Effects of intercropping component of conservation agriculture on sorghum yield in the Sudan Savanna

Conservation agriculture (CA), which consists of minimum soil disturbance, soil cover, and crop rotation/association, has been promoted as an indivisible three-component package to control water erosion in the Sudan Savanna. However, CA has not been adopted by local smallholder farmers, probably because the three-component package constitutes a large burden for the farmers. Our previous study revealed that two components – minimum tillage and crop residue mulching – are sufficient for soil conservation and intercropping, when used in combination with minimum tillage and crop residue mulching, had no effect on erosion control. In the present study, we conducted a 3-year field experiment in Burkina Faso to evaluate the effects of the intercropping component on sorghum yield. The four treatments employed were conventional practice (full tillage, no sorghum residue mulching, no intercropping), two-component CA (minimum tillage and sorghum residue mulching without intercropping), and three-component CA with velvet bean (VB) or pigeon pea (PP) intercropping. We found that sorghum yield was similar between treatments during the first 2 years but higher for CA with PP intercropping than for conventional practice in the third year. This increased yield was mainly attributed to higher soil nitrogen and carbon content as well as panicle mass and harvest index observed for CA with PP intercropping than for conventional practice. Unexpectedly, however, PP produced few seeds and did not survive the dry season. Therefore, we concluded that CA with PP intercropping is effective to increase sorghum yield but practical only for the prosperous farmers who can afford to purchase PP seeds every year and accept no increased yield during the first 2 years after its installation. For most smallholder farmers, it would be realistic to promote two-component CA without intercropping because it can effectively control water erosion and reduce the farmers’ burden of its adoption in the Sudan Savanna.