Multi-Site Time-Trend Analysis of Soil Fertility Management Effects on Crop Production in Sub-Saharan West Africa

Abstract

Soil fertility constraints to crop production have been recognized widely as a major obstacle to food security and agro-ecosystem sustainability in sub-Saharan West Africa. As such, they have led to a multitude of research projects and policy debates on how best they should be overcome. Conclusions, based on long-term multi-site experiments, are lacking with respect to a regional assessment of phosphorus and nitrogen fertilizer effects, surface mulched crop residues, and legume rotations on total dry matter of cereals in this region. A mixed model time-trend analysis was used to investigate the effects of four nitrogen and phosphorus rates, annually applied crop residue dry matter at 500 and 2000 kg ha 71 , and cereal-legume rotation versus continuous cereal cropping on the total dry matter of cereals and legumes. The multi-factorial experiment was conducted over four years at eight locations, with annual rainfall ranging from 510 to 1300 mm, in Niger, Burkina Faso, and Togo. With the exception of phosphorus, treatment effects on legume growth were marginal. At most locations, except for typical Sudanian sites with very low base saturation and high rainfall, phosphorus effects on cereal total dry matter were much lower with rock phosphate than with soluble phosphorus, unless the rock phosphate was combined with an annual seed-placement of 4 kg ha 71 phosphorus. Across all other treatments, nitrogen effects were negligible at 500 mm annual rainfall but at 900 mm, the highest nitrogen rate led to total dry matter increases of up to 77% and, at 1300 mm, to 183%. Mulch-induced increases in cereal total dry matter were larger with lower base saturation, reaching 45% on typical acid sandy Sahelian soils. Legume rotation effects tended to increase over time but were strongly species-dependent. introdutionThe yield-enhancing effects of surface-applied crop residue (CR) mulch, mineral phosphorus (P) and nitrogen (N) fertilizers, and of legume rotations have been reported frequently with respect to the nutrient-depleted, acid sandy soils of West Africa Buerkert and Hiernaux, 1998;Bationo and Ntare, 2000). However, most of the available results and the derived conclusions referred to pearl millet (Pennisetum glaucum), sorghum (Sorghum bicolor), and maize (Zea mays). Much less is known about the effects of CR, P, and N on legume growth and on cereal legumes (Hafner et al., 1992;Rebafka et al., 1993b).

Climate-smart soil water and nutrient management options in semiarid West Africa: a review of evidence and analysis of stone bunds and zaï techniques

“…Indeed, plant nutrient use efficiency in cereal-based farming systems is often very low because of limited soil moisture conditions [26]. The low soil quality combined with the harsh Sahelian climate leads to a low efficiency of fertilizers [19].…”

A critical analysis of challenges and opportunities for soil fertility restoration in Sudano-Sahelian West Africa

“…On most soils medium-and long-term SOM therefore remains low, even if elevated amounts of plant biomass are recycled during fallow periods or with mulching and manuring (Feller and Milleville 1977;De Ridder and Van Keulen 1990;Renard et al 1993;Bacye´et al 1998). Buerkert et al (2000Buerkert et al ( , 2002 have summarized how short-term effects of mulch application on soil physical and soil chemical properties and finally on crop growth depend in magnitude on the specific soil type (such as its clay content) and the climatic conditions (intensity and length of the rainy season). Mulching effects certainly also depend on the kind of organic material applied (branches of woody species, crop residues such as stover, household waste, compost and hand-spread manure) even if to our knowledge comparative data on the effects of different mulch materials have not been published.…”

A comparison between legume technologies and fallow, and their effects on maize and soil traits, in two distinct environments of the West African savannah

“…There is also little information from multi-site trials comparing the performance of legume-cereal rotations (Buerkert et al 2002;Fofana et al 2005). Such information is important for targeting legume technologies appropriate to different biophysical and socio-economic environments, which in turn enhances the likelihood that such technologies will be adopted by farmers.…”