Växtföljder vid ekologisk odling i växthus

Summary

In June 2018, the EU decided on a new regulation for organic production (2018/848) that gained force on January 1, 2022. The new regulation demands that also greenhouse production must take place in natural soil that is in contact with the subsoil. In addition there must be a crop rotation containing a legume and a green manure crop. In this two-year-long project funded by the Swedish Board of Agriculture, the consequences of the new legislation were evaluated. We employed three short (one-year) vegetable crop rotations, grown year-round in low-tech polytunnels. The trial was conducted on a field certified for organic production in Scania in 2021-2023. The rotations included cucumber as the main crop, sugar pea as a nitrogen-fixing legume, common rue and Japanese radish as an agroecological service crop and leafy vegetables. The rotations were evaluated in terms of agronomic factors, nutrient dynamics, microbial diversity and activity, as well as disease incidence.
We found that a two-year trial period provides indications, but allows only limited long-term conclusions after such a short term of observation. Low-tech cultivation with short crop rotations led to limited yields. Common rue as an agro-ecological service crop is not a suitable crop when grown during autumn. No negative effects by common rue on the next crop were observed in the autumn cultivation. Crop rotation related diseases were not notably present. Soil pH and plant available phosphorus increased over time, as did microbial activity. Microbial activity was influenced by the crop grown, but there were no differences between crop rotations. Alpha-diversity in bacterial and fungal communities was high in all rotations. During the short observation period no differences between the crop rotations could be found (beta-diversity).