Effects of Cropping and Tillage Systems On Soil Erosion Under Climate Change In Oklahoma.

Soil erosion under future climate change is very likely to increase due to projected increases in frequency and magnitude of heavy storms.  The objective of this study is to quantify the effects of various cropping and tillage systems on soil erosion and surface runoff during 2010-2039 in central Oklahoma.  A combination of 18 cropping and tillage systems is evaluated using the Water Erosion Prediction Project (WEPP) model for 12 climate change scenarios projected by four GCMs (CCSR/NIES, CGCM2, CSIRO-Mk2, and HadCM3) under three emissions scenarios (A2, B2, and GGa). Tillage systems include conventional, reduced, delayed, and no-till.  Cropping systems include continuous monoculture (winter wheat, soybean, sorghum, and cotton) and double crops of winter wheat and summer soybeans.  Compared with the present climate, overall t-tests (n=12) show that during the next 30 years mean precipitation will decrease by some 6% (>98.5% probability), daily precipitation variance increase by 12% (>99%), and mean temperature increase by 1.36 °C (>99%).  However, under the same tillage systems, runoff and soil loss will increase (>90%) due to an increase in heavy storms, despite the projected decreases in precipitation amounts.   Overall results show that soil loss rates are positively related to the frequency and severity of tillage disturbances under all cropping systems.  Compared with the conventional tillage systems, reduced till, delayed till, and especially no-till substantially reduce soil loss rates, indicating that adoption of conservation tillage systems will be effective in keeping soil erosion at acceptable levels in the region during the next three decades.