Modification of Switchgrass Substrate pH Using Compost, Peatmoss, and Elemental Sulfur

Abstract

Switchgrass (Panicum virgatum) biomass is being evaluated as a potential alternative to pine bark as the primary potting component in containerized nursery crops. Substrates composed entirely of switchgrass have higher pH than what is considered desirable in container substrates. The objective of this research was to evaluate the influence of elemental S, sphagnum moss, and municipal solid waste compost (MSC) as amendments for reducing substrate pH and buffering it against large changes over time. Three experiments were conducted; the first two experiments were conducted using annual vinca (Catharanthus roseus ‘Pacifica Blush’) to quickly assess how pH was affected by the three amendments, and the final experiment was conducted with blueberry (Vaccinium corymbosum ‘Duke’) to assess the long-term effects of substrate amendments. Summarizing across the three experiments, elemental S was effective in reducing substrate pH; however, rates 1 lb/yard3 or greater reduced pH below the recommended level of 5.5 and lower S rates did not maintain lowered pH over time. Sphagnum moss and MSC together at 20% and 10% (v/v), respectively, were effective at reducing substrate pH and buffering against change. Sphagnum moss and MSC provided the additional benefit of improving physical properties of the switchgrass substrates.