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Tottori University (2018)

Characterization of Paddy Soils for Fertility Based Interventions in Kenya


Titre : Characterization of Paddy Soils for Fertility Based Interventions in Kenya


Université de soutenance : Tottori University

Grade : Doctor of Philosophy (PhD) 2018

Sommaire partiel
The demand for rice continues to increase owing to continued population growth and it is predicted that a 50-60% increase in rice production will be required to meet the demand from this growth by 2025. In the face of this and with the pressure on available land for cultivation, the increases in rice yields are likely to occur through enhancement of crop production systems. Successful management of crop production systems requires analysis and design of practices that enhance yield by ensuring that growth limiting factors are minimized or completely eliminated. High availability and efficient utilization of soil nutrients are major determinants of healthy plant growth and realization of optimum yield returns. Thus an assessment of nutrient availability, uptake and utilization by plants is vital for optimized crop productivity. In Kenya, rice production has stagnated while consumption has greatly escalated in the recent past. About 74% of the rice produced is from government established irrigation schemes namely ; Mwea, Ahero, Bunyala and West Kano. In these irrigation schemes however, soil chemical and physical degradation among other factors has led to low productivity. The variability in soil properties in the rice growing irrigation schemes has not been exploited for appropriate targeting of soil fertility investment programs. The hypothesis is that there exists high variability in soil properties which requires fertility based soil management strategy for realization of enhanced productivity. Three irrigation schemes namely Mwea (Central), Ahero and West Kano (Western Kenya) were identified for this study from where surface 0-15 cm soil samples were collected and prepared for laboratory analysis using standard set procedures. Rice plant samples (straw with rachis branch and grain) were collected at harvest from selected paddy fields in Mwea irrigation scheme and analyzed for total for nutrient. The results obtained for soil and plant were evaluated by comparing with nutrient management guidelines for rice issued by IRRI (2000). Results showed that soil pH ranged from 6.2 to 8.0 and 5.4 to 7.5 in Ahero and West Kano irrigation schemes respectively, while in Mwea, values from 4.5 to 7.7 were recorded. As per the ratings by the Kenya soil survey, the soil pH was moderately high on average which is attributed to the basaltic parent material and the dry climate which favor the formation of Vertisols that largely cover the sites. In terms of soil salt concentration, the surface soils in all the three schemes are regarded as non-saline as low EC values (< 0.4 dS/m) were observed


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