The Organic ApproachA healthy soil is primarily defined by its fertility, representing two essential components for farming. Soils are a living system of organisms reacting with organic and inorganic matter. Soil quality comprises a range of chemical, physical and biological factors which together affect the productive potential of the land. A soil’s physical properties determine how well a plant’s roots grow and proliferate. Plant roots thrive in soil that has good aggregate stability (tilth), porosity, infiltration, drainage, water-holding capacity, bulk density, and resistance to crusting and compaction. An extensive root system that explores more soil volume naturally has access to more soil moisture and nutrients. The following figure illustrates the ideal physical properties distribution in an ideal soil.
Figure 2- Physical properties distribution
Source: https://content.ces.ncsu.edu/extension-gardener-handbook/1-soils-and-plant-nutrients Soil chemical properties control the availability of nutrients to plants. Nutrients must be present in sufficient quantities, or yields will be limited. As a consequence, the primary focus of fertility management on many conventional farms has been the application of chemical fertilizers. Less attention has been given to other soil management practices that also contribute to fertility. In contrast, most organic farmers take a much broader long-term approach to building soil fertility. For example, organic farmers strive to increase cation exchange capacity, thereby increasing nutrient storage. Organic farmers are encouraged to work to enhance soil biological properties. Soil organisms control many important processes, such as nutrient cycling. In a process called mineralization (immobilization is the opposite) microbes break down organic plant and animal residues to produce plant nutrients. Plant roots take up these inorganic nutrients and convert them into organic forms, such as leaf, stem, and root tissue.
Figure 3- Mineralization and Immobilization
Source: http://slideplayer.com/slide/8767684/ When these plants die, the nutrients are recycled once again. Soil organisms also promote the development of soil structure by excreting chemicals that bind soil particles together into aggregates. An aggregated soil is said to have good soil tilth. Typically, soils with good tilth have good water infiltration and drainage, and are easy to work.