Get reliable rangeland science

The land application of biosolids (composted sewage solids) has been shown to improve forage production on semi-arid grasslands. In 2002, an experiment was established on a ranch in the central interior of British Columbia to evaluate the long-term effects of a one-time biosolids surface application on grassland soil quality and the plant community. Two treatments were evaluated: surface biosolids application at 20 Mg ha-1 and a control (no biosolids). Both treatments were replicated in four blocks which were excluded from grazing. Soil samples were collected in April, June, August and October 2016, while plant species composition and above ground biomass were assessed in June 2016. Fourteen years following the biosolids application, aboveground plant biomass was almost two times greater on treatment with biosolids application than on control. Despite differences in aboveground biomass there was no difference in total soil C. However, biosolids amended soil did exhibit significantly stronger aggregates in the October sampling event (though not in the other three sampling events), and a greater ability to retain soil water at high tensions. Available P was the only macronutrient that was significantly higher in the biosolids treatment 14 years after application relative to the control. The increased soil water and nutrients from the biosolids may have benefitted an exotic agronomic perennial, Kentucky Bluegrass, which now covers 25.83 �13.83% of the biosolids blocks and 0.13 �0.13% of the control. This study showed that a single biosolids application led to greater forage yields and improved aspects of soil quality 14 years following that application; however, this also led to a change in plant species composition, which may be less desirable from a restoration perspective.