Abstract

A joint contribution from the Department of Soil Science, Egerton University, PO Box 536, Njoro, Kenya, and the Agricultural Research Organization, the Volcani Center, Israel, No. 603/01, 2001 series.

Smallholder farmers in arid and semi-arid regions use indigenous soil and water conservation (ISWC) techniques, such as trash lines and stone lines spaced about 15 m apart across the slope. This work evaluated the effects of size of trash lines and decreasing the space between trash or stone lines to 2 m on runoff, erosion, and corn and cowpea yields. Big trash line (BTL), small trash line (STL), and stone line (SL) techniques, and a control (no ISWC technique) were evaluated in 12 runoff plots (2 by 6 m each) with 10% slope in a semi-arid area in Kenya, during 5 consecutive rainy seasons. The ISWC techniques significantly (P ≤ 0.05) decreased runoff and soil loss, and increased corn and cowpea yields, compared with the control treatment in most of the rainy seasons. The BTL was, in general, the most effective technique; no consistent differences were found between the STL and SL techniques. In BTL, STL, SL, and control, the seasonal average runoff for each treatment was 25, 31, 29, and 51 mm, respectively; the seasonal average soil loss was 0.23, 0.33, 0.3, and 0.67 Mg/ha, respectively; and the seasonal average biomass (grain and stover of corn and cowpea) was 4.8, 4.0, 4.0, and 2.5 Mg/ha, respectively. The seasonal biomass increased linearly and significantly (P ≤ 0.01) with increasing water infiltration. As more water infiltrated, more water was available for crop production, and the yield was higher.