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Low soil fertility and moisture deficits are major constraints to crop production in the semi-arid areas of Kenya. Farmers in these areas use farmyard manure (FYM) as a cheaper alternative source of plant nutrients as opposed to the more costly inorganic fertilizers. Community based on-farm trials were conducted in 4 hot and dry semi and districts (Machakos, Kitui, Mwingi and Mbeere), and in 2 cool and dry semi and parts of Laikipia and Kiambu districts. The trials were aimed at evaluating the effect of improved soil fertility and water harvesting technologies (open furrows and tied ridges) on the yield of maize and beans over a period of 4 seasons. The study also aimed at identifying opportunities for improvement and modification of the technologies from farmers' observations and feedback. A number of technological options were offered to farmers for testing and treatments were replicated on between 20 to 30 farms. The treatments were 10 t FYM ha(-1), 20 t FYM ha(-1), 20 kg N + 20 kg P2O5 ha(-1), 10 t FYM + 20 kg N ha(-1) and 10t FYM + 20 kg N + 20 kgP(2)O(5) ha(-1) for maize. For the beans-based trials the treatments included 5 t FYM ha(-1), 10 t FYM ha(-1), 50 kg DAP ha-1, 100 kg DAP ha-1 and 5 t FYM + 50 kg DAP ha-1. The fertility treatments were all tested with or without water harvesting in a randomised complete block design (RCBD). In all the clusters, use of manure or inorganic fertilizer increased the yield of maize and beans. Treatments that received 10t FYM + 20 kg N + 20 kg P2O5 ha(-1) produced the highest yields followed by treatments that received 10 t FYM + 20 kg N ha(-1). The trend was similar for treatments that received 100 kg DAP ha(-1) and those that received 5 t FYM + 50 kg DAP ha(-1) for the bean trials. Higher net benefits were realised when organic and inorganic fertilizers were applied as compared to the control. Treatments that received both organic and inorganic fertilizer (10 t FYM + 20 kg N ha (-1)+ 20 kg P2O5 ha(-1)) bad the highest net benefits of Kenya Shillings (KShs.) 19,166 for maize while for the beans the highest net benefits (KShs. 27,535) were obtained with 5t FYM + 50 kg DAP ha(-1). It is therefore recommended that farmers need to augment the limited quantities of farmyard manures available on smallholder farms with inorganic fertilizers and combining with appropriate water harvesting techniques for increasing the yields of maize and beans.