Assessing and Predicting Effects of Input and Crop Diversity on Soil Nitrate, Extractable Phosphorus, and Organic Carbon from a Long-Term Rotation in the Semi-Arid Canadian Prairie.

The relative impact of climate change, management, diversity, and environment on soil carbon, nitrogen, and phosphorus has seldom been assessed in the scientific literature. Experimental results for a case study of the effects of agricultural inputs and cropping diversity on environmental quality were previously assessed with the Environmental Policy Integrated Climate (EPIC) model. Three levels of agricultural inputs [organic (ORG), reduced (RED), and high (HI)] and sub-plots comprised of three levels of cropping diversity [low (LOW), diversified annual grains (DAG), and diversified annual perennial (DAP)] were used in this study. This modeling study assessed soil organic carbon (SOC), CO2 emissions from microbial respiration (CO2-MR), nitrate leaching, and labile phosphorus (P) content (0-15 cm) simulated with the EPIC model for historical (1971-2000) and future climate scenarios (2041-2070) under A2 high emissions global scenario. Under climate change, SOC decreased by 1.3% of original stocks in the 0-90 cm. Emissions and nitrate losses increased by 17 and 28%, respectively, while labile P decreased by 12%. Precipitation in May accounted for 16% of total variation in SOC. June temperature accounted for 9% of variation in CO2-MR. The combination of input and diversity was correlated with 3, 7, 23, and 20 percent of variation in SOC, CO2-MR, NO3-N losses, and labile P, respectively. The combination of RED inputs and DAG diversity reduced the impact of climate change on SOC, CO2, and nitrate losses.