RIDGE, MOLDBOARD, CHISEL, AND NO-TILL EFFECTS ON TILE WATER-QUALITY BENEATH 2 CROPPING SYSTEMS

Soil conservation tillage systems, including ridge-tillage, often redu ce surface water contamination by pesticides because soil erosion and surface runoff are reduced. However, the effects on losses through sub surface drainage tile are somewhat uncertain. Our field study quantifi ed the effects of four tillage practices in continuous corn (Zea mays L.) and corn-soybean [Glycine max (L.) Merr] rotations on herbicide an d nitrate N losses in tile drainage water. Fertilizer and pesticide ap plication methods were uniform for ridge, moldboard, chisel, and no-ti ll systems. Pesticide and nitrate N leaching losses were significantly affected by crop rotation. Tillage practice had little influence on n itrate N and pesticide losses to the subsurface drainage water within a corn-soybean rotation. However, ridge-till and no-till resulted in l arger losses of atrazine than the moldboard plow and chisel based syst ems under continuous corn, Tillage system did not affect the timings o f peak tile flow occurrences, although peak tile flow volume was affec ted by tillage, presumably because each system had its own macropore s ystem related to preservation or annual destruction of biopores by til lage. Corn yields were significantly higher under corn-soybean rotatio n than with continuous-corn for all tillage practices, These results i ndicate that continuous corn production is not an environmentally sust ainable practice for this area because it resulted in higher nitrate N leaching losses to groundwater, received higher N-applications, and r esulted in lower corn yields than the corn-soybean rotation, The resul ts also reinforce the need for studies on chemical placement, rate, an d timing for various tillage practices to reduce tile drainage losses of agricultural chemicals.