Effets des fumures organo-minérales et des rotations culturales sur la qualité des sols

Les sols des regions semi-arides de l’Afrique de l’Ouest sont sujets a une degradation graduelle de leur fertilite. Ils sont connus etre d’une productivite tres limitee et les moyens modernes pour augmenter et maintenir cette productivite sont le plus souvent tres onereux pour les petits exploitants. Ainsi, pour trouver de solutions probantes pour une gestion durable de la fertilite des sols, une etude a ete conduite a la station de recherche agricole de Saria au Centre Ouest du Burkina Faso sur un dispositif implante depuis 1960 ou des fumures organique et/ou minerale combinees a des systemes de cultures sont testes. L’objectif de cette etude est d’evaluer les effets de ces fumures combines aux rotations culturales, sur le statut organique et la qualite des sols. Ce dispositif experimental est du type Split splot a 6 repetitions, combinant six niveaux de fertilisation et a trois types de rotation. La monoculture de sorgho et la rotation sorgho/niebe ont ete retenues dans cette etude. Des echantillons de sol ont ete preleves a 0-20 cm dans les parcelles du dispositif, et dans une jachere naturelle jouxtant le site experimental et qui a servi de reference. La texture du sol et les teneurs en carbone et azote ont ete determinees. Les resultats obtenus montrent que, plus que le carbone organique total du sol, c’est plutot sa fraction labile qui se revele etre un indicateur tres sensible aux changements precoces qui affectent le statut organique des sols. En effet, l’indice de gestion du carbone qui apparait tres correle avec la stabilite structurale du sol se positionne comme un outil fiable d’evaluation de la qualite des sols soumis aux pratiques culturales. Par ailleurs, les rotations sorgho-niebe se revelent etre des pratiques culturales les plus appropriees pour assurer une durabilite de la qualite des sols et des productions agricoles. © 2016 International Formulae Group. All rights reserved. Mots cles: Fumures minerales et organo-minerales, rotations culturales, carbone, azote, Burkina Faso English Title: Effects of organo-mineral fertilizers and crop rotations on soil quality English Abstract In the semiarid tropics of west Africa, agricultural lands are gradually degrading leading to decline soil fertitily. The low soil fertility is also increasingly recognized as a fundamental cause of declining food security in small-farm households. In this region, sustainable soil fertility management is constantly a challenge for crop productions. To come with an alternative soil fertility management practices, a trial was set up in 1960 in the agricultural research station of Saria to identify the optimal soil management strategies for specific cropping systems to ensure sustainability of productivity. The experimental design is a split plot with 6 replications, with the main plots being three rotation system and the subplots consisting to 6 fertility management options. The main objective of this study was to evaluate the effects of soil fertility management practices combining crop rotation and fertility management options under continuous sorghum cropping and sorghum-cowpea (Vigna unguiculata) rotation systems in Burkina Faso on soil organic matter status and soil quality. Soil samples were collected at 0–20 cm depth. A bush fallow (more than 60 years old) of Andropogon gayanus located near the experimental siten is consider as natural condition for accessing changes due to landuse practices. Particle-sizes distribution, soil total N and carbon were determinated. The results indicated that labile organic pools are more sensitive to land use than total soil organic carbon. Carbon management index (CMI) which appeared highly correlated with soil structural stability is positioned as a reliable tool for soil quality assessment under several cropping systems. Furthermore, cowpea - sorghum rotation system seem to be the most appropriate cultural practice in ensuring sustainability of soil quality and agricultural production. © 2016 International Formulae Group. All rights reserved. Keywords: Mineral fertilizer combined with organic manure, crop rotation, carbon, nitrogen, Burkina Faso