Soil Chemical Properties, Sunflower Growth and Yields as Affected by Double Digging, Mulch and Compost in Central Kenya

Double digging as a form of deep tillage and the between late October and late December. The utilisation of compost and mulch for improved crop experiments were conducted on a humic Nitisol production in the densely populated areas of Kenya (FAO-UNESCO, 1988) whose characteristics are is rapidly gaining attention the Kenya Institute of presented in Table I. Organic Farming (KIOF, 1994). The aim of double digging is to loosen the deep soil layers for intensive crop production. Compost is aimed at supplying essential plant nutrients and enhancing soil physical properties through addition of organic matter (FAO, 1977; Pfirter et al., 1981). Organic matter has beneficial effects on soil fertility because it increases nutrient storage capacities (Tisdale et al., 1985; Woomer et al., 1995). Mulch modulates soil diurnal temperature, reduces evaporative soil water loss and improves infiltration (Russell, 1988). All these have positive influences on crop growth.