Soil nitrate-nitrogen under tomato following tillage, cover cropping, and nitrogen fertilization

Management practices can influence NO3-N content and movement in the soil. We examined the influence of 3 yr of tillage [no-till (NT), chisel (CH), an d moldboard (MB)], cover crop [hairy vetch (Vicia villosa Roth) (HV), and n o hairy vetch (NHV)], and N fertilization (0, 90, and 180 kg N ha(-1)) on r esidual NO3-N content and movement on a Norfolk sandy loam (fine-loamy, sil iceous, thermic, Typic Kandiudults) under tomato (Lycopersicon esculentum M ill) in central Georgia. Because of low N recovery by tomato, NO3-N content in the soil increased with depth, regardless of treatments, and ranged fro m 127 to 316 kg ha(-1) at 0- to 120-cm depth in the fall (September 1997). The content increased with increasing rate of N addition from cover crop re sidue and N fertilizer. From fall to spring (March 1998), 22 to 58% (37 to 129 kg NO3-N ha(-1)) of this content was lost, mostly due to leaching. Grea ter loss occurred in NT than in CH or MB, with HV than with NHV, and with 1 80 or 90 than with 0 kg N ha(-1). Similarly, greater loss at 0- to 60-cm th an at 60- to 120-cm depth and significant correlation between soil NO3-N an d clay concentration with depth indicates that NO3-N moved from the surface layer to the underlying clay layer, where it moved slowly. Nitrate-N conte nt and movement in the soil from cover crop residue and N fertilizer were s imilar. Minimum tillage reduced NO3-N movement compared with NT, yet avoide d the negative effects on soil and water quality associated with MB. Althou gh HV increased tomato N uptake and recovery, it was not effective in reduc ing NO3-N content and movement com pared with N fertilizer.