Identification of mechanisms influencing nutrient transport on sites containing beef cattle manure

Authors: Gilley, John; Wacha, Kenneth

Submitted to: Journal of Environmental Engineering
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/16/2024
Publication Date: 1/11/2025
Citation: Gilley, J.E., Wacha, K.M. 2025. Identification of mechanisms influencing nutrient transport on sites containing beef cattle manure. Journal of Environmental Engineering. 151(3). Article 04025004. https://doi.org/10.1061/JOEEDU.EEENG-7838.
DOI: https://doi.org/10.1061/JOEEDU.EEENG-7838

Interpretive Summary: This investigation was conducted to identify the mechanisms influencing nutrient transport on sites containing beef cattle manure. The data which was examined was obtained from previously reported field rainfall simulation studies performed on either 2 or 4 m long plots located on cropland areas and beef cattle feedlots in southeast Nebraska. In those studies, inflow was added to the top of experimental plots in four successive increments to simulate runoff rates occurring at greater downslope distances. Runoff rates on the experimental sites ranged from 2.90 to 22.9 L min-1 and equivalent downslope distances varied from 5.3 to 42.3 m. It was observed that nutrient transport rates increased in a linear fashion with runoff rate on sites where beef cattle manure was applied at rates < the annual nitrogen (N) requirement for corn. Two mechanisms were thought to influence nutrient transport under this condition: the quantity nutrients that were released by manure at a particular runoff rate and the amount of overland flow available to transport the released nutrients. Maximum phosphorus (P) transport rates were not affected by runoff rate on sites where beef cattle manure was applied at rates = the annual N requirement for corn and on beef cattle feedlots. The maximum rate at which manure can release P to overland flow had been reached and the P transport rate – runoff rate relation became constant. The maximum rate at which beef cattle manure can release P to overland flow on land application sites can be estimated from the P content of the applied manure. N transport rates were found to vary in a linear fashion with runoff rate on both land application sites and beef cattle feedlots. Further testing of the transport equations is needed at other locations with varying soil, cropping, and management conditions.

Technical Abstract: The application of manure to agricultural areas reduces crop fertilizer expenses and can also improve soil quality. However, water quality concerns may arise if nutrients are transported by runoff to receiving water bodies. Simulated rainfall has been applied to small plots to identify the effects of varying soil, cropping, and management conditions on nutrient transport. In this investigation, a rainfall simulator was used to identify the effects of varying runoff rates on nutrient transport from sites containing beef cattle manure. When nutrient transport rates are related to runoff rates, nutrient delivery to the edge of a field can be estimated. In addition, many of the analytical procedures and computer models used for predicting runoff rates on cropland areas can be expanded to also include water quality constituents. In this investigation it was found that: 1. Phosphorus transport rates increase linearly with runoff rate on sites containing small amounts of beef cattle manure. 2. Phosphorus transport rates do not vary with runoff rate on sites with larger amounts of manure. 3. The maximum phosphorus transport rate can be related to the phosphorus content of applied manure. 4. Nitrogen transport rates increase linearly with runoff rate on sites containing beef cattle manure.