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.

Surface-Applied Biosolids Enhance Soil Organic Carbon and Nitrogen Stocks but Have Contrasting Effects on Soil Physical Quality

“…Haney et al [17] found that in 0-30 cm soils increased with application rate, presumably as a result of higher wheel traffic required to land-apply at greater biosolids rates, but not with application duration at the lowest rate [17]. Results from the current study and previous reports are consistent with the variability in soil responses found in other studies on surface-applied biosolids which have reported no effects or increased [12,32,33,40] or decreased due to biosolids application [24,27].…”

“…Soils under long-term application had a C : N of 11.5 ± 0.3, similar to control soils. Measured soil C : N values were within the range of reported values following biosolids applications [6,24,33,37,39] and followed expected decreases in C : N values associated with increasing rates or repeated applications of biosolids [6].…”

“…Site-specific increases in SOC have been reported for application rates as low as 2 to 7 Mg ha −1 yr −1 [24,30]. Field studies following a single application of surface-applied biosolids also report increases in SOC [8,[30][31][32][33].…”

The role of organic amendments in soil reclamation: A review

“…In 2005, Metro Vancouver applied Â15000 Mg (dry wt.) of biosolids to land throughout British Columbia (Wallace et al 2009). The largest use was mine reclamation (78%) with a smaller proportion (10%) for fertilization of degraded rangelands and pastures, mostly in the semiarid southern interior of the province.…”

Sediment, Nutrient, and Bacterial Runoff from Biosolids and Mineral Fertilizer Applied to a Mixed Cool- and Native Warm-Season Grassland in the Ozark Mountains

“…Among the benefits, biosolids provide recycled nutrients to soils and can serve as an alternative or a substitute to costly mineral fertilizers (MF). In addition to providing nutrients, biosolids provide organic matter to soil [4,5], increase infiltration [6], potentially improve soil quality [5,7,8], and increase agronomic productivity [5,7,[9][10][11][12]. Using biosolids as a substitute for MF also helps reduce energy use which would have been associated with production and transportation of MF.…”