Yields of Forages Irrigated with Wastewater and the Fate of Added Nitrogen‐15‐Labeled Fertilizer Nitrogen¹

Abstract

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 sativaL.). 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 arundinaceaL.) 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.

Effect of fertilizer rate and water irrigation quality on the recovery of 15N-labeled fertilizer applied to Sudangrass

“…Very few data are published on the effects of treated wastewater on the balance sheet of the N fertilizer supplemented. In their study concerning the fate of N in a system irrigated with wastewater, Bole et al [7] noted that Reed canarygrass recovered nearly 50% of applied fertilizer 15 N over 2 years with about 80% of total uptake in the first harvest after N application. Alfalfa only recovered 24% of applied 15 N at a low irrigation rate and 14% at a higher rate.…”

Cutting frequency and stubble height of reed canary grass (Phalaris arundinacea L.): influence on quality and quantity of biomass for biogas production

“…Reed canary grass (RCG), Phalaris arundinacea L., has been extensively used as a catch crop for nutrients in land treatment of waste water. The RCG crop is irrigated with pre‐treated waste water and often cut several times per year (Marten et al ., 1979; Linden et al ., 1981; Bole et al ., 1985; Talik, 1985; Vymazal, 1995). Because of the pathogenic risks and high mineral content, the herbage produced from such a crop is suitable neither as fodder nor as raw material for combustion.…”