Chapter 5 Soil Organic Carbon, Nitrogen and Fertility

This chapter discusses the concepts of soil organic carbon, nitrogen, and fertility. Soil fertility is defined as the status of the soil in relation to the amount and availability to plants of elements necessary for plant production. A fertile arable soil has to meet the current and future needs of cultivated plants. All fertile soils have an adequate supply of organic matter. Soil organic matter refers to the organic fraction of the soil; it includes plant and animal residues at various stages of decomposition, cells (living and dead) and tissues of microbes, and substances synthesized by the soil population. In a fertile soil, the function of a organic matter is both direct and indirect. Its direct role is concerned with the provision of plant nutrients via the processes of decomposition and mineralization; its indirect role is associated with its effect on the physicochemical properties of the soil. The chapter further describes the nutrients required by plants.