Carbon-water relations of drought management in annual crops in California

Under pressure to avoid irrigation water use in California’s drought-prone environment, growers of annual crops are considering changing the crop types, avoiding crops or doing deficit irrigation. We are addressing the knowledge gap in the carbon-water relations of these new practices by doing water balance of the whole fields and carbon-water fluxes using eddy covariance and deep soil moisture monitoring at 6 different fields. Our area of interest is in Sacramento-San Joaquin Delta in California where soils are high in organic matter and the changes in management might exacerbate soil subsidence. We designed the experiment with 3-year duration plan and this talk will present our first full year of data collected throughout different crop drought management, seasons and locations.

Wet winter in the first year supported the drought management to be based on no irrigation for growing safflower, corn, sorghum, pasture and natural vegetation within our study. During winter time, some growers were even flooding their fields for wildlife and birds habitat. This rich dataset allowed us to quantify annual water and carbon balance based on the seasonal fluxes and soil moisture. In addition, we were able to evaluate remote sensing products for evapotranspiration estimates that are recommended in California (OpenET). Our results will benefit growers that host our experiments, State water managers, Carbon accounting for the State’s Carbon neutrality goals, university students research and education and cooperative extension outreach among others. We welcome constructive feedback and collaboration as we are trying to develop the best knowledge for direct societal benefits.