LONG-TERM EFFECTS OF EROSION AND CLIMATE INTERACTIONS ON CORN YIELD

An accurate assessment of the impacts of soil erosion on corn producti on ss needed for conservation and management programs. Climatic variab ility produces a range of crop yield responses on eroded and non-erode d soil profiles and often masks the long-term trends and differences. Short-term corn yield data from representative soils across the North Central region were supplemented with calculated yields from the NTRM model to develop long-term yield responses for the historical climate records at each of seven highly-managed rainfed sites across the regio n. Results showed that long-term average regional corn yields were red uced by 10% for severely eroded versus control plots. Till-derived soi ls showed yield reductions averaging 12%, while loess soils lost an av erage of 7%. Sensitivity runs with the NTRM model made after field val idation with 119 plot-years of data suggested that changes in soil phy sical properties, especially plant-available water bolding capacities, probably accounted for most of the yield differences. Mean growing se ason (May-September) precipitation across all sites for the short-term field study was 35.3 cm, compared with 36.3 cm for the long-term hist orical record. This resulted in a mean short-term corn yield reduction of 9% for severely eroded soils versus a reduction of 10% for the sam e soils based on long-term climate projections. However, the close agr eement between the short- and long-term studies with regard to mean gr owing season precipitation and corresponding corn yields should not be used to make the general conclusion that 3 to 6 years is an adequate time period for research on long-term crop response to eroded soil con ditions.