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Follow-up study of biological soil disinfestation

Published on
June 7, 2012

Biological soil disinfestations using Herbie is seen as a low-energy alternative to steaming. In 2011 Wageningen UR Greenhouse Horticulture studied how the Herbie product affects disinfestation in a company that grows greenhouse vegetables and chrysanthemums. This year the study has a follow-up. Researchers will investigate the effects of adjusting the dosage and stimulating natural micro-biology. The Product Board of Horticulture and the Ministry of Economic Affairs, Agriculture & Innovation (Dutch: EL&I) are financing this study as part of the project ‘Greenhouse as a source of energy’ (Dutch: Kas als Energiebron).

Soil disinfestation

Steaming costs an average of 5 m3 natural gas per m2.  Therefore, an alternative method of disinfestations is preferred. This method showed good results in a test plot at a chrysanthemum grower. For stubborn fungus, such as Verticillium dahliae, the mortality effect was even better than with prolonged steaming with steam drainage. On the other hand, one particular grower of curled endive (Frisée) was disappointed with the results.

Soil resetting

A commonly used term for deploying Herbie is soil resetting.  Herbie is an organic product based on residual flows from the food processing industry. Adding this product to the soil and then covering it with air-tight plastic foil creates an oxygen-free (anaerobic) condition. This condition stimulates the development of soil bacteria that can live without oxygen and when converting into organic products, they produce toxic substances. This can effectively kill many harmful organisms in the soil, such as eels and stubborn soil fungus.

Chrysanthemum

“The test results of using Herbie for disinfestations show that this method has good prospects for cultivation in open fields,” states Daniël Ludeking. “For applying this to the year-round cultivation of chrysanthemum, however, the reliability of the system must be increased and the costs must be reduced in order to make biological soil disinfestations economically feasible. That is why a follow-up study was started this year in which researchers will experiment with a lower dosage. They will also examine the effect of actively introducing soil-specific micro-organisms via a graft produced by the company. The experiment started in week 22 and will run up to the end of week 26.

Field vegetables

The experiment had been repeated last year during the cultivation of curled endive. Since the results in 2011 were disappointing, researchers sought to make adjustments in order to let the process make headway. Here too, they are working with a graft and, in contrast to chrysanthemums, a higher dosage will be applied.

Additional side-effects

In the experiments of last year, various variables related to fertilization and soil life were monitored. All the experiments showed that the application increased the content of nutrients in the soil. This influence on the fertilization can be used effectively on condition that growers take this into account prior to the start of a new crop. In addition, effects were also registered in terms of soil life and soil resistance. These will be monitored in future experiments and conclusions will be made a later stage.