Mycorrhizal root extenders which magnify access to nutrients and moisture while simultaneously promoting growth of existing roots.
Vesicular Arbuscular Mycorrhiza (VAM) are fungi that grow as fine filaments which attach to the plant roots forming a pipe-life network, effectively extending the original root coverage by several hundred percent.
This filament system retains and delivers moisture and nutrients supplied to the fungi by the plant. The host plant produces a larger root structure in response to stimulating compounds excreted by the fungi which are attempting to increase the available surface area to which they can attach.
VAM are capable of extending the nutrient scavenging capacity of the plant on a purely physical basis, but they also release compounds which dissolve the elements prone for forming insoluble compounds - phosphorus and zinc are primary examples. VAM improve soil structure through the release of organic glues that bind the soil particles into aggregates forming a highly desirable crumb structure.