KindHarvest summary: Soil rich in organic carbon often holds more plant-available water, but the size of that benefit varies by soil. Research from the Soil Health Institute developed new predictive equations using a broad North American dataset to estimate the relationship more accurately.
Why earlier estimates differed
Previous studies reported effects ranging from negligible to substantial. The newer work used more naturally preserved soil structure and accounted for calcium carbonate, which can alter water-holding behaviour. Separating calcareous and non-calcareous soils improved the estimate.
What the study adds
Lead author Dianna Bagnall reported that the increase in water-holding capacity associated with organic carbon in non-calcareous soils was more than twice that estimated in earlier studies. The resulting pedotransfer functions are intended to predict how a change in soil carbon may affect available water for a particular soil.
Useful without becoming a universal promise
More soil carbon can support infiltration, storage and drought resilience, but texture, structure, carbonate content, rooting depth and rainfall still shape the farm result. The equations improve planning; they do not mean a fixed carbon increase will store the same amount of water everywhere.
Related KindHarvest reading
For the erosion side of water management, read How South Dakota’s inability to track soil erosion is putting farmers at risk.
Source and credit
This KindHarvest Team research brief is based on a No-Till Farmer report published 14 May 2022, drawing on Soil Health Institute research. Read the full No-Till Farmer article or view the peer-reviewed study.