Should we use soilless media in organic greenhouses?
EC regulation 834/2007 suggests that growing in soil is the only acceptable method in Organic agriculture (OA) both in open field and in greenhouses. Therefore, the use of growing media in OA is forbidden in EU countries and in Israel. This is not the case, however, in China, the US, Canada, Australia, New Zealand, the Gulf States and few other countries. Few exceptions exist even within Europe: several Scandinavian countries allow greenhouse growers to grow crops in natural substrates, assuming that containerized natural substrates are not inherently different from soil. Another acceptable exception, common to all EU countries, is the production of transplants and plants that are grown and sold in pots to the consumer. I intend to question this restriction and to show how, by changing it, organic greenhouses will benefit, without damaging the environment and the logic of OA. There are several main reasons why this regulation should be reconsidered: (1) in many parts of the world, fertile soils are rare or do not exist. Overcoming this infertility requires high fertilization levels, which in addition to its high cost, may lead to percolation and pollution of underground water. Leachates of container-grown plants, on the other hand, can be collected, treated and reused, thus leading to much high water- and nutrient-use efficiencies. (2) The possibility of greenhouse growers to maintain a proper rotation is very limited. This may lead to a rapid infestation of the soil with soil-borne pests and diseases. The few eradication tools available for organic growers are inefficient. By growing the crops in a containerized medium such infestation may be prevented, and, if occurs, the medium can be replaced. (3) By including mature composts, growing media can be fully suppressive to soil-borne diseases. (4) Unlike soil, growing in soilless media is weed-free.
Raviv, M. 2017. Should we use soilless media in organic greenhouses?. Acta Hort. (ISHS) 1164:535-540
greenhouse, growing media, hydroponics, organic agriculture, soil-borne diseases, soilless culture, substrates