A multivariate analysis of covariance to determine the effects of near-stream best management practices on nitrogen and phosphorus concentrations on a dairy farm in the New York Conservation Effects Assessment Project watershed

Abstract

Near-stream best management practices (BMPs), such as exclusionary fencing or cattle crossings, are often recommended to improve water quality, but quantification of their impacts is limited. Surface and subsurface processes in these near-stream areas impact the contribution of nitrogen and phosphorus to watercourses and the effectiveness of near-stream BMPs. To test the impact of the near-stream BMPs, groundwater samples from 30 piezometers and streamwater samples along two adjacent creeks (one control and one with BMP treatment) were collected over a three-year period before and after installation of exclusionary fencing with a cattle crossing in the Catskill Mountains of New York State. Samples were analyzed for nitrate nitrogen (NO 3 --N), soluble reactive phosphorus (SRP), dissolved oxygen, and dissolved organic carbon. Analysis results and other ancillary variables (rainfall and groundwater table depth) were incorporated into a multivariate statistical model to evaluate the impact of the BMPs on the concentrations of NO 3 --N and SRP in the treatment creek. Results of the analysis indicate that the installation of the near-stream BMPs resulted in a 27% yearly (34% during the growing season) reduction in treatment creek SRP concentrations, while there was little impact on NO 3 --N concentrations. Incorporating the SRP concentrations measured in a nearby control creek and controlling for the effects of groundwater SRP levels and groundwater hydrology (water table height) had a significant effect on the overall analytical model performance. These results indicate that protecting near-stream areas from potentially pollution-causing practices can be an important means of controlling phosphorus levels in water bodies.

Factors Affecting Phosphorous in Groundwater in an Alluvial Valley Aquifer: Implications for Best Management Practices

“…The farm does not have any manure storage so the manure is generally handled and applied daily as a solid and milkhouse wastewater is sometimes added to it for its disposal. In the winter about eighty percent of the manure is spread on the valley bottom lands (average rate of 35 Soil samples taken in the field around the farm in 2004 showed that total P concentrations were above the levels that indicate of high P accumulation in the soil [12].…”

“…The partial years sampled during this study had approximately normal precipitation levels [12]. The average precipitation during the growing season (May to September) and the non-growing season were 596 mm and 661 mm, respectively [46] …”

“…Sampling site B4 was located directly upstream from the confluence with the main stream. More information about stream water quality data and analysis are given in [12]. Piezometers and Creek B were sampled on the same day at 15-day-intervals.…”

“…To protect New York City's water supply, located in the Catskill Mountains of New York State, the New York State Department of Environmental Conservation (NYSDEC) requires that reservoir P levels not exceed 20 μg L −1 [11]. As a result, Best Management Practices (BMPs) have been installed in order to control surface derived nutrient losses to water bodies (e.g., exclusionary fencing and cattle crossing [12], drainage ditch short circuiting [13], vegetative filter strips, [14,15] and other BMPs' types [16][17][18][19][20][21]. Although recent research has shown that groundwater discharge can play a significant role in the loading of dissolved nutrients to surface water [22][23][24], limited research in the Catskill Mountains and elsewhere has been conducted on controlling Soluble Reactive Phosphate (SRP, or orthophosphate <45 µm) contributions from baseflow and groundwater [3,[25][26][27].…”

USDA water quality projects and the National Institute of Food and Agriculture Conservation Effects Assessment Project watershed studies

“…In "A multivariate analysis of covariance to determine the effects of near-stream best management practices on nitrogen and phosphorus concentrations on a dairy farm in the New York Conservation Effects Assessment Project watershed," Flores-Lopez et al (2010) demonstrated using paired field design that stream fencing with a width of 5 m (16 ft) and cattle crossing (same width) reduced annual soluble reactive P loading by 27%, but did not reduce NO 3 -N, probably due to large carbon availability from the dairy waste and saturated soils, which together facilitated denitrification.…”