Effect of Plant Density on Nutritional Quality of Green Chopped Corn

Abstract Text: The hypothesis of this study was that seeding corn at high plant densities results in greater concentrations of neutral detergent fiber (NDF) and lower concentrations of starch in corn whole plant. Therefore, the objective of this study was to determine the effect of planting density on whole-plant dry matter (DM) yield and its nutritional quality. The study was performed in a commercial dairy farm located in General Villegas, Argentina. Preceding crop was corn for silage. Total rainfalls during fallow and crop season were 719 mm. Two commercial corn hybrids (Dekalb747 and Duo548) were sown at 60000, 70000, 80000 and 90000 plants.hectare^-1 in four plots using a no-till corn seeder with a pneumatic dosing machine (TX Mega, Agrometal, Argentina). Plots were composed of eight 50-m rows separated by 52 centimeters. Corn was sown on October 13, 2012 and chopped on February 1, 2013. Crop was fertilized with 90 kg N and 31 kg P2O5 per hectare. Ten consecutive corn plants, randomly selected from each plot, were manually cut at 15 centimeters above ground, chopped with a forage chopper (TRF 70, Trapp, Brasil) and weighted to determine DM yield. Nutritional quality of chopped corn was determined by NIRS. Because the resulting densities were inferior and more variable than targeted (likely due to soil temperature variation linked to no-till conditions) statistical analysis was performed by linear regression. Average DM concentration of the chopped corn was 31.1 and 34.5% for the Duo548 and Dekalb747 hybrids, respectively. Plant density did not affect whole plant dry weight (P > 0.51) in either hybrid (285 and 252 g DM.plant^-1 for Duo548 and Dekalb747, respectively). Therefore, DM yield was linearly increased with plant density (slope = 237 kg DM.1000 plants^-1.ha^-1, P < 0.01). Contrary to the hypothesis, plant density did not affect either NDF concentration (P > 0.25) nor starch concentration (P > 0.72) of chopped corn (47.2 and 50.2% NDF and 27.5 and 21.3% starch for Dekalb747 and Duo548, respectively). Estimated DM digestibility was not affected (P > 0.24) by plant density in either hybrid (65.5 and 67.2% for Duo548 and Dekalb747, respectively). We concluded that, with abundant rainfalls (i.e., >700 mm), plant density does not affect nutritional quality of corn. Whether plant density affects nutritional quality of corn under lower rainfall regimes still needs to be elucidated.

Keywords: corn, density, quality