Soil Nitrate-Nitrogen under Tomato following Tillage, Cover Cropping, and Nitrogen Fertilization
1999
Sainju, Upendra M. | Singh, Bharat P. | Rahman, Syed | Reddy, V. R.
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), and moldboard (MB)], cover crop [hairy vetch (Vicia villosa Roth) (HV), and no hairy vetch (NHV)], and N fertilization (0, 90, and 180 kg N ha⁻¹) on residual NO₃-N content and movement on a Norfolk sandy loam (fine-loamy, siliceous, thermic, Typic Kandiudults) under tomato (Lycopersicon esculentum Mill) in central Georgia. Because of low N recovery by tomato, NO₃-N content in the soil increased with depth, regardless of treatments, and ranged from 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 residue 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. Greater loss occurred in NT than in CH or MB, with HV than with NHV, and with 180 or 90 than with 0 kg N ha⁻¹. Similarly, greater loss at 0- to 60-cm than at 60- to 120-cm depth and significant correlation between soil NO₃-N and clay concentration with depth indicates that NO₃-N moved from the surface layer to the underlying clay layer, where it moved slowly. Nitrate-N content and movement in the soil from cover crop residue and N fertilizer were similar. Minimum tillage reduced NO₃-N movement compared with NT, yet avoided the negative effects on soil and water quality associated with MB. Although HV increased tomato N uptake and recovery, it was not effective in reducing NO₃-N content and movement compared with N fertilizer.
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