Effects of Municipal Wastewater Effluent and Cutting Management on Persistence and Yield of Eight Perennial Forages1
Authors: Marten G. C. , Clapp C. E. , Larson W. E. 
Published: July 2010

Studies of municipal wastewater effluent utilization by perennial forages have not included alternative harvest schemes or long‐term measurements of species yields and persistence at high levels of effluent application. Our principal objective was to determine the persistence and yields of dry matter and feed nutrients of seven cool‐season perennial grasses and alfalfa (Medicago sativa L.) when they were harvested at each of three cutting schedules and received commercial fertilizer (control) or two levels of effluent over a 5‐year period.

Four replications of three soil treatments (control that received well water and mineral fertilizer, and municipal wastewater effluent levels of either ≃ 5 or 10 cm/week) were established on a well‐drained soil having a water table at about 150 cm. Plots of alfalfa, smooth bromegrass (Bromus inermis Leyss.), orchardgrass (Dactylis glomerata L.), Kentucky bluegrass (Poa pratensis L.), tall fecue (Festuca arundinacea Schreb.), timothy (Phleum pratense L.), reed canarygrass (Phalaris arundinacea L.), and quackgrass (Agropyron repens L.) were each harvested at schedules that ultimately included two, three, and four‐time cutting per season.

Failure of alfalfa to persist well in any of the effluent‐treated plots was due primarily to a root‐rot complex that developed by the 2nd year. Vigorous smooth bromegrass stands were severely damaged in effluent‐receiving plots after the second harvest during year 1 (when all plots were cut three times) due to a failure of new tillers to develop; this grass did not recover well thereafter. Tall fescue and Kentucky bluegrass failed to persist well when they were cut twice annually in the presence of high N (control and high effluent level), but both had excellent persistence when they were cut four times annually. Timothy persisted poorly in all treatments, but its best persistence occurred when it was cut four times annually. The species having least variation in persistence among all cutting schedules and soil treatments was reed canarygrass.

Alfalfa, timothy, and smooth bromegrass did not persist sufficiently well beyond the 2nd year to merit consideration as forages for livestock feed in wastewater effluent systems that utilize the levels of effluent we applied in this experiment. Reed canarygrass was either the highest yielding or among the highest yielding species at all cutting schedules in high effluent plots. When all species and cutting schedules during the first 3 years were averaged, high effluent plots yielded 10.5 metric tons/ha (100%), control plots yielded 10.0 (95%), and low effluent plots yielded 8.0 (76%), indicating that effluent applications of at least 10 cm/week during the growing season in temperate regions can lead to maximum yields of forage dry matter and feed nutrients by persistent species.

Reed canarygrass always yielded the most crude protein per hectare, marking it as the best species for removing N from wastewater effluent at both low and high levels of application. If one assumes that the high effluent level is most likely to have practical application in wastewater renovation on grasslands, then reed canarygrass, orchardgrass, or tall fescue should be among the species of choice because they often outyielded the other persistent species (quackgrass and Kentucky bluegrass). if one assumes that the low effluent level is most likely to have practical application, then reed canarygrass or tall fescue should be the species of choice.