Corn yield and fertilizer N recovery in water-table-controlled corn-rye-grass systems

Concern about NO3- leaching and groundwater pollution from corn monoculture has prompted an investigation of alternative production systems that reduc e leaching. It is hypothesized that both intercropping and water-table cont rol could increase N uptake and reduce the quantity of N that might be lost due to leaching. This study compared corn (Zea mays L.) with annual Italia n rye-grass (Lolium multiflorum Lam) intercropping and corn monocrop system s under three controlled drainage levels [free drainage (water table 1 m be low soil surface), and water-table depths maintained at 0.70 or 0.80 m, bel ow the soil surface via subirrigation]. Annual Italian rye-grass was plante d 10 days after the corn was planted. Grain yield, above-ground dry-matter production, N uptake and fertilizer N recovery (FNR) were assessed over 2 y ears on a fine, silty, mixed, non-acid, frigid Typic Humaquept sandy loam s oil. Corn grain yields were unaffected by the annual rye-grass/weed compone nt of the intercropping system or the various water-table depths in either year. Intercropping increased the total above-ground dry-matter production by 3.2 and 2.4 Mg ha(-1) and N uptake by 71 and 49 kg ha(-1) in 1993 and 19 94, respectively. Fertilizer N recovery from corn was not different between the two cropping systems. Water table depth had no effect on grain yield a nd N uptake. Previous published results from the same site indicated decrea sed soil N-NO3- content in the top 1 m of the soil profile in the fall of 1 993 and less denitrification due to intercropping, demonstrating that a cor n-annual rye-grass intercropping system, especially with rye-grass establis hing well later in the season, may be an effective practice for increasing soil N uptake without reduction of corn grain yield when adequate N and moi sture are present. (C) 2000 Elsevier Science B.V. All rights reserved.