Minimizing Phosphorus Loss with 4R Stewardship and Cover Crops

Crops: Corn for grain Corn for silage Soybeans
4R Practices: Time Place

Minimizing Phosphorus Loss with 4R Nutrient Stewardship and Cover Crops

Project Summary

Fertilizer timing and placement can have large impacts on P loss. Currently recommended BMPs have focused on sub‐surface fertilizer placement as the recommended method for reducing P loss. In contrast, economic and farm management factors may encourage producers to use surface‐broadcast P applications in the fall. Weather patterns typical of the Great Plains indicate that a shift to fall applications may also reduce P loss from surface applied P fertilizer compared to spring surface applications. We need field-scale data comparing P loss from fall surface applied P fertilizer to sub‐surface spring‐applied P fertilizer so we can make accurate recommendations for the right timing and placement combinations to minimize P loss.

Furthermore, cover crop use may protect against potential increased P loss associated with fall surface‐applied fertilizers, thereby allowing producers wider flexibility in fertilizer management while maintaining minimal P loss. However, we need more information about the effects of cover crops on P loss and the interaction between cover crops and P fertilizer management. Because cover crops can also impact crop yields, we need comprehensive analysis that includes cover crop and fertilizer management impact on multiple agronomic, environmental, and economic factors, including grain yield, N uptake and use, and P uptake and use, input costs, gross return, net return, N and P loss, sediment loss, and runoff volume. Producers and fertilizer dealers recognize the value in this information.

Project Goals:

• Determine the agronomic, environmental, and economic impacts of fall surface‐applied P fertilizer compared to currently recommended BMPs for P fertilizer (spring injected P) and no P fertilizer application in corn‐soybean rotations.
• Determine the agronomic, environmental, and economic effects of winter cover crops in corn‐soybean rotations.
• Determine the interaction of fertilizer management and cover crop use on agronomic, environmental, and economic measures in corn‐soybean rotations.

Project Results:

• Spring subsurface placement of P fertilizer maintains lower dissolved P concentrations in runoff water compared to fall broadcast fertilizer application and resulted in lower total P concentrations.
• Changing P fertilizer management, transitioning from surface broadcast to sub-surface placement, was the most economical methods of reducing P loss.
• Cover crops in a no-till corn-soybean rotation reduce annual sediment loss by 60 to 70%.
• Cover crops increased annual average dissolved and total P losses by 28%, varying greatly by runoff year.

Annual Reports

2014

2015

2016

2017

2020

Publications

• Carver, R. E., Nelson, N. O., Roozeboom, K. L., & Kirkham, M. B. (2020). Species and termination method effects on phosphorus loss from plant tissue. Journal of Environmental Quality, 49(1), 97-105. Read More