Soil water crop modeling for decision support in millet-based systems in the Sahel: a challenge

Abstract

Food insecurity in the Sahelian environment was extensively shown to be a result of low soil fertility and high climate risks. But decisions and recommendations made from the great wealth of research have little been adopted by farmers. Soil water crop models (SWCM) can assist researchers and development actors in this environment if they can appropriately deal with the constraints and mainly farmers' agricultural development goals. We reviewed the Sahelian agricultural constraints and farmer management practices with an emphasis on Niger and pearl millet. Significant results derived from research works to improve crop productivity are presented and analyzed with regard to the main agricultural constraints. Potential and currently used SWCMs are presented and compared for relevance for use in such a particular environment for decision support (DS). This shows that crop modeling in millet-based agricultural system of the Sahel should be addressed with an integrated approach that can handle the multiple and usually connected agricultural constraints of the region: low soil fertility and spatial variability, time and space rainfall variability. Recommendations were made regarding the relevant and minimum aspects that SWCM should take into account for a successful and reliable use for DS in the complex Sahelian environment.

Impact of Agropastoral Management on Wind Erosion in Sahelian Croplands

“…In the simulations, it is assumed that fields are also weeded at the beginning of crop growth and that each hole has three plants after thinning. Under these conditions, simulated plant densities are set to 10,000plants ha −1 at the lowest and reach up to 50,000 plants ha −1 , in agreement with previous studies in southwestern Niger (Buerkert et al ., ; Saidou et al ., ; Marteau et al ., ), although these values are relatively high for the study site strictly speaking (Hiernaux & Turner, ). Use of manure: Manuring is a common practice in the study area (de Ridder et al ., ; Andrieu et al ., ; Valbuena et al ., ); its effects on soil fertility in the model are expressed by modifying the coefficient of vegetation production in SarraH. Crop residue management: Three crop residue management practices are simulated based on observations in southwestern Niger (e.g., Akponikpe et al ., ): collection (to be used as forage) or flattening of (i) none, (ii) half, or (iii) all of the residues after harvest. Fields are cleared (i.e., remaining standing vegetation is laid down as litter) at different dates during the dry season, until the latest possible (in June) just before the start of the following rainy season. Grazing: In the simulations, grazing pressure ranges between no grazing and 50 TLU km −2 (tropical livestock units).…”

“…However, the application of 2,000 kg ha −1 was considered hardly achievable by farmers due to plant production limitation (Sterk, ; Ikazaki et al ., ). Additionally, crop residues, the management of which depends on socioeconomic factors, are increasingly collected by farmers to be sold or to feed livestock (Akponikpe et al ., ; Schlecht & Buerkert, ; Rasmussen & Reenberg, ; Valbuena et al ., ). Subsequently, there is a decrease in the amount of protective residue on the surface.…”

Integrated use of fertilizer micro-dosing and Acacia tumida mulching increases millet yield and water use efficiency in Sahelian semi-arid environment

“…Although the contribution of crop residues in increasing yields and maintaining soil fertility is evident, the use of this material for agricultural purposes in the Sahelian zones is restricted due to the intense competition for use as animals feed, fuel and building material (Bationo et al 1998;Valbuena et al 2014). Furthermore, the rates of crop residues reported to achieve the beneficial effects are much higher than what is available to smallholder farms (Akponikpè et al 2014). For instance, in Niger the recommended rate of crop residues is around 2000 kg ha -1 year -1 (Rebafka et al 1994), while the quantity of millet straw in farmer fields is merely around 1200 kg ha -1 (Baidu-Forson 1995).…”

Wind erosion response to past and future agro-pastoral trajectories in the Sahel (Niger)

“…The local land use evolved from very slight human impact in the 1950s to cropping, fallowing and livestock grazing in the 1990s and ongoing cropland expansion today, with the major staple-crop being millet (Pennisetum glaucum). Over the same period, land management changed with increasing grazing pressure and collection of crop residues (Schlecht et al, 2001;Akponikpè et al, 2014).…”