Effectiveness of best management practices in improving water quality in a pasture-dominated watershed

Abstract

Abstract:The nonpoint source pollution problem can be controlled by implementing various best management practices (BMPs) in the watershed. However, before such practices are adopted, their effectiveness at various spatial and temporal scales must be evaluated. The objective of this research was to evaluate a suite of BMPs in a pasture-dominated watershed in their effectiveness at controlling nutrient losses. A total of 171 different BMP combinations incorporating grazing and pasture management, riparian and buffer zones, and poultry litter applications were evaluated for their effectiveness using the Soil and Water Assessment Tool (SWAT) model. The SWAT model was parameterized using detailed farm and watershed-scale data. The stochasticity in weather was captured by generating 250 various possible weather realizations for a 25-year period, using measured historical climate data for the watershed. Model results indicated that losses of both total nitrogen, mineral phosphorus, and total phosphorus increased with an increase in litter application rates. For the same application rates, greatest losses were predicted for fall application timings compared to spring and summer applications. Overgrazing resulted in greater nutrient losses compared to baseline conditions for all application rates, timings, and litter characteristics, indicating that overgrazing of pasture areas must be avoided if any improvement in the water quality is to be expected. Variability in weather conditions significantly affected BMP performance; under certain weather conditions, an increase in pollutant losses can be greater than reductions due to BMPs implemented in the watershed. Buffer strips and grazing management were two most important BMPs affecting the losses of total nitrogen and total phosphorus from the pasture areas.

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

“…Better reduction of both nutrients and sediments was obtained from the intact riparian buffers, which are probably the most important conservation practice in this watershed. Chaubey et al (2010) used SWAT and a combination of 171 conservation practices to derive the "Effectiveness of best management practices in improving water quality in a pasture-dominated watershed." By modeling a combination of grazing and pasture management, riparian and buffer zones, and poultry litter applications over a 25-year weather period, results indicated that greater amounts of litter significantly increased N and P losses.…”

Agricultural Best Management Practice Abundance and Location does not Influence Stream Ecosystem Function or Water Quality in the Summer Season

“…However, past studies exploring the relationship between BMPs and stream ecological condition have shown more equivocal results, despite also frequently reporting reduced concentrations of nutrients and sediments associated with BMP use [14,15,[17][18][19][20][21]. To date, past studies have largely focused on taxonomic based measures of community condition, particularly aquatic invertebrates.…”

Climate Change: A Call for Adaptation and Mitigation Strategies

“…However, changes in temperature and precipitation caused by climate change can lead to reduced BMP effectiveness (Woznicki et al, 2011;Woznicki and Nejadhashemi, 2012;Bosch et al, 2014;Woznicki and Nejadhashemi, 2014;Renkenberger et al, 2015). In general, BMPs that utilized plants, such as native grass or cover crops, that produced the greatest reduction in sediment and nutrient loading, were found to be more sensitive to climate change (Chaubey et al, 2010;Woznicki et al, 2011;Bosch et al, 2014;Renkenberger et al, 2015). However, BMPs that utilized structural changes and management operations, such as no tillage and porous gully plugs, that produced lower reductions in sediment and nutrient loading, were found to be less sensitive to climate change (Chaubey et al, 2010;Woznicki et al, 2011;Woznicki and Nejadhashemi, 2012).…”

“…In general, BMPs that utilized plants, such as native grass or cover crops, that produced the greatest reduction in sediment and nutrient loading, were found to be more sensitive to climate change (Chaubey et al, 2010;Woznicki et al, 2011;Bosch et al, 2014;Renkenberger et al, 2015). However, BMPs that utilized structural changes and management operations, such as no tillage and porous gully plugs, that produced lower reductions in sediment and nutrient loading, were found to be less sensitive to climate change (Chaubey et al, 2010;Woznicki et al, 2011;Woznicki and Nejadhashemi, 2012). This results in an overall decrease in BMP effectiveness as the climate continues to change.…”