Illinois Crop Consultant Discusses C:N Ratios of Cover Crops Ahead of Termination

In concluding the Illinois Cover Crop On-Farm Network’s (ICCON) three-part series on soil health testing, David Kleinschmidt, owner of Progressive Agronomy Consulting in Illinois, shared valuable insights into how he uses the Haney Soil Health Test to guide crop nutrition programs for his clients, emphasizing a holistic approach that considers soil as a dynamic system.

Working closely with his farmer clients, David stresses the importance of understanding nutrient cycling in the soil before devising fertility programs. While conventional methods often rely on inorganic fertilizers, it’s essential to recognize that these nutrients undergo a complex journey through microbial communities before becoming available to plants. Therefore, nurturing the well-being of these microbial communities is crucial—a shift from traditional chemical-centric approaches.

When examining a Haney report, David focuses on indicators such as CO2 respiration, organic carbon content, and % microbially active carbon (MAC). These metrics offer insights into microbial activity, organic carbon availability, and microbial preferences, respectively. Armed with this understanding, David develops tailored fertilizer plans to meet crop needs efficiently.

When examining a Haney report, David focuses on indicators such as CO2 respiration, organic carbon content, and %MAC. The higher the respiration rate, the more microbial activity is occurring in the soil. As respiration increases, organic carbon should also increase. The %MAC ultimately indicates if the microbial diet is effective in other words, that the microbes are responding positively to the cover crops being utilized.


David emphasized the importance of considering the C:N ratios of cover crops and residues, particularly in determining termination decisions. By matching cover crop species with microbial preferences, farmers can boost microbial activity and nutrient cycling, making better use of crop residues and cover crop biomass. Understanding soil respiration rates guides optimal cover crop termination timings, ensuring that microbial communities are not overwhelmed by high C:N ratios. This approach not only improves soil health but also helps to reduce costs and promote sustainability.


David recommends farmers to home in on the microbial diets to understand the importance of C:N ratios to compliment cash crop production with cover crops.


David Kleinschmidt’s methodology for nutrient management revolves around crediting the mineralization of nutrients from soil organic materials and cover crop biomass. By identifying opportunities to reduce nutrient inputs without compromising productivity, farmers can achieve better net profits while mitigating nutrient loss and limiting input expenses. This approach is particularly compelling for farmers already invested in cover crop systems, offering tangible economic benefits through improved nutrient cycling.

As soil health continues to take center stage in agricultural practices, the integration of comprehensive soil health tests and nutrient management strategies is poised to become increasingly popular among farmers. These innovative approaches not only enhance productivity but also promote sustainability, reinforcing the importance of prioritizing soil health in farming systems.

David Kleinschmidt’s  full presentation can be viewed on ISAP’s YouTube channel. There will be no call in May, happy planting! ICCON calls will continue in June with policy updates and recaps surrounding cover crops. Register for upcoming ICCON call here.  If you are interested in joining the  Illinois Cover Crop On-Farm Network to learn about new research and hear from cover crop specialists across the Midwest, please join our google group by sending an email to 

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Torey Colburn

Torey Colburn is a Conservation Agronomist with American Farmland Trust. Torey is a Certified Crop Advisor who provides conservation and agronomy technical assistance to farmers and landowners. The technical assistance will result in increased farmer participation and engagement in programs and projects that improve productivity, profitability, and sustainability.