3rd UF Water Institute Symposium Abstract

Submitter's Name Runbin Duan
Session Name Posters - Efficacy of Nutrient Source Control Strategies 2
Category Efficacy of nutrient source control strategies
Poster Number 8
Author(s) Runbin Duan,  Soil and Water Science Department, University of Florida (Presenting Author)
  George Hochmuth,  Soil and Water Science Department, University of Florida
  Wendy Graham, Agricultural and Biological Engineering Department, University of Florida
  Don Graetz, Soil and Water Science Department, University of Florida
  Long-Term Nitrate-Nitrogen Trends in Groundwater and Soil at a Dairy Farm in the Suwannee River Basin
  Potential nitrate pollution to groundwater has been an important concern at dairy farms in the Suwannee River Basin, Florida for many years. Various best management practices (BMPs) have been developed to reduce nitrate leaching from dairy farms. However, little information is reported on trends of nitrate-N at a dairy farm scale before and after implementing BMPs. The objective of this study was to determine long-term trends of nitrate in groundwater and soil from 2000 to 2007 including pre-BMP and post-BMP periods. One of four planned BMPs, rotation grazing, was implemented since 2004. Twenty one wells were installed at different representative points to monitor the groundwater quality at the dairy farm. Soil samples were taken to the depth of the continuous clay layer on a 5-week basis at locations providing a representative coverage of the various farm components. Mann-Kendall trend analysis was employed to determine the trends in nitrate-N and the change degree after detecting seasonality. Notched box plots indicated that there were significant differences between median soil nitrate-N at sprayfield, pasture, and cattle holding areas, and between median groundwater nitrate-N under different land uses. An increasing trend of nitrate-N was observed in pasture and sprayfield soils while an insignificant trend was observed in animal holding area soils. Nitrate-N in all three soils varied with change of season. An increasing trend of nitrate-N in groundwater was observed under intensive area and sprayfield, a decreasing trend of nitrate was observed under drainage area, and an insignificant trend was observed under pasture. Nitrate in groundwater under different land uses showed seasonal variance with concentrations greater than 10 mg/L. Spearman analysis did not show strong relationships between groundwater nitrate and rainwater, and between soil nitrate and rainwater. Comprehensive BMPs are strongly recommended to control nitrate leaching at dairy farms with similar field conditions.