Phosphorus management of a millet/cowpea intercrop system on sandy dunal soils of western niger

Abstract

Intercropping millet with cowpea is a widespread practice throughout the semi‐arid regions of West Africa. Low soil phosphorus (P) is one of the main limiting factors for crop production in this region. The objective of this study was to determine optimum methods and rates of P application to a millet/cowpea intercrop on a sandy, dunal soil of western Niger. Triple super phosphate was applied by three different methods: broadcast, in millet hills, and in cowpea hills. Three rates (0, 22.5, and 45.0 kg P/ha) were applied by each method. Treatments were replicated four times in a randomized complete block design. Cowpea yields were not affected by P applications, but millet yields were maximum with 45.0 kg P/ha applied to the millet hills. The 45.0 kg P/ha broadcast and millet hill applications resulted in significantly higher leaf P levels for millet, but no significant differences were found in cowpea leaf P levels. The 45.0 kg P/ha treatment applied to millet hills also resulted in the maximum P uptake, greatest biomass production, and highest economic yield. However, P use efficiency was higher in the treatment with 22.5 kg P/ha applied to the millet hills. Phosphorus management systems must be developed which optimize yield and economic return, as well as nutrient and water use efficiencies.