Effect of placement of straw mulch on soil conservation, nutrient accumulation, and wheat yield in a humid Kenyan highland

Abstract

Mulching affects soil nutrient dynamics and crop yields. The effects of quantity and method of application of wheat straw mulch on soil loss, nutrient accumulation, nutrient loss, and wheat yield were evaluated in a field experiment in the acidic, d ark red, Rhodic Ferralsols of Kenya. The experiment involved three levels of wheat straw mulch (0, 3, and 5 Mg · ha –1 ) either incorporated in the soil (0 to 0.2 m) or surface applied. Surface application at 5 Mg · ha –1 decreased annual soil loss to 1.82 Mg · ha –1 from 14 Mg · ha –1 in the control. Deep placement of 5 Mg · ha –1 of straw, however, increased soil organic matter content by 23%. Annual losses of NH 4 –N, NO 3 –N, PO 4 –P, and available K in the sediments were 0.02, 0.04, 0.06, and 0.44 kg · ha –1 , respectively in the 5 Mg · ha –1 surface treatment. Straw mulch treatments also enriched NO 3 –N concentration in the 0 to 0.4 m soil layer. Surface application of 3 Mg · ha –1 straw gave the highest grain yield of wheat and the highest net returns (US$ 747), which was 30% more than that of the control.