IMPACT OF LIGHT REGIME ON SOIL RESPIRATION AND CARBON STATUS IN A MODEL EXPERIMENT

Extending the list of factors and studying their effects on soil carbon transformation offers new opportunities for carbon balance regulation. One of the factors is electromagnetic waves. To determine their impact on the soil carbon status, a two-stage model experiment was conducted at the Centre for Decarbonisation of the Agroindustrial Complex and the Regional Economy of Kabardino-Balkarian State University named after Kh.M. Berbekov. The experiment aimed to verify soil respiration response to light radiation. A key feature of the experiment was that light radiation was applied directly to plant-free soil samples. Three different light modes were used: mode A (day/night photocycle – 18/6 hours), mode B (day/night photocycle – 0/24 hours) and mode C (day/night photocycle – 24/0 hours). The first part of the experiment established the fact of a soil response to light regime. Mode A, which lasted 4 days, demonstrates a change in soil respiration under light conditions. The average amount of CO2 absorbed by the soil during the light phase is 77 ppm in the soil respiration chamber. The average amount of CO2 released during the transition to the dark phase is 96 ppm. Over the next 3 days, under sustained dark exposure (mode B), soil exhibits increased respiration without detectable CO2 uptake. The concentration in the chamber rose by 271 ppm, from 1087 to 1358 ppm. Under continuous light exposure (mode C), a protracted decline in CO2 concentration from 1210 ppm to 1101 ppm is observed throughout the entire period. The second part of the experiment involved a quantitative assessment of the effect of the light factor on soil carbon content. To a greater extent, carbon transformation is observed in the fine-earth soil (≤ 1.0 мм). The lowest HWEC (hot water extractable carbon) content (424.5 mg/kg) was observed in mode B. In modes A and C, HWEC is 1046.6 and 1102.5 mg/kg, respectively. The maximum carbonate carbon is in the dark phase of the experiment (2.09 %), the minimum (1.89 %) is in the light phase. In mode A, the proportion of carbonates is 2.0 %. The maximum value of soil organic carbon was recorded in the mode with periodic lighting (3.11 %), and the minimum value was in the mode with permanent lighting (2.15 %). In the dark phase, the organic matter content is 2.44 %.