In recent years, policymakers across the world have launched initiatives to increase the amount of “soil organic matter,” or SOM, as a way to improve soil health and boost agricultural production. Surprisingly, however, there is limited evidence that this strategy will actually improve crop output.
A new paper by Yale researchers quantifies this relationship between soil organic matter and crop yields at a global level. Writing in the journal SOIL
, they affirm that greater concentrations of organic matter indeed produce greater yields — but only to a certain point.
Specifically, they find that increasing soil organic carbon — a common proxy for soil organic matter — boosts yields until concentrations reach about 2 percent, at which level they tend to hit a saturation point. Thereafter, the researchers say, the increase in SOM begins to deliver diminished returns.
Even still, they find that roughly two-thirds of agricultural soils dedicated to two of the world’s most important staple crops — maize and wheat — fall below that 2-percent threshold, suggesting the vast potential for agricultural policies that promote increased soil organic matter.