Evaluation of Climate Change Adaptation Options for Agricultural Systems.

Agricultural responses to climate change suggest a deterioration of selected soil properties and an increased vulnerability of crop yields to elevated temperature, water availability, and nutrient stresses. Biochar amendments are viewed as a potential adaptation to  climate change because of its positive effects on crop yields, greenhouse-gas emissions, soil physical properties, and soil carbon sequestration. The objectives of this project were to (a) develop new algorithms for the EPIC (Environmental Policy Integrated Climate) model to quantify the influence of biochar amendments on crop yields and selected soil properties; (b) validate the modified version of EPIC using observations reported for a 5-yr study  on an Amazonian Oxisol amended with biochar at rates of 0, 8, and 20 Mg ha^-1; and (c) use the modified version of EPIC to predict long term climate change and management effects for representative farms in ten southeastern states. Algorithms were modified in EPIC to simulate short- and long- term responses of crop yields, CEC, pH, bulk density, and organic carbon to biochar amendments.  After validating the EPIC model, a 25 year simulation was performed. Concurrent with observations, simulated yields of biochar-amended treatments were significantly different than control yields at p<0.05. Soil pH increased from 3.9 to 4.17 after 5 years of biochar application in the field study while EPIC simulated a final soil pH of 4.19.  Soil CEC increased from 9.76 to 10.9 cmol_c kg^-1 in the field with biochar additions of 20 Mg ha^-1. The corresponding CEC simulated by EPIC was 11.5 cmol_c kg^-1.  EPIC provided acceptable values of increased soil organic carbon and decreased soil bulk density. In conclusion, the new EPIC algorithms  produced simulated values in agreement with the observed effects of biochar amendments on crop yields and changes in soil properties of an Amazonian Oxisol. 

The modified EPIC model was then used to evaluate the potential effects of climate change adaptations on crop yields, carbon respiration, soil carbon dynamics, and nitrate losses in runoff and leaching from representative farms in Alabama, Arkansas, Missouri, Mississippi, Florida, Kentucky, Louisiana, Texas, Georgia, and Tennessee. Adaptations included annual biochar applications, irrigation, and combined biochar and irrigation applications. Baseline (1979 – 2009) and future (2038 – 2068) scenarios were used for simulations with baseline and future CO₂ concentrations of 360 ppmv and 500 ppmv, respectively. Climatic data for baseline scenarios used NOAA’s North American Regional Reanalysis (NARR) database. Climatic data for the future scenarios used the North American Regional Climate Change Assessment Program (NARCCAP) database. Four regional climate models were used for the future simulations to project different patterns of changes in air temperatures, precipitation, and solar radiation that are expected to occur over time. Climate had significant effects on all response variables for at least 2 of the 4 regional climate models. Biochar treatments did not display significant effects on yield that were different from the climate effects. Climate had a significant effect on nitrate leachate losses in comparison to the control for all the regional climate models. Although not significantly different from the other treatments, trends indicate that leachate nitrate losses were largest for the irrigation and climate treatments and lowest for the biochar treatment. Climate was significantly different from control for all four regional climate models. The trends in the data suggest that biochar was not effective in reducing nitrate loss in runoff. Soil organic carbon dynamics displayed significantly higher accumulations of carbon for the biochar and combined irrigation and biochar treatments for all models. Under some weather scenarios, EPIC simulation results suggest that irrigation and biochar applications may be considered as promising potential adaptation strategies for agriculture in the Southeastern United States.