Evaluating Hybrid-Maize Simulation Model for Grain Yield Estimation in Hybrid Seed Maize Production
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The study was carried out to determine the effect of Male Planting Date (MPD) and Female Plant Population (FPP) on the Grain Yield (GY), yield components and flowering of a three-way hybrid. The study also evaluated Hybrid-Maize simulation model for grain yield (GY) estimation in hybrid seed maize production. Seed grading of harvested three-way hybrid seed was also carried out to determine the seed grades based on the principle of length and thickness of the seed according to the Zimbabwe screen sizes. A CIMMYT three-way hybrid, with pedigree of (CML395/CML444//CML443) was used in this research. The experiment was laid out in (5 x 3) two-way factorial arrangement in a Randomized Complete Block Design (RCBD) at CIMMYT-Harare research station. Fifteen treatment combinations of five MPD as a deviation from the female planting date and three FPP replicated three times were used. The Hybrid-Maize simulation model programme was used to forecast the possible GY outcomes for the fifteen treatments of the experiment using estimated parameters and weather data for the 2006/7 season. The field experiment produced significant (P<0.005) main effects but non-significant interaction effects for grain yield, yield components and ASI. Female seed yield was affected by time of male pollen shed relative to female silking (Anthesis-Silking Interval, ASI), with highest yields associated with close synchrony (ASI= +/-3 days). ASI had a significant effect on the number of Kernels Per Ear, KPE, with the greatest KPE (318) associated with an ASI of +/-3 days. FPP effects on yield are typical for maize, showing a curvilinear response from low to high density. The optimum population density for grain yield was 5.4 plants m-2. Simulation output from the Hybrid-Maize model showed an overestimation of GY compare to the observed yield. Furthermore, the model was unable to predict yields for the low FPP of 2.7 plants m-2. This model would need to be modified for estimating seed yield of a three-way hybrid through the inclusion of male and female components. Seed grading data produced significant (P<0.005) difference for main effect FPP for medium size kernel weight but non-significant effects for the other FPP grades, MPD and interaction effects.