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

Irrigation and nitrogen (N) fertilizer are essential components affecting growth and development of corn for silage. Two separate field studies were conducted at the University of Wyoming Research and Extension Center located in Powell, WY. The first study was conducted on a sprinkler-irrigated field using a split-plot arrangement with three replications. The main treatment was irrigation, including 100% ETc (100ETc), 80%, 60%, and 50% of the 100ETc and the sub-treatment was N rates, including 75, 130, and 200 kg of N ha^-1. The second study was a preliminary assessment and was conducted on an on-surface drip-irrigated field with three nitrogen rates including 75, 130 and 200 kg of N ha^-1. The soil on both locations was characterized as clay-loam. The objectives of the study were to compare the effect of different irrigation levels and nitrogen rates on yield of corn for silage and to determine the effect of the interaction irrigation x N on yield of corn for silage. Phenology was monitored during the growing season. Aboveground plant biomass was harvested at physiological maturity for growth analysis. Results from the first year of research indicate that full irrigation and 80ET produce higher yields. Significant yield differences (P=0.0006) amongst irrigation treatments but no interactions between irrigation and N rates, were observed. The best combinations of irrigation x N were 100ETc water x 200 kg ha^-1 N and 80ET water x 130 kg ha^-1 N. This resulted in 19,377 kg ha^-1 and 19,335 kg ha^-1 of biomass as dry matter, respectively. Further studies include field experiments under on-surface and sub-surface drip irrigation systems to determine water use, water productivity, N uptake, and the use of aerial imagery for early detection of N content in corn for silage.