Economic Evaluation of Organic and Inorganic Sources of Nitrogen under Striga Infestation in Western Kenya

Abstract

Due to escalating cost of imported fertilizers, there is renewed interest in the use of local nutrient resources in managing soil fertility in Kenya. The effect of integrated use of urea and Calliandra or maize stover on maize yields, financial benefits was assessed in a field experiment carried at Nyabeda in western Kenya. Urea and Calliandra or maize stover were combined in a way to supply N at 75 kg ha-1 from both sources in 100:0, 80:20, 60:40, 40:60, 20:80, 0:100, 0:0 ratios arranged in randomized complete block design (RCBD) with 12 treatments replicated four times in five consecutive seasons. Gross margins and benefit cost ratios were used for the analysis. Overall, maize stover (30 kg N ha-1) combined with urea (45 kg N ha-1) and Calliandra ( 45 kg N ha-1) combined with urea (30 kg N ha-1) gave the highest mean total biomass yields of 8.3 and 7.9 t ha-1 respectively. The two treatments out yielded the control by 89 and 80% respectively. The control and sole maize stover (75 kg N ha-1) had the lowest yields across all the seasons. The highest net benefits (71 USD) were recorded under maize stover (45 kg N ha-1) combined with urea (30 kg N ha-1) followed by Calliandra (30 kg N ha-1) combined with urea (45 kg N ha-1) at (68 USD). Sole application of maize stover gave the lowest benefit (-553 USD). Calliandra (30 kg N ha-1) combined with urea (45 kg N ha-1) was the only treatment that had a benefit: cost ratio approaching 2, and therefore, the most likely of the tested technologies to be adopted by farmers. These results suggest that the use of both Calliandra and maize stover with modest amount of inorganic fertilizers (urea) is more profitable than sole use of either of the two N sources.