Increased interest in peat-alternative substrates has contributed to the development of both regional and global wood substrates. Utilizing different manufacturing equipment to produce wood fiber components allows producers to modify wood fibers/inputs through chipping, milling, heat, pressure, or various combinations, to alter physical properties and yield suitable material for horticulture use. Commercial substrates available for plant production include peat-reduced formulas with various percentages (by volume) of wood fiber. Current lime amendment suggestions to bring substrates into the optimal pH range for plant growth are based on peat as the main component. Wood fiber has variable initial pH across manufactured type and reacts differently to lime amendments compared to peat. To aid in the understanding of lime amendments to wood fiber substrate blends, this study was designed to measure the pre-plant pH response over time of substrates influenced by wood component type, peat inclusion percentage, and dolomitic lime amendment rate. Three types of manufactured wood substrates (hammermilled, screw-extruded, and disc refined) were individually blended with Sphagnum peat at 20% increments (20, 40, 60, 80, and 100%). Each substrate was amended with 0, 4, 8, or 12 lbs/yd3 dolomitic lime and incubated in plastic bags to measure pH change at 0, 1, 3, 5, 7, 14, 21, and 28 days after blending. Resulting pH values indicate dolomitic lime amendment rates will need to be adjusted based on peat:wood volume ratios. Wood fiber exhibited a higher initial pH than Sphagnum peat and within blends, as wood fiber rate increased, pH increased across all lime rates. Dolomitic lime amendments should be closely monitored at 40% volume or more wood fiber. Moderate pH differences were measured between manufactured wood fiber type within the same peat:wood volume ratio and lime rate, emphasizing interchangeability of wood component type.
