Plant density, distribution, and fertilizer effects on yield and quality of irrigated corn silage

Grain deficits frequently occur in the Southeastern Atlantic Coastal Plain [USA] because erratic rainfall patterns and soil properties often limit corn (Z. mays L.) yields, harvesting corn for silage may enable farmers to produce a 2nd grain crop during the same calendar year. Effects of row spacing, plant population and fertilizer program on yield, quality and mineral concentrations of corn silage grown with irrigation on Typic Paleudult soils were investigated. Two plant population treatments which averaged 7.0 and 10.1 plants m-2 were evaluated with 2 fertilizer programs that differed in N, N and K, and N, P, and K in 1980, 1981, and 1982, respectively. Each plant density by fertilizer combination was evaluated in single 96 cm rows and in twin rows which approximately doubled the intrarow plant spacing. Yield, quality, and mineral concentrations of corn silage grown in single rows spaced 96 or 75 cm apart and twin rows were also evaluated in large (185 m2) plots under center pivot irrigation during 1981 and 1982. Dry matter yields of 22-26 Mg ha-1 were achieved with plant densities of 6.7 to 13.5 plants m-2 at both sites. Highest yields were produced with stand densities of 9 m-2 or more planted in single 75 cm or twin rows, but yield differences were statistically significant at P (0.05) in only 2 of 5 site years. Increasing total N-P-K application beyond 200-30-167 kg ha-1 increased crude protein slightly in 1980 and significantly in 1981 and 1982. Concentrations of Mn and Zn in silage were increased by higher fertilization, presumably because nitrification reduced surface soil pH and increased their availability. Dry matter yield, fiber, energy and other mineral nutrients were not significantly influenced by fertilizer. These experiments identified management practices for the Atlantic Coastal Plain which resulted in corn silage yields equal to those produced in the cooler mountain region of Georgia and that exceeded current average production in South Carolina by approximately 40% without reducing apparent feed quality.