Research on nutrient flows and balances in west Africa: state-of-the-art1Paper contributes to EC INCO-DC project IC18-CT96-0092 (Spatial and temporal variation of soil nutrient stocks and management in sub-Saharan African farming systems).1

Abstract

West Africa is poorly endowed when it comes to soil fertility. Unlike for example the Rift Valley area, west African soils never enjoyed volcanic rejuvenation. At low agricultural intensity, this does not matter as nutrients cycle through the soil and the natural vegetation and losses are few. However, the past decades have shown high population increases, the breakdown of traditional shifting cultivation systems, and a rapid decline of land productivity and soil fertility in particular. The present review paper shows how much is known about the severity of this process and the technologies at hand that can stop it. The information provided shows that on the technical side much is known now, but research output still is poorly integrated into development efforts.

Benefits of integrated soil fertility and water management in semi-arid West Africa: an example study in Burkina Faso

“…These results indicate that during welldistributed rainfall years in the Sahel, implementing water conservation measures without adding nutrients induced little or even negative influence on crop yields. This may be explained by the inherent low nutrient content of soils, mainly for N and P (Bationo et al 1998). Also, thanks to the better water availability induced by the runoff barriers, nutrient needs of sorghum plants may increase, leading to greater deficits and competitions between sorghum plants and those from the grass strips.…”

“…As the productivity of most soils in their native state in the study zone is very low (Bationo et al 1998), applying plants nutrients (50 kg N ha -1 ) in these poor soils induced great positive reaction in crop production (Table 2), particularly during good rainfall years ( Fig. 1) when soil moisture constraint is small.…”

Population Pressure and Land Degradation in the Ethiopian Highlands: A Bio-Economic Model with Endogenous Soil Degradation

“…Although fertiliser use may temporarily offset soil degradation and improve yields in the short-term, sustained loss of organic matter, water holding capacity, and soil depth is very difficult to replace (Nandwa & Bekunda, 1998;Bationo et at., 1998). Therefore, without proper soil fertility management, increased use of fertilisers could be a non-sustainable path in the long run, since mineral fertilisers are unlikely to substitute for the eroded soil stock.…”

Assessing soil nutrient change under long-term application of mineral fertilizer micro-dosing to pearl millet [Pennisetum glaucum (L.) R. Br.] on a sahelian sandy soil

“…A combined application of manure and mineral fertilizer enhances increased grain yield in Sahel (de Rouw and Rajot 2004;Ibrahim et al, 2015a;Suzuki et al, 2016). Earlier manure application is favourable for root system development (Michels and Bielders, 2006) and allows faster initial leaf growth, thereby increasing water use efficiency and crop productivity (Shapiro and Sanders, 1997;Bationo et al, 1998). Similarly, in Sahelian cropping system, many studies have shown the importance of crop residue in the Sahel Region.…”