MODELING OPTIMAL YIELD OF MAIZE UNDER DEFICIT IRRIGATION AND NUTRIENTS LEVELS IN UASIN GISHU COUNTY, KENYA.

Abstract

Agriculture uses the largest volume of water which is a scarce natural resource and equally demanded for both industrial and domestic requirements. Increasing demand in agricultural production for food and industrial products necessitates careful management of the limited resources. High uses of agricultural chemicals and diminishing production levels have continued stressing livelihoods with a basis on the environment. Mitigation measures of the challenges facing agricultural development require a policy shift that adopts research tools on productivity and limit the gaps generated by poor practices. The current research investigated the relationship between the levels of nutrient fertilizer and amount of water applied to achieve optimum yields for maize crop grown under deficit irrigation. Field trials were applied to achieve the following research objectives: (1) to establish the response of maize yields to various levels of moisture and fertilizer, (2) to determine and correlate residual soil nutrient levels in the soil at harvest as function of moisture and fertilizer treatments, (3) calibrate and validate AquaCrop model using data from field trials of deficit irrigation and fertilizer application levels, and (4) use AquaCrop model to predict maize yield gaps as a result of water and fertilizer stress in Uasin Gishu County. The results were subjected to AquaCrop model for water productivity simulation and have clearly shown that the use of high nutrients in the soil does not translate into high yields in maize. Deficit irrigation has led to a lot of water saving and increased area put under maize production. Optimum yield of maize requires application of about 65% of the conventional rates of nitrogenous fertilizer and 80% of moisture requirements of maize crop in Uasin Gishu County. Model prediction of maize yields and the prevailing yield gaps supported the level of moisture and had higher than the non-stressed conditions of 100% moisture applications. Statistical analysis results were supported by the model and recommend that application of fertilizer in crop production need to be re-considered to control the negative impacts on the environment.