Enzymatic activity of sod-podzolic loamy sand soil under different mobile potassium supply | Ферментативная активность дерново-подзолистой рыхлосупесчаной почвы при разной обеспеченности подвижным калием

In the conditions of the Republic of Belarus in course of a model field experiment there was studied the influence of sod-podzolic loose sandy loam soil supply with mobile forms of potassium on its enzymatic activity by the following indexes: dehydrogenase, invertase, urease and polyphenol oxidase activity of soil. As a result of realized research it was revealed that the most adequate enzymatic indicators for determination of potassium doses were dehydrogenase, invertase, urease and polyphenol oxidase activity of soil. There were determined the quantitative changes in enzymatic activity of sod-podzolic sandy soil depending on K2O content in soil and increasing doses of potash fertilizers. Soil saturation with K2O and application of potash fertilizers led to increase of soil contamination with microorganisms, to intensification of processes of lignin humification of vegetative rests and ammonification of organic nitrogen containing compound with allocation of inorganic nitrogen. Also it increased the speed of mineralization sucrose in soil. Optimum indicators of soil enzymatic activity (dehydrogenase - 320-440 mg triphenylformazan/kg, invertase - 3290-3760 mg glucose/kg, polyphenol oxidase - 42-49 mg of quinones/kg and urease activity - 250-270 mg of N-NH4/kg) were marked at the content of 196-288 mg of K2O per 1 kg of soil. Application of increased doses of K90-120 on the background content of 196 mg of K2O/kg of soil or K60-90 at content of 288 mg of K2O/kg of soil made it possible to provide an optimum level of soil enzymatic activity. In these agrochemical variants there was marked the highest crop rotation yield (54-57 centner of fodder units /ha). In the conditions of content of mobile potassium at the level about 390 mg/kg there was noted an essential decrease of enzymatic activity and lowering of crop productivity.