RICE Culture in the Sacramento-SAN Joaquin DELTA to Mitigate PAST Agricultural Impacts, Improve WATER Quality and Sequester Carbon.

The long-term goal of this project is to demonstrate rice based cropping systems will provide a sustainable (e.g. economic, environmental) solution for soil subsidence in the Sacramento-San Joaquin Delta and in so doing provide for the security of water supply for San Joaquin agriculture. This analysis focuses on implementing rice at the field scale, but also strategies for integrating rice into a crop mosaic on Delta islands and strategies for regional implementation to reduce risks to the Delta water conveyance system.  The Delta serves as the confluence of major river systems including the Sacramento, American and San Joaquin, which supply the majority of the water for California State Water Project. This essential water hub serves 3 million acres of irrigated agriculture in the south state.   Within the Delta, farming is the predominant land use and an important economic driver, comprising two thirds of the 740,000-acre Delta island network. This land use requires dewatering the land which has caused peat oxidation, the primary factor behind major land subsidence – 300,000 acres are 3 to 6m or more below sea. These cultural practices have had other impacts including on C cycling and sequestration, GHG emissions (i.e. carbon dioxide, methane, nitrous oxide), water quality and regional and state economics. During the first two years of the project we have found that rice slows soil C loss compared to rice, but we have insufficient results to determine if rice can reverse subsidence.  However, rice is producing similar quantities of N₂O compared to corn and methane production in rice is lower than that found in mineral soils.  We are continuing to investigate water usage and quality in rice compared to corn.  Previous studies have shown rice has promise to improve island drainage water quality. Our result will be used in a comprehensive biogeochemical/economic modeling effort assessing local, regional and state-scale impacts to determine the effectiveness of rice as an alternative crop for this region.