Continous application of no-tillage to Ohio soils

No-tillage (NT) crop production practices have been continuously maintained at four sites in Ohio for more than 25 yr. The original experiments involving NT were designed to determine how much tillage was required to produce crops with satisfactory yields and how tillage and rotation interact to effect crop yields, especially corn (Zea mays L.). Long-term effects of NT on crop yields and soil properties are generally not known because few sites exist with histories of greater than or equal to 20 yr of NT. This paper reports yield trends of corn and soybean [Glycine max (L.) Merr.] and changes in soil properties that occurred when NT was continuously practiced on soils in Ohio. Significantly lower yields for NT, as compared to conventional tillage (CT), were observed for monoculture corn and for soybean in rotation during the first 18 yr on a very poorly drained Mollic Ochraqualf soil. The yield differences observed for corn could be largely eliminated by crop rotation and for soybean by the use of phytophthora resistant/tolerant soybean cultivars. On a well-drained Typic Fragiudalf soil, crop yields were always higher with NT than with CT. After 18 yr, yield trends indicated the negative impact of NT on the very poorly drained soil was greatly decreased and the yield advantages associated with NT on the well-drained soil became even more pronounced. The change in yield treads did not appear to be associated with change in weather patterns. The long-term NT sites also revealed organic matter, nutrients, and soil enzymes accumulated at the soil surface but decreased deeper (>20 cm) in the soil profile. Surface water runoff was found to be greatly decreased from the long-term NT watershed site (approximately 9% slope) with only 12 mm of runoff measured between 1979 and 1985.