Submitted to: Journal of Environmental Quality
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/26/1996
Publication Date: N/A
Interpretive Summary: Many dairy farmers in the northeastern U.S. are are starting to use management intensive grazing (MIG) to reduce equipment and fuel costs and increase farm profitability. But the uneven recycling of nitrogen through feces and urine on pasture can increase nitrogen leaching to the groundwater beneath this type of grazing. We measured nitrogen leaching loss from urine and feces beneath a pasture grass using 2 foot diameter by 3 foot deep intact soil cores. We found that about 20% of the total nitrogen applied to our soil cores in animal excreta leached beneath the root zone and could contaminate the groundwater. If farmers in the northeast U.S. continue to increase utilization of MIG, the amount of N leached to the groundwater from beneath urine patches could contaminate groundwater if not mitigated by improved grazing management currently being developed.
Technical Abstract: While management intensive grazing (MIG) has the potential to increase dairy farm profitability in the northeast U.S., the uneven recycling of N through feces and urine can increase NO3-N leaching. We measured NO3-N leaching loss from urine and feces beneath N-fertilized orchardgrass using 60 cm diameter by 90 cm deep drainage lysimeters. Averaged over the three years of the study, NO3-N losses were 1.17, 1.68, 22.0, 24,0, and 31.5 g m-2 for the control, feces, and spring, summer, and fall applied urine. These loses represent about 2 percent of the N applied in the feces and about 18, 28, and 31 percent of the spring, summer, and fall applied urine N. If dairy farmers in the northeast U.S. continue to increase utilization of MIG, the amount of N leached to the groundwater from beneath urine patches could become substantial if not mitigated by improved grazing management currently being developed.