The influence of long-term application of mineral fertilizers on soil biological activity

Biological activity of soil is an important factor of productivity from agriculture and ecology standpoint as well as sensitive indicator of anthropogenic impact. Such as enzyme activity, microbial biomass and soil respiration respond more quickly to change in crop management practices or environment conditions than agrochemical characteristics in soil. They are one of the most important indicators that give the most exact description of biological activity. For determine biological activity of different genesis soils the long-term fertilization trials were established on moraine sandy loamy Cambisol in 1971 and limnoglacial silty loamy Cambisol in 1990. Experimental data of the period 1999–2002 show, that in the soil developed on different glacial deposits the enzyme activity and respiration intensity are different, In limnoglacial silty loamy Cambisol urease and dehydrogenase activity is higher, while in moraine sandy loam are higher – sacharase activity and soil respiration intensity. In sandy loamy Cambisol with application annual of 180 kg ha-1 phosphorus in combinations with nitrogen and potassium fertilizers increases the amount of available phosphorus in soil from 43–61 to 499–503 mg kg-1 and lowers the activity of enzymes and urease in silty loam – the change of available phosphorus amount in soil is significant, therefore, the changes of urease activity are slight. In sandy loamy Cambisol mineral fertilizers slightly influence the sacharase activity, while in silty loam – the tendency of sacharase activity weakening has been revealed. Mineral fertilizers inhibit the dehydrogenase activity in soils. Soil hydrolases activity is higher soil under cereal crops, while that of oxidoreductases – under roots crops. The highest respiration intensity has been established in soil under sugar beet cropsVytauto Didžiojo universitetasŽemės ūkio akademij