Compost Functions as Effective Replacement for Peat-Based Potting Media in Organic Greenhouse Transplant Production

Abstract

Commercial horticulture in many regions of the world depends upon Sphagnum peat as a potting-media substrate, but extracting peat has serious environmental consequences. Composts may be able to serve as effective substitutes for peat and offer potential environmental advantages. The suitability of compost as potting media depends upon the raw materials as well as processing methods used. This study includes two related experiments—one with beet (Beta vulgaris L.) and the other with tomato (Solanum lycopersicum L.)—aimed at assessing the potential viability of farm-produced, food-residuals compost as a replacement for peat-based potting media in the production of organic vegetable transplants. The experiments were conducted in 2021 on the Berea College Farm in Kentucky, USA, a USDA certified organic farm. The results indicated that potting media composed of 75% to 100% compost performed as well as fertilized, peat-based growing media for plant growth. Further, although weeds were present in the compost, weed pressure was not severe enough to adversely affect crop growth. Thus, sterilization of compost, which did eliminate weeds in the compost, was not deemed necessary for using the compost as a partial or complete potting medium. Compost pasteurization was also assessed but was ineffective in destroying weed seeds.