Abstract
Declining soil fertility poses a serious threat to food production and food security to most farming households. Integrated Soil Fertility Management (ISFM) comprising the combination of organic and mineral fertilizer and other practices such as cereal-legume intercropping, diversified crop rotation and farmers’ knowledge has been promoted in various countries in Sub-Saharan Africa (SSA) including Kenya. This study aimed at evaluating adoption, productivity and return to investment of ISFM technologies among sorghum farmers in Tharaka-Nithi County, Kenya. Cross-sectional data was obtained from a sample of 370 sorghum farmers through multistage stratified random sampling technique. The study employed a semi-structured questionnaire that was administered to the respondents to obtain relevant data. The SPSS and STATA softwares were used to analyze data and results presented using descriptive and inferential statistics. Cragg`s Double Hurdle model was used to assess the influence of socioeconomic and institutional factors on the adoption intensity of ISFM technologies among sorghum farmers. Propensity Score Matching (PSM) and (Inverse Probability Weighting Regression) IPWRA models were applied in determining the effect of selected ISFM technologies on sorghum productivity among farmers. Budgetary technique was used to evaluate return on investment while Endogenous switching regression (ESR) model was used in determining the effect of selected ISFM technologies on return on investment (ROI) of sorghum. The results revealed that gender, dependents, farming goal for subsistence purpose, decision on information use, farm size, extension services, research awareness, ISFM awareness and ISFM access, significantly affected household decision on adoption of ISFM technologies. On the other hand, gender of household head, farm size, main source of agricultural information and formal agricultural training had significant influence on adoption intensity of ISFM technologies. The first stage results of PSM shows that extension services and ISFM awareness was significant in influencing adoption of the ISFM technologies positively while farming goal for subsistence, decision on information use and cost of ISFM affected adoption negatively. The second stage determined average treatment effect on adopters of ISFM and the results was 1.268, 1.120 and 1.192 bags of sorghum for nearest neighbor, kernel based and radius matches respectively. The results reveal that farmers who use ISFM technologies would produce 4.696 bags of sorghum compared to 1.424 bags obtained from not using the technologies. The expected ROI of farmers growing sorghum under ISFM technologies was reported to be 1.945 while that of non-adopters was 0.783. Based on the counterfactual outcomes ROI would have was 2.409 for adopters and 0.734 for non-adopters. It was therefore concluded that socio-economic and institutional characteristics continue to influence the choice to adopt ISFM technologies. The performance of adopted technologies on productivity and returns on investment as well remains high compared to non-adoption. There is a thus a crucial need for integration of determinants surrounding adoption and adoption intensity of ISFM technologies in policy making and planning processes to enhance decision on pro-adoption, which will improve sorghum productivity and returns in Tharaka-Nithi County.