PNNL

Abstract

The Huang-Hai Plain in northeast China has been cultivated for thousands of years and is the most productive wheat growing region in the country. Its agricultural future will be determined in large part by how global climatic changes affect regional conditions and by the actions China takes to mitigate or adapt to climate change impacts. One potential mitigation strategy is to promote soil carbon (C) sequestration, which would improve soil quality while simultaneously contributing to the mitigation of climate change. The IPCC estimates that 40 Pg of C could be sequestered in cropland soils worldwide over the next century. Here we assess the potential for soil C sequestration with conversion of a conventional till (CT) continuous wheat system to a wheat-corn double cropping system and by implementing no till (NT) management for both continuous wheat and wheat-corn systems. To assess the influence of these management changes under a changing climate, we use two climate change scenarios at two time periods in the EPIC agro-ecosystem simulation model. The applied climate change scenarios are from the HadCM3 Global Climate Model for the time periods 2015-2045 and 2070-2099. The HadCM3 model projects that both temperature and precipitation will increase throughout the next century with increases of greater than 5 °C and up to 300 mm possible by 2099. An increase in the variability of temperature is also projected and is, accordingly, applied in the simulations. The EPIC model indicates that winter wheat yields would increase on average by 0.2 Mg ha-1 in the 2030 period and by 0.8 Mg ha-1 in the 2085 period due largely to the warmer nighttime temperatures and higher precipitation projected by the HadCM3 model. Simulated yields were not significantly affected by imposed changes in crop management. Simulated soil organic C content was higher under both NT management and double cropping than under CT continuous wheat. Soil C sequestration rates for continuous wheat systems were increased by 0.5 Mg ha-1 yr-1 by NT in the 2030 period and by 0.4 Mg ha-1 yr-1 in the 2085 period. With wheat-corn double cropping, NT increased sequestration rates by 1.3 and 1.0 Mg ha-1 yr-1 in 2030 and 2085, respectively. The total C offset due to a shift to NT management over 16 million hectares of agricultural land on the Huang-Hai Plain is 240 to 180 Tg C for continuous wheat management in 2030 and 2085, respectively and 675 to 495 Tg C for wheat-corn double cropping in 2030 and 2085, respectively.