Arable farming is facing a variety of challenges: In addition to climate change, there are new political and social requirements. Intercropping in particular represents an opportunity to increase environmental compatibility in the sense of integrated crop production without negatively impacting the main task - the production of food. Catch crops are grown between two main crops. These intercrops serve in particular to regenerate the soil and at the same time produce animal feed. The aim of the BonaRes CATCHY project was to better utilise the potential of intercropping and contribute to the development of innovative cultivation systems. In long-term crop rotation trials, the effect of cultivating various catch crop species alone and species-rich mixtures was investigated in comparison to fallow with the following focal points: Soil structure and quality, microbiome, nutrient and water balance, yields and profitability. The long-term trials followed the wheat-intercrop-maize cropping pattern. Yellow mustard, phacelia, rough oats and alexandrine clover were used as catch crops as pure seeds and in a mixture of four. A 12-crop mixture was also trialled. The trial sites were located in Asendorf in Lower Saxony and Triesdorf in Bavaria.

Whether main or catch crop: Each plant family, species and variety has an individual spectrum of activity. Legumes, for example, fertilise the soil thanks to nitrogen-fixing nodule bacteria on their roots. Other plants root through the soil or suppress the growth of weeds. By combining the different functions in seed mixtures, the entire spectrum of effects can be expanded and the stability of the catch crop increased.

Intercrop mixtures offer agronomic, ecological and social advantages over individual components. The prerequisite is that a mixture adapted to the crop rotation, location and sowing time is used in accordance with the farm's individual objectives. In addition, the effects are weaker in intensively managed crop production systems than in more extensive production systems that are closer to the natural ecosystem.

Intercrop mixtures offer agronomic, ecological and social advantages over individual components.The prerequisite is that a mixture adapted to the crop rotation, location and sowing time is used in accordance with the farm's individual objectives.In addition, the effects are weaker in intensively managed crop production systems than in more extensive production systems that are closer to the natural ecosystem.

The cultivation of catch crops promotes the build-up of humus. Over nine years of intercropping, the humus content of all variants in the upper 0-10 cm increased continuously by 10-15%. However, this effect could not be clearly separated from other influencing factors such as reduced tillage and crop rotation.However, the results correspond very well with comparable studies and model projections within the project. Legumes and mixtures with legumes in particular have a high potential for building up humus.It is important to understand the long-term nature of this process.An effective increase in humus build-up can only be achieved by continuously integrating catch crops into the crop rotation.

Intercropping minimises nutrient losses caused by leaching into deep soil layers with seeping rainwater. Intercropping is therefore an important instrument for groundwater protection and serves to implement the Water Framework Directive.Furthermore, catch crops, especially in mixtures, improve the formation of larger and more stable soil aggregates.These are crucial for a better water balance and the stability of the soil structure against compaction.In addition, the negative effects of necessary tillage measures can be offset by intercropping.

Catch crops can be an effective and environmentally friendly tool for achieving positive effects on microbial functions in the soil. Increasing plant diversity in intercropping results in a greater variety of active microorganisms in the soil.The greater this diversity, the more stable the ecosystem is against disturbances.This is because almost all soil functions are linked to microbial processes.

As each plant species develops a site-specific microbiome, it makes a difference whether and which individual component or mixture is placed in the crop rotation.Catch crops make a significant contribution to closing the nutrient cycles in arable farming.The nutrient utilisation of a catch crop depends on the location, the management and the plant species/mixture.

The CATCHY project has provided important scientific findings on the diverse effects of intercropping in arable farming. This enables the further optimisation of intercropping management. The use of mixtures and the resulting increase in diversity leads to greater resilience in the crop production system. However, this added value can only be achieved through continuous integration into the cropping system. The use of catch crops can only be one of many measures to develop resilient crop production systems.