Counteracting effects of a pesticide-free cultivation system on soil microorganisms, meso- and macrofauna

Agricultural practices have historically diverged into two main paradigms: intensively managed cropping systems which rely on mineral fertilizer and pesticides to ensure high and stable yields and organically managed systems which prioritize environmental protection at the risk of significant yield gaps. The project ‘Sustainable agriculture 4.0 without chemical-synthetic plant protection’ aims to develop a hybrid cultivation system designed to be pesticide-free, yet productive. In this system, pesticides are substituted by mechanical weeding, while mineral fertilizers are applied at adjusted rates to maintain yields comparable to conventional practices. Additionally, two seeding techniques, standard and equidistant, were evaluated. Using a large-scale field experiment, we compared conventional practices with our novel approach examining soil microbial, meso- (springtails, predatory mites), and macrofauna (earthworms) abundance in the first four years after treatment establishment. We found that pesticide-free practices had counteracting effects on different soil organism groups. While soil microbial abundance and activity remained consistent across cultivation systems, springtail abundance showed a slight increase under pesticide-free management. Conversely, the mechanical weed control used to substitute pesticides harmed earthworm abundance and biomass. These counteracting effects were further enhanced in new systems under the equidistant seeding technique. Our results suggest that pesticide-free practices do not uniformly affect soil organisms after four years of field experiment. Specifically, the mechanical weeding required to substitute pesticides, may harm some soil organisms and, therefore, necessitate a more nuanced view on developing sustainable cultivation systems.