Alley cropping sequentially cropped maize and cowpea with leucaena on a sandy soil in Southern Nigeria.

Abstract

The potential of alley cropping maize and cowpea with giant leucaena (Leucaena leucocephala) cultivar K-28 was studied on an Entisol in Southern Nigeria. The crops were grown in 4 m wide alleys formed by periodically pruned leucaena hedgerows. The effect of application of leucaena prunings, nitrogen fertilizer and tillage was studied. Despite the very intensive pruning regime (five prunings/year) for a six-year period, the leucaena hedgerows continued to produce substantial amounts of prunings, nitrogen yield and stakes. Application of nitrogen (80 kg N/ha) to the maize crop increased the dry matter and nitrogen yields of the leucaena prunings. Although high nitrogen yield was obtained from the prunings, the application of low nitrogen rates was still required for high maize yields. Maize grain yield was sustained at about 2.0 t/ha with continuous application of leucaena prunings only. Without application of leucaena prunings or nitrogen, maize yield continued to decline with subsequent croppings. Cowpea grain yield was not affected either by leucaena prunings or by residual nitrogen, although nodulation was reduced. Tillage (rototilling) resulted in either higher or the same maize and cowpea yields in comparison with no-tillage. Application of leucaena prunings resulted in higher soil moisture retention, organic matter, exchangeable K, Ca, Mg and nitrate levels in the soil solution. Leucaena and maize appear to extract soil moisture from different zones in the soil. Timely pruning of hedgerows is necessary to minimize shading.