Row spacing, plant density, and nitrogen effects on corn silage

Dairy producers in the northeastern USA who grow corn (Zea maps L,) forage in narrow rows plant at 125 000 plants ha(-1) and fertilize at 225 kg N ha( -1) because they believe narrow-row corn yields best at high plant densitie s and N rates. We evaluated corn in 1996 and 1997 at two raw spacings (0.38 and 0.76 m), two harvest densities (80 000 and 116 000 plants ha(-1)), and six N rates (0, 50, 100, 150, 200, and 250 kg ha(-1)) to determine if row spacing x plant density x N rate interactions existed for drg matter (DM) a nd calculated milk yields. No interactions existed for DM yield, forage qua lity characteristics, and milk yields. Corn had greater DM and milk yields at 0.38-(20.3 and 16.1 Mg ha(-1), respectively) vs. 0.76-m spacing (18.9 an d 15.2 Mg ha(-1), respectively). Dry matter and milk yields had quadratic-p lus-plateau responses to N rates with maximum yields (20.6 and 17.1 Mg ha(- 1), respectively) at an N rate of 150 kg ha(-1). Nitrogen accumulation st h arvest, which had a row spacing x N rate interaction, had a linear response to N rates at 0.38-m spacing and a quadratic response at 0.70-m spacing, D airy farmers in the northeastern USA san produce corn silage at similar pla nt densities and N fertility, regardless of row spacing, Dairy producers wh o have excess animal waste could apply slightly more N to narrow-row corn s ilage because it accumulates more N at harvest.