Tile Effluent Quality and Chemical Losses Under Conventional and No Tillage — Part 1: Flow and Nitrate

Abstract

The effect of no-tillage (NT) and conventional tillage (CT) treatments on tile drain flow, and nitrate concentration and loss in tile effluent was studied over a 40-month period in loam soil, corn fields (Zea mays L.) of approximately 3 ha each. Specific conductivity and pH of tile effluent, and corn silage yield were also determined. During the January 1991 to early May 1994 study period, flow was significantly (p < 0.05) higher under NT than CT mainly due to flow difference during the snowmelt and spring periods. The drinking water limit of 10 mg/L for nitrate-nitrogen (NO3-N) was exceeded in over 90% of the 1010 tile effluent samples that were analyzed. Flow-weighted average NO3-N concentrations during tile flow events tended to be higher under CT than NT but treatment effect was significant (p < 0.05) only in one crop-year, 1993-1994. The nitrogen lost as nitrate during the study period represented more than 20% of the amount applied as anhydrous ammonia. Annual losses ranged from 10% to 30%. Most loss occurred during the spring period when tile flow was highest. Over the 40-month study period, NO3-N loss in tile effluent was not significantly different for the two treatments. It was significantly (p < 0.05) higher under NT than CT only in one crop-year due to significantly higher flow under NT. There was no tillage treatment effect on tile effluent pH and specific conductivity. Corn silage yield was significantly higher (p < 0.01) under CT than NT during two years only when a burnout herbicide was not used prior to planting.