Without the contribution of plants, ‘soil’ is only decomposed rock particles.
Plants contribute sugars, organic matter, carbon, the energy that sustains microbial populations.
Plants, through photosynthesis, are the only way we have of bringing new energy into the system.
The photosynthetic engine of most crops is only running at 15%-20% efficiency. (Charles Tsai, et al.) It makes sense to increase the efficiency of this engine as much as we are able.
The first priority of a successful foliar application is to increase photosynthetic efficiency. A foliar application that only addresses nutrient deficiencies and does not increase photosynthesis will not be nearly as effective as a foliar which does both. In fact, a foliar which does not increase photosynthesis can facilitate more efficient extraction of soil nutrients and increase soil degradation. Foliar design matters.
The nutrients which need to be present in adequate supply to increase photosynthesis are nitrogen, manganese, iron, magnesium and phosphorus. Obviously, many others are also important, but these are key.
We can use foliars as a tool for soil regeneration when we use them to increase photosynthetic efficiency and transfer a larger portion of plant photosynthates to the roots to feed soil biology.
When a well designed foliar is applied, the spike in photosynthesis can be observed in sap sugar content and dissolved solids, or brix. (Measured actual sugars on a plant sap analysis is best by far. Brix can be highly variable because of environmental conditions.)
After a successful foliar application, the photosynthetic rate will gradually drop back down, but not quite down to the previous baseline. With each successive application spike, and return to baseline, the baseline level increases. When photosynthetic efficiency baseline improves to a high enough plateau plants contribute more carbon energy to the soil than they withdraw mineral energy and the entire ecosystem becomes self-sustaining.
The drop back to the new baseline can occur quickly or slowly, depending on the level of ecosystem health. In a compromised and degraded ecosystem, the spike may last for as little as 3-5 days before it drops back down. In a healthy soil, with good biology, the elevated spike may last for as long as 5-6 weeks or even longer.
The healthier soils and plants become the fewer foliars are needed until the point is reached where they are completely unnecessary to sustain a level of health where plants are completely resistant to diseases and insects.
While on the pathway to this point, we can still use the photosynthetic efficiency spikes to produce interesting and valuable effects. If we have the presence of larval or sucking insects, a spike in photosynthesis is often successful in giving them a dose of sugar they can’t tolerate.
A slide from an academy presentation. Academy.regen.ag