Water-harvesting for supplementary irrigation of cereal crops to overcome intra-seasonal dry-spells in the Sahel

Sub-Saharan Africa is experiencing a steadily aggravated food security cris is. "New" approaches are necessary to ensure tomorrow's food-bowl. With a g rowing population and diminishing resources, any investment (labour or mone tary) to improve self-suffiency must produce an acceptable return. Sufficie nt water commonly represents one crucial factor in farmers' yearly gamble i n securing a harvest. If the availability of water is better ensured, the f armer could be spurred to invest his limited means to further improve the p robability of obtaining a harvest. Cereal crops are essential, yet for many self-subsistence farmers on the African continent, it is considered a "was te" of efforts to irrigate if - "irrigation is for more economically worthw hile crops". Surface run-off dynamics in the Sahel have in a number of stud ies proven to be of considerable magnitudes. Rainwater harvesting into smal l ponds for supplemental irrigation during intra-seasonal dry-spells during crop growing seasons could therefore prove to be a viable solution. During an on-farm study carried out in semi-arid Burkina Faso, supplemental irrig ation during dryspells increased sorghum harvests by 41%, and in combinatio n with added fertilization, by 180 %. Only applying fertilization gave yiel d improvements of 132% indicating that nutrients and not water was the most limiting factor in 1998. This paper aims to present a theoretical situatio n for a small self-subsistence farmer in a semi-arid context using suppleme ntal irrigation in order to better secure the cereal needs of an average si ze family. A project description of an on-farm trial site in the Yatenga re gion of Burkina Faso is presented. The focus is on water and nutrient balan ces. (C) 2000 Elsevier Science Ltd. All rights reserved.