Agroecological analysis and economic benefit of organic resources and fertiliser in till and no-till sorghum production after a 6-year fallow in semi-arid West Africa

A field experiment was conducted in Gampela (Burkina Faso) in 2000 and 2001 to assess the impact of organic and mineral sources of nutrients and combinations thereof in optimising crop production in till and no-till systems and to assess the economic benefit of these options. The study showed that under conditions of rainfall deficiency, the use of a single organic resource at an equivalent dose of 40 kg N ha⁻¹ better secured crop yield than the application of an equivalent amount as urea-N, while a combination of organic resources and fertiliser was better in increasing crop yield than the application of the same N amount in the form of urea. In a year of rainfall deficiency, a mix of organic resources and fertiliser in both till and no-till systems increased crop water use efficiency, with the result that the farmer was able to purchase only half of the normal quantity of N fertiliser to obtain a higher yield that he would have done when all of the N was supplied in the form of urea. Under conditions where soil N is deficient, an economic benefit was achieved when urea was combined with easily decomposable organic material (e.g. sheep dung); mixing the urea at a dose of 40 kg N ha⁻¹ with maize straw was not sufficient in alleviating the negative interaction due to the enhanced N immobilisation. The results demonstrate that the use of N fertiliser alone was risky and that a higher yield, with the accompanying economic benefit, was scarcely achieved under the prevailing rainfall conditions. The application of soil and water conservation measures can contribute greatly to increasing the economic benefit of mineral, organic or combined organic and mineral-derived nutrient application under semi-arid conditions.