Effect of Irrigation and Nitrogen Rates on Yield and Quality of Corn for Silage.

Corn for silage requires adequate amount of water, nitrogen (N), and good management practices for profitable production. In 2014, two separate experiments (on-surface drip irrigation (ODI) and sub-surface drip irrigation (SDI) systems) were conducted at the University of Wyoming Research and Extension Center in Powell, WY to study the effect of different irrigation levels and N rates on yield and quality of corn for silage. Both experiments were laid out as a randomized complete block design in a split-plot arrangement with four replications for the SDI and three replications for the ODI experiment. Irrigation was the main treatment and included full irrigation (100ETc, Crop Evapotranspiration), 80% (80ETc), and 60% (60ETc) of the full irrigation treatment while N rate was the sub-treatment and included 0, 90, 180, 270, and 360 kg N ha^-1 as urea-ammonium-nitrate aqueous solution applied at planting, V4, V8, and V10 growth stages. Selected plants were harvested five times during the growing season for growth analysis. Total dry matter (DM) yield and quality parameters such as crude protein, fibers, and relative feed value were determined at harvest (Milk-Dough stage). The irrigation levels and N rates affected the corn for silage DM yield. For both experiments, the irrigation levels 100ETc and 80ETc produced the highest DM (16129 kg ha^-1 vs. 16076 kg ha^-1, and 16994 kg ha^-1 vs. 15241 kg ha^-1 for the SDI and ODI respectively). However, no difference was observed between them. In both experiments, the highest DM was at 270 kg N ha^-1 (17053 kg ha^-1 for the SDI and 16612 kg ha^-1 for the ODI). For the quality parameters, no difference was observed among treatments in both experiments suggesting no effect of irrigation on silage quality. The irrigation treatment 80ETc under SDI and ODI seemed to have potential for beneficial corn silage production.