Soil microbial populations, community composition, and activity as affected by repeated applications of hog and cattle manure in eastern Saskatchewan

A field site near Humboldt, Saskatchewan, was annually treated with hog or cattle manure and cropped to canola, spring wheat, barley, and canola from 1997 to 2000. During each growing season, soil was analyzed for microbial populations in terms of activity and community structure, and crops were assessed for root rot and foliar diseases. Microbial activity in soils treated with cattle manure was higher than in soils treated with hog manure or urea. Similarly, nitrous oxide emissions from soil increased with increasing rates of hog and cattle manure. Potential human pathogens, including Rahnella, Serratia, Proteus, Leclercia, and Salmonella species, were identified in soils that received cattle manure, whereas pseudomonads were the dominant species in the hog-manure-treated soil. Fecal coliforms were confirmed in soils that received hog or cattle manure. However, Enterobacteriaceae populations were 10-fold higher in soils receiving cattle manure than in soils receiving the other treatments. Increasing cattle manure rates increased fecal coliform population, but there was no indication that increased hog manure rates increased fecal coliform populations. Addition of urea, hog manure, or cattle manure to the soil did not increase foliar disease in wheat, barley, and canola and had variable effects on root rot incidence in cereals.