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.