Abstract #M170

# M170
Effect of plant population and hybrids varying in relative maturity on yield, nutrient composition and ruminal in vitro NDF digestibility in whole-plant corn forage.
L. F. Ferraretto*1, J. G. Wasdin1, C. R. Staples1, D. Grabow2, 1University of Florida, Gainesville, FL, 2Grabow Seed Services Inc, Atlanta, GA.

The objective of this study was to evaluate the effect of plant population and hybrid relative maturity on yield, nutrient composition and ruminal in vitro NDF digestibility at 30 h (ivNDFD) in whole-plant corn forage. Five hybrids varying in relative maturity (115 [M115], 118 [M118a, M118b], 124 [M124] and 130 [M130] days) were each planted at 2 different plant populations (60,000 [60K] or 70,000 [70K] plants/hectare) during the summer, in quadruplicate. Samples were analyzed via NIRS at Dairyland Labs (Arcadia, WI). Data were analyzed as a completely randomized design using Proc Glimmix of SAS with the Fixed effects of hybrid, plant population, and their interaction. A plant population × hybrid interaction was observed (P = 0.001) for DM content, with greater values observed for 70K than 60K on M118a (33.9% vs. 32.1%) but the opposite on M118b (28.6% vs. 31.1%). Despite the greater (P = 0.02; 8.9% vs. 8.3%) CP content for 60K than 70K, plant population did not affect (P > 0.10) ADF, aNDFom, and starch concentrations. Greater starch (40.0% vs. 26.3% on average) but reduced CP (7.5% vs. 8.0% on average), ADF (22.7% vs. 28.8% on average) and aNDFom (36.0% vs. 44.7% on average) concentrations were observed (P < 0.01) for M118a than other hybrids. Increasing plant population from 60K to 70K tended (P = 0.08) to increase ivNDFD by 1.5%-units. This is related to reduced lignin (P = 0.02; 4.5% vs. 4.0%) and a trend for decreased uNDFom240 (P = 0.09; 14.3% vs. 13.0) concentrations for 70K. Yield of DM, milk/t and milk/ha were unaffected by plant population and averaged 13.2 t of DM/ha, 1263 kg of milk/t of DM, and 13952 kg of milk/ha, respectively. In addition, M118a tended to have greater ivNDFD (P = 0.06; 51.1 vs. 47.4% of NDF on average). This is related to the 1.1%- and 4.0%-unit lower (P < 0.01) lignin and uNDFom240 concentrations, and led to enhanced (P = 0.01) milk/t and milk/ha estimates. Yield of DM was 1.2 t/ha greater (P = 0.01) for M130 than other hybrids, on average. Plant population slightly improved NDF digestibility whereas hybrids varying in relative maturity affected yield and quality of whole-plant corn forage.

Key Words: corn silage, plant population, NDF digestibility