Yield and Quality of Corn and Grain Sorghum Grain and Residues as Influenced by N Fertilization1

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Abstract
Crop residues of grain sorghum (Sorghum bicolor (L.) Moench) and corn (Zea mays L.) have attracted attention as an alternate economical forage resource for livestock utilization. There are little data available on agronomic production factors affecting yield and quality of crop residues. We evaluated the effect of rate and time of N fertilization on irrigated corn and grain sorghum grain and residue yields, grain N content, and forage quality of the residues.During 1972 and 1973 irrigated corn and grain sorghum plots were fertilized with O, 90, 180 and 270 kg/ha of N as a 32% N solution at planting or sidedress with two P levels (O and 22 kg/ha) incorporated prior to planting. Grain and residue samples were analyzed for grain N content, and residue crude protein and in vitro dry matter digestibility (IVDMD).Corn grain yields increased significantly with N applied at 90 and 180 kg/ha, while grain sorghum grain yields increased significantly only at the 90 kg/ha rate. Grain N content increased with N fertilization for both crops. Grain sorghum N content was generally equal to or greater than corn. Residue yields of both crops were increased significantly by 90 kg/ha with no further increase at the higher N rate. Corn grain/stover ratios increased with increasing N levels. Crude protein of grain sorghum residues was consistently higher than corn while IVDMD values were consistently lower in grain sorghum. Crude protein increased significantly in grain sorghum residue with each increasing N level while little increase occurred in corn.We conclude that N rate and time of application does affect yield and quality of row crop residues. This would have an affect on supplementation of livestock grazing row crop residues.

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