Tillage and N-Source Effects on NO3-N Leaching Losses to Subsurface Drainage Water

Abstract

An appropriate combination of tillage and source of nitrogen fertilizer can reduce NO3-N leaching losses to subsurface drain water. A field study was conducted from 1999 through 2003 on tile drained fields to determine the effects of liquid swine manure (LSM) application under no-till (NT) and urea ammonium nitrate (UAN) application under chisel plow (CP) on corn [Zea mays L.] and soybean [Glycine max (L.) Merr.] yield and NO3-N leaching losses with subsurface drain water. Four treatments of LSM (165 kg-N ha -1 ) with NT and UAN (170 kg-N ha -1 ) with CP applied to corn were replicated three times in a randomized complete block design. Seasonal effects were found to be significant (P<0.01) and above normal rainfall during the growing season for the months of July and August in 2002 resulted in highest corn and soybean yields of 12 Mg ha -1 and 3.6 Mg ha -1 , respectively, with minimum NO3-N leaching loss of 3 kg-N ha -1 . The LSM with NT plots in comparison to UAN application to CP plots resulted in significantly (P<0.01) lower flow weighted average NO3-N concentrations (12 vs. 16 mg L -1 ) due to dilution effects of greater subsurface drainage volume from NT plots by 73% (142 vs. 82 mm). Treatment effects on corn-soybean yields and NO3-N leaching losses were not significant but LSM with NT gave higher NO3-N leaching losses in comparison with UAN under CP treatment (15 vs. 11 kg-N ha -1 ).