Irrigated sorghum and cowpea after wet-season rice as a pathway out of subsistence agriculture in the Senegal River Valley in Mauritania

摘要

Livestock is more important to the Mauritanian economy (13% of National Gross Domestic Product) compared with just 4% from crop production. It is surprising, therefore, that irrigation has so far contributed little to animal productivity given the limited carrying capacity and irregular inter-annual production of the extensive rangeland, and the need to import fodder concentrates to sustain livestock during the hot-dry season (April to June). Our hypothesis is that growing irrigated sorghum and cowpea planted late in the mild-dry season (December-January after rice harvest (November-December) would improve profitability and sustainability of irrigation schemes. The objective is to replace fodder concentrates, currently purchased abroad, by fodder grown in irrigation schemes. To test our hypothesis we performed an extensive survey of 12 villages located within a significant gradient of rainfall from West to South-East along the northern bank of the Senegal River and used a simulation model constructed to study interactions between traditional and irrigated grain and/or fodder crop. The results of this study reveal how the introduction of irrigated sorghum and cowpea sown late in the mild-dry season would, even at relatively moderate yields (2.8-4.1 and 1.4-2.1 t grain ha-1, for sorghum and cowpea, respectively), provide additional grain required by smallholder farmers and reduce costs of livestock production (30%). In addition, the introduction of these crops increases by 31- to 54% the household net agricultural production of households having only small ruminants and by 14 to 23% of households having both small ruminants and cattle. Extending the irrigated cropping season shares the depreciation costs over more crops and improves the sustainability of the irrigation schemes. The regions that would most benefit from these additional irrigated crops are Trarza and Gorgol where the demand and hence prices of sorghum and cowpea grain and fodder are higher than in the other regions.