Soil organic matter content and crop yield

M ost agricultural soils are depleted of their soil organic matter (SOM) reserves. A severe loss of SOM content may degrade soil functionality, its capacity for provisioning of essential ecosystem services, and soil health. Therefore, restoration of SOM content in soils of agroecosystems may reverse the degradation trends, enhance ecosystem services (Banwart et al. 2015), and advance Sustainable Development Goals of the United Nations. (Lal et al. 2018a). Increase in SOM content may also partially replace the use of chemical fertilizers and supplemental irrigation, while restoring the environment. Some critical questions to be objectively addressed regarding the restoration of SOM include the following: 1. Is there a critical limit or range of SOM content for soils of temperate and tropical climates below which the crop yield declines? 2. If such a limit/range can be established, what are its principal determinants? 3. Can an increase in SOM content of a severely depleted soil lead to increase in crop yield under both nutrient/water limiting and sufficient conditions? 4. Can any positive impact of increase in SOM content be masked by use of chemical fertilizers and supplemental irrigation? 5. Is restoration of SOM content a resource-saving (i.e., land, water, energy) option? Therefore, the objective of this article is to deliberate the impacts of SOM content on crop yield under diverse climate, soil, land use, and management systems. Healthy soils are important to growing healthy crops, raising healthy animals, and supporting a healthy human population through nutritionally balanced diets and environmentally healthy habitats. Favorable SOM content is critical to attaining such a vital interconnectivity. The importance of SOM content to crop yield has been known to ancient civilizations for millennia (Manlay …