New research published by the Soil Health Institute (SHI) provides fresh insights into the vital role that soil organic carbon levels can play in preventing drought, reducing flooding and improving the health and water retention of soils used to grow crops.

New pedotransfer function equations, which are predictive functions of certain soil properties, were developed, enabling more precise measurement of the correlation between carbon levels, water retention and various soil types. These new equations will allow scientists to better predict how much water farmers can provide to their crops by raising their soil carbon.

According to SHI, healthy soil that is rich in carbon acts like a sponge to soak up rainfall and store it for crops. While farmers have known this for a long time, it has been hard for scientists to predict how much extra water farmers can expect when they use regenerative agriculture practices that improve soil carbon. This is important because many farmers consider water management to be the biggest reason to adopt soil health management practices like reduced tillage, no-till or cover crops.

Dianna Bagnall, an SHI soil research scientist and the publication's lead author, said previous research has been mixed. Some findings showed negligible impact on soils’ water-retention capacities from higher soil carbon levels, while others showed a substantial increase in water holding. This new study drew on a more comprehensive sample of soil from locations throughout North America, using more natural, preserved soil structures and identifying levels of calcium carbonate, which can impact water-holding capabilities, in the soil samples as part of its analysis.

“Our findings showed an increase in water-holding capacities for non-calcareous soils (those lacking calcium carbonate) resulting from soil organic carbon that was more than double that of earlier studies,” Bagnall said. “This is an exciting development, since it provides a concrete incentive for farmers to adopt more responsible soil management practices that will positively impact their productivity and profitability.”

To help farmers evaluate the impact carbon sequestration and other practices might have on their businesses, SHI is developing a decision support tool.

“The new SHI tool will allow farmers to review various management practices to achieve a targeted increase in available water-holding capacity and better drought resilience in their soils,” Bagnall said.

The complete SHI study, entitled “Carbon-Sensitive Pedotransfer Functions for Plant Available Water,” can be accessed at https://acsess.onlinelibrary.wiley.com/doi/abs/10.1002/saj2.20395.

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