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This article in JEQ

  1. Vol. 38 No. 1, p. 291-298
    Received: Nov 15, 2007

    * Corresponding author(s): brian.wallace@gov.bc.ca
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Biosolids Increase Soil Aggregation and Protection of Soil Carbon Five Years after Application on a Crested Wheatgrass Pasture

  1. Brian M. Wallace *a,
  2. Maja Krzica,
  3. Tom A. Forgeb,
  4. Klaas Broersmac and
  5. Reg F. Newmand
  1. a Faculty of Land and Food Systems, Univ. of British Columbia, Vancouver, BC, V6T 1Z4 Canada
    b Agriculture and Agri-Food Canada (AAFC), Pacific Agri-Food Research Centre, Agassiz, BC, V0M 1A0 Canada
    c AAFC, Kamloops Range Research Station, Kamloops, BC, V2B 8A9 Canada
    d Research Branch, BC Ministry of Forests and Range, Kamloops, BC, V2C 2T7 Canada


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.

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