Quantified land evaluation for maize yield gap analysis; At three sites on the eastern slope of mount Kenya

This thesis presents an analysis of maize yield levels and yield gaps between predicted and observed yield types in the coffee-tea, main coffee and cotton agro-ecological zones on the eastern slope of Mount Kenya, in Embu district. Maize yield data were obtained from experiments performed by the Fertilizer Use Recommendation Project for the 1986-91 period, plus the results of maize trials executed during this study for seasons I (mid-March to September) and II (October to mid-March) of 1992-93. Investigations on the influence of fertilizer application, weeding and insect control on maize yields were included in the latter trials at Embu study site. Maize yields from selected farm fields within the three agro­ecological zones were determined from crop cuttings. Soil and climatic data related to three specific study sites (Kavutiri, Embu and Gachoka, representing the coffee-tea, main coffee and cotton agro-ecological zones, respectively) were used in the WOFOST crop growth simulation model to determine calculated potential and calculated water-limited yields. The calculated water-limited yields were used in ALES to determine estimated yields. The yield gaps were analysed within and between the three study areas. Natural factors causing yield gaps include the inherent soil fertility and the climate, particularly the rainfall amount and distribution. Low soil fertility could be ameliorated by application of fertilizers and manures, but it is not feasible to entirely rectify soil moisture constraints under rainfed conditions. The human causal factors include the non-application or inadequate application of essential inputs and losses due to weeds, pests, diseases, birds and wild animals. It is not possible for farmers to eliminate most of these limitations because of lack of funds for purchasing inputs, lack of adequate agricultural knowledge and lack of technological capability. Since weeds were found to be a very important yield-controlling factor, efficient weeding by family labour could contribute substantially towards improving maize yields. Under the present traditional farming practices, the coffee-tea zone is marginally suitable for maize production in seasons I and II, while the cotton zone is marginally or severely limited for maize production in seasons I and II. The main coffee zone has high and marginal suitabilities for maize production in seasons I and II. The current farmers' maize yield levels can be increased and sustained by improving the efficiency all along the maize production line, beginning with better land preparation, more timely planting of the most suitable maize varieties, proper fertilization, and improved control of weeds, pests and diseases. More research is needed to determine the right types and quantities of inputs for maize production in the different agro-ecological zones. Appropriate arrangements should be made to promote efficient agricultural extension services, provide adequate credit facilities and put in place proper maize pricing policies.