Effect of planting density on yield, nutritional quality, and ruminal in vitro digestibility of corn for silage grown under on-farm conditions

The objective of this on-farm study was to determine the effect of planting density on yield, nutritional composition, and fiber digestibility of corn silage. This study was performed during the spring and summer seasons of 2014 and 2015 at 2 commercial dairy farms located in Virginia. The study included 7 cornfields with different growing and harvesting conditions. In each cornfield, corn was planted in plots at a theoretical seeding rate of 55,000, 70,000, 85,000, and 100,000 seeds/ha (55K, 70K, 85K, and 100K, respectively). Each seeding rate had 4 replicates within each cornfield. The preceding crop was annual ryegrass that was harvested for silage within 10 d before planting corn. Plant DM biomass decreased linearly (376 vs. 253 g of DM/plant for 55K and 100K, respectively; P < 0.01), but DM yield increased linearly (19.8 vs. 26.0 Mg/ha for 55K and 100K, respectively; P < 0.01) when planting density increased. The number of kernels per ear and the stem width decreased proportionally as corn population density increased. Planting density did not affect, or minimally affected, the concentrations of ash, CP, NDF, ADF, ADL, starch, and sugar of fresh corn and corn silage. Also, planting density did not affect ruminal in vitro NDF digestibility of fresh corn and corn silage. In conclusion, increasing corn planting density increased forage yield when planted in a double-cropping system, minimally affecting nutritional quality and ruminal in vitro digestibility of corn silage.