Researchers have used various soil conservation methods to find scientific answers to this limitation of maintaining soil quality under intensive cropping system; of equal importance to the methods, however, is the shift in perspective on soils: to view soils as living entities teaming with billions of microbial life (NRCS) - hence, the concept of soil health as an apt descriptor of soil quality.
The NRCS web resource defines soil health as “the continued capacity of soil to function as a vital living ecosystem that sustains plants, animals, and humans”. The indicators of soil health include soil organic matter (SOM) that supplies nutrients for plant growth and provide soil structure and aggregate stability, among other functions (NRCS). Our knowledge of what soils are and how successful we put soils to productive use depends on our understanding of what constitute SOM, and how well this information can be used to evaluate and predict moisture retention and nutrient cycling in soils, as well as how gas exchange occur in soils.
 |
| Retrieved, on 28 Feb 2020, from: https://natureconservancy-h.assetsadobe.com/is/image/content/dam/tnc/nature/en/photos/2017-03-15_cornerstoneoflife_1640x1025.jpg?crop=0,0,1640,1025&wid=1640&hei=1025&scl=1.0 |
Soil organic matter (SOM) is a heterogeneous mixture of organic compounds of plant, animal, and microbial origin at various stages of decomposition. Typically, the content of organic matter in soils is low, but it accounts for the function of soils for agricultural purposes. As the mainstay of soil fertility, SOM directly influences soil health by supplying energy for the microbes driving soil development, and other important soil processes- thereby determining the properties of soil, and other important ecosystem functions. Soil organic matter comprises two categories of chemical compounds: non-humic substances and humic substances. The “non-humic substances are the parent material of humic substances”; they are transitory in soils; and they decompose into humic substances: the dark colored, highly transformed, and amorphous component of SOM.
Humic substances contain many functional groups attached to a carbon backbone structure, and this accounts for the reactivity of SOM, and how it influences cation sorption, and the mobility and bioavailability of cationic nutrients and metals .
Organic amendments is a source of plant-available nutrients and organic matter supply to soils, and for these reasons they are applied to agricultural soils as a means of improving SOM content and maintaining SOM levels under intensive cropping system. When properly applied, organic amendments result in improvements of soil health indicators; however, inappropriate application increases the risk of impacting the environment adversely, resulting in nutrients loss that cause environmental pollution.
An understanding of the characteristics of organic amendments is required for their continuous application as a sustainable means of managing soil health.
