PHD-School of Environmental Studies

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This collections contains bibliographic information and abstracts of PHD theses and dissertation in the School of Environmental Studies held in Kenyatta University Library

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Browsing PHD-School of Environmental Studies by Author "Kimaru, Serah Wairimu"

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    Zai pits and integrated soil fertility management enhances crop yields in the drier parts of Tharaka Nithi County, Kenya
    (2017) Kimaru, Serah Wairimu
    Low crop yields due to low erratic rainfall, high evapotranspiration, and deteriorating soil fertility in smallholder farmersā€˜ fields of sub-Saharan Africa have led to a quest for sustainable production practices with greater resource use efficiency. To alleviate water stress, soil fertility decline and reduce runoff, water harvesting technologies and integrated soil fertility management (ISFM) are alternative promising options whose impact on agricultural productivity are not yet clear. The study therefore aimed to assess the effect of using zai pits in combination with organic/inorganic ammendments and conventional cropping technique on sorghum production. Effects of zai pit and conventional cropping techniques combined with integrated soil fertility management (ISFM) (organic materials as sole or combined with inorganic fertilizer) on selected soil physico-chemical properties and sorghum yields were assessed in a field experiment. Economic performance of all the treatments was evaluated using standard enterprise budgeting techniques to determine production costs and profitability. Descriptive statistics, chi-square, paired t tests and binary logistic regression were used in analysis of socio-economic data. Experimental data were subjected to analysis of variance and mean separation done using least significant difference (LSD) at p<0.05. The results of the study indicated that number of non-formal trainings, beneficiaries of NGOs, membership of group and visits by non-governmental extension agents play an important role in adoption of zai pits. Manure application led to a significant (p=0.014) increase in pH and a significant (p=0.05) increase in nitrogen under zai pit. The aggregate stability of zai and sole tithonia (ZT) was significantly higher (p=0.03) than conventional planting with sole tithonia (CT) at the end of the experiment. High volumetric water content (VWC) was recorded at the depth of 35 cm for zai treatments compared to conventional treatments. Zai pit in combination with tithonia amendment had the highest yields of 4.3 Mg ha-1 during short rains season of 2013 (SR13) while zai pit in combination with cattle manure had the highest yield of 4.18 Mg ha-1 during short rains season of 2014 (SR14). During the SR14, grain yields of zai pit with cattle manure (ZC) were significantly (p=0.016) higher by 53.7% compared to conventional planting with cattle manure (CCM). Conventional planting with full rate NPK (CF60) had the highest benefit cost ratio (BCR) of 3.58 while zai pit without input (ZNO) had the least BCR of 0.94. The experiment showed that zai pit technology contributed to increments of grain and stover yields in comparison to conventional planting although its BCR was lower than conventional planting with similar amendments. Based on the findings, there is need for agricultural policy makers to develop and implement appropriate agricultural guidelines for extension service providers and smallholder farmers on the effectiveness and efficiency of the technologies in the study. This will enable small holder farmers to make informed decisions on adoption of the technologies as a coping mechanism to climate change, enhancement of food security and alleviation of poverty in in the semi-arid tropics in Sub Saharan Africa