Costello, Ryan C.Sullivan, Dan M.Bryla, David R.Strik, Bernadine C.Owen, James S.2020-02-272020-02-272019-060018-5345http://hdl.handle.net/10919/97071Newmarkets for organic northern highbush blueberry (Vaccinium corymbosum L.) have stimulated interest in using composts specifically tailored to the plant's edaphic requirements. Because composts are typically neutral to alkaline in pH (pH 7 to 8), and blueberry requires acidic soil (pH 4.2 to 5.5), we investigated elemental sulfur (S-0) addition as a methodology for reducing compost pH. The objectives were to 1) characterize initial compost chemistry, including the pH buffering capacity of compost (acidity required to reduce pH to 5.0), 2) measure changes in compost chemistry accompanying acidification, and 3) evaluate plant growth and mineral nutrition of blueberry in soil amended with an untreated or acidified compost. Ten composts prepared from diverse feedstocks were obtained from municipalities and farms. Addition of finely ground S-0 reduced compost pH from 7.2 to 5.3, on average, after 70 d at 22 degrees C, and increased the solubility of nutrients, including K (from 22 to 36 mmol((+))/L), Ca (from 5 to 19 mmol((+))/L), Mg (from 5 to 20 mmol((+))/L), and Na (from 6 to 9 mmol((+))/L). Sulfate-S, a product of S-0 oxidation, also increased from 5 to 45 mmol((-))/L. The composts were incorporated into soil at a high rate (30% v/v) in a greenhouse trial to evaluate their suitability for use in blueberry production. Shoot and root growth were strongly affected by compost chemical characteristics, including pH and electrical conductivity (EC). Potassium in compost was highly variable (2-32 g center dot kg(-1)). Concentration of K in the leaves increased positively in response to compost K, whereas shoot dry weight and root growth declined. Leaf Mg also declined in response to compost K, suggesting that elevated K concentrations in compost may cause Mgdeficiency. Composts with the highestKwere also high in total N, pH, andEC. Compost acidification to pH <= 6 improved growth and increased leafMg concentration. On the basis of these results, composts derived from animal manures or young plant tissues (e.g., green leaves) appear to be unsuitable for high-rate applications to blueberry because they usually require high amounts of S-0 for acidification and are often high in EC and K, whereas those derived from woody materials, such as local yard debris, appear promising based on their C:N ratio, compost acidification requirement, and EC.application/pdfenCC0 1.0 UniversalVaccinium corymbosumelemental sulfurmulchdouglas fir sawdustsoil amendmentsArticle - Refereedhttps://doi.org/10.21273/HORTSCI13599-185462327-9834