Biochar and ash, both as separate products and including ash as a component of biochar, are produced as by-products from thermochemical decomposition and bio-energy generation processes such as combustion, gasification, or pyrolysis. The addition of biochar to improve nutrient uptake and retention has been studied in various settings and with a variety of crops. However, biochar, when applied without other treatments, has often been found to have limited impact on crop yields in Canadian prairie soils. This study aimed to determine the effects of biochar amendments, with and without added phosphorus fertilizer, on soils and crops in the Canadian prairies as related to crop yield, phosphorus uptake and recovery, soil phosphorus retention, water dynamics and phosphorus loss in leachate and runoff. This thesis reports on studies undertaken in 2022 with biochar and phosphorus fertilizer amendments on nutrient poor soils from the brown and black soil zones in southern Saskatchewan (controlled environment study) and from the brown soil zone at a site near Central Butte, Saskatchewan (field study). Under optimal conditions of the growth chamber, biochar derived from canola hull, manure and willow feedstocks were shown to contribute some available P for plant uptake, with observed recovery of applied biochar P being at best about 50% of Triple Superphosphate fertilizer. The biochars increased residual P in soil in both chamber and field depending on feedstock, with manure and willow biochars as well as the meat and bonemeal ash being the most effective, but the effects of biochar amendments on crop yield were variable, leading to the conclusion that the effects are at least partly related to the biochar feedstock and production conditions, as has been shown in many other studies on biochar. An important benefit of biochar amendment observed in the study was increased phosphorus retention in soil that contributed to increased post-harvest labile P as well as reduced leaching and snowmelt runoff export. To a lesser extent the biochars contributed to increased water holding capacity and water infiltration. The results of this study indicate that biochars and ash can potentially benefit canola and wheat production, by enhancing P nutrition and recovery, and that a balance may be obtained between biochar supplying P during the growing season while at the end of the season reducing P loss in the spring snowmelt runoff or during leaching events. Biochar added at 10 tonnes per ha showed the best performance in terms of agricultural improvement potential under both controlled environment and field conditions when applied to brown and black chernozem soils from southern Saskatchewan
