Yields of Forages Irrigated with Wastewater and the Fate of Added Nitrogen-15-Labeled Fertilizer Nitrogen1
- J. B. Bole,
- W. D. Gould and
- J. A. Carson2
Irrigation of legume and nonlegume forage species with municipal waste water at rates designed to approximate and double the net evapotranspiration minus precipitation deficit was studied for 11 yr at Taber, Alberta, Canada. The soil was a Brown Chernozemic Cavendish loamy sand (Aridic Haploboroll). Reed canarygrass required additional N to give yields similar to those of the alfalfa (Medicago sativa L.). Alfalfa yields were not greatly affected by increasing levels of N and P fertilizer or by the application of excess wastewater. The N uptake by reed canarygrass (Phalaris arundinacea L.) was considerably less than that of alfalfa when the N supply was limited, but about the same when the N supply was adequate. Reed canarygrass recovered nearly 50% of applied fertilizer 15N over 2 yr with about 80% of total uptake in the first cutting after N application. Alfalfa only recovered 24% of applied N at low irrigation rates and 14% at the higher rate. Estimates of fertilizer N uptake based on the increase in N yield of reed canarygrass due to fertilization would have been much higher. About 25% of the fertilizer N remained in the soil after two irrigation seasons, independent of forage species or irrigation rate. Sixty percent of that N remained in the surface 15 cm. Losses of N from alfalfa were nearly double those from reed canarygrass plots. Wastewater irrigation did not lead to levels of any element phytotoxic to plants or harmful to animals consuming the forage and probably increased the nutritional quality of the forage.Please view the pdf by using the Full Text (PDF) link under 'View' to the left.
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