Evaluation of Biochar Applications and Irrigation as Climate Change Adaptation Options for Agricultural Systems

Abstract

The Environmental Policy Integrated Climate (EPIC) model was updated with algorithms to determine the effects of biochar applications on crop yields and selected soil properties. EPIC was validated using the results of a 4-yr field experiment performed on an Amazonian Oxisol amended with biochar. Simulations were conducted for 20-yr into the future and predicted increased values of soil cation exchange capacity, pH, soil C content, and decreased soil bulk density values after biochar applications. EPIC was then used to evaluate climate change impacts and effectiveness of annual biochar applications and irrigation as adaptation options on yields of C3 and C4 crops from representative farms in 10 Southeastern US states. Simulations were conducted for 1979- 2009 historical baseline climate data and 2038-2068 time periods using four regional climate models (RCM). Future corn (Zea mays L.) yields initially increased, but corn and soybean (Glycine max L.) yields had decreased by 2068. Future C4 crops generally produced higher yields compared to the historical yields of C4 crops. Historical baseline yields of C3 crops and future C3 crop yields were not significantly different. Biochar amendments had no effects on yields and in some cases resulted in significant yield decreases. Irrigation caused increases in corn yields, but not for soybean yields. Irrigation did result in increased C3 and C4 crop yields for some farms that were typically in drier areas. Further EPIC simulations were conducted to estimate the effects of climate change impacts and adaptations on microbial respiration, soil C content, and nitrate losses in runoff and leachate. Microbial respiration was higher under C4 crops than under C3 crops. Biochar amendments increased microbial respiration, although the relative relationship of C4>C3 microbial respiration was maintained. Nitrate losses were significantly higher in the future and followed a C3>C4 pattern. The greatest nitrate losses were observed under C3 crops with even greater losses due to irrigation. Biochar amendments resulted in reduced losses for nitrate in leachate, but not in runoff. C sequestration increased under C4 crops and biochar applications. Under some RCM weather scenarios, biochar applications and irrigation are promising adaptation strategies for agriculture in the Southeastern US.