Changes in Soil Properties and Enzymatic Activities Following Manure Applications to a Rangeland

Abstract

Manure amendments to rangelands may alter soil functions related to nutrient recycling. We investigated the influence of grazing and cattle manure on soil carbon, nitrogen, Mehlich 3 phosphorus, and activities of alkaline phosphatase and dehydrogenase. Fertilizer treatments (unamended, manure, or urea + potassium dihydrogen phosphate [KH2PO4] fertilizer) were imposed under grazed and nongrazed conditions in a short-grass native rangeland. Manure was applied at rates of – 125 kg N ha-1 and – 42 kg P ha-1, and urea + KH2PO4 was applied at 75 kg N ha-1 and 20 kg P ha-1, respectively. Total aboveground biomass and soil samples at 4 depths (0-200 mm) were collected throughout 2 growing seasons. A controlled environment study also evaluated fertilizer source effects on enzymatic activities at 5 P rates (0-120 mg kg-1 P as manure or urea + KH2PO4). Amendments significantly (P < 0.05) increased extractable P following the second application for the 3 uppermost depth increments. Extractable P was greatest on manure-amended plots, increasing 44% from February 1999 to July 2000 at the surface. However, increases in P extractability as a proportion of total P applied were similar for manure and KH2PO4. Enzymatic activities were significantly (P < 0.001) influenced by sampling date and soil depth. There were no consistent grazing effects on enzyme activities. Amendments did not influence dehydrogenase activities in the field; however, in the controlled environment, activities averaged 16% greater across all rates for manure-amended soil as compared with urea + KH2PO4-amended soil (P = 0.025). Phosphatase activities increased significantly following manure applications under both field (P = 0.007) and controlled environment (P = 0.003) conditions. Elevated phosphatase activities following manure applications probably led to enhanced P mineralization and similar P extractabilities as a proportion of total P applied for manure- and KH2PO4-amended soils. Therefore, when determining applications rates, total manure P should be considered bioavailable.

Soil mineral nitrogen responses following liquid hog manure application to semiarid forage lands

“…Furthermore, almost all of those studies on forage lands have generally been done under moist conditions favorable for plant growth (e.g., Bittman et al 2005;Van Vliet et al 2006). In contrast, little information exists on the effect of manure addition to native grassland soils, particularly in semi-arid regions, except those that have examined responses to cattle manure (Power and Alessi 1971;Stavast et al 2005;Bell et al 2006).…”

“…Most previous studies have assessed varying rates of manure addition for altering production on cultivated lands (e.g., Schmidt et al 2000Schmidt et al , 2001, with fewer studies exploring the same aspects on perennial forage crops (Lowrance et al 1998;Bittman et al 2005;Bell et al 2006;Van Vliet et al 2006) or annual crops intended for forage (Gangbazo et al 1995(Gangbazo et al , 1999. Furthermore, almost all of those studies on forage lands have generally been done under moist conditions favorable for plant growth (e.g., Bittman et al 2005;Van Vliet et al 2006).…”