Carbon and Nitrogen Cycling in Agroecosystems: An Overview

Soil organic carbon (SOC) is the key constituent of soil organic matter (SOM). As a sign for soil health, SOC plays significant contributions to food production, extenuation, and variation to climate change. High SOM content delivers nutrients to plants and enhances water availability, both of which improve soil fertility and eventually enhance food production. Additionally, SOC enhances soil structural firmness by encouraging aggregate development which, together with porosity, warrants adequate aeration and water infiltration to support plant growth. Soils are also a source of greenhouse gas (GHG) emissions into the atmosphere. While the general effect of climate change on SOC stocks is very inconsistent according to the region and soil type, increasing temperatures and enhanced frequency of extreme events are likely to lead to enhance SOC losses. Global nitrogen fixation is the main contributor of the reactive nitrogen (Nr) to terrestrial and marine ecosystems, for which the anthropogenic activities are responsible. Majority of the conversions of anthropogenic Nr are on land within soils and vegetation. Emissions of ammonia (NH3) and nitrogen oxides (NOx) in the atmosphere lead to the productions of secondary pollutants such as ozone and other photochemical oxidants and aerosols (specially ammonium nitrate and ammonium sulfate). This chapter aims to deliver an outline to decision-makers and specialists of the key scientific details and information concerning the existing knowledge and knowledge gaps on carbon and nitrogen cycling in the agroecosystem.