Intensity cultivation induced effects on soil organic carbon dynamic in the western cotton area of Burkina Faso

摘要

The soil organic carbon(SOC)dynamic is a key element of soil fertility in savannah ecosystems that form the key agricultural lands in sub-Saharan Africa.In the western part of Burkina Faso,the land use is mostly linked to cotton-based cropping systems.Use of mechanization,pesticides,and herbicides has induced modifications of the traditional shifting cultivation and increased the need for sustainable soil fertility management.The SOC dynamic was assessed based on a large typology of land cultivation intensity at Bondoukui.Thus,102 farm plots were sampled at a soil depth of 0-15 cm,considering field-fallow successions,the cultivation phase duration,tillage intensity,and soil texture.Physical fractionation of SOC was carried out by separating the following particle size classes: 2,000-200,200-50,50-20,and 0-20 mu rn.The results exhibited an increase in SOC stock,and a lower depletion rate with increase in clay content.After a long-term fallow period,the land cultivation led to an annual loss of 31.5 g m~(-2)(2%)of its organic carbon during the first 20 years.The different fractions of SOC content were affected by this depletion depending on cultivation intensity.The coarse SOC fraction(2,000-200 mu m)was the most depleted.The ploughing-in of organic matter(manure,crop residues)and the low frequency of the tillage system produced low soil carbon loss compared with annual ploughing.Human-induced disturbances(wildfire,overgrazing,fuel wood collection,decreasing fallow duration,increasing crop duration)in savannah land did not permit the SOC levels to reach those of the shifting cultivation system.