How much carbon is needed for sustainable agriculture? -

Researchers from Yale and The Nature Conservancy released the results of a study that was conducted to determine the optimal amount of organic matter needed for the best crop production. Their research was conducted under the hypothesis that the introduction of organic matter in agricultural lands would improve soil quality. Soil organic matter (SOM) affects many soil properties including providing proper structure for efficient drainage and aeration and minimizing erosion.

The majority of studies thus far have focused on the quality or yield of crops grown when organic matter is introduced with very little attention spent on finding the optimal amount for their results. Oldfield, Bradford, and Wood sought to determine the relationship between SOM and yield by interpreting global data that has been published in other studies. This data included soil texture, crop type, and latitude.¹ By quantifying the relationship between SOM and yield, they are hoping to assist in future policy initiatives.

Wheat and maize account for two-thirds of the energy produced in human diets and were the crops chosen for interpretations. The largest gains in yield occurred between Soil Organic Carbon (used to account for SOM) concentrations of 0.1% and 2.0%. Gains in yields were leveled off at approximately 2% SOC. It would take approximately 47 years to increase a field of 0.5% SOC to 2% SOC or approximately 9 years with higher percentage ranges. The researchers also tested their hypothesis by comparing SOC levels to fertilizer input levels.1 This data is important for supporting the need for decreased use of Nitrogen fertilizers. Globally, optimal yields could be maintained if cornfields decreased N input by 7% and 5% for wheat.¹

The decomposition of organic matter is important for environmental health far beyond crop production. Healthy soils contain bacteria that aid in carbon sequestration and reduce the need for additional fertilizers. Studies such as this provide important quantitative data that can be used for further soil research. By understanding how our soils function, we are better able to develop sustainable agriculture practices.