The effect of various fertilizer systems on sequestration of organic carbon in soddy-gley soil
The influence of the mineral and organic fertilizer systems on the organic carbon sequestration in gley soils (Liege-suo swamp 61 ° 49ʹN33 ° 10ʹE, Korsinskaya lowland, Essoila farm, Karelia, Russia) was studied. The experimental site consisted of two plots: the first - without manure application (WM), and the second - with manure application, 60 t/ha of farm yard manure (M). Each plot was divided into seven sub-plots with various fertilizer rates: N0 P0 K0; N120 P0 K0; N240 P0 K0; N0 P0 K120 N0 P0 K240; N120 P0 K120 N240 P0 K240. Timothy grass (Phleum pratense L.) was grown on all the plots. The soil from the upper horizon of pine-birch forest was selected as a natural control.The content of total organic carbon and organic carbon associated with the clay fraction of the soil was measured by the Tyurin method. The mineralogical composition of the soil clay fraction was determined by the X-ray method with DRON-3M X-ray diffractometer. For both experimental plots the maximum total organic carbon content was measured in the N240P0K240 treatment. The minimum C  org  content was found in the N120P0K0 treatment on the WM plot and in the N240 P0 K0 treatment in the M plot. Significantly the highest amount of the soil total organic carbon was found on the M plot (p <0.002). Sequestration of carbon associated with clay in the M soil was facilitated by the use of potassium fertilizer at a rate of 240 kg/ha, or by the combined application of nitrogen and potassium fertilizers at the same rate. The soil of the WM plot was characterized by maximum value of the carbon associated with soil clay fraction in the N240 P0 K0 variant. X-ray analysis showed that plagioclase and potassium feldspar were the main minerals that sequester carbon in the soil clay fraction of the WM plot. The predominance of the influence of a particular mineral on the sequestration of carbon in the soil clay fraction of the M plot depended on the composition and the rate of the mineral fertilizer used.