Shift in C and N humification during legume litter decomposition in an acid tropical Ferralsol

Several long-term studies on tropical soils have shown that legume residue incorporation increases soil nitrogen (N) sequestration more than that of carbon (C), resulting in a fall in the C/N ratio. This study was designed to assess the short-term effect of legume litter addition on N supply and the long-term effect on soil organic matter (SOM) formation and soil C/N decrease. The long-term effect was evaluated in a 2-year mesocosm experiment with high and frequent organic inputs from two types of legume litter with different C/N ratios, using stable isotope techniques. The short-term effect of litter was analysed using four different litters in 3-month laboratory incubations. A model of litter decomposition was used to describe C and N kinetics in the laboratory experiment and to verify whether the long-term effect of litter may be predicted from short-term incubations. The results of the mesocosm experiment confirmed that legume inputs increased soil organic N (mean +21%) more than organic C (mean +15%) (P = 0.05). Although no differences between litters were observed for C dynamics, N sequestration (14% and 28%) and the final soil C/N (12.0 and 10.8) varied with litter C/N (34.4 and 16.1, respectively). The laboratory experiment and model outputs confirmed these findings and indicated that the higher N sequestration was due to a change in the parameters describing humification of C and N coming from litter. This change depended on litter quality and was greater for litters with low C/N-C humification 0.66 g C g-1 C and N humification 0.76 g N g-1 N for litter C/N 16.1. Carbon and N sequestration were greater in the laboratory experiment, due to a higher mineralisation of the new SOM derived from litter in the mesocosm experiment-32% and 15% for the mesocosm and the laboratory experiments, respectively. Our results indicated that the decrease in soil C/N and the rapid mineralisation of new SOM should be considered in models of litter decomposition to respond correctly to the long- and the short-term effects of legume litter inputs in tropical soils.

Bibliographic Details

Main Authors:	Sierra, Jorge, Motisi, Natacha
Format:	article biblioteca
Language:	eng
Subjects:	F04 - Fertilisation, F08 - Systèmes et modes de culture, P33 - Chimie et physique du sol, Gliricidia sepium, Canavalia ensiformis, litière végétale, ferralsol, biodégradation, modèle, teneur en azote, matière organique du sol, http://aims.fao.org/aos/agrovoc/c_3278, http://aims.fao.org/aos/agrovoc/c_1244, http://aims.fao.org/aos/agrovoc/c_24064, http://aims.fao.org/aos/agrovoc/c_2858, http://aims.fao.org/aos/agrovoc/c_9261, http://aims.fao.org/aos/agrovoc/c_4881, http://aims.fao.org/aos/agrovoc/c_5193, http://aims.fao.org/aos/agrovoc/c_35657, http://aims.fao.org/aos/agrovoc/c_3406, http://aims.fao.org/aos/agrovoc/c_3081,
Online Access:	http://agritrop.cirad.fr/565622/ http://agritrop.cirad.fr/565622/1/document_565622.pdf
Tags:	Add Tag No Tags, Be the first to tag this record!