24 ORGANIC AMENDMENTS, SUCHas manure, are a double-edged sword for grain farmers. They obviously boost crop performance through providing both plant-available nutrients and adding organic matter to the soil. “However, these amendments can be a serious environmental concern when improperly managed, especially with regard to phosphorus (P),” explains Dr. Paul Voroney, professor at the University of Guelph, School of Environmental Sciences. “Runoff from farmland with significant amounts of P continues to receive attention due to the critical impact this nutrient can have on water quality.” Organic amendments, which typically contain high concentrations of calcium and P in addition to organic matter (OM), affect soil P chemistry by altering both the amounts and distribution of the various forms of P. But much more needs to be learned about just how they govern the chemistry of P in soil. In 2019, Voroney began more research in this area, with colleagues Dr. James Longstaffe at University of Guelph, Dr. Tiequan Zhang at Agriculture and Agri-food Canada, and Dr. Yuki Audette, a special graduate faculty at the University of Guelph. The research is being conducted by PhD candidates Busayo Kodaolu and Ibrahim Mohammed. The project will finish in 2024. Soil health and phosphorus efficiency MANAGEMENT OF ORGANIC AMENDMENTS Treena Hein BUSAYO KODAOLU, PH.D. STUDENT, SCHOOL OF ENVIRONMENTAL SCIENCE, IS CONDUCTING RESEARCH INTO ORGANIC AMENDMENTS UNDER THE SUPERVISION OF DR. PAUL VORONEY. COURTESY DR. PAUL VORONEY. Research ONTARIO SCENARIO Most soils in southern Ontario are calcareous (rich in calcium carbonates). The fate of inorganic P (applied in fertilizer) is very much controlled by chemical reactions with calcium carbonates, iron, and aluminium oxides. A variety of calcium-phosphate (CaP) compounds are formed, and the majority of these are what is called ‘stable’ and not available to plants. Overall, of the fertilizer applied each year, only 15 to 20 per cent of the P is taken up by plants. The remainder accumulates and is converted into stable forms and adsorbed to soil particles which can be lost in erosion runoff outside the growing season. The good news is that in greenhouse studies, Voroney and his colleagues have found that
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