A REVIEW: EFFECTS OF NITROGENOUS FERTILIZERS ON SOIL (PH, MICROBIAL COMMUNITY, GREENHOUSE GASES EMISSION AND CARBON POOL)

With world population increasing at such fast rate and land available to cultivate decreasing substantially, it is of prime need to increase the productivity. This is the reason of increasing use of fertilizer in the world especially N fertilizer because of its direct influence on growth attributes. The main objective of this article is to review the existing literature regarding the effect of nitrogen fertilizer application in soil pH, microbial community, soil carbon pool and emission of Green House Gases. Most researches have shown urea to be the major source of anthropogenic N addition to soil. Studies have concluded that the unmanaged application of N fertilizers in excess amount than what crops utilize is the nerve center favoring pH change. In regards to their impact in microbial community, previous land management practice seemed pivotal. Also, abundance and diversity of greater fraction of microbes (fungi and bacteria) narrowed down with intensified application in cultivated soils in majority of trails studied. Increased efflux of CO2 and N2O was observed in soil fertilized with N however, CH4 emission was limited as methanotrophs were replaced with nitrifiers. Acid rain was highly favored with such emissions. No changes in soil organic carbon pool were seen in short period but in due course of time, decomposition or turnover rate decreased increasing the stability of carbon under lignin rich root residues. Therefore, alterations varying with depth have been noticed in soils treated with N due to mineral association.