~(15)N Isotopic Techniques to Study Nitrogen Cycle in Soil-Plant-Atmosphere System

摘要

Intensification of agriculture to meet the increasing food demand has caused severe disruption in natural balance of global as well as regional nitrogen cycle, potentially threatening the future sustainability of agriculture and environment. Of the total fertilizer nitrogen used in agriculture globally, only less than half is recovered by crop plants, rest is lost to the environment, resulting in several environmental problems such as ground water pollution and global warming, besides huge economic loss of this costly input in agriculture. Improving fertilizer nitrogen use efficiency and minimising N loss to the environment is the key to regain the lost control of nitrogen cycle in agriculture. Fertilizer nitrogen use efficiency depends largely on Nrequirement of crops, N supply from soil and fertilizer through N transformations in soil, and N losses from the soil-water-plant system. ~(15)N isotopic techniques have the potential to provide accurate measurement/ quantification of different processes involved in N cycle such as fixation of atmospheric N_2, transformations- mineralization and immobilization- of soil and fertilizer N which governs N supply to plants, and N losses to the environment through ammonia volatilization, denitrification andnitrate leaching. ~(15)N tracers can also give precise identification of ways and sources of N loss from agriculture. These informations can be used to develop strategies for increasing fertilizer N use efficiency and minimizing the loss of this costly input from agriculture to environment, which in turn will help to achieve the tripartite goal of food security, agricultural profitability and environmental quality.