Even in dry years non-winter hardy cover crops do not compete for water with the subsequent main crop and even improve the soil water balance. This is a result of the German Federal research project "CATCHY". "The higher the diversity of plants in catch crops, the higher the diversity of the microbial community in the root zone. In the correct combination, mixtures can be used as an effective tool for efficient nutrient ingestion and release, making the main crop more powerful and robust," says Dr. Norman Gentsch, Institute of Soil Science Leibniz University, Germany.
CATCHY is part of the "Soil as a Sustainable Resource for the Bioeconomy - BonaRes" initiative and was launched by the German Federal Ministry of Education and Research (BMBF) in 2010. Over a total of nine years, two different crop rotations are used to investigate how cover crops affect the soil and its biology and consequently the yields of the main crops. Participants in the project are microbiologists from Bremen, soil scientists from Hanover, plant nutritionists from Gatersleben, crop farmers from Triesdorf, socio-economists from Giessen and the Deutsche Saatveredelung AG (DSV). DSV brings its many years of experience with cover crops and the blending of intelligent mixtures for cover crop cultivation.
Water management is of central importance
Climate change has increased spring and summer drought and consequently water management on the cultivated land is of central importance. Here non-winter hardy cover crops offer a clear advantage over overwintering crops or fallow land. Standing crops and increased evaporation on the fallow land can lead to the loss of water reserves over the winter if there is insufficient rainfall. In contrast, the cover crop forms a mulch cover after freezing. Compared to fallow, all cover crop varieties in the CATCHY project, except for mustard in spring 2019, had a significant increase in soil moisture in the maize sowing. Using different plant heights in the species-rich mixtures leads to the formation of different levels with a very dense plant vegetation similar to mixed woodland. The result is a microclimate that maintains the moisture close to the soil surface. This special microclimate ensures that the total water loss of the surface via evapotranspiration is less and optimises water balance.
Optimum nutrient supply through species-rich cover crops
At the time of soil tillage in spring, some of the non-winter hardy cover crop biomass has already decomposed. The readily available nitrogen content is converted early, especially with a crop such as mustard. What remains is a litter-rich bedding with a wide C/N ratio, which is incorporated into the soil in spring. To decompose the mustard litter, the microorganisms make use of the mineral fertilizer depot of the subsequent crop throughout the vegetation period. The result is nitrogen immobilisation in the microbial biomass. In comparison, the C/N ratio in cover crops can be significantly optimised by skilful plant selection. Within the CATCHY project the most effective nutrient release was provided by the diverse TerraLife® MaisPro TR Greening mix (int. MaizePro DT Greening). Continuous N replenishment of the subsequent crop was measured and an increase of 62% N, 40% P and even 91% K compared to mustard was found.
With its TerraLife® brand programme, the Deutsche Saatveredelung AG (DSV) offers in several European markets a comprehensive cover crop portfolio for all sowing times, crop rotations and conditions of use.