Soil is the most important resource for the production of food. The multitude of microorganisms (bacteria, fungi) in the soil (soil microbiota) are involved in almost all soil processes and are therefore of enormous importance for soil fertility and thus for plant growth and health. Microorganisms not only provide the nutrients necessary for plant growth, but also help the plant to cope better with stress conditions.

In order to utilise the useful potential of the soil microbiota in agricultural practice, a better understanding of the influence of cultivation measures on the soil microbiota is necessary. This is the aim of the DiControl project. The influence of tillage, fertilisation regime, previous crop and the application of beneficial microorganisms on the microbial community in the soil and in the rhizosphere was investigated in long-term trials.

The rhizosphere is the space in which the plant interacts with the soil and its microorganisms. The project focussed on the interaction of the plant with the microbial community in the rhizosphere and its influence on plant growth and health. The experimental sites included the long-term trial at Anhalt University of Applied Sciences in Bernburg and the ‘Arable Farming Systems’ demonstration site at HU Berlin in Thyrow.

Each site's soil is characterized by a specific microbial community. Cultivation measures such as tillage, fertilization regime and previous crop change these communities. Compared to conventional N fertilization and ploughing tillage, non-rotational tillage and reduced N fertilization showed a higher microbial biomass in the soil. This had a positive effect on plant growth and health. Organic compared to mineral fertilization also promoted plant health. Changes in the soil microbiota were also observed due to the previous crop with regard to the occurrence of fungal genera with known plant pathogens. Maize, for example, leads to an accumulation of Septoria in the soil, while the previous crop rapeseed supports Verticillium. Cultivation measures influence the microbiota of the rhizosphere. Its composition and complexity differs significantly from that in the soil, as the plant exerts a selective influence. The plant selects certain microorganisms from the soil via root exudates and supports specific communities in the rhizosphere.

Project results show that tillage in particular changes the profiles of root exudates. For example, winter wheat excretes a higher amount of bioactive secondary metabolites in the soil under non-rotational tillage. The resulting change in plant-microorganism interaction in the rhizosphere had a positive effect on plant health. Analyses of physiological stress indicators underline the higher tolerance of these plants to stress factors. The positive effect of beneficial microorganisms on the plant has been proven many times, but varying effects are often reported under field conditions. A prerequisite for a positive effect of applied beneficial microorganisms on the plant is their establishment in the rhizosphere. As part of the project, the effect of a consortium of three beneficial microorganisms (Bacillus atrophaeus ABi03, Pseudomonas sp. RU47, Trichoderma harzianum OMG16) was investigated as a function of cultivation practice and the year of cultivation at a site. Regardless of these factors, the individual microorganisms successfully established themselves in the rhizosphere. Periods of drought reduce the availability of nutrients for the plant and cause physiological stress reactions. Under these conditions, it was shown that treatment of the plants with the consortium not only improved growth, but also significantly reduced the plant's stress response. Under more optimal growth conditions, improved plant health was demonstrated in the plants treated with the consortium.

The DiControl project has obtained relevant scientific results on the influence of cultivation measures on the soil/rhizosphere microbiota and their effect on plant-microorganism interaction in the rhizosphere, taking plant health into account. Crop management measures such as non-inversion tillage and reduced N fertilisation as well as the application of beneficial microorganisms as a consortium can support the resilience of cropping systems.

Furthermore, it was shown that the application of beneficial microorganisms as a consortium supports the plant in dealing with stress factors. The results can promote the sustainable management of current cropping systems and contribute to their resilience.