Author : Chanchai Kamolratana

Summary : A field experiment was conducted to determine the effects of population density, nitrogen level and the interaction of the yield, harvest and index and other agronomic characteristics of corn cv Pioneer 6181. The main plot (plant density) treatments were 38 095, 53 333 and 88 889 plants/ha and the subplot (nitrogen level) treatments were 0, 45, 90, 135 and 180 kg N/ha. Split-plot design with three replications was used. Grain yield, biological yield, harvest index and other agronomic characteristics of the crop were significantly affected by both plant density and level of nitrogen as well as the interaction between them. However, neither the plant density nor the nitrogen levels significantly influenced the days of silking. Ear height and harvest index were enhanced by increasing the level of nitrogen but not by plant density. Plant density showed appreciable influence on growth and yield of corn. Increasing plant density from 38 095 to 88 888 plants/ha resulted in increased plant height, ear height, leaf area index, grain yeild and biological yeild per plot, but decreased length of ear, diameter of ear, weight of ear, number of kernels per ear, weight per 1000 kernels, grain yeild and biological yield per plant. Results of the study disclosed appreciable yeild response to plant density, especially at 88 888 plants/ha while nitrogen level at the rate of 180 kg/ha gave the most favorable effect. The highest grain yield of 8.71 t/ha was recorded at plant density of 88 888 plants/ha with the application of 180 kg N/ha. Harvest index was highest at plant densities of 38 095 and 53 333 plants/ha fertilized with 135 kg N/ha. The nitrogen level and plant density x nitrogen level effects on harvest index were highly significant.