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Long-Term Tillage and Crop Rotation Impacts on a Northern Great Plainsmollisol

Ibrahim MA, Alhameid AH, Kumar S, Chintala R, Sexton P, Malo DD and Schumacher TE

Soil properties can be altered by tillage and rotation, however, these effects cannot be detected in short-term studies. This study was conducted to assess the long-term (14 years) tillage and rotation impacts on selected soil surface properties. A long-term experimental site comprised of two tillage systems [no tillage (NT) and conventional tillage (CT)], and three crop rotations [corn (Zeamays)-soybean (Glycinemax), corn-soybean-wheat (Triticumaestivum), and corn-soybean-wheat-alfalfa (Medicagosativa)] were used for the present analysis. Surface (0-15 cm) soil samples were collected every year from 1991 through 2004 and analyzed for soil organic matter (SOM), available P, available K, and nitrate (NO3�?�?-N). Results indicated that SOM concentration (averaged across all years) under NT (37 g kg-1) was significantly higher compared to that of CT (36 g kg-1). However, overall crop rotation did not impact SOM. Soil P concentration under NT (208 mg kg-1) was significantly higher (8.3%) than that of CT (191 mg kg-1). Available P concentration was the highest in the 2-year-rotation, intermediate in the 3-year-rotation, and lowest in the 4-year-rotation. Tillage system did not significantly impact NO3 - concentration; nonetheless, its concentration was the highest in the 4-year-rotation followed by the 3-year-rotation, and the lowest was in the 2-year-rotation. The available K concentration under NT was not significantly different from that under CT; however, its concentration under the 2-year-rotation (340 mg kg-1) was significantly lower than those under the other two rotations. This 14-year tillage and rotation study had minimal impact on surface soil properties at this location.