Intrusion into the Nitrogen Cycle:

Human intervention can disturb  the nitrogen cycle. Let us see how. When we grow and harvest crops. there is loss of  nitrogen from the soil, as it is utilised  in the building up of plant body. Similarly,  harvesting of  timber results in heavy outflow of niirogen from our forest ecosystem. You may say that we can compensate for the loss of nitrogen by adding commercial fertilisers  to our fields or by  large scale cultivation of nitrogen-fixing plants. Yes. you'are right. so long as  the right type of  fertilisers are applied in proper quantities. Heavy addition of commercial  fertilisers  cause excessive build up of  nitrogen  in  the soil and groundwater, and nutriept enrichment of rivers, lakes etc. Automobile and industrial exhausts add nitrogen oxides,  especially nitrogen dioxide, at an alarming rate to the atmosphere. Nitrogen dioxide reactg with moisture in the atmosphere to form weak nitric acid, which  is carried  to the soil dyring rainfall, and ultimately to the water table. The results of nutrient enrichment of  rivers, lakes etc; presence of excessive nitrogen oxides in  the atmosphere; and the excessive formation and addition of nitric acid to the soil.