Without the soil, no farming would exist. Growers should be fixated with maximizing every inch of soil and improving the various factors that impact soil health.

A study done by Steve Hall, an assistant professor at Iowa State University, found that systems with cover crops generally increase the total amount of plant residue inputs compared with traditional grain cropping systems. Hall’s group focuses on research related to soil organic matter and nutrient cycling across a broad spectrum of ecosystems and how that research might apply to agriculture. The study findings were published in conjunction with visiting doctoral student Chenglong Ye from Nanjing Agricultural University in China.

The scientists discovered that residue management and nutrient availability may play a key role in controlling carbon gains and losses in systems.

“When nitrogen becomes limiting, microbes can actually ‘mine’ it from soil organic matter — contributing to increased decomposition rates,” says Hall.

Cover crops can stimulate microbial activity, providing soil fertility benefits and reducing nutrient loss from the soil, the study says. This is even more critical when growers plant cover crops, primarily for the purpose of improving soil biology and increasing soil organic matter.

According to the 2020 Cover Crop Benchmark Study published by Cover Crop Strategies, more than a fifth of growers stated that improving soil biology was specifically their most important reason for growing covers, and another 18% said that increasing soil organic matter was their most important reason.

Hall’s team has evaluated the correlation between the rate of nitrogen fertilizer applied and the physical and biological soil conditions. Soil conditions control greenhouse gas emissions.

“All else equal, we expect greatest nitrous oxide emissions where nitrogen fertilizer rates are high and soils are wet and warm,” he says. “As nitrogen fertilizer rates increase, nitrous oxide emissions increase exponentially.”

Hall’s research provides yet another reason for growers to consider using cover crops for weed suppression purposes, instead of nitrogen fertilizer.