title: Biosolids increase soil aggregation and protection of soil carbon five years after application on a crested wheatgrass pasture.
abstract: Biosolids application to rangelands and pastures recycles nutrients and organic matter back to soils. The effects of biosolids (20 and 60 dry Mg ha(-)(1)) and N+P fertilizer on soil aggregate stability, bulk density, aeration porosity, and total C and N of stable aggregates were evaluated 4 and 5 yr after surface application to a crested wheatgrass [Agropyron cristatum (L.) Gaertn.] pasture in the southern interior of British Columbia (BC). The experiment was established in 2001 in a randomized complete block design with four replications. The 60 Mg ha(-1) biosolids treatment (Bio 60) had a greater aggregate mean weight diameter (MWD) and proportion of water-stable soil aggregates > 1 mm relative to the control and fertilizer treatments. Temporal variation in aggregate stability was attributed to seasonal variations in soil water content. Surface application of 60 Mg ha(-1) of biosolids increased C concentrations within water-stable aggregates relative to the control from 29 to 104, 24 to 79, and 12 to 38 g kg(-1) for the 2 to 6, 1 to 2, and 0.25 to 1 mm size fractions, respectively. The concentration of N within aggregates increased in similar proportions to C. Neither soil bulk density, nor aeration porosity were affected by biosolids application. Increased aggregation and the accumulation of soil C within aggregates following biosolids application creates a potential for better soil C storage, soil water retention, nutrient availability, and ultimately the overall health of semiarid perennial pastures.
authors.affiliation: Faculty of Land and Food Systems, University of British Columbia, Vancouver, BC, V6T 1Z4 Canada. brian.wallace@gov.bc.ca
authors.forename: Brian M
authors.initials: BM
authors.lastname: Wallace
authors.forename: Maja
authors.initials: M
authors.lastname: Krzic
authors.forename: Tom A
authors.initials: TA
authors.lastname: Forge
authors.forename: Klaas
authors.initials: K
authors.lastname: Broersma
authors.forename: Reg F
authors.initials: RF
authors.lastname: Newman
mesh_terms: D031702:Agropyron; D001955:British Columbia; D002244:Carbon / Q000032:analysis*; D005308:Fertilizers; D009584:Nitrogen / Q000032:analysis*; D016062:Porosity; D012621:Seasons; D012722:Sewage; D012987:Soil / Q000032:analysis*; D013997:Time Factors
chemical_list: D005308:Fertilizers; D012722:Sewage; D012987:Soil; D002244:Carbon; D009584:Nitrogen