Modelling Yield Gap Trends of Maize (Zea mays L.) Production under Soil Fertility Stress for Uasin Gishu Plateau Climate

Abstract

Results of maize yield under fertility stressed conditions were predicted using AquaCrop model by comparing a reference non- fertility stressed field with a stressed condition for levels of soil stress from 5% to 95% corresponding to biomass production levels of 95% to 5% respectively. Fertility stress level in the field reduces the amount of biomass produced and maximum canopy cover attained. Soil fertility module in AquaCrop model derives and calibrates specific level of stress crop parameters as a proportion of the reference plot data. Maize crop yield findings indicate a general decrease with increase in the soil fertility stress under the three weather conditions of dry, normal and wet categories. Similarly canopy growth coefficient (CGC) parameters decreased from 7.92% to 4.0% and an increase in the length of growth to maximum canopy cover from 109 to 134 (DAS). Maximum canopy cover (CCx) achieved was lower than that of the reference plot value of 81% and vary from 75% to 11% (model minimum value) applied under conditions of dry, normal and wet climate of Uasin Gishu plateau. Prediction of maize dry grain yield under dry weather condition recorded values below controlled demonstration plot (F100W100). Results of normal and wet weather conditions recorded positive yield gap values for soil fertility stress below 15% and 25% respectively, and all other levels of predictions are belowF100W100 yield level. Maize dry grain yields reduction vary gently for soil fertility stress range from 0% to 50% levels but greater variation occurs for values above 50% in all the weather conditions. Comparison of grain yield results simulated under soil fertility stress and soil nutrient application levels used in the demonstration plots are given in Table 4.33 for similar range of 20% to 80% maize nutrition levels.