Michael Bruentrup, and Andreas Buerkert
Nutrient Cycling in Agroecosystems


Phosphorus (P) deficiency is a major impediment to securing crop productivity on the acid, sandy soils of Sudano-Sahelian West Africa (SSWA). However, given the low profitability of many annually applied fertilization strategies with imported P, the effects of yield enhancing, alternative P-sources, such as rockphosphate (RP), should be considered. Therefore, the financial performance of 14 strategies— including 2 annual and 11 long-term fertilization strategies plus 1 farmers’ practice—were compared in three rainfall zones in SSWA. The comparison comprised the net present value, the annuity, the internal rate of return, and a risk analysis. Agronomic data came from a four-year, five-location trial complemented by information on farming systems, labor demands, and input–output prices. Compared with farmers’ practices, none of the P-fertilization strategies examined were financially superior at all locations. The financial performance of medium-term RP-strategies tended to increase with rainfall, but remained highly variable. Net returns to land with high rates of RP were often superior to annual inputs of mineral-P, but never the best alternatives. In most cases, the most profitable strategies comprised medium-level RP-applications with or without supplementary hill-placed NPK-fertilizer (also known as ‘‘micro-dosing’’). The financial performance of medium quantities of RP sometimes increased and sometimes decreased with supplementary nitrogen (N) additions. The combination of hill-placed NPK and broadcast RP as well as N-applications with broadcast RP are alternatives to the use of RP alone. Our results can assist researchers and development institutions in advocating and implementing more effective strategies to enhance agricultural production in SSWA.