Land Application of Municipal Sewage Waste Water: Yield and Chemical Composition of Forage Crops

Abstract

AbstractAlfalfa (Medicago sativa L.) outyielded four grass species (reed canarygrass [Phalaris arundinacea L.], bromegrass [Bromus inermis Leyss.], Altai wildrye [Elymus angustus Trin.], and tall wheatgrass [Agropyron elongatum Beauv.]) when the forages were irrigated with sufficient lagooned municipal sewage waste water to meet the evapotranspiration minus precipitation deficit (about 50/cm per year). The yields were increased and the yield differential between the alfalfa and the grasses was reduced when additional N was added as fertilizer or by doubling the amount of waste water. The grasses, with the exception of tall wheatgrass, out‐yielded the alfalfa when fertilizer was added at the high waste water level. Since water did not limit growth, yields were controlled by the N supply. Waste water‐N and fertilizer‐N were equally effective in stimulating forage production.Nitrogen yield of alfalfa was double that of the grasses with the unfertilized waste water treatment, and considerably greater than the N yield of the grasses with the other treatments. Nitrogen uptake by all the forages, except tall wheatgrass, exceeded N application by waste water and fertilizer.Phosphorus application, in the waste water or as fertilizer P, exceeded plant uptake. The P content of the forage was unaffected by the treatment; thus, uptake was determined by the yield.Alfalfa was the most suitable forage crop when the system was operated for optimum utilization of the waste water. When high levels of waste water were applied, reed canarygrass removed most of the nutrients while withstanding flooding and higher soil moisture without stands being reduced by winterkilling, as occurred with alfalfa.