In 1953, the U. S. Atomic Energy Department provided a grant and radioisotopes of all nutrients to Michigan State University. The objective was to study the foliar absorption of fertiliser nutrients and trace their movement in the plants.
Isotopes are different forms of an atom of the same chemical element.
Some isotopes are referred to as 'stable' and others as 'unstable' or 'radioactive'.
It is the radioactive nature of these unstable isotopes, usually referred to as 'radioisotopes', which gives them so many applications in modern science and technology.
Fertilisers 'labelled' with a radioactive isotope, provide a means of finding out how much is taken up by the plant and how much is lost. Efficient use of fertilisers is a concern. It is important that as much of the fertiliser as possible finds its way into plants and that the minimum is lost to the environment.
Radioisotopes showed that all foliar applied nutrients, are absorbed by the leaves. They were even absorbed through the woody tissue of trees.( bark)
In fact, these isotopes showed that it was 8-10 times more effective to foliar feed a plant as far as the amount of nutrients required and the speed with which those nutrients were utilized.
The beneficial effects of a foliar is due to an increase in cellular based chlorophyll synthesis.
This means that chlorophyll production and synthesis is increased in the cells of leaves most exposed to sunlight. Chlorophyll is the green you see in leaves.
We can actually see this increase in chlorophyll, cellular activity and respiration, as one of the first signs you will see in a crop, after the application of foliar fertiliser is the leaves turning a darker green. This can be measured by a Refractometer in as little as 4 hours.
This increased cellular activity and respiration, increases uptake of water by the vascular system in response to increased needs of water by the leaf (this automatically brings more fertilising elements into the plant via the vascular system)
This does not mean that the application of foliar fertiliser replaces the soil applied fertiliser, but increases their uptake.
Rapidly growing plants require large quantities of water, far in excess of that found in the plant for normal synthesis of new materials. This increase in uptake automatically brings more fertilising elements to the plant via the vascular system.
This increased efficiency can reduce the need for soil applied fertiliser, which reduces leaching and run off of fertilising nutrients. Some of the latest research shows increased quality and yield by increasing the uptake of N and P, and providing cellular phosphate at a time of high usage by the plant.
A small amount of potash or phosphate can increase the yield so significantly, actually providing a better return per dollar outlayed than soil applied fertiliser..
The need for more water and greater gaseous exchange stimulates additional root mass to provide it.
Excess carbohydrate produced by the plant, due to greater synthesis of sugars by the increased chlorophyll, are excreted by the root hairs which stimulate microbial colonies on the root by providing additional energy sources.
The bacterial colonies in turn provide auxins and other root stimulation compounds.
More root tissue and root hairs increases the plants ability to uptake water and fertiliser ions.
A chain reaction is set up if the right material is applied at the right time to set up this feedback loop.
Greater efficiencies are to be obtained with foliars because we are stimulating the entire 'pumping' system that comprises the leaf cells.
The important thing to remember is that a small amount of fertiliser used, actually increases the uptake in terms of total uptake by several fold over the amount of fertiliser applied. Some researchers suggest a 6:1 return.
By applying a foliar fertiliser directly to the leaf, it increases the activity in the leaf, at the same time increasing chlorophyll and thus photosynthesis. Because of this increased activity, it increases the need for water by the leaf. In turn this increases water uptake by the plants vascular system, which in turn increases the uptake of nutrients from the soil.
By increasing photosynthesis, we increase production and efficiency.
How do we know this?
Although photosynthesis has interested mankind for eons, rapid progress in understanding the process has come in the last few years. One of the things learned is that overall, photosynthesis is relatively inefficient.
For example, based on the amount of carbon fixed by a field of corn during a typical growing season, only about 1 - 2% of the solar energy falling on the field is recovered as new photosynthetic products. The efficiency of uncultivated plant life is only about 0.2%.
In sugar cane, which is one of the most efficient plants, about 8% of the light absorbed by the plant is preserved as chemical energy.
Some 49 years, after the Michigan State university radioisotopes showed that it was 8-10 times more effective to foliar feed a plant as far as the amount of nutrients required and the speed with which those nutrients were utilized, Washington State University genetically engineered a new rice variety containing a corn gene for higher photosynthesis and thus produced 35% more rice per hectare.
Quote from newsletter 2001. 'A new genetically engineered rice variety from Washington State University contains a corn gene for higher photosynthesis and thus produces 35% more rice per hectare.'
Whether you agree with genetic engineering or not, is not the point here.
The point here is, that by increasing photosynthesis they are able to produce 35% more.
The principle with foliar fertiliser is the same...increased photosynthesis.
Foliar fertiliser, amongst other things, increases chlorophyll production and photosynthesis in the leaves, (which can be measured in as little as 4 hours), which in turn increases the uptake of soil applied fertiliser, in response to increased need for water by the leaf, bringing more fertilising elements to the plant via the vascular system.
The aim of fertilisation is the same for both soil applied as well as foliar applied, but it is, in fact 8-10 times more effective to foliar feed a plant as far as the amount of nutrients required and the speed with which those nutrients were utilized.
This does not mean that the application of foliars fertilisers replace soil applied fertiliser, but increases their uptake.