Impact of Various Land Use Systems on Nitrogen Dynamics: A Review

Abstract

Rapid and unregulated conversion of agricultural fields into non-agricultural lands is becoming a major concern in many countries. The shortage of cultivable lands will make it harder to achieve ever-increasing food demands in upcoming years. Assessing land use-induced changes in soil nitrogen is essential for addressing agroecosystem transformation and sustainable land productivity issues. Numerous studies have shown that land use pattern has a significant effect on nitrogen storage and turnover along with varied degrees of mineralization rate and nitrogen forms present. The content of nitrogen fraction can be used as an indicator of the rate of mineralization and eventually microbial richness of soils. As per the study, it is observed that inorganic nitrogen fractions constitute hardly 1-2% of total nitrogen, whereas organic nitrogen takes up almost 98-99% of total nitrogen that is majorly sourced from organic residues in soils. The exchangeable NO3-N and exchangeable NH3-N are majorly plant-utilizable, easily mineralized forms whereas only amino acid-N has been proved to be directly utilizable organic nitrogen form. Even today large number of producers are dependent on synthetic nitrogen sources for crop production. Improving nitrogen use efficiency by reducing the natural losses and improving the inherent mineralization rate of organic nitrogen might help lower fertilizer dependency and so the cost of production.  In this paper, soil inorganic and organic nitrogen contents, types, and its contribution to plant production are reviewed to explore the exact role of nitrogen forms as influenced under different land use systems.