Evaluation of narrow-row corn forage in field-scale studies

Some dairy producers in the northeastern USA grow corn (Zea mays L.) in narrow rows at high plant densities and N fertility. We evaluated first-year, second-year, and continuous corn in field-scale studies at 0.76- and 0.38-m row spacings at recommended densities (approximate to85 000 plants ha(-1)) and N fertility (approximate to165 kg ha(-1)) and at 0.38-m spacing at high densities (approximate to100 000 plants ha(-1)) and N fertility (approximate to225 kg ha-1) in 1998, 1999, and 2000 to determine if narrow-row corn forage requires high densities and N fertility for optimum yield and quality. Narrow-row corn at high vs. recommended densities and N fertility had similar soil NO3-N concentrations in the upper 0.3-m depth and whole-plant N concentrations at the sixth leaf stage of corn (V6) as well as similar ear-leaf N concentrations at silking in eight of the nine site-year comparisons. All treatments were above critical concentrations for soil NO3-N concentrations (>25 mg kg(-1)), whole-plant N concentrations (>35 g kg(-1)), and ear-leaf N concentrations (>25 g kg(-1), except in the cool 2000 season). Consequently, narrow-row corn at high vs. recommended densities and N fertility had similar dry matter yield and quality in eight site-year comparisons. Furthermore, narrow-row corn at high vs. recommended densities and N fertility had greater residual soil NO3-N concentrations in three site-year comparisons. We recommended that dairy producers in the northeastern USA grow narrow-row corn forage at recommended plant densities and N fertility.