On the other hand, mineral-associated organic matter is a more persistent form of soil carbon that can remain in the soil for decades or even centuries. Increasing the amount of that type of soil carbon can help keep carbon out of the atmosphere over longer time periods.
The researchers recently published their findings in Global Change Biology, reporting that the soil organic carbon content was higher in all cover crop treatments than in fallow plots. Compared to the legume, soils under monocultures of grass and brassica had a higher proportion of plant-derived carbon in particulate organic matter. In contrast, soils under legumes had greater accumulation of microbial-derived carbon in mineral-associated organic matter.
The study results revealed, for the first time, that the cover crop mixture contributed to a higher concentration of plant-derived compounds in particulate organic matter, explained Ziliang Zhang, who spearheaded the study. As a postdoctoral scholar in the Department of Plant and Environmental Sciences at Clemson University when the research was conducted, he performed the huge volume of soil and data analysis involved in the study.
“In terms of the global carbon cycle, understanding how plant carbon gets into soils, and how long it stays there, that’s a big deal,” he said. “This study advances our fundamental understanding of how we might manage the global carbon cycle. Our discovery that the different plant species tend to create different types of carbon – that we think have different lifespans in the soil – is significant.”