower values in forage of pure and mixed crops. The table shows that the legumes exceeded the cereal crops in phosphorus content, reaching values of 0.334% (var. 4) and 0.348% (var. 3) as against 0.275% (in winter barley) and 0.309% (in triticale). It is obvious that in pure crops the standard deviation of phosphorus content was almost similar and in low limits ­ from 0.04% (var. 1 and var. 4) to 0.08% (var. 2). The lowest variations (as a medial value) were observed in winter vetch (13.00%) and winter barley (13.97%) and the relatively higher in winter pea (16.95% ­ also a medial value) and a higher value in triticale (26.21%). The forage of winter barley mixed crops (var. 5 and var. 6) showed a higher value of phosphorus ­ 0.312% (min 0.275% and max 0.350%; min 0.285% and max 0.340%). The four mixed crops had almost the same deviation of this chemical indicator ­ from 0.03% (var. 6, 7 and var. 8) to 0.04% (var. 5) as well as a low coefficient of variation ­ from 8.80% (var. 6) to 12.00% (var. 5). An important forage indicator is the correlation between calcium and phosphorus, as the most favourable ratio is considered to be 1:1.5 ­ 1:2.5 (Buxton and Fales 1994). In this study, the most favourable proportion close to above-mentioned for pure crops was found in cereals (var. 1 and var. 2) ­ 2.46 and 2.23 ­ while in legumes (var. 3 and var. 4) was about one point more ­ 3.20 and 3.46. In three of the pure crops the least and almost identical significant deviations of this proportion were established as follows: 0.23% (triticale), 0.25% (winter pea) and 0.29% (winter vetch), while in winter barley the value was about five times greater ­ 1.21%. Three of the studied crops had a low coefficient of variation ­ 7.96% (var. 3), 8.51% (var. 4) and 10.51% (var.2) ­ but in winter barley it was a medial value ­ 15.02%. It was established that the mixed crops had a closer ratio to the favourable indicators than the pure crops and varied from 1.76 (var. 5) to 2.57 (var. 6) and the comparatively higher value of var. 7 (3.33). Var. 5 and var. 8 had almost identical values of deviation, while in var. 6 and var. 7 they were higher ­ 0.34 and 0.45%. In all mixed crops there was found a medial variation rate of the Ca:P-proportion ­ from 12.38% (var. 8) to 14.20% (var. 5). In conclusion, in pure crops the crude protein content had lower values compared to mixed crops ­ from 8.21 to 8.97% against 8.93­11.37% respectively. Low coefficients of variation of this chemical indicator were established in pure and mixed crops. The cereals accumulated less crude fat in comparison with legumes. In almost all pure crops were established medial coefficients of variation. In mixed crops the crude fat was from 1.99 to 2.82%, a relatively lower coefficient of variation was found in comparison with pure crops. More crude fibre was found in winter barley, triticale and winter vetch. In all pure crops a low coefficient of variation (from 7.21% to 10.26%) of the same indicator was established. The lowest values of crude fibre were displayed by the mixed crops with winter pea and they had a lower coefficient of variation compared to pure crops. In regard to crude ash content the legumes exceeded the cereals. In legume pure crops a low coefficient of variation was established, while in the cereals it was a medial rate. On the whole all mixed crops had a low coefficient of variation. Journal of Agrobiology, 29(1): 15­21, 2012 In legumes the calcium content was higher but with a lower coefficient of variation than cereals. In mixed crops irrespective of the cereal and legume component the calcium content in forage varied from 0.530 to 0.870%. In mixtures the calcium variation was mostly with a medial value. The phosphorus content had lower values in forage of pure and mixed crops. The least variation (as medial value) was observed in winter vetch and winter barley. In mixed crops winter barley had a low coefficient of variation in regard to this indicator. The most favorable proportion between calcium and phosphorus for pure crops was found in cereals (triticale and winter barley) ­ respectively 2.46 and 2.23 and for mixed crops ­ in Winter barley+winter pea and Winter barley+winter vetch ­ from 1.76 to 2.57. Harper HJ (1962): Yield and chemical composition of Austrian winter peas, hairy vetch and biennial sweetclover, and the effect of fertilization on sweetclover roots. Oklahoma State University, Experiment Station, p. 17. Kertikov (2003): Quality of production of winter forage pea harvested twice for forage. In: Proceedings of EGF Symposium "Grassland Science in Europe": "Optimal Forage Systems for Animal Production and the Environment". 26­28 May 2003, Pleven (Bulgaria), pp. 404­ 407. lev , Ivanova R (2004): Testing of triticale cultivars under agro-ecological conditions of Plovdiv region. lant Sci 6: 509­513. Lingorski V, Kertikov T (2006): Suitability of annual winter cereal and legume crops and mixtures for green forage production under the conditions of Central Balkan Mountains. Journal of Mountain Agriculture on the Balkans 6: 1041­1055. Miller PR, Lighthiser EJ, Jones A, Holmes JA, Rick TL, Wraith JM (2011): Pea green manure management affects organic winter wheat yield and quality in semiarid Montana. Can J Plant Sci 91: 497­508. Orak A (2000): An investigation on yield and yield components of some common vetch (V. sativa L.) genotypes. Acta Agronomica Hungarica 48: 295­299. Schulz S, Keatinge J, Wells G (2000): Effect of legume management on forage production and residual effects on upland rice. J Agronomy Crop Sci 184: 173­182. Zhelyazkova TS (2010): Nutritive value and energy efficiency of winter pea production, treated with plant growth regulators. Thracian J Sci 8: 44­51. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Journal of Agrobiology de Gruyter

Variation of some chemical indicators in forage of annual winter pure and mixed crops cultivated in Central Balkan Mountains (Bulgaria)

Journal of Agrobiology , Volume 29 (1) – Jan 1, 2012

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Publisher
de Gruyter
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Copyright © 2012 by the
ISSN
1803-4403
eISSN
1804-2686
DOI
10.2478/v10146-012-0002-6
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Abstract

The aim of this experiment was to determine the variations in some important chemical indicators of annual winter cereal and legume pure and mixed crops for green forage production under the conditions of the fore-mountain regions of the Central Northern Bulgaria (Troyan region). In pure crops the crude protein content had fewer values compared to mixed crops. The cereals accumulated less crude fat in comparison with legumes. In mixed crops the crude fat was from 1.99 to 2.82%, with a relatively lower coefficient of variation in comparison with pure crops. More crude fibre was indicated in winter barley, triticale and winter vetch. All pure crops displayed a low coefficient of variation (from 7.21% to 10.26%). The lowest values of crude fibre were in the mixed crops with winter pea and they had a lower coefficient of variation compared to pure crops. In regard to crude ash content the legumes exceeded the cereals. In the legume pure crops a low coefficient of variation was established, while in cereals it was a medial value. On the whole all mixed crops had a low coefficient of variation. In legumes the calcium content was higher but with a low coefficient of variation than cereals. In mixed crops irrespective of whether it had a cereal or legume component the calcium content in forage varied from 0.530 to 0.870%. In mixtures the calcium variation was mostly with a medial value. The phosphorus content had lower values in forage of pure and mixed crops. The least variation (as a medial value) was observed in winter vetch and winter barley. In mixed crops with winter barley this indicator had a low coefficient of variation. The most favorable proportion between calcium and phosphorus for pure crops was found in cereals (triticale and winter barley) ­ respectively 2.46 and 2.23 and for mixed crops ­ in Winter barley+winter pea and Winter barley+winter vetch ­ from 1.76 to 2.57. Key words: annual winter crop; variation; chemical indicator; Central Balkan Mountains (Bulgaria) Vladimir Lingorski, Research Institute of Mountain Stockbreeding and Agriculture (RIMSA), 281, Vasil Levski Street, 5600 Troyan, Bulgaria vilievl@yahoo.com INTRODUCTION In the last two decades, the climate of Central and Eastern Europe has begun to be characterized by arid conditions and that makes agricultural production in these areas very difficult. Therefore it is reasonable that agriculture should be 15 Journal of Agrobiology, 29(1): 15­21, 2012 placed in a closer dependence on environmental conditions. The objective is to seek biological and technological decisions for the most efficient use of soil water resources, and the growing of wintering forms of any forage crops serve this end well. These crops utilize more efficiently the moisture from winter and spring precipitation and ensure the production of green fodder at the end of May and June. After harvesting there is the possibility for growing second crops, which would achieve a compacted usage of the agricultural areas. In this respect in recent years several attempts have been conducted in Bulgaria and abroad. In various regions of Bulgaria a number of studies of the annual winter forage crops (cereals and legumes) have been conducted with regard to the conditions and factors forming their yields (Gramatikov 2002, Kertikov 2003, Kolev and Ivanova 2004), as well as estimating the nutritive value and quality parameters of the forage obtained (Zhelyazkova 2010). In this connection winter forage cereals (such as barley and triticale) and legumes (such as pea and vetch) and their mixed crops are of particular interest also abroad. The studies conducted are aimed at the development of the technology of cultivation as well as the establishment of quality indicators for the forage (Harper 1962, Buxton and Fales 1994, Orak 2000, Schulz et al. 2000, Annicchiarico and Iannucci 2007, Miller et al. 2011). At present such developments are incomplete and insufficient for the conditions of fore-mountain regions in Bulgaria and have been conducted up to now with a low priority in the region of the Central Balkan Mountains (Lingorski and Kertikov 2006). The objective of this experiment was to determine the variations of some important chemical indicators of annual winter cereal and legume pure and mixed crops for green forage production under the conditions of the fore-mountain regions of the Central Northern Bulgaria (Troyan region). measures were applied according to the biophysiological and technological requirements of the respective forage crop. The application of phosphorus fertilizer (as double superphosphate) was made once before basic soil cultivation (in September of the previous year) at 60 kg ha­1 active substance (a.s.). The nitrogen fertilizer (as ammonium nitrate) was applied only once in early spring (in March of the following year), as follows: 80 kg ha­1 a.s. for winter barley and triticale, 50 kg ha­1 a.s. for winter pea and winter vetch and 60 kg ha­1 a.s. for the mixed crops. The following species and cultivars of annual winter cereal and legume crops were studied: as pure crops: var. 1 ­ Winter barley cv. Kaskadyor 3 (Standard 1 ­ for cereals); var. 2 ­ Triticale cv. Rakita; var. 3 ­ Winter pea cv. Mir (No 12) (Standard 2 ­ for legumes); var. 4 ­ Winter vetch cv. Asko 1 and as mixed crops: var. 5 ­ Winter barley+winter pea (Standard 3 ­ for mixed crops); var. 6 ­ Winter barley+winter vetch; var. 7 ­ Triticale+winter pea; var. 8 ­ Triticale+winter vetch. Sowing was performed at an inter-row spacing of 12 cm and a depth of 3­5 cm for barley, triticale and vetch to 5­7 cm for pea with rolling before and after. In the experiment the sowing rates per 1 m2 of pure crops were: winter barley ­ 450 germinable seeds, triticale ­ 450 germinable seeds, winter pea ­ 120 germinable seeds and winter vetch ­ 260 germinable seeds. The components of the cereal-legume mixed crops were sown in a ratio of 1:3 depending on the sowing rates of pure crops. Every year the trial plots were harvested for green forage by cutting them at the following phenological stages: for pure crops ­ at the earing of winter barley and triticale and at the flowering of winter pea and winter vetch; for mixed crops ­ at the early flowering of the legume component (Lingorski and Kertikov 2006). The samples (100­200 g depending on the relevant forage crop) for chemical analyses were taken before harvesting of the trial plots for each variant and repetition. The chemical composition (in %) of absolutely dry matter included the following indicators: content of crude protein (by the Kjeldahl method), crude fibre (by the Heteron and Jensen method), nitrogen-free extract matters (NFEM) ­ by the Weende method (according to Hennenburg and Stohmann), crude ash (through dry incineration in a muffle oven at a temperature of 550 °C), crude fat (by the Soxlet method), calcium (by the Stotz method ­ complexmetrically) and phosphorus (by the vanadiummolybdenum method of Gericke and Kurmis). MATERIAL AND METHODS Treatment of the experiment The field experiment was carried out over the period 2003­05. Crops were sown every year in early autumn (in October) in the Experimental field of RIMSA in Troyan at 384 m above sea level. The block-method with four replications and a harvest plot of 6 m2 was used. The agricultural Journal of Agrobiology, 29(1): 15­21, 2012 The ratio between calcium and phosphorus was determined by mathematical calculation. The standard deviations (SD, %) and coefficient of variations (CV, %) in the dynamics of the chemical indicators studied for all pure and mixed crops, were determined mathematically by the computer program Microsoft Excel (AVERAGE, STDEV, COVAR). Ecological characteristics of the region The experiment was carried out on light grey pseudopodzolic soil without irrigation. This soil type has a low natural fertility, humus content 2.21% and 0.123% total nitrogen. Th soil resources for total and assimilable phosphorus (0.194% and 14.3 mg/100 g soil) were good, with assimilable potassium low (10.2%) and with soluble nitrogen, medium (29.4 mg/100 g soil). The soil reaction was slightly acidic (pHH20 5.2). The territory of the RIMSA in Troyan is a foremountain climate region and it is characterized by a temperate continental climate. The average annual air temperatures during the trial period ranged from 10.0 °C (in 2005) to 10.2 °C (in 2003) as against 10.0 °C for the 1967­2005 period. The average air temperatures during the vegetation period (April­October) ranged from 15.3 °C (in 2004) to 16.3 °C (in 2003) as against 15.4 °C for the 38-yearly period. It is obvious that air temperature conditions had allied values compared to the period 1967­2005. The sum of rainfall during the growing season varied from 557.7 mm (in 2003) to 1151.3 mm (in 2005), while for a longer period (30 years) it was 591.1 mm. It is obvious that the sum of rainfall was almost similar in comparison to the longer period and only in 2005 was it twice as high (Lingorski and Kertikov 2006). obvious that the crude protein content in the legumes (var. 3 and 4) was more than the cereals (var. 1 and var. 2): an average of 8.92% and 8.97%, respectively. In both legume crops the crude protein content had a very weak coefficient of variation ­ 2.17 and 3.14%, while the standard deviations reached 0.19 and 0.28%, respectively. Depending on the legume component, the same chemical indicator in the mixtures was more than in the pure crops only in two of the variants. For the mixed crop Winter barley+winter pea was distinguished with a maximum crude protein content of 10.77% (min) to 12.97% (max) at very weak coefficient of variation of 5.28%. For the mixed crop the minimum protein content indicator (in the Triticale+winter vetch mixture) varied from 8.60% (min) to 9.26% (max) at very weak coefficient of variation of 3.69%. In the both variants low standard deviations ­ 0.28 and 0.33%, were reported respectively. There was a reverse dependency between the crude protein and crude fibre contents during the vegetation period, i.e. in the different phenophases of plants (Kertikov 2003). In the pure crops more crude fibre was indicated in the winter barley and triticale of the cereals and in the winter vetch of the legumes. Their average values were respectively 25.19, 26.14 and 26.12%, as against to the winter pea ­ 22.38%. The standard deviations for cereals were 2.58% and for legumes (var. 3 and var. 4) ­ 1.61 and 2.65%. In all pure crops a low coefficient of variation ­ 7.21% (winter pea), 9.87% (triticale), 10.14% (winter vetch) and 10.26% (winter barley) was established. The lowest values of crude fibre were shown in the mixed crops with winter pea, and reached 23.58% (var. 5) and 24.67% (var. 7), while for the rest of the mixed crops (var. 6 and var. 8) higher values ­ 28.61 and 28.79% respectively ­ were shown. The standard deviations varied from 0.58% (var. 5) to 1.49% (var. 7). The mixed crops had a lower coefficient of variation of this indicator compared to the pure crops ­ from 2.41% (var. 8) to 6.06% (var. 7). It was established that among pure crops, the cereals accumulated less crude fat in comparison with legumes. So, in winter vetch and winter pea the mean values of this indicator reached 2.62 and 3.16% as against 2.25% (in triticale) and 2.45% (in winter barley), respectively, but, only for the winter pea, was fixed at a very weak coefficient of variation of 4.26%. The results from the presented study were in agreement with other findings by Harper (1962) as regard to Austrian winter peas and hairy vetch. For all the rest of the pure crops RESULTS AND DISCUSSION It is evident from Table 1 that between the cereals, triticale had more crude protein accumulation in forage compared to winter barley crop ­ average 8.39% as against 8.21%. The results presented in the current study related to crude protein content are in agreement with the results of lev and Ivanova (2004) with regard to some triticale cultivars and with the results of Zhelyazkova in relation to (2010) to winter pea pure crops. In the winter barley a very weak coefficient of variation ­ 3.10% was reported, while with the triticale it was a low 7.44%. The standard deviations amounted to 0.25 and 0.62%, respectively. It is Journal of Agrobiology, 29(1): 15­21, 2012 Table 1. Variation of some biochemical indicators in forage of annual winter pure and mixed (cereal and legume) crops average for the 2003­05 period Chemical composition of dry mass, % min max xaverage SD CV, % Var. 1 ­ Winter barley (Standard 1) Crude protein Crude fat Crude fibre NFEM1 Crude ash lcium hosphorus Ca:P 7.96 1.98 22.61 42.52 5.97 0.390 0.237 1.25 8.47 2.93 27.78 48.83 8.69 0.870 0.314 3.67 Var. 2 ­ Triticale Crude protein Crude fat Crude fibre NFEM Crude ash lcium hosphorus Ca:P 7.77 1.96 23.56 42.62 5.50 0.550 0.228 2.00 9.02 2.55 28.72 50.13 7.74 0.790 0.390 2.47 8.39 2.25 26.14 46.37 6.62 0.670 0.309 2.23 0.62 0.29 2.58 3.75 1.12 0.12 0.08 0.23 7.44 13.08 9.87 8.10 16.92 17.91 26.21 10.51 8.21 2.45 25.19 45.67 7.33 0.630 0.275 2.46 0.25 0.47 2.58 3.15 1.36 0.24 0.04 1.21 3.10 19.35 10.26 6.91 18.55 38.09 13.97 15.02 Var. 3 ­ Winter pea (Standard 2) Crude protein Crude fat Crude fibre NFEM Crude ash lcium hosphorus Ca:P 8.78 3.03 20.77 48.66 7.45 0.950 0.289 2.95 9.17 3.3 24.00 52.95 8.81 1.260 0.407 3.46 8.97 3.16 22.38 50.80 8.13 1.100 0.348 3.20 0.19 0.13 1.61 2.14 0.68 0.15 0.06 0.25 2.17 4.26 7.21 4.22 8.36 14.03 16.95 7.96 Var. 4 ­ Winter vetch Crude protein Crude fat Crude fibre NFEM Crude ash lcium hosphorus Ca:P 8.64 2.21 23.47 43.44 7.22 1.000 0.291 3.17 9.20 3.03 28.77 46.67 8.89 1.200 0.378 3.76 8.92 2.62 26.12 45.05 8.05 1.100 0.334 3.46 0.28 0.41 2.65 1.61 0.83 0.10 0.04 0.29 3.14 15.65 10.14 3.58 10.37 9.09 13.00 8.51 Var. 5 ­ Winter barley+winter pea (Standard 3) Crude protein Crude fat Crude fibre NFEM Crude ash lcium hosphorus Ca:P 10.77 2.59 23.00 46.90 7.77 0.470 0.275 1.51 11.97 3.05 24.16 50.00 8.62 0.600 0.350 2.01 11.37 2.82 23.58 48.45 8.19 0.530 0.312 1.76 0.60 0.23 0.58 1.55 0.42 0.06 0.04 0.25 5.28 8.16 2.46 3.19 5.19 12.15 12.00 14.20 Var. 6 ­ Winter barley+winter vetch Crude protein Crude fat Crude fibre NFEM Crude ash lcium hosphorus Ca:P 8.88 1.77 27.67 42.63 7.10 0.690 0.285 2.23 9.45 2.22 29.55 46.12 8.17 0.880 0.340 2.92 9.16 1.99 28.61 44.37 7.63 0.780 0.312 2.57 0.28 0.22 0.94 1.74 0.53 0.09 0.03 0.34 3.11 11.28 3.28 3.93 7.01 12.10 8.80 13.40 Journal of Agrobiology, 29(1): 15­21, 2012 Chemical composition of dry mass, % min max xaverage SD CV, % Var. 7 ­ Triticale+winter pea Crude protein Crude fat Crude fibre NFEM Crude ash lcium hosphorus Ca:P 8.88 2.15 23.18 47.50 6.04 0.770 0.225 2.88 9.39 2.34 26.17 52.51 6.83 0.970 0.286 3.78 9.13 2.24 24.67 50.00 6.43 0.870 0.255 3.33 0.25 0.09 1.49 2.50 0.39 0.10 0.03 0.45 2.79 4.23 6.06 5.01 6.14 11.49 11.94 13.51 Var. 8 ­ Triticale+winter vetch Crude protein Crude fat Crude fibre NFEM Crude ash lcium hosphorus Ca:P = nitrogen-free extract matters medial coefficients of variation were established ­ from 13.08% (triticale) to 19.35% (winter barley). The standard deviations had very low values: for cereals 0.29% (triticale) ­ 0.47% (winter barley) and for legumes 0.13% (winter pea) ­ 0.41% (winter vetch). Similar results were reported by Kertikov (2003). after experiments with winter pea pure crop. In the study of mixed crops the same chemical indicator was average from 1.99% (var. 6) to 2.82% (var. 5). The rest of the mixed crops occupied medial positions. In two of the mixed crops (var. 7 and 8) very small coefficients of variation were established ­ 4.23 and 4.43%, but in others (var. 5 and 6) ­ low coefficients of variation ­ 8.16 and 11.28%, respectively. With regard to the nitrogen-free extract matters (NFEM) there were no significant differences between pure and mixed crops. Among the pure crops winter pea had a larger mean value, 50.80%, than the other crops (var. 1, 2 and 4) ­ 45.67, 46.37 and 45.05%, respectively. The cereals displayed higher values of NFEM: standard deviations of 3.15 and 3.75% while the legumes had lower values ­ 1.61% (var. 4) and 2.14% (var. 3). Therefore in legumes there was a lower coefficient of variation compared to cereals ­ 4.22 and 3.38% as against 6.91 and 8.10%. In mixed crops the highest mean value (50.00%) of this indicator was displayed by Triticale+winter pea (var. 7) followed by Winter barley+winter pea (48.45%), Triticale+winter vetch (46.56%) and Winter barley+winter vetch (44.37%). The highest deviation of this indicator was obtained in var. 7 ­ 2.50%, while in the rest of the mixed crops it was the lowest ­ from 1.54% (var. 8) to 1.74% (var. 6). Iin var. 7 a higher coefficient of variation ­ 5.01% as against of 3.19% (var. 5) ­ 3.93% (var. 6) was established. On the whole, all mixed crops had a very weak coefficient of variation with regard to this indicator. The same table shows that in regard to crude ash content the legumes exceeded the cereals. Thus, in legume pure crops this indicator had values of 8.05% (var. 4) and 8.13% (var. 3), while in the cereals it was less ­ 6.62% (var. 2) and 7.33% (var. 1). In comparison with the legumes the highest values of deviation were reported in the cereals ­ 1.12% (triticale) and 1.36% (winter barley) as against 0.68% (winter pea) and 0.83% (winter vetch). In legumes also a less coefficient of variation ­ 8.36 and 10.37% (a low value), was established while in the cereals it was a medial rate ­ of 16.92% (var. 2) and 18.55% (var. 1). The mixed crops had a higher mean ash content ­ in winter barley (var. 5 and 6) ­ a 8.19% (min 7.77%, max 8.62%) and 7.63% (min 7.10%, max 8.17%). The triticale mixed crops (var. 7 and var. 8) had a lower ash content (6.43 and 5.89%). In mixtures with winter barley (var. 4 and var. 5) the standard deviation showed higher values compared with triticale mixtures ­ 0.42 and 0.53% as against 0.39 and 0.44%. In three of the mixed crops (var. 5, 6 and 7) very little variation of this chemical indicator (5.19, 7.01 and 6.14%) was observed but Journal of Agrobiology, 29(1): 15­21, 2012 only one of them (var. 8) had a low coefficient of variation ­ 7.47%. It is evident that among the pure crops the calcium content was higher in the legume than the cereals. So, in winter pea and winter vetch values of 1.100% were established while in the cereals (var. 1 and 2) were reported at 0.630 and 0.670%, respectively. The variation of the above-mentioned values was as follows: in winter barley ­ from 0.390% (min) to 0.870% (max) with a deviation rate of 0.24%, while in triticale the calcium content varied from 0.550% (min) to 0.790% (max), but with a lower deviation ­ 0.120%. In winter pea the calcium variation was in the limits: 0.950% (min) and 1.260% (max) and the standard deviation was 0.15%, while in winter vetch 1.000, 1.200 and 0.10%, respectively. In cereals the greatest variation was observed in winter barley (38.09% ­ a high value) following by triticale (17.91% ­ a medial value). In legumes of winter pea there was found also a medial coefficient of variation (14.03%) higher than the winter vetch (9.09% ­ a low value). In mixed crops irrespective of cereal and legume component the highest calcium content in forage was found in var. 7 and var. 6 ­ 0.870 and 0.780% following by var. 8 and var. 5 ­ 0.630 and 0.530%. The lowest deviations (0.06 and 0.09%) were established in the mixed crops with winter barley (var. 5 and var. 6), while in those with triticale (var. 7 and 8) were slightly more ­ 0.10 and 0.12%. In mixtures with winter barley the calcium variation was almost similar and with medial values (12.15 and 12.10%), while in the triticale crops ­ with a low value (11.49%) and with a medial value (19.68%). Compared to calcium content, phosphorus showed lower values in forage of pure and mixed crops. The table shows that the legumes exceeded the cereal crops in phosphorus content, reaching values of 0.334% (var. 4) and 0.348% (var. 3) as against 0.275% (in winter barley) and 0.309% (in triticale). It is obvious that in pure crops the standard deviation of phosphorus content was almost similar and in low limits ­ from 0.04% (var. 1 and var. 4) to 0.08% (var. 2). The lowest variations (as a medial value) were observed in winter vetch (13.00%) and winter barley (13.97%) and the relatively higher in winter pea (16.95% ­ also a medial value) and a higher value in triticale (26.21%). The forage of winter barley mixed crops (var. 5 and var. 6) showed a higher value of phosphorus ­ 0.312% (min 0.275% and max 0.350%; min 0.285% and max 0.340%). The four mixed crops had almost the same deviation of this chemical indicator ­ from 0.03% (var. 6, 7 and var. 8) to 0.04% (var. 5) as well as a low coefficient of variation ­ from 8.80% (var. 6) to 12.00% (var. 5). An important forage indicator is the correlation between calcium and phosphorus, as the most favourable ratio is considered to be 1:1.5 ­ 1:2.5 (Buxton and Fales 1994). In this study, the most favourable proportion close to above-mentioned for pure crops was found in cereals (var. 1 and var. 2) ­ 2.46 and 2.23 ­ while in legumes (var. 3 and var. 4) was about one point more ­ 3.20 and 3.46. In three of the pure crops the least and almost identical significant deviations of this proportion were established as follows: 0.23% (triticale), 0.25% (winter pea) and 0.29% (winter vetch), while in winter barley the value was about five times greater ­ 1.21%. Three of the studied crops had a low coefficient of variation ­ 7.96% (var. 3), 8.51% (var. 4) and 10.51% (var.2) ­ but in winter barley it was a medial value ­ 15.02%. It was established that the mixed crops had a closer ratio to the favourable indicators than the pure crops and varied from 1.76 (var. 5) to 2.57 (var. 6) and the comparatively higher value of var. 7 (3.33). Var. 5 and var. 8 had almost identical values of deviation, while in var. 6 and var. 7 they were higher ­ 0.34 and 0.45%. In all mixed crops there was found a medial variation rate of the Ca:P-proportion ­ from 12.38% (var. 8) to 14.20% (var. 5). In conclusion, in pure crops the crude protein content had lower values compared to mixed crops ­ from 8.21 to 8.97% against 8.93­11.37% respectively. Low coefficients of variation of this chemical indicator were established in pure and mixed crops. The cereals accumulated less crude fat in comparison with legumes. In almost all pure crops were established medial coefficients of variation. In mixed crops the crude fat was from 1.99 to 2.82%, a relatively lower coefficient of variation was found in comparison with pure crops. More crude fibre was found in winter barley, triticale and winter vetch. In all pure crops a low coefficient of variation (from 7.21% to 10.26%) of the same indicator was established. The lowest values of crude fibre were displayed by the mixed crops with winter pea and they had a lower coefficient of variation compared to pure crops. In regard to crude ash content the legumes exceeded the cereals. In legume pure crops a low coefficient of variation was established, while in the cereals it was a medial rate. On the whole all mixed crops had a low coefficient of variation. Journal of Agrobiology, 29(1): 15­21, 2012 In legumes the calcium content was higher but with a lower coefficient of variation than cereals. In mixed crops irrespective of the cereal and legume component the calcium content in forage varied from 0.530 to 0.870%. In mixtures the calcium variation was mostly with a medial value. The phosphorus content had lower values in forage of pure and mixed crops. The least variation (as medial value) was observed in winter vetch and winter barley. In mixed crops winter barley had a low coefficient of variation in regard to this indicator. The most favorable proportion between calcium and phosphorus for pure crops was found in cereals (triticale and winter barley) ­ respectively 2.46 and 2.23 and for mixed crops ­ in Winter barley+winter pea and Winter barley+winter vetch ­ from 1.76 to 2.57. Harper HJ (1962): Yield and chemical composition of Austrian winter peas, hairy vetch and biennial sweetclover, and the effect of fertilization on sweetclover roots. Oklahoma State University, Experiment Station, p. 17. Kertikov (2003): Quality of production of winter forage pea harvested twice for forage. In: Proceedings of EGF Symposium "Grassland Science in Europe": "Optimal Forage Systems for Animal Production and the Environment". 26­28 May 2003, Pleven (Bulgaria), pp. 404­ 407. lev , Ivanova R (2004): Testing of triticale cultivars under agro-ecological conditions of Plovdiv region. lant Sci 6: 509­513. Lingorski V, Kertikov T (2006): Suitability of annual winter cereal and legume crops and mixtures for green forage production under the conditions of Central Balkan Mountains. Journal of Mountain Agriculture on the Balkans 6: 1041­1055. Miller PR, Lighthiser EJ, Jones A, Holmes JA, Rick TL, Wraith JM (2011): Pea green manure management affects organic winter wheat yield and quality in semiarid Montana. Can J Plant Sci 91: 497­508. Orak A (2000): An investigation on yield and yield components of some common vetch (V. sativa L.) genotypes. Acta Agronomica Hungarica 48: 295­299. Schulz S, Keatinge J, Wells G (2000): Effect of legume management on forage production and residual effects on upland rice. J Agronomy Crop Sci 184: 173­182. Zhelyazkova TS (2010): Nutritive value and energy efficiency of winter pea production, treated with plant growth regulators. Thracian J Sci 8: 44­51.

Journal

Journal of Agrobiologyde Gruyter

Published: Jan 1, 2012

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