An evaluation of organic and inorganic inputs for soil nutrient replenishment in Mukuuni and Murugi Central Kenya
Muriuki, Justin Pascal
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Declining land productivity due to declining soil fertility has led to decrease in the contribution of agricultural sector to the Gross Domestic Product (GDP) of nations in subSaharan Africa. Due to the high costs and poor supplies, most farmers are not able to afford sufficient amounts of mineral fertilizers to replenish soil fertility. Cost effective soil nutrient replenishment technologies involving organic and inorganic inputs have been developed and tested. However, few studies have been carried out to evaluate these inputs under farmer management. This study, designed to evaluate the performance of these inputs under farmer management, was carried out in two sites, Mukuuni and Murugi in Meru south district of central Kenya. The two sites were selected because research managed trial sites had been set up in the study area in 2003 by scientists from Kenyatta University, KARI and KEFRI with the various combinations of organic and inorganic inputs for soil fertility improvement. Farmers were exposed to the technologies through field days and village training workshops before the commencement of the study. The study involved 132 farmers, 73 in Mukuuni and 59 in Murugi. Farmers tested pure organic inputs (tithonia, manure and calliandra), mineral fertilizers, and combinations of organic and inorganic inputs. Costs and benefits from the selected technologies were evaluated for two seasons; short rains (SR) 2005 and long rains (LR) 2006. Net benefits, benefit cost ratio and returns to labor were used as the main economic tools in data analysis. Comparison of farmers' perception and choices of technologies with economic costs and benefits was done through correlation analysis. All biophysical data was subjected to analysis of variance (ANOVA) and means separated at p < 0.05 while significance in correlation was done using spearman's correlation coefficient at p < 0.05. Labor costs comprised over 60% of the total variable costs when organic inputs were used solely or in combination with mineral fertilizers. Tithonia plus manure plus mineral fertilizer had the highest mean total variable costs of KSh. 24,819 ha' and KSh. 26,631 ha"' in Mukuuni and Murugi, respectively, over the two seasons. Returns to labor were highest for mineral fertilizer in both study sites (5.1 and 4.1 in Mukuuni and Murugi, respectively). Tithonia plus manure plus mineral fertilizer had the lowest mean return to labor of 2.9 and 2.8 in Mukuuni and Murugi, respectively. Tithonia plus mineral fertilizer had the highest mean net benefits of KSh 29,464 ha"' in Mukuuni and KSh 23,650 ha' in Murugi. Males differed with females significantly in their perception of some input combinations on perceived costs and benefits. These differences were attributed to differences in access and control of resources at the household level. A positive relationship was found between farmers ranking of technologies based on perceived costs and benefits and ranking based on the calculated costs and benefits. This indicates that economic costs and benefits is a tool that can be used to predict how farmers are likely to rate technologies introduced to them. It also implies that farmers ranking can be used to set priorities in the promotion of these technologies to other farmers. Similarly, ranks of farmers' choices of technologies for further trial had a positive relationship with ranks of technologies based on calculated economic returns. This implies that economic returns can be used to predict technologies that are more likely to be preferred by farmers. Majority of the farmers (71% in Mukuuni and 54.1% in Murugi) chose technologies combining organic and inorganic inputs for further trial. Manure and tithonia were the preferred organic inputs mainly due to local availability and multiple benefits perceived, though labor requirements were high.