Influence of Moisture Content of Sod-Podzolic Soil on the Content of Mobile Forms of Iron, Manganese, Nickel, Copper, Cobalt and Zinc

Excessive moistening of soils can lead to changes in a number of soil properties, which in turn affects the content of mobile forms of elements. However, the gradations were developed for air-dry soil samples of automorphic landscapes, and therefore may not fully reflect the real picture for soils under overwatering conditions. The aim of the work was to assess changes in the content of mobile forms of trace elements in soil samples of field experiments with different levels of mineral fertilizer application on sod-podzolic sandy (Stagnic Podzol (Pantoarenic, Buthyloamic, Abruptic, Aric)) soil under different moisture conditions. The content of mobile forms of Fe, Mn, Ni, Cu, Co and Zn in the samples of sod-podzolic soil (arable layer 0–20 cm and sub-plough layer 20–40 cm), selected on the plots of field experiment– control (without mineral fertilizers), average rates of mineral fertilizers, high rates ofmineral fertilizers were estimated. Extraction of mobile forms of elements was carried out from air-dry soil samples, samples with field moisture and samples incubated in laboratory conditions at different moisture content and for different time. Soil samples were incubated at 60% and 100% of ultimate field water capacity for 3 and 6 weeks. It is shown that differences in the moisture content of samples can significantly change the content of mobile forms of Mn and Fe, which in turn affects the mobility of other elements – Cu, Co, Ni. For most of the studied elements, except for Zn, higher content of mobile forms of TM in moistened samples compared to air-dry samples is shown. An increase in the content of mobile forms of Zn in air-dry samples of the arable layer of soil under the influence of high rates of fertilizer application compared to the control was revealed. The increase in the content of mobile forms of Cu and Co under moistening conditions in the incubation experiment leads to changes in the gradations of soil supply with these trace elements from low to high, which may determine the need to adjust the existing gradations of soil supply taking into account their moisture content.