Exploring Substrata Flexibility and Peat Reduction with Wood Fiber in Stratified Substrates

Considerable research has investigated solutions for alternative substrates in reducing horticulture peat applications. Among many options, soilless substrate stratification has been shown to reduce peat inputs by upwards of 50%, and coconut coir and wood fiber are two popular alternatives to peat in many soilless substrates. Most stratified studies have used a pine bark–based substrata; however, scant research has explored substrata variations to promote more flexibility in stratified substrate management decisions. Therefore, the objective of our study was to explore different variations of the top-strata and substrata materials to identify the potential of reduced-peat and no-peat production of greenhouse-grown petunias. A commercial peatlite or coirlite (7:3 blend of peat/coir:perlite by volume) was layered over pine bark or wood fiber (HydraFiber) at a 50/50-by-volume ratio, as well as an unstratified peatlite or coirlite control. Results show that a petunia plant can be produced successfully with equal quality growth using 50% less peat-based media when pine bark or wood fiber is layered below. Moreover, greenhouse petunias can still be grown to salable and marketable quality (with slightly less shoot, root, and flower development) using systems with 100% peat elimination in coir-based unstratified and stratified (coirlite layered over pine bark or wood fiber) profiles. This work provides more options for growers seeking flexible solutions.