The profitability of traditional and innovative mulching techniques using millet crop residues in the West African Sahel

To try to maintain soil fertility in the West African Sahel (WAS), research and development organisations promote the use of mineral fertilizers, especially phosphate (P), and an improved management of crop residues (CR). While researchers have achieved considerable increases in yield using broadcast mulch rates of 2000 kg CR ha(-1), farmers traditionally apply CR only on selected microsites with low productivity. The economic analyses in this paper were based on the results of an on-station field experiment presented previously. The yields were analysed according to a set of hypothetical application methods, that is assuming that: (1) all fertilisers were broadcasted evenly, (2) all fertilisers were applied to poorly producing microsites only, and (3) all fertilisers were applied to good producing microsites only. Linear programming models were used to estimate the comparative advantages of traditional and innovative mulching techniques for typical farms in western Niger. The following scenarios were tested: (1) application of CR only to poorly producing microsites when the latter comprised 10%, 30% and 50% of the total farm land; (2) applying CR mulch to poorly and good producing microsites or broadcasting it with or without the addition of P fertilizers; and (3) the amount of CR available for mulching was compared between sites where there was or was not a market for buying and selling CR. The data came from an experiment conducted between 1991 and 1992 at the ICRISAT Sahelian Centre in Niger and from several household surveys used to characterise a typical farm in western Niger. The optimum solutions to the linear equations suggest that farmers' concentrated microsite techniques are more profitable than broadcast applications due to the higher productivity of the traditional techniques per unit of labour input. At a proportion of 10% poor microsites, it is not profitable to treat the poorly producing parts, However, as the proportion of the low fertility land increases the profitability of treating these areas increases, High relative costs of P fertilizer and low millet grain prices render P application beneficial only if applied to good producing microsites. In the short run, the farmers' mulching techniques are currently rational from an agronomic and economic viewpoint. Yet, as the proportion of low fertility land increases, traditional techniques need more CR which can only be assured by P inputs. A more favourable agricultural price policy may improve adoption of P fertilizers by Sahelian farmers. (C) 1998 Elsevier Science B.V.