Most agricultural enterprises’ both long-term viability and success are dependent on the health of their soil. This applies to beef operations on the Southern Great Plains and rows of crop farms throughout the Midwest. The agricultural industry has studied, understood, and mastered the physical and chemical characteristics (e.g. soil texture, pH, etc.) for many decades. However, biological constituents have been neglected and are crucial for healthy, functional soil.
Soil Is Alive And Active
Soil isn’t just a medium to grow plants. It is a living ecosystem and can put on quite a show if you know what to look for. Living soil is a dynamic and complex environment that has as much drama as a Hollywood movie. Living soil can be described as a combination of predator-prey conflicts, high-speed action, and even mutual partnership.
Unfortunately, we can’t see the big picture. These activities occur daily in the soils we stand on, but only microscopically. Many people know about bacteria, fungi, and protozoa. So, what happens? How does this matter? Healthy soil depends on earthworms. Worms improve soil water dynamics. They burrow to create water and root tunnels. Soil biology is important to:
1. Decomposition Of Organic Matter & Material
Organic matter from the soil is a source of energy and nutrients. It can be used by soil microbes and plants. Organic matter is a byproduct of biological degradation and is a primary food source for soil microbes. One type of bacteria and fungi is called a decomposer. This means that they can break down organic material and release useful nutrients. Decomposing soil fungi can decompose more difficult carbon sources than bacteria. Functional soil biology relies on organic matter as a major driver of soil productivity. Soil organic matter is the foundation of functional soil biology.
2. Nutrient Cycling
Soil biology plays a key role in soil nutrient cycling. Soil bacteria use active carbon, which is directly available to microbes. Exudates from plants are the main source of active carbon. These exudates from plant roots are a primary food source for soil bacteria. They release nitrogen and mineralize as bacteria die. This allows them to cycle nutrients. Microbes in the soil are responsible for significant nutrient cycling through their biomass. Microbial biomass can be 2 to 5% of total organic matter. This fraction, however, is self-motivated. This fraction contains essential nutrients for plants. Biologically significant amounts of sulfur, nitrogen, and phosphorus in this fraction are converted into plant-available forms when microbes die.
3. Soil Aggregation
The soil’s ability holds the particles together is called soil aggregation. The soil biology process aids in this process by simply reducing organic material and creating organic matter. The soil’s ability to make soil aggregates is enhanced as more organic matter is added. The soil fungi play a role in this process, helping to keep the particles together. Glomalin, a compound made by arbuscular mycorrhizal fungal fungi, coats their hyphae. It protects plants from nutrient and water losses during transportation. It can also be used as a soil glue to stabilize soil aggregates. These processes, among others, improve soil structure and help soil resist disruptions such as wind and water.
4. Nutrient Availability
Microbial activity can reduce nutrients. Fungi play an important role in soil. Fungi make long hyphae. Hyphae are found between soil aggregates, particles, and rocks. Mutualistic relationships exist between mycorrhizal fungi and plants. It uses root carbon. The fungi help solubilize nutrients and phosphorus for plants. This process increases plant roots’ ability to absorb nutrients. To increase nutrient availability, soil bacteria form symbiotic relationships with plants. Root hairs of some legumes are infected with Rhizobium. Bacteria fix atmospheric carbon for carbon. Nitrogen is used by the plant. When a plant dies, excess nitrogen is released into the air and made available to other plants.
5. Water Dynamics
Soil biology aids soil water dynamics in the above ways. This includes infiltration and water holding. Soil aggregates when organic matter increases. As soils agglomerate, pore size and porosity grow. Earth-worms help by digging tunnels for water or roots to travel. Water can penetrate the soil better as its pore space increases. We want to get water into the ground and reduce runoff. Biology also helps soils retain water. It holds water well. More water can be held in biologically active soils. This works best on coarser soils. Clay substrate soils have a smaller impact because clay is the key to holding water.