Water Quality of Irrigation and Surface Return Flows from Flood-Irrigated Pasture and Alfalfa Hay1
- W. W. Miller,
- J. C. Guitjens and
- C. N. Mahannah2
Pollutants from agricultural irrigation practices continue to require empirical definition. This paper reports results from a 3-yr investigation of pollutants and pollutant loads carried in irrigation and surface return flows from grass pasture (Bromusinermis Leyss, Dactylis glomerata L., Poa pratensis L., Festuca arundinacea Schrib.) and alfalfa hay lands (Medicago sativa L.) to adjacent receiving waters. Irrigation and surface return flows were metered and the volume of infiltrated water determined at four sites during three irrigation seasons. Concentrations of total dissolved solids (TDS), 5-day biochemical oxygen demand (BOD5), nitrate-N (NO3−-N), total N (TN), phosphate-P (ortho PO43−-P), and total P (TP) were combined with flow volumes to compute changes in surface loading per individual irrigation and cumulative throughout the irrigation season. Of those parameters studied, BOD5 and P (PO43−-P, TP) were found to have a net loss from the fields via surface return flow. Statistical relationships among the water quality parameters varied seasonally. Differences were attributed to seasonal changes in irrigation water supply and availability. Levels of constituent contributions to surface runoff appeared to be more related to site characteristics, water management practice, and hydrologic variation than to the presence or absence of grazing animals. Future efforts in water quality management and control should be directed towards quantifying the relationship between water quality as affected by specific management activities, followed by appropriate economic impact assessment of the control measure effects on agricultural productivity.Please view the pdf by using the Full Text (PDF) link under 'View' to the left.
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