Changes in pH an physical properties of pine bark substrates amended with parboiled rice hulls and the growth of container-grown shrubs during long-term nursery crop production.

摘要

The most common compowent of soil-less container media used by the nursery industry in the East Coast, Midwest, and Southern United States is loblolly pine (Pinus taeda L.) bark (PB). The decline in the availability of PB supplies and increasing prices have caused concerns in the nursery industry. Rice (Oryza sativa L.) hulls are a relatively sustainable container substrate and are normally considered a waste by-product of the rice industry. Numerous studies have evaluated different forms of rice hulls as alternative substrates in propagation, greenhouse, and nursery production. However, no studies have evaluated the effect of parboiled rice hulls (PBH) as an amendment for PB-based container media in the long-term container production of ornamental plants. Research was conducted to evaluate the effect of PBH as an amendment to PB-based container substrates on the growth of Spiraea x bumalda L. 'Anthony Waterer' and Abelia x 'Rose Creek' and to examine the changes in pH and physical properties of the substrates during long-term production cycles under outdoor nursery conditions. Six substrates were formulated by blending PB with 0%, 20%, 40%, 60%, 80%, or 100% PBH (by volume). Substrate composition had an effect on plant growth components evaluated, generally decreasing growth as the amount of PBH increased. However, amending PB with up to 40% PBH did not result in a significant decrease in plant growth or increase the volume or frequency of irrigation for container-grown spirea and abelia. Substrate pH generally decreased over time. Physical properties of substrates amended with PBH improved over time. Based on these results, PB-based substrates amended with up to 40% PBH retained physical properties that were generally within current guidelines for nursery container substrates after one (25 and 20 weeks) and two (67 weeks) growing seasons.