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Nitrogen-fixation dynamics in a cut-and-carry silvopastoral system in the subhumid conditions of Guadeloupe, French Antilles

Nitrogen-fixation dynamics in a cut-and-carry silvopastoral system in the subhumid conditions of... This paper summarizes several studies on N recycling in a tropical silvopastoral system for assessing the ability of the system to increase soil fertility and insure sustainability. We analyzed the N 2 fixation pattern of the woody legume component ( Gliricidia sepium ), estimated the recycling rate of the fixed N in the soil, and measured N outputs in tree pruning and cut grass ( Dichanthium aristatum ). With this information, we estimated the N balance of the silvopastoral system at the plot scale. The studies were conducted in an 11-year-old silvopastoral plot established by planting G. sepium cuttings at 0.3 m × 2 m spacing in natural grassland. The plot was managed as a cut-and-carry system where all the tree pruning residues (every 2-4 months) and cut grass (every 40-50 days) were removed and animals were excluded. No N fertilizer was applied. Dinitrogen fixation, as estimated by the 15 N natural abundance method, ranged from 60-90% of the total N in aboveground tree biomass depending on season. On average, 76% of the N exports from the plot in tree pruning (194 kg (N) ha –1 yr –1 ) originated from N 2 fixation. Grass production averaged 13 Mg ha –1 yr –1 and N export in cut grass was 195 kg (N) ha –1 yr –1 . The total N fixed by G. sepium , as estimated from the tree and grass N exports and the increase in soil N content, was about 555 kg (N) ha –1 yr –1 . Carbon sequestration averaged 1.9 Mg (C) ha –1 yr –1 and soil organic N in the 0-0.2 m layer increased at a rate of 166 kg (N) ha –1 yr –1 , corresponding to 30% of N 2 fixation by the tree. Nitrogen released in nodule turnover (10 kg (N) ha –1 yr –1 ) and litter decomposition (40 kg (N) ha –1 yr –1 ) contributed slightly to this increase, and most of the recycled N came from the turnover or the activity of other below-ground tree biomass than nodules. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Agroforestry Systems Springer Journals

Nitrogen-fixation dynamics in a cut-and-carry silvopastoral system in the subhumid conditions of Guadeloupe, French Antilles

Dulormne, M.; Sierra, J.; Nygren, P.; Cruz, P.
Agroforestry Systems , Volume 59 (2) – Sep 1, 2003
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References (27)

Publisher
Springer Journals
Copyright
Copyright © 2003 by Kluwer Academic Publishers
Subject
Life Sciences; Agriculture; Forestry
ISSN
0167-4366
eISSN
1572-9680
DOI
10.1023/A:1026387711571
Publisher site
See Article on Publisher Site

Abstract

This paper summarizes several studies on N recycling in a tropical silvopastoral system for assessing the ability of the system to increase soil fertility and insure sustainability. We analyzed the N 2 fixation pattern of the woody legume component ( Gliricidia sepium ), estimated the recycling rate of the fixed N in the soil, and measured N outputs in tree pruning and cut grass ( Dichanthium aristatum ). With this information, we estimated the N balance of the silvopastoral system at the plot scale. The studies were conducted in an 11-year-old silvopastoral plot established by planting G. sepium cuttings at 0.3 m × 2 m spacing in natural grassland. The plot was managed as a cut-and-carry system where all the tree pruning residues (every 2-4 months) and cut grass (every 40-50 days) were removed and animals were excluded. No N fertilizer was applied. Dinitrogen fixation, as estimated by the 15 N natural abundance method, ranged from 60-90% of the total N in aboveground tree biomass depending on season. On average, 76% of the N exports from the plot in tree pruning (194 kg (N) ha –1 yr –1 ) originated from N 2 fixation. Grass production averaged 13 Mg ha –1 yr –1 and N export in cut grass was 195 kg (N) ha –1 yr –1 . The total N fixed by G. sepium , as estimated from the tree and grass N exports and the increase in soil N content, was about 555 kg (N) ha –1 yr –1 . Carbon sequestration averaged 1.9 Mg (C) ha –1 yr –1 and soil organic N in the 0-0.2 m layer increased at a rate of 166 kg (N) ha –1 yr –1 , corresponding to 30% of N 2 fixation by the tree. Nitrogen released in nodule turnover (10 kg (N) ha –1 yr –1 ) and litter decomposition (40 kg (N) ha –1 yr –1 ) contributed slightly to this increase, and most of the recycled N came from the turnover or the activity of other below-ground tree biomass than nodules.

Journal

Agroforestry Systems – Springer Journals

Published: Sep 1, 2003

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