Cropping System Effects on NO3-N Loss with Subsurface Drainage Water

An appropriate combination of tillage and nitrogen management practices will be necessary to develop sustainable farming practices. A six-year (1993-1998) field study was conducted on subsurface-drained Clyde-Kenyon-Floyd soils to quantify the impact of two tillage systems (chisel plow vs. no tillage) and two N fertilizer management practices (preplant single application vs. late-spring soil test based application) on nitrate-nitrogen (NO3-N) leaching loss with subsurface drain discharge from corn ( Zea mays L.) soybean ( Glycine max L.) rotation plots. Preplant injected urea ammonium nitrate solution (UAN) fertilizer was applied at the rate of 110 kg ha-1 to chisel plow and no-till corn plots, while the late-spring N application rate averaged 179 and 156 kg ha-1 for the no-till and chisel plow corn plots, respectively. Data on subsurface drainage flow volume, NO3-N concentrations in subsurface drainage water, NO3-N loss with subsurface drainage flow, and crop yield were collected and analyzed using a randomized complete block design. Differences in subsurface drainage flow volume due to annual variations in rainfall significantly (P = 0.05) affected the NO3-N loss with subsurface drainage flows. High correlation (R2 = 0.89) between annual subsurface drainage flow volume and the annual NO3-N leaching loss with subsurface drainage water was observed. The flow-weighted average annual NO3-N concentrations varied from a low of 6.8 mg L-1 in 1994 to a high of 13.9 mg L-1 in 1996. Results of this study indicated that NO3-N losses from the chisel plow plots were 16% (16 vs. 19 kg-N ha-1) lower in comparison with no-till plots, while corn grain yield was 11% higher in the chisel plow plots (8.3 vs. 7.5 Mg ha-1). Late-spring N application applied as a sidedress resulted in 25% lower NO3-N leaching losses with subsurface drainage water in comparison with preplant single N application and also significantly (P = 0.5) higher corn grain yield by 13% (8.4 vs. 7.4 Mg ha-1). These results clearly demonstrate that chisel plow tillage with late-spring soil test based N application for corn after soybean can be a sustainable farming practice for the northeast part of Iowa.