Labour biologique contre labour mécanique : comparaison de leurs effets sur la structure du sol au Nord Cameroun

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The present study was carried out in the cotton belt in the Far-North Province of Cameroon. It has been focused on the physical properties of soils under mulch-based cropping systems. The experimental design was drawn from one on Direct seeding Mulch-based Cropping system (DMC) trial location under a controlled conditions in the region of Kaéle (700-800 mm mean annual rainfall), and where a network of 20 farmers is carrying out on-farm trials in the region of Maroua (800 mm mean annual rainfall),. Plots under mulch-based cropping systems established 2, 3 or 4 years ago were compared against farmers' traditional plots under direct seeding without mulch or with tillage practice. These plots were cropped with sorghum or cotton. Using the gravimetric method it has been shown that the apparent density of soils on the upper horizons under DMC was lower compared to soils from the farmers' traditional cropping systems. Bulk density values lie between 1.2 g/cm3 to 1.5 g/cm3 against 1.6 g/cm3 to 1.7 g/cm3 for farmers' traditional control plots. These results are due to an increase in soil porosity induced probably by a higher soil biological activity. A better water infiltration was also obtained'under DMC against the farmers' traditional systems. These mean infiltration values were obtained using the double ring and «Beer can» methods, and lie between 0.9 to 5 mm min-1 for the mulch-based system against 0.6 to 1 mm min-1 for the farmers' traditional systems. This study shows that after a period of less than 3 years under DMC an improvement of the physical properties of the soil was clearly obtained, notably soil porosity and consequently soil water dynamics. This improvement affects the soil water availability and therefore water supply to the crops.

Mots-clés : Climat, eau, sorgho, brachiaria, TCS - Techniques culturales simplifiées, propriétés physico-chimiques du sol, gestion du sol, scv, Coton

Rapport de stage sur la modification du bilan hydrique par les systèmes de culture sur couverture végétale - cas du cotonnier et du sorgho dans l'Extrême Nord du Cameroun.

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Dans l'Extrême-Nord du Cameroun, les systèmes de culture conventionnels du sorgho et du cotonnier impliquent des travaux du sol ainsi que l'absence de restitution de la matière organique.On constate depuis plusieurs années un processus de dégradation des sols. Cela se traduit entreautre par une intensification du ruissellement qui diminue une ressource en eau déjà limitée. Des enquêtes imputent cette dégradation aux pratiques conventionnelles. Ainsi, la Sodecoton teste etdiffuse depuis 2001 des systèmes de culture avec semis sur couverture végétale (SCV). Les systèmes SCV sont un ensemble de systèmes techniques dans lesquels on pratique le semis direct de la culture, sans travail du sol ni sarclage mécanique, avec une couverture par des résidus végétaux

Mots-clés : Climat, sorgho, ruissellement, érosion, propriétés physico-chimiques du sol, Bilan hydrique, scv, Socio-économie, Coton
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