DSV | CATCHY research project

Benefits of species-rich cover crop mixtures now proven

The effect on crop rotation of a cover crop is not easy to measure. With the CATCHY project, new insights into the effect of an intercrop have been gained using elaborate research methods.
The CATCHY cover crop project is part of the initiative "Soil as a Sustainable Resource for the Bioeconomy - BonaRes" and was launched by the Federal Ministry of Education and Research (BMBF) in 2015. Over a total of nine years, two different crop rotations were studied to determine how cover crops affect the soil and its biology and thus the yields of the main crops. In addition to DSV, microbiologists from Bremen, soil scientists from Hanover, plant nutritionists from Gatersleben, crop farmers from Triesdorf and socio-economists from Gießen are involved in the project. DSV is contributing its many years of experience with cover crops and the compilation of intelligent mixtures for cover crop cultivation.

What can cover crop mixtures do in my crop rotation?

Soil is one of our most important resources, it is scarce and cannot be increased

After the end of greening, many farmers are faced with the question of the value of catch crops for crop rotation. The CATCHY research project has produced results that are extremely valuable in practice.

Since 2015, individual components have been compared as pure seeds and catch crop mixtures with a black fallow in crop rotation trials. The agronomic findings are summarised below.

Humus formation & soil structure

Catch crops have been shown to improve the formation of water-stable soil aggregates (Ø +16 %). Mixtures of different species provide even better options here than individual components. The resulting improved soil structure is the basis for healthy soil and the arable farming that takes place on it. Cover crops can also increase the humus content in the long term if they are continuously integrated into the crop rotation. Due to the favourable C/N ratio of the chaff, the 12-crop mixture (TerraLife®-MaizePro) showed the highest potential in the CATCHY trials.

Microbial fingerprint and the stabilisation of crop health

All soil functions are influenced by microbes. The more diverse the microbiome (totality of microorganisms) is, the more stable the agroecosystem can be against disturbances such as extreme weather conditions. The CATCHY project was able to show that each plant species develops an individual microbiome. A combination of different species in mixtures can lead to a greater diversity of the microbiome, depending on the location and year. It therefore plays a role whether the soil is fallow, whether catch crops are grown in pure seeds or in mixtures.

It has also been shown that catch crops influence the microbiome of the following main crop: For example, different cover crop types and mixtures were cultivated and the roots of the subsequent maize were analysed. The most health-promoting fungi were found after phacelia in pure stands and after the TerraLife®-MaizePro mixture. Harmful Fusarium fungi occurred most frequently after fallow or mustard.

Nutrient efficiency - save fertiliser with catch crops

Catch crops make a significant contribution to closing nutrient cycles in arable farming. It should be noted that individual plant species can mobilise different nutrients in very specific ways. Key factors here are biomass formation, root architecture and specific mobilisation mechanisms (e. g. the excretion of specific organic acids or enzymes via root exudates). These properties can be specifically combined in mixtures to optimise nutrient management. This leads to more stable biomass formation and nutrient utilisation in different environments.

The long-term crop rotation trials have shown that nutrient leaching is between 80 – 90 % lower under catch crops compared to fallow. It was also found that nutrients are released from the catch crop not only into the following crop, but also into the entire crop rotation via organic nutrient depots in the soil! This results in potential fertiliser savings throughout the entire cultivation system.

Managing the water balance with catch crops

„Don't catch crops just steal water from my main crop?" many farmers ask themselves. No, this assumption is not correct across the board. The project results show that catch crops can be used to actively control the site-specific water balance.

Freezing catch crops can provide the following main crop with more water than a fallow (+11.3 % soil water supply for maize sowing) and are therefore particularly advantageous in the case of increasing early summer droughts.In the dry years during the project, this effect led to additional yields of up to +11 % for silage maize.It is important to bear in mind that catch crops that do not freeze also extract water over winter and especially when vegetation returns in spring.In dry locations, this can lead to a lack of water in the following main crop.On moist sites, however, this can be utilised in a targeted manner to ensure successful spring cultivation of the main crop.

Long-term yield stability

The diverse influencing factors described above also result in a complex effect of catch crops on the yields of the main crops. If managed correctly, this is positive. The short-term yield effects on the direct subsequent crop are rather low (0.8 % additional yield in the following silage maize). However, it has been proven that there are effects beyond the following crop on the entire crop rotation: In winter wheat after silage maize, long-term trials showed yield increases of 1 to 4 %.

Conclusion

The CATCHY project has significantly improved our understanding of the many benefits of catch crops in arable farming. The properties and effects of different plant species and their societies are very complex. When considering all the parameters as a whole, it becomes clear that the targeted combination of species in mixtures leads to greater resilience in the crop production system. Continuous integration of the right catch crops into the crop rotation is essential to realise the many benefits.

Results

Scientific posters with CATCHY results