Biochar Amendments to Improve Soil Phosphorus Fertility and Retention in Canadian Prairie Soils

The utilization of biochar, a carbonaceous substance derived from pyrolysis, has been extensively investigated in various agricultural settings. However, applying biochar to Canadian prairie soils without additional fertilizer treatments generates minimal benefits for crop productivity. This study investigated the effects of biochar amendments, with and without addition of Triple Superphosphate (TSP) fertilizer, on phosphorus (P) availability and retention in Canadian prairie crops and soils. Specifically, the study assessed crop yield, P uptake and recovery by canola plants, soil P retention, infiltration rates and P losses in simulated snowmelt runoff. Controlled environment and field studies were conducted with biochar and TSP fertilizer on nutrient deficient soils in the Saskatchewan Brown and Black soil zones. Under both growth chamber and field conditions, biochar derived from canola hull, manure, and willow feedstocks were shown to contribute some available P for plant uptake, with observed recovery of biochar P by canola up to ca. 50% of that found for TSP fertilizer. Among these biochar feedstocks canola meal biochar was least effective in supplying plant available P in the year of application. Willow biochar applied alone, or co-applied with TSP, may be an effective strategy for reducing P losses in snowmelt runoff compared with TSP alone and willow biochar also contributed to increased water infiltration. Biochars can potentially benefit canola production by enhancing P nutrition and recovery. Moreover, a balance may be obtained between biochar supplying P during the growing season, while reducing P losses in the spring snowmelt runoff.