Variability of agroecosystem carbon cycle in Grey-Luvic Phaeozems Hortic treated with live cultures of cyanobacteria and microalgae

Agroecosystem soils contribute significantly to the variability of carbon cycling in the biosphere. Intensive agricultural development has led to historic losses of organic carbon in soils in recent decades. According to FAO, greenhouse gas emissions in the agricultural sector have doubled over the past 50 years. In the coming decades CO2 emissions are expected to increase by another 30%. We studied the effect of treating Gray-Luvic Phaeozems Hortic with biological products based on the cyanobacterium Nostoc punctiforme Hariot and microalgae Chlorella sorokiniana Shihira & R.W. Krauss on soil CO2 emissions under Glycine max (L.) Merr., Hordeum vulgare L., Avena sativa L., and Secale cereale L. in the Kursk agglomeration. We revealed that the above soil treatment changes the intensity of soil carbon cycling. In laboratory and field studies we found that soil surface treatment with C. sorokiniana live culture increases the main groups of soil microorganisms abundance (bacteria – 25.6 times, fungi – 37.9 times and actinomycetes – 57.3 times). In addition, it can result in both an increase in soil CO2 emission rate of 6.0 to 41.8%, and decrease of 6.1% to 50.8% depending on the cultivated crop. Cultivating G. max, A. sativa, and S. cereale in Gray-Luvic Phaeozems Hortic treated with C. sorokiniana, reduced the total amount of organic carbon emitted into the atmosphere by 10.8%. The application of a biological product based on C. sorokiniana in spring and summer decreased the CO2 emission rate, while autumn treatment, on the contrary, promoted soil CO2 emission. Regardless of soil treatment with microalgae-based biopreparation, losses of soil organic carbon were observed in the topsoil in the studied time period, which under different cultivated crops ranged from 0.6 to 3.4 t/ha.