Soil Fertility: What We've Learned
Through our work we’ve found that light applications of organic plant and animal-based inputs is the appropriate way to feed the soil; the appropriate way to feed the microorganisms. Organic materials, by definition, contain bonded carbon from biological processes and do not easily dissociate/solubilize in water.
Microorganisms, like all living things, depend on the carbohydrates, lipids, and proteins derived from organic materials.
They are evolutionarily specialized in breaking down organic materials in order to replenish the carbon and nitrogen (and phosphorus, sulfur, potassium, sodium, calcium, magnesium, etc.) demands of their cells.
Conversely, excessive rates of organic inputs can cause a frenzy of microbial feeding and reproduction, thus utilizing oxygen in soil faster than it can be replaced, which leads to anaerobic conditions where beneficial aerobic microorganisms cannot thrive and harmful anaerobic organism can.
In this scenario, remaining nutrients from organic inputs are off-gassed by anaerobes who also consume the deceased or dormant aerobes as a food source, rendering the soil of its fertility and beneficial biology. We can literally watch these types of microorganism responses with the microscope as they’re occurring. There is a strong correlation with the occurrence of pest and disease pressure here.
In addition to light applications of organic amendments, light applications of mineral amendments that are deemed deficient through soil chemistry testing are sometimes recommended to support plant growth and yields while we work on improving the microorganism biomass and populations of a fully functioning soil food web. These mineral materials are also food sources for members of the soil food web, such as fungi, but given the solubility of finely ground mined mineral salts (limestone, dolomite, langbeinite, etc.); the hindrance of extracellular enzyme production by fungi under high concentrations of soluble salts; and the phenomenon of exosmosis and plasmolysis in which water and pressure is stripped from roots and microorganisms as a result of high soluble salt concentrations; it is imperative that application rates are low.
In cases where there are severe mineral deficiencies and no biology at the onset of a project, we often recommend low application rates in conjunction with multiple applications over time. This ensures a steady stream of food for microorganisms and plants without causing a shock response.