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Crop yield in sub-Saharan Africa is often limited by low phosphorus fertility. Farmers in the region can apply phosphate rock, which should increase the plant-available phosphorus level, but this may be prone to sorption in acid soils of the Sahel. The objective of this study was to determine phosphorus (P) sorption characteristics of four representative soil series in Sahelian Mali namely, Longorola (Gleysol), Danga (Fluvisol), Niessoumana (Arenosol) and Konobougou (Acrisol) under Tilemsi Phosphate Rock (TPR) treatment. Data for phosphorus sorption was obtained by equilibrating 5 g of soils for 7 days at room temperature in 50 ml of 0.01M CaCl2 containing six (6) rates of phosphate as TPR (0, 10, 20, 40, 80,160 mg/L). The linear form of the Langmuir equation was used to calculate sorption parameters of the soils. The Gleysol with the greatest clay content had the highest phosphorus sorption maximum which was over three times greater than that of the Acrisol with the least clay content. The sorption maxima in the range of 59–200 mg/kg were well estimated with Langmuir sorption isotherm (R2 ≥ 0.78). Soil organic matter and clay contents influenced phosphorus sorption from the TPR. The degree of phosphorus saturation ranged from 2.39 to 6.47 %, being greater in the Arenosol. In a two-season field experiment on the Haplic Acrisol, we tested on maize, the TPR in two forms (powder and pellet) in addition to water-soluble diammonium phosphate at different rates (0, 11 and 16 kg P /ha). The water-soluble DAP and TPR (powder) had similar effects (p < 0.05) on soil P availability but with DAP producing greater grain yields. This shows that application of TPR in powder form can improve phosphorus availability as water-soluble DAP with positive impact on grain yield. The study provides useful information on P sorption characteristics of TPR amendment in the Sahel.

Food security issues continue to be a challenge in most parts of the globe, especially in sub-Saharan Africa (SSA). Several research attempts on addressing this issue have mainly been on nutrient replenishment using combined nutrient application of organic amendments and mineral fertilizer inputs. However, there is limited information available on the potential mechanisms underlying nutrient interactions associated with co-application of organic amendments and mineral fertilizers. Therefore, this review focuses on the mechanisms underlying crop nutrient interactions, with particular emphasis on improved nutrient synchrony, priming effect, general soil fertility improvement and balanced proportion of nutrients required by crops. Following a brief overview of the mechanisms, the review describes four common pre-determined nutrient ratios required by plants depending on its life cycle, environment and genotypic characteristics in order to attain the crop’s maximum genetic potential. The review concludes with the need for future research to understudy mechanisms causing nutrient interaction under cropping systems, so as to apply nutrients at the most appropriate time to synchronize nutrient release with crop uptake, with the utmost goal of promoting sustainable crop production and enhancing food security.