Rising phosphorus levels within field soil has been a topic of concern, particularly in some dairy regions of the country. Our dairy checkoff team of environmental scientists, in partnership with Amir Sadeghpour from Southern Illinois University and his graduate students, approached this subject head on and is pleased to share the results of some recent research on manure management.

The Journal of Agriculture and Food Research published our first paper titled “Influence of manure injection versus surface application on corn for silage and winter rye yield, quality, phosphorus balance, and soil test phosphorus.”

This study was completed over three years on an Illinois dairy farm and took a deep dive into manure application rate (nitrogen-based versus phosphorus-based), application method (surface applied versus injected), and cover crop presence (with or without cereal rye cover crop) to generate solutions for soil phosphorus management.

Here are two outcomes from this research I want to share:

• Phosphorus-based manure offers benefits to soil and environment: By switching from the common nitrogen-based manure rate to a phosphorus-based manure rate for field application, soil phosphorus buildup is kept at a manageable level. The phosphorus-based manure provides vital nutrients to the soil without adding an overabundance of phosphorus. More supplemental nitrogen will be needed to ensure optimum yield in this system. Best management practices for supplemental nitrogen can further improve environmental and agronomic outcomes in this system.
• Changes to manure application method can improve agronomic and environmental impacts: Advances in technology within manure application allow for manure to be injected beneath the soil instead of broadcasted to the surface. When applied on surface, manure needs to be immediately incorporated into the soil, otherwise most of the inorganic nitrogen in manure will be lost via ammonia volatilization. Manure injection eliminates the need for additional tillage for incorporating manure into the soil and prevents ammonia volatilization. Manure injection also decreases the amount of nutrient run-off when compared to surface application. This means manure injection can work in tandem with no-till and cover crop fields to preserve soil health and minimize nutrient pollution.

Although the implementation of manure injection versus the traditional “spreading” is more expensive, many individual watersheds may incentivize manure injection. Farmers can reach out to local and state government agencies, soil and water conservation districts, Natural Resources Conservation Service offices, or extension offices to determine if their watershed has dedicated funding for this practice.

This project is just one piece of the puzzle, with additional studies being conducted to continue developing environmental stewardship practices for our nation’s dairy farms. These research-based tools will support the strong environmental legacy of U.S. dairy farmers, who work diligently to make strides in reducing the environmental impact of dairy production through practices that best work for their production system.

By continuing to partner with researchers and harnessing the power of innovation, I am optimistic about the environmental initiatives the checkoff and the other dairy industry partners can help develop for farmers, driving the industry toward greater sustainability and efficiency.

Solutions backed in sound science will assist farmers in overcoming challenges and adhering to environmental regulations while satisfying growing consumer expectations for dairy products produced responsibly and with environmental awareness.