Soil fertility is dependant upon the continued replenishment of nutrients and organic matter that is depleted each cropping season. Soil requires more than NPK (Nitrogen, Phosphorous and Potassium) to maintain fertility, it must be capable of storing nutrients and transferring these nutrients to the root surface for uptake by the plant.

Unhealthy plants result from unhealthy soil. Perhaps the most depleted component in our soil is humus, (decomposed organic matter). Geological humus is produced as dead plant and animal material is metabolized by soil microbes. Organic matter cannot be built up permanently because it continually decomposes. Soil building must be an on going process.  To ensure continued soil fertility, organic matter, in the form of green manure, compost,  crop residues and similar materials should be incorporated into the soil after harvest