Nitrogen Transformation in Soil: Effect of Heavy Metals

Nitrogen is the key nutrient factor that influences soil fertility and productivity. It is the mineral nutrient that exists in different forms, but nitrate form is the most preferred form by plants. Irrespective of the form in which N is applied to soil, it undergoes transformation viz. mineralization (ammonification, nitrification), denitrification etc. by enzymes produced by micro organisms. The rate of these processes are influenced by a number of factors, one such being heavy metals accumulated in soil by various anthropogenic activities like disposal of sewage sludge, domestic and industrial effluents discharge, deposition of air borne particulates from mining on agriculture land etc. The heavy metals cause long term hazardous effects on soil eco system and negatively influence the soil biological processes, soil microbial biomass and functions associated with soil N transformation. Hence, there is a need for the study and to monitor heavy metal concentration in soil. The effects of heavy metal contamination on soil are quite alarming and cause huge disturbances in the ecological balance and health of living organisms on earth. Micro organisms and enzymes associated with N transformation in soil are inhibited directly or indirectly by heavy metals. The extent of inhibition depends on the concentration and oxidation state of heavy metals and on soil characteristics.