Using species-rich mixtures of green manures creates a greater carbon flow between plant and soil than using a single type of green manure. This has been shown by research within the German project CATCHY.
In a field trial, scientists investigated how different green manure crops transport carbon from photosynthesis to the root area. To this end, greenhouses have been set up in the field with an artificial atmosphere with CO2 to which a stable carbon isotope has been added, so that the transport of carbon in the plant could be monitored.
A comparison was made between a fallow plot, a plot with yellow mustard, a plot with a mixture of 4 components and a plot with a mixture of 12 green manure varieties. It was shown that the CO2 absorption of the 4-species mix was twice as high and the 12-species mix was three times as high as that of yellow mustard.
The higher carbon uptake leads to a higher production of photosynthesis assimilates and transport to the root space. However, these sugar compounds are not only used as energy storage in the root. In the root space, plants secrete these altered assimilates as root exudates. That also stimulates the growth and activity of the soil organisms in the root zone.
The collective biomass in the arable land increased markedly for all green manure crops compared to fallow. The higher carbon supply in the soil stimulates the development of certain fungi and actinobacteria in particular. These soil organisms are important in unlocking nutrients for the plant in the soil and for building up the soil structure.
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