ABSTRACT
The nutrient cycle is made up of two important geochemical fluxes, namely, nitrogen and phosphorous. The nutrient cycle asks for timely action on the environmental policy front in terms of soil management, farming systems, sewage treatment, and so on. The nutrient cycle unfortunately is not getting the necessary attention it deserves as the nutrients policy is vulnerable. Nutrients such as nitrogen (N) and phosphorus (P) are essential for the growth and development of organisms. Ecosystems are responsible for controlling the flows and concentration levels of nutrients through a host of complex processes including biodiversity. Nutrients cycles have so far been modified to a substantial extent by human intervention mainly agriculture over the time, with its own consequences for not only a range of ecosystems but also to human wellbeing. The nutrients absorption and retention capacity of terrestrial ecosystems supplied by way of fertilizers or deposition have been depleted because of many large ecosystems into large scale but low diversity agricultural systems. Further with the reduction in the buffering capacity of ecosystems like riparian forests, wetlands, and estuaries, the nutrients in excess leach into groundwater, rivers, and lakes and are subsequently transported to coastal ecosystems. Although agriculture intensification is the only option to meet the future 184food demands and to check conversion of land from natural vegetation to agriculture, excessive flows of N have contributed to eutrophication, acidification of freshwater bodies, and coastal marine ecosystems. Nitrogen losses promote global warming and, to a certain extent, instrumental in creating ground-level ozone and depletion of stratospheric ozone layer.
This chapter is an overview of the sources of N losses at the different stages of N cycling in agro-ecosystems, technical solutions to cut down the quantum of N losses, and throw light on the analysis supported by integrated tools and indicators in two contrasting situations: a low-input and a high-input system from the developing and an industrial world, respectively. Moreover, the research needs for better assessment of the expected benefits to be achieved at a global level in land productivity and erosion in environmental impact by improving nutrient cycling management discussed too.
