Have been known for decades, but have not gained traction in a business environment that offers no economic incentives to agribusiness for reducing or eliminating the need for applied fertilizers. Applied fertilizers produce an apparent magical response, and we are discovering that is indeed magical since it can not be sustained into the future.
Soil Microorganisms and Higher Plants is a classic, and worth reading if you desire to understand more of what soil biology can deliver, here are a few excerpts:
The biogeny of soil is the most significant indicator of its fertility. As soon as the activity of a microbial population begins in a rock, the first signs of fertility are manifested. The degree of soil fertility is determined by the intensity of the life processes of the microbial population.
It is impossible to solve problems of pedology, not to speak of agriculture and plant growing, without taking into account the microflora of soil. Plants are a very strong ecological factor, selecting certain species of bacteria, fungi, actinomycetes and other inhabitants of soil. As a result of wrong agricultural practices and crop rotation, the soil becomes infested with harmful microbial forms. By use of suitable plants in the crop rotation, one may change the microflora of soil in the desired direction and eliminate harmful organisms, in other words – restore the health of soil. Page 2 – 3
Increased accumulation of microbes in the root soil was first observed by Hiltner in 1904. He proposed the term “rhizosphere”. In investigating the root system of various plants, Hiltner came to the conclusion that the accumulation of microbes in this area was not accidental and it was caused by the biological activity of the roots. Page 281
The microflora of the root zone is of great importance in plant nutrition. Growing near or on the roots, microorganisms, together with the plants, create a special zone – the rhizosphere. Soil in this zone differs in its physical, chemical, and biological properties from that outside the rhizosphere. The interactions between microbial species and between microbes and plants result in the formation of plant nutrient compounds. Substances present in the soil are subjected to a greater or lesser extent of processing before their absorption by the roots. The plants do not absorb those compounds which are characteristic of soil outside the rhizosphere but rather they absorb metabolic products of the rhizosphere. The rhizosphere microflora prepares organic and inorganic nutrients for the plants. Page 264
In the rhizosphere, iron, manganese, and other metals occur in combination with organic compounds formed by microbes. Amino acids, organic acids, and other metabolites of microbes form stable complex compounds. They are utilized by plants and used as a source of specific organometallic nutrients. These are found in greatest concentration in the rhizosphere and are preserved in the soil for long times. Page 281