ABSTRACT OF THESIS NOVEL CORN HYBRIDS FOR SILAGE PRODUCTION

Four corn (Zea mays) hybrid types at three plant densities and two nitrogen rates were evaluated for forage yield, forage quality and ensilage quality. The four hybrid types over the first two year of the study included nutri-dense, waxy, leafy, and dualpurpose, the third year a second dual purpose hybrid was added; while the three target plant densities were 54 000, 68 000, and 81 000 plants per hectare; and the nitrogen rates were 134 and 224 kilograms per hectare. The dual-purpose hybrid consistently had high forage yields compared with the other types. When averaged over nitrogen rate and hybrid type, the two highest plant densities typically had higher yields. Across all hybrids nitrogen had no effect on forage yield when averaged across plant density. The leafy hybrid had a lower harvest index than other hybrid types indicating that leaves accounted for much of the harvested weight. Hybrids were examined both at harvest (green chop) and after ensiling for protein and digestibility. Higher nitrogen rates increased crude protein when averaged over all hybrids and plant densities. Dual purpose and waxy hybrid types typically had the lowest acid detergent fiber (ADF) and neutral detergent fiber (NDF) and the highest relative feed values (RFV); while the nutri-dense and leafy hybrids typically had the highest ADF and NDF values and lowest RFV