ASSESSMENT OF SOIL BIOLOGICAL ACTIVITY UNDER CONDITIONS OF LONG-TERM DIVERSIFIED MINERAL FERTILIZATION

Biological activity is investigated at different levels in cases of disturbances of processes, taking into consideration C and N changes in time and modern models of carbon sequestration. Soil properties created by fertilization are one of the factors influencing soil respiratory activity. This activity was measured by the manometric method in the conditions of long-term fertilizing experiment after 44 years management of the mountain meadow. One object chosen for the investigation was fertilized only with P and K and two objects were fertilized with ammonium nitrate in two doses: 90 and 180 kgN.ha(-1) in the background of PK. The experiment was conducted with the limed soil and in series without liming. Manometric measurement comprised change of pressure in a closed container which was proportional to oxygen consumption and created by respiratory processes taking place in it. The equivalent amount of created CO2 was absorbed by 1 mol.dm(-3) NaOH solution. Biological activity of materials was expressed in mgO(2).g(-1) d.m..d-1. Equations of pressure changes indicate differences in soil respiration caused by fertilization intensification. Generally, systematic soil liming caused an increase in its biological activity. However, liming influenced this activity to a lower degree than mineral fertilization. The highest respiratory activity and dehydrogenase activity (mu g TPF.g(-1) f.m.d(-1)) was observed in the soil of the object fertilized with 90 kg N + PK.ha(-1) and the object with fertilization increased P and K availability causing an increase in biological nitrogen fixation.