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Title: Soil fertility and nutrient cycling in the pure and mixed fodder bank systems using leguminous and non-leguminous shrubs
Author: Sánchez, F. J. S.
Awarding Body: University of Edinburgh
Current Institution: University of Edinburgh
Date of Award: 2005
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The overall objective of this thesis work, in the Yucatán peninsula (México), was to establish a system with mixed woody species (leguminous/non-leguminous) to investigate the extent to which they increase nitrogen uptake and growth. The study tested the hypothesis that such mixtures may stimulate of N2 fixation from the atmosphere and the transfer of N from leguminous to non-leguminous plants. Three woody species were selected: Leucaena leucocephala (legume), Moringa oleifera (non-legume) and Guazuma ulmifolia (non-legume). More than 80% of planted seedlings survived and grew rapidly. Total biomass (fodder) production was 1.9-7.7 ton ha-1 for monocrops and 6-9 ton ha-1 for the mixtures. Nitrogen yield in the fodder was higher in the Leucaena+Guazuma mixture (285 kg N ha-1), followed by Leucaena monocrop and Leucaena+Moringa mixture (244 and 183 kg N ha-1, respectively). The δ15 N of samples from non-fixing species ranged from 2.7 to 3.2‰ (mean 3.0 ± 0.45‰). The δ15 N of L. leucocephala (0.8‰) was significantly lower, indicating that nitrogen fixation occurred in the Leucaena plants. The % Ndfa in the Leucaena mixtures ranged from 58 to 72% while in the Leucaena monocrop it was 69%, at 11 months old. Moringa leaves decomposed most rapidly, followed by Leucaena+Moringa, and, was best described by a double exponential model. The combination of Leucaena+Guazuma decomposed more slowly and pure Leucaena leaves decomposed at an intermediate rate. Over 16 weeks, Leucaena+Moringa released 65-75% of the initial N, Leucaena+Guazuma released 46-63%, and Leucaena leaves alone released, on average, 54% of their N. Lignin+polyphenols and tannins had a strong negative correlation with the rate of nitrogen release. The alteration of the decomposition and N release patterns observed when mixing plant materials of different quality provides good prospects for improving synchrony between N availability and plant N uptake.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available