I am surprised none of the posts above raised the issue of land tenure. Large scale irrigation schemes in Mali are dominated by the government and access to fertile perimeters is open to corruption. Individuals have little incentive to invest in canal maintenance, desalinization or soil fertility. Productive farmers who would like to buy more land to increase scale cannot because of restrictions on land and control of land by the government. Until government facilitates transparent buying and selling of agricultural land, large scale schemes will fail.