Biological soil disinfestation consists of the incorporation of fermented organic material after which the soil is covered with plastic. This results in the release of compounds with a disinfecting effect. These compounds are effectively killing nematodes and persistent soil fungi. This was found in preliminary research by PPO-AGV and Wageningen UR Greenhouse Horticulture. The method needs further development for practical application in chrysanthemum cultivation and other soil-bound cultivations under glass.
Soil steaming to suppress persistent soil-bound pests is frequent practice in chrysanthemum cultivation. This costs much energy; an average amount of some 35.000 m3 gas per hectare is required. And often steam sterilisation is only effective for a restricted number of cultivations, after which serious problems with pests and soil diseases may re-emerge.
Wageningen UR Greenhouse Horticulture is therefore currently working on a new soil disinfestation method as possible alternative for steaming. This method involves the incorporation of an amount of fermented organic material with a known and standard composition. Anaerobic conditions are formed after covering the soil with plastic, which initiates natural transformation processes. These processes result in the release of compounds that have a disinfecting effect on the soil.
Effective but slow
Preliminary research has shown that the disinfesting effect of the methods is impressive. Harmful nematodes, such as the root lesion nematode, and complex survival spores of the Verticillium dahliae wilting disease are killed. The new disinfestation method, however, requires two to four weeks, which is long when compared to regular steaming.
The time required for effective disinfestation is currently still presenting a bottleneck for broad application of biological soil disinfestation in practice. A possible advantage in comparison with steaming is that the disinfectinig effect would hold out over a longer period. Further research is required to answer these and other questions surrounding the new method. Because the method is interesting for all soil-bound cultivations and because much energy can be saved, the research will not only cover chrysanthemums but other soil-bound cultivations as well.