Soil Nitrogen and Forage Yields of Corn Grown with Clover or Grass Companion Crops and Manure

Abstract

Few studies have compared the agronomic performance of cover crop and living mulch systems for no‐till silage corn (Zea mays L.). In a 4‐yr Wisconsin study, we evaluated soil N levels and forage yields from manured rotations of corn grown with kura clover (Trifolium ambiguum M. Bieb.) living mulch or interseeded red clover (T. pratense L.) followed by a year of clover production and from manured continuous corn grown with interseeded Italian ryegrass (Lolium multiflorum Lam.), fall‐seeded winter rye (Secale cereale L.), or no companion. Companion crops influenced spring and fall nitrate concentrations near the soil surface but had little effect on total residual fall nitrate to a 1.2‐m depth. Residual nitrate was not related to N balance (inputs minus outputs), but excessive N inputs into corn–clover systems accumulated as organic soil N. Averaged across both phases of the rotation, corn–clover systems provided 0 to 23% less dry matter yield, but 26 to 60% more crude protein yield than continuous corn systems, with corn–red clover often producing the highest silage corn and clover yields. Kura clover provided superior ground cover and nitrate uptake, but it often excessively competed with corn and had low forage yields. Applying fall manure to ryegrass and spring manure to rye maximized silage yields of continuous corn, but manure application time had no other effect on forage yields or on soil N. Overall, no system excelled in all characteristics, thus selection of companion crop and manure management systems for silage corn will depend on feed production and environmental goals.