Raviv, M., Ministry of Agriculture and Rural Development, Agricultural Research Organization, Newe ya'Ar Research Center, PO Box 1021, Ramat Yishay, Israel

Organic greenhouse production is an intensive, high-input operation, with limited possibilities for crop rotation. For these reasons crops are at a constant risk of damage or even total loss caused by soil-borne diseases (SBD) and/or nematodes that can rapidly proliferate under these conditions. Important tools to counteract these risks such as grafting on resistant rootstocks and the use of resistant cultivars are beyond the scope of the current paper. This paper deals with soil-related, nonchemical methods to minimise such risks. These methods include the use of pathogen eradication techniques, such as steaming and soil solarization, alone or in combination with toxic volatiles such as ammonia and glucosinolates (biofumigation), and enriching the soil with composts and other types of organic matter that can serve as carriers for beneficial microorganisms and can induce systemic plant resistance. Normally, beneficial microorganisms cannot act without adequate carriers. The use of thermal treatments, with or without biofumigation, although efficient in the short term, may have a detrimental effect on soil biota and must be accompanied by suitable correction measures, aimed at restoring soil microbial activity. It is well established that well-cured, mature composts, applied at the appropriate dose can turn many soils suppressive to a wide variety of SBDs. High application rates that are not feasible while growing field crops and orchards can be used economically in greenhouses. In addition to their soil-health effect, these composts improve soil physical characteristics and contribute a significant amount of slow-mineralising nutrients. In order to maintain soil health, compost applications must be repeated annually, but subsequent application rates should be lower and must rely on soil analyses.