Colorado State University research has found that soil organic carbon does not improve crop yields during extreme drought, challenging the commonly held belief that its greatest benefits occur under severe water stress.
The study by scientists in CSU’s College of Agricultural Sciences and Warner College of Natural Resources found that soil organic carbon provides the greatest yield benefits when water supplies are moderate. The research was published in May in Global Change Biology.
Soil organic carbon increases the capacity of soil to store water, but when water is extremely scarce, the additional storage capacity may not provide enough water for plants to benefit.
The researchers examined corn, soybeans and spring wheat, three important rainfed crops grown across a wide range of weather and soil conditions in the United States. They used decades of county-level crop yield records from the U.S. Department of Agriculture, along with daily soil moisture and atmospheric water demand data, to develop models examining how crops respond to weather conditions and how soil organic carbon affects those responses.
The models showed that soil organic carbon increases crop yields overall and improves yield stability from year to year. However, the benefits were greatest under moderate water conditions rather than extreme drought.
Researchers said the findings have implications for how the value of soil organic carbon is communicated to farmers. While additional soil organic carbon can improve soil water storage and crop performance, sufficient water must be available for plants to take advantage of that increased capacity.
Because moderate weather conditions occur more frequently than extreme drought, the researchers said yield gains associated with higher soil organic carbon can accumulate over time.
The study, titled Soil Organic Carbon Improves Crop Yield and Yield Resilience, is the first to quantify potential gains in crop resilience from soil organic carbon at a national scale, according to CSU researchers.
Source: Colorado State University, "Soil organic carbon increases crop yield but can’t help with extreme drought"