Le carbone et l'azote dans les différentes fractions granulométriques d'un sol brun eutrophe tropical sous irrigation de Bagré au Burkina Faso : effets de modes d’apports différents de matières organiques et minérales.

Abstract

Objective: A study was carried out to evaluate the influence of cropping systems (modes of different contributions of organic and mineral fertilizers) on the qualitative evolution of soil organic carbon and nitrogen of a tropical eutrophic brown soil under irrigation of Bagré, Burkina Faso. Methodology and results: The granulometric soil organic matter fractionation method was used and allowed to follow the qualitative evolution of soil organic carbon and total nitrogen. The results show that rice cultivation leads to reduction of soil organic carbon and total nitrogen in the upper horizons (0-20 cm) while an accumulation is observed in lower horizons (20-50 cm). In the lower horizons, the importance of accumulation depends of organic manure restitution level. Conclusion and application: Contrary to results obtained under upland cropping systems, irrigated rice cultivation leads to an accumulation of soil organic carbon and nitrogen compared to "fallow". Even complete crop residues removing in irrigated soil may result in organic carbon accumulation. This result has a great interest in organic and fertilizer management all the more reason that soil organic carbon accumulation result of lower soil organic matter mineralization. Thereby, for irrigated crops like rice which is exigent to nutrients mostly nitrogen, the combination of mineral fertilizers with organic manure well decomposed could allow a better nutrient nutrition. Furthermore, despite the production of methane, irrigated rice system could all the same contribute to atmospheric carbon sequestration.Keywords: carbon; nitrogen; accumulation; irrigated soil