Arwenyo, Beatrice  Varco, Jac J.Dygert, Andrew Mlsna, Todd 2023-12-162023-12-162021-08-04Arwenyo, B., Varco, J. J., Dygert, A., & Mlsna, T. (2022). Phosphorus availability from magnesium‐modified P‐enriched Douglas fir biochar as a controlled release fertilizer. Soil Use and Management, 38(1), 691-702.Print: 0266-0032Electronic: 1475-2743https://hdl.handle.net/20.500.14270/428Arwenyo_Phosphorus_availability_article_2023Phosphorus (P) is one of the essential elements required for plant growth and de velopment. However, worldwide, many agricultural soils can be deficient in P. The use of fertilizers and manures as a source of P can be costly, limited in sup ply in some regions of the world and ecologically unfavourable. Nutrient-enriched biochar has been suggested as a relatively cost-effective and eco-friendly P source. This study investigated P availability from Douglas fir biochar modified with mag nesium chloride and potassium hydroxide solutions only (B), and modified P enriched Douglas fir biochar B50, B100 and B150 corresponding to B treated with 50, 100 and 150  mg P  L−1  solutions of potassium phosphate monobasic. Triple super phosphate fertilizer (FC) and a control treatment without phosphate added (C) used as a reference treatment. Treatments were added to soil in varied amounts to obtain the same P rate of 30 kg P ha−1. Aboveground biomass dry weight yield (R2  = .7) and plant height (R2  = .86) improved with P contents. After harvest, re sidual soil P for the FC treatment was significantly greater than all other treatments (p-value = 1.7848 E-6, R2  = .8). Plant height and aboveground dry weight biomass were greater with B150 compared to B50 at the same total P loading, suggesting that the greater P concentration of the biochar (B150) resulted in less tightly bound P and was therefore more available for plant uptake. This study showed promise of utilizing P-enriched Douglas fir biochar as a slow-release P fertilizer.enAttribution-NonCommercial-NoDerivs 3.0 United Statesnutrient managementP availabilityP-enriched Douglas fir biocharsoil amendmentsustainabilityArticle