Soil resetting is a biological system that fights diseases in the soil and simultaneously strengthens the biology in the soil. "Hence, 'resetting' and not 'disinfecting'," explains Henk Meints. "In theory, it is a little bit more complicated, but the methods are reasonably easy to teach to growers. Also, experience amongst growers is growing steadily. If done properly, there is no better method. There is a solid scientific basis, excellent results are increasingly being achieved and once growers have got a feel for it, they are very positive about it."
Meints is an agricultural scientist specializing in soil disinfection and has been involved in studies on soil improvement and crop protection for years. He gladly explains to us all about is, but for someone not into the topic it quickly becomes complicated. "It is no ordinary field of study, but one way to explain it is as follows," says Meints. "First, Herbie granules are scattered over the land and these are then mixed well with the soil. Herbie is a natural and balanced nutrition for soil bacteria. Bacteria can grow explosively and it has been discovered that good nutrition is really important. Then, the grower seals the ground treated with Herbie, so that the oxygen in the soil falls rapidly and then cannot be replenished from the air. This takes two to four weeks. The first group of bacteria consumes all the oxygen in the covered ground, the second group consumes, for example, the oxygen from sugars, and the third group may even attract oxygen from a variety of compounds. The latter, so-called strictly anaerobic bacteria are responsible for killing off, for example, nematodes and persistent fungal spores. These bacteria occur naturally in the soil, but under normal circumstances, they have almost no chance at all to grow. With good soil structure, they are as a group kept at bay, especially by the first group.
After a while, all the Herbie is transformed into bacteria. At the moment that the soil opened up again, the curtain falls for the anaerobic bacteria: they can not live with the oxygen, they die and from that moment, they serve as a food supply for the recovery of the good soil life. First scientific reports indicate that the restoration of all types takes some time, but it always happens. Research in the US has reported that there are more good types to come back than were originally present. This provides opportunities for continuous cultivation of peonies or helichrysums, for example."
"The bottom line is that you have two results: a soil free of diseases and a soil richer in soil life."
In florticulture, the technique is still pretty exclusive, but thanks to the search for residue-free crops and increasingly greener systems, it is growing vigorously. It has also emerged that with soil resetting, diseases that usually cannot be tackled can be combated. "There are a number of crops, such as peony, campanula and delphinium, which are difficult to grow year after year on the same land. It causes a particular soil fatigue, other than that traced back to only fungi or nematodes. Perhaps because the soil biology selected by a continuous cultivation of the same crop is a too one-sided good soil biology (less species) whereby soil resistance decreases from that soil. With soil resetting, we also aim for this. Another reason is that steaming for smaller growers is a relatively expensive technology and in terms of diseases, inferior results are obtained."
Perhaps the biggest challenge lies in properly sealing the ground. There can be (almost) no oxygen getting in. To that end, Thatchtec, the company behind Soil Resetting, uses airtight films. The working of the soil also sometimes plays a crucial role. Particularly on peat soils, but increasingly also on sandy soils, harrows are used with an additional hydraulically driven roller. This means that the Herbie granules, just like seed, are well covered and become wet, in particular in the top layer, which is needed for the bacteria. And the top layer gets more moisture from the bottom up, thus improving the effect on weeds and diseases in the top layer. In addition, the soil warms up better in that the solar heat is radiated more easily downwards. "In practice, nothing complicated, and experience shows that growers are getting better at it."
This type of rotation in agriculture is relatively new. Increasingly, the system is capturing the attention of scientists and from abroad. Especially when diseases emerge that cannot be addressed in a different way. Because of the complexity of all kinds of soil processes, the system is not immediately easy to understand and probably never will be, emphasises Meints. "There is now proof that it works and that growers are able to to implement it."
Also it is actively considered how the sealing time can be shortened - a demand of cultivation, where the turnover rate is high and steaming offers too little solace. Solutions are sought in, for example, increasing the soil temperature or the use of better products. Yet another development in which Meints himself is closely involved, is the replacement of films in outdoor cultivation with another type of cover. In particular, in windy regions, the use of a film is inhibiting market development. "Now the last and only remaining soil fumigant, Metam sodium has become practically unworkable for the outdoor cultivation since September 2014, this causes extra concern. If we can develop a wind insensitive cover that is relatively easy and practical to apply, that would really help us. And then, it gets really fun and professional," laughs Meints.