Features of leaf feeding
The plant can assimilate the elements of nutrition in large volumes only with the help of the root system. Sufficient supply of plants with nutrients at the beginning of the growing season «programs» their high-yielding type of development.
Foliar top dressing is most effective on well-fertilized soils and with intensive cultivation technology, where one of the macro - or microelements can be a limiting factor for yield growth.
In stressful situations (low temperatures, frosts, lack of moisture, etc.), the assimilation of nutrients by the root system is insufficient, and this slows down the growth and development rates. At low temperatures, they are not fully absorbed even with the optimal amount of available macronutrient compounds and moisture in the soil. The ability of nitrogen assimilation by the root system is especially reduced. In the second place – phosphorus. Potassium is relatively less sensitive to a decrease in temperature.
Often, critical periods regarding the lack of macro-and microelements in cereals occur in the phase of entering the tube-earing. Due to the intensive, rapid growth of the vegetative mass, the reserves of easily accessible nutrients from the soil are exhausted or their assimilation «does not keep up with the growth rate of plants». This is especially noticeable in years with cold nights.
In such a situation, the plant can be helped by foliar (leaf) fertilizing.
The degree (percentage) and rate of assimilation of nutrients from fertilizers through the foliage is significantly higher than when assimilation from fertilizers introduced into the soil. But the volume of assimilation of elements through leaves is limited. The leaves absorb nitrogen, magnesium, potassium the fastest, sulfur is slower, phosphorus, calcium and trace elements are even slower. Despite this difference in the rate of penetration of nutrients into the plant, in general, they are absorbed by the leaves much faster than the root system from the ground.
It is difficult to consider leaf feeding as a method of using phosphorus, potassium, calcium, etc.Nevertheless, nitrogen can be introduced in much larger quantities, and the need for trace elements is often completely satisfied by this method. Microelements during leaf feeding are 10 times more effective than when they are introduced into the soil, where they can bind into inaccessible compounds.
What the leaves digest
Leaf feeding with potassium is inefficient and economically unprofitable due to insufficient and slow assimilation through the foliage. Potassium is absorbed 21 times slower than nitrogen from a urea solution and 15 times slower than magnesium. The rate of leaf assimilation of potassium (it is necessary in large quantities) is significantly lower than that of trace elements (micro-quantities). It is more difficult for him to pass through the cuticle of the leaves. This is due to the fact that the potassium ion (K+) is twice as large as the copper (Cu+) and magnesium (Mg2+) ions. Potassium cations are 2.66 A, and magnesium (Md2+) – only 1.30 A, copper (Cu2+) – 1.38 A. There is evidence of the expediency of leaf application of potassium only in dry weather to maintain the turgor of leaf cells.
Even less effective is leaf feeding with phosphorus, which is absorbed by the foliage 30 times slower than nitrogen from a urea solution. The reason is a very difficult penetration of phosphorus through the cuticle of the leaf. The H2PO4 ion is 9.97 A, which is 7.6 times more than the magnesium ion, and 7.2 times more than the copper ion. In addition, if phosphorus is contained in large quantities in fertilizers for leaf application, this leads to precipitation and clogging of sprayers in sprayers.
Magnesium is very well absorbed by the leaves. It is absorbed 10.4 times faster than potassium and 15 times faster than phosphorus. Sorption of magnesium through the leaves is accelerated by 2-3 times if it is applied simultaneously with urea.
Magnesium sulfate is an important fertilizer in modern crop cultivation technologies to solve the problem of rapid compensation of magnesium and sulfur deficiency.
The introduction of trace elements in the form of inorganic salts is ineffective for the following reasons:
1. Plants are not adapted for the complete assimilation of inorganic salts of trace elements, so the percentage of assimilation is insignificant relative to the amount introduced.
2. Metal salts are toxic substances for plants if the optimal application rate is exceeded, causing burns at the point of contact with the plant.
3. In the soil, metal salts react with soil components and turn into compounds inaccessible to plants.
The ability of the elements to penetrate through the leaves: nitrogen, magnesium, sodium penetrates the fastest, sulfur is slower, and calcium, potassium, phosphorus and trace elements are even slower. Nevertheless, even calcium and phosphorus are absorbed through the leaf surface several times faster than from the ground.
Chelated micro-fertilizers. The main disadvantages: The chelating agent has a large size and can penetrate into the plant only through the stomata, and therefore the effectiveness is 30-40%. Trace elements enter the intercellular space and not all of them can penetrate into the cell itself. Chelated micro-fertilizers are on the surface of the leaf for only 2-3 days, and then they are destroyed.
The fundamental difference between «Aquadon-Micro» and other trace element fertilizers is that «Aquadon-Micro» is a water-polymer high-molecular complex of long hydrocarbon chains with trace elements attached to them, which are in ionic form. Due to ion-polymer and coordination bonds, they are not oxidized, but are absorbed by plants; due to polymer chains, fertilizers are retained on leaves, root hairs and soil particles and have a long-term effect on the plant during various periods of vegetation. The conducted scientific and industrial tests allowed us to assert that when using Aquadon-Micro, the processes of plant photosynthesis are intensified, the growing season is shortened (up to 10 days), the content of sugars, carotene, starch, and vitamin C in the cultivated crops increases. It should be noted that the first treatment stimulates the growth of plants, and the second affects the quality of products. Due to the unique composition, trace elements are distributed evenly throughout the solution (Flory's theory), trace elements are firmly held in the matrix due to intermolecular interaction(Van der Waals forces), promotes dissolution and uniform distribution of other drugs in the tank mixture(the Rebinder Effect).
On a plant leaf, the matrix forms a monomolecular layer that does not wash off, but is vapor - and air-permeable. In 1l of «Aquadona-Micro», the polymer matrix is 15%. Experiments were carried out on freezing-thawing for 15 cycles at a temperature of -25 degrees, after that the fertilizer retained its properties. In experiments on heating the drug, it was kept for six months at a temperature of 55 degrees and it also retained its properties. Its freezing point is about -5 degrees. The shelf life is virtually unlimited.to the section