Nutrient concentrations in leachate and runoff from dairy cattle lots with different surface materials

Authors: Vadas, Peter; Powell, Joseph

Submitted to: Journal of Soil and Water Conservation
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/19/2018
Publication Date: N/A
Citation: N/A

Interpretive Summary: Nitrogen (N) and phosphorus (P) loss from agriculture continues to be a water quality issue, and outdoor lots on dairy farms can have a high loss potential. We monitored hydrology and nutrient concentrations in leachate and runoff from heifer lots constructed with three surface materials (soil, sand, bark mulch). The percent of annual precipitation that leached though plots was most for sand and mulch, but much less for soil lots. Nitrogen amounts in leachate were similar in soil and sand plots, but were less for mulch lots. Soil had the least and sand lots had the most P in leachate, with mulch in between. In runoff from soil lots, erosion amounts often determined how much N and P was lost. In runoff water, the form of dissolved N was mostly ammonium nitrogen. Runoff dissolved P increased slightly over time, with most runoff P when cows were recently on plots. Data show that N and P loss from dairy lots lot are highly influenced by surface material. Information can help producers determine if alternative lot management can help them reduce nutrient loss from outdoor lots.

Technical Abstract: Nitrogen (N) and phosphorus (P) loss from agriculture persists as a water quality issue, and outdoor cattle lots can have a high loss potential. We monitored hydrology and nutrient concentrations in leachate and runoff from dairy heifer lots constructed with three surface materials (soil, sand, bark mulch). The percent of annual precipitation collected as leachate averaged 36% for soil, 79% for sand, and 68% for mulch plots. For soil plots, the percent of annual precipitation collected as runoff ranged from 13% to 51%, with the percent increasing with precipitation. Leachate N in soil and sand plots behaved similarly, with NH4-N much less than NO3-N and total N. Leachate N was generally least from mulch, suggesting more microbial N retention. Soil had the least and sand plots had the most P in leachate, with mulch in between. Leachate P concentrations increased over time for soil and sand plots, but there was no pattern of change for mulch. In runoff from soil plots, particulate N and P were well related to sediment concentrations. Compared with leachate from soil and sand, soil runoff NO3-N was typically less, but was similar to leachate in mulch plots. Conversely, soil runoff NH4-N was typically greater than in leachate for any treatment. Soil runoff dissolved P increased slightly over time, with most runoff P when cows were recently on plots, and was typically greater than in leachate for any treatment. Data demonstrate quite different controls on N and P availability for loss in runoff and leachate based on lot surface material.