Organic matter has a complete line of macro/micro nutrients but they are in forms that are not available to the plant for immediate uptake. These forms of nutrients are non-leechable and do not wash away with rain but are held in the soil until needed.
Grass plants need sun, water and nutrients in the soil to thrive. The sun's rays provide the means for the plant to turn the sun's energy into sugars, proteins and carbohydrate (photosynthesis) and store this food in the root. Up to 40% of the food stored in the root is pushed out through openings that feed the good guys in the soil that live there, beneficial microorganisms.
Organic matter has a complete line of macro/micro nutrients but they are in forms that are not available to the plant for immediate uptake. These forms of nutrients are non-leechable and do not wash away with rain but are held in the soil until needed. The good guys in the soil love to eat organic matter and through a process called nutrient cycling make these nutrients available to the plant. This process of applying organic matter and supporting the good guys in the soil increases soil fertility which, in turn, increases soil porosity, disease resistance, drought resistance and makes healthy green turf.
We support and increase the good guys in the soil by applying compost teas. These compost teas do not contain any animal waste, but are a rich mix of organic nutrients with dense populations of the good guys that live in the soil. The beneficial microorganisms in compost teas populate the root, shoot and soil of the turf and begin a process termed "the soil food web". The soil food web describes in scientific terms the symbiotic relationship between plants and beneficial microorganisms in the soil.
Clay soils have 1000's of years of nutrients in them, it just that the nutrients are not in plant available forms. By initiating the process of adding organic matter and supporting the good guys in the rhizosphere, the root tips begin to reach deep into the soil increasing the soil tilth and root mass and tapping sources of nutrients that have until now been unavailable to the plant.
Synthetic or non organic nutrients
The application of synthetic fertilizers to the soil discourages root growth and drought resistance. Think of it this way, if someone was to feed you all of your nutrients needs, eggs, steaks, french fries, etc. in the same place every day why would you ever go somewhere else? Well, OK you have a car but plant roots don't.
As we apply these, immediately plant available, nutrients to the soil, they melt and drop into the top one, maybe two inches of soil. If you ever dig in your yard you will notice that the roots really do not go down that far. Why would they, all of the nutrients are in the top 2 inches of soil. During times of low moisture and high heat, which is known around here as SUMMER, the roots do not penetrate far enough into the soil to be able to reach cooler wetter soils and suffer the consequences. If we begin a program that encourages increased root mass and penetration into the soil we dramatically increase drought resistance for turf.
A more technical note on nutrient cycling and root mass
Root-soil contact is determined by root length, root branching, and root hairs. Root hairs are located just behind the root tip and have a relatively short life span of a few days to a few weeks. Actively growing feeder roots are necessary to continually renew these locations for nutrient uptake. Nutrient absorbing capacity is also increased by symbiotic associations between fungi and plant roots. These fungi, called mycorrhizae, function as an extension of plant root systems. Mycorrhizae obtain food from plant roots and in return increase the nutrient absorbing surface for the plant through their extensive network of fungal strands, called hyphi. Ther can be hundreds of feet of hyphi in a single teaspoon of soil.
Root activity also has direct effects on nutrient availability in the soil. Insoluble nutrients are released and maintained in solution by the action of organic acids and other compounds produced by roots. Nutrients are also released because the soil immediately adjacent to roots, the rhizosphere, often has a lower pH than the bulk soil around it as a consequence of nutrient uptake. The rhizosphere stimulates microbial activity and microbes also release organic acids and other compounds that solubilize nutrients.
A number of soil factors and management practices affect root growth, distribution, and health. Compacted soil layers restrict root penetration, low pH in the subsoil can restrict rooting depth, water saturation and poor aeration inhibit root growth, and roots will not grow into dry zones in the soil. It is important to be able to look and test for these undesirable conditions. Practices that maintain soil biodiversity promote healthy root systems, since an active and diverse microbial population competes with root pathogens and reduces root disease.