Evaluation of Buffers to Improve the Quality of Runoff from Irrigated Pastures

ABSTRACT:

Non grazed, vegetated buffer strips are often recommended as best management practices to protect waterhodies from sediments and nutrients in runoff from grazed pastures. The objectives of this study were to characterize levels of nitrate/nitrogen (NO3-N), total phosphorus (Total P), and total suspended solids (TSS) in runoff and evaluate the potential water quality improvements from 10 m buffer strips on irrigated Sierra Nevada foothill pastures. We found that 15% and 69% of irrigation water applied to sprinkler and flood irrigated pastures became runoff, respectively. There were distinct temporal patterns of constituent concentration in runoff during irrigation events having ramifications for effective water quality monitoring and study design. The 10 m buffer did not significantly reduce concentrations and loads of NO3-N in runoff from sprinkler and flood irrigated pastures. The buffer also failed to reduce Total P concentration under either irrigation schemes, or Total P and TSS load under sprinkler irrigation. The buffer did reduce TSS concentration under both irrigation schemes, TSS load under flood irrigation, and Total P load under flood irrigation. These results reflect the effectiveness of buffers during the first year following buffer establishment. Improved irrigation efficiency to reduce runoff generation is perhaps the most readily acceptable and practical first step for reducing the potential for negative water quality impacts from these systems.