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Why foliar feed?

The value of foliar feeding was proven many years ago at Michigan State College by Dr. H. B. Tukey. The project used radioactive tagged nutrients to prove that plants absorb nutrients not only through the roots, but also through the foliage, the fruit, the twigs, the trunk and even the flowers. Plants can absorb nutrients 8 to 10 times more efficiently through their leaf surfaces than through their roots. When applying nutrients to the leaf, the nutrients move through the stomata downward through the plant--at the rate of about a foot an hour. When applying nutrients to the leaves in soluble forms, as much as 95 percent of what is applied may be used by the plant. If a similar amount is applied to the soil about 10 percent of it is available. Foliar feeding is effective even on dormant plants and trees. As a result, spraying foliage with liquid organic nutrients can produce remarkable results without reliance on synthetic fertilizers
1.
Foliar Feeding
Of Nutrients
Foliar application of plant nutrients can produce higher yields and make your nutrition program more efficient

For many years, horticulturists and agronomists have largely subscribed to the belief that foliar feeding of plant nutientsis an idea of dubious merit best employed only where a specific minor element deficiency may exist. Dramatic and fast correction of such nutrient deficiencies are generally always seen from such foliar applications.
Dr. H.B.Tukey, renowned plant researcher and head of the Michigan State University Dept of Horticulture in the 1950's,working with research colleague S.H. Wittwer at MSU, first proved conclusively that foliar feeding of plant nutrients really works. Researching possible peaceful uses of atomic energy in agriculture, they used radioactive phosphorous and radio-potassium to spray plants, then measure with a Geiger counter he absorption, movement, and utilization of these and other nutrients within plants. They found plant nutrients moved at a rate of about one foot per hour to all parts of the plants.
Comparing efficiency of plant use of foliar-fed nutrients versus soil-applied nutrients near roots, they found foliar feeding provided about 95% efficiency of use compared to about 10% of use from soil applications. Likewise, speed of absorption and use by foliar applications was immediate, whereas from soil applications absorption and plant use both were very slow, thus providing a major benefit of foliar feeding where a specific plant nutrient deficiency may exist, be it majoe or minor nutrient.
You’ll note from references of these researchers’ work cited herein that this very important finding was published, but only in research journals and symposia proceedings. These findings rarely made their way into the ranks of Extension educators or their grower focused publications and other teaching materials or programs. Now, half a century later, it is important to bring these science based findings to light and publisize this work to benefit growers and their crops.

Putting it to good use
Armed with this knowledge dug from research journals, commercial agricultural chemists began developing foliar feeding formulations. Their continuous product improvement research has resulted in products containing not only specific plant nutrients , but also natural plant sugars that aid rapid entry and movement into and through plants, plus cytokinins: natural plant growth hormones extracted from seaweed, now stabilized for several years of shelflife. Together with nutrients, they aid natural plant defense mechanisms to resist many diseases and insect pests.
Such products can help improve your soil and your plants’ health for higher yields with lower pest control inputs and plant nutrients cost, based on tests over the past year. A small amount of plant nutrients, foliar applied, can replace a much greater amount that is soil applied, and is immediately available.

A Range of Benefits
At recent meetings, growers have expressed great interest in nutritional plant health products:
1) Some, for soil application, contain enzymes that cause an increase in the soil’s native population of bacteria and fungal microflora to improve soil structure, water and air permeability, and help unlock bound-up, currently unavailable soil nutrients.
2) Some, for drip irrigation, improve plants without nitrogen
3) Some, for foliar application, provide the fastest plant response.
All are designed to supplement and improve your soil fertility program. Several are certified by the organic materials review board institute, and some are formulated for sustainable non toxic use. With improvements in plant absorption technology, use of food grade nutrients prevents plant absorption of possible impurities that may be contained in non food grade formulations. Such impurities could become part of the fruits and vegetables that we would consume. Check the plant food labels!

FOLIAR FERTILIZATION IMPROVES NUTRIENT USE EFFICIENCY
Studies are showing foliar fertilization is more efficient and reduces potential environmental impact

Summary: Isotope studies have shown that the quantity of soil applied nitrogen (N) failing to get into the crop can range from 85 percent in the worst case to 38 percent in the best. By contrast, foliar applied N can be up to seven times more efficient than soil applied N. Other benefits of foliar applied N include lower application rates (higher efficiency), plus the relative ease of obtaining timely, uniform applications.. A combination of soil applied and foliar applied N is the best management practice to reduce the potential for nitrates in groundwater.

Research has shattered the belief that only roots absorb nutrients. The use of radioactive and isotopically tagged nutrients has confirmed that plants can be fed through there leaves Foliar n, in particular, is absorbed through other green tissue including stems, buds, blossoms, and fruit. Loss pathways for foliar applied nutrients are few, but they are many with soil applications.
During the past several decades, increased levels of nitrate in the groundwater have occurred in many agricultural areas. Soil applications of N fertilizer, when associated with porous soils and irrigation or with shallow water tables, are linked to increases of groundwater nitrates. By contrast, foliar applications have provided a highly efficient alternative for feeding N to plants. The propensity for nitrate to move below the root zone and eventually to groundwater is being significantly reduced with foliar applied N. Slow release N in the form of technologically advanced liquid polymethylene urea-methylene diurea is being applied with a high degree of plant safety. Applications are being made at agronomically significant rate at any time in the vegetative growth cycle.

PATHWAYS FOR SOIL LOSS
Plant roots usually occupy less than one percent of the soil volume, hence less than one percent of soil applied N will be directly contacted by growing roots. Pathways for soil applied N losses include:
• Mineralization
• Clay particle fixation
• Leaching
• Microbial immobilization
•
Denitrification
• Volatilization
Considerable N can be lost through volatilization and denitrification. Some N is immobilized by microbial activity and clay fixation.
These pathways reduce the amount of N available for plant uptake. The efficiency of this uptake can be defined as the ratio of fertilizer N in the crop to fertilizer N applied to the soil. By any measure of efficiency, uptake of soil applied n is relatively low. Even in best case studies the crop did not recover 38 percent of the soil applied N. In worst case scenarios,85 percent of the soil applied N failed to reach its intended target.

HOW IT MOVES
During the growing season, most of the available N is in the nitrate form. The direction and degree of its movement is dependent on the amount of water entering the soil and the rate of its downward movement. Nitrate can move downward at a rate greater than that which is used by the crop. The depth it moves is dependent upon the amount of water entering the soil and the texture of the soil.
Studied have shown that the vertical downward movement of nitrate in a sandy soil at field moisture capacity was about 45 inches for 10 inches of water entering the soil. Downward movement was 30 inches in medium textured soil (loam) and 20 inches in a clay soil for every 10 inches of water entering the soil. All too frequently, soil applied nitrate N is positionally unavailable to plants. By comparison, foliar applied N is always positionally available.

FOLIAR EFFICIENCY
Foliar applied nutrients have the benefit of being 4 to 30 times more efficient and there is no risk of groundwater contamination. Studies using labeled phosphorus (P) on apple, cherry, corn, tomato, potato, and bean crops have shown that as much as 12 to 14 percent of the total P can be very immobile in the soil, foliar applications can be up to 20 times more effective than soil applications.
The benefits of foliar N sprays compared to soil applications include lower application rates and ease of obtaining timely, uniform applications. With attention to best use guidelines, the efficiency of foliar applied N may be optimized at nearly 95 to 100 percent. Based on the foregoing information, if the recovery of soil applied N ranges from 15 to 62 percent, it can be concluded by the method of estimation that foliar applied N has an efficiency of 1.3 to 1.6 times soil applied N at the low end and 7 at the upper end. Compared to soil applied N , on a pound-for-pound basis, foliar applied N can be up to 7 times more efficient.

STIMULATES PLANT
There is a direct link betwen foliar feeding and the activities of the enzymatic systems of the plant. The timeliness and ready availability of nutrients provided by foliar feeding stimulate enzymatic cycles to greater efficiency and quicker response. Elements have been shown to translocate as much as one foot per hour from the leaves to the roots. This rapid movement may be explained by the triggering of auxins or the stimulation of the energy mechanisms within the plant.
The “law of little bits” always applies to foliar feeding. It is better to spray small amounts of material more frequently than to drench the foliage with large amounts of material. Small quantities of key elements such as n “speed up” the physiological functions of the plant.
If foliar feeding is done correctly, visual results may be seen within 48 hours.

GENERAL TIPS
From what we have learned, the following five points are the most important to getting best results from every application of foliar applied N and protecting the environment.

• Make sure products used are in proper form
• Apply prior to growth stage to be affected
• Make certain coverage is thorough and complete
• Make applications when they wil be most effective
• Make sure of compatibility when tank mixing with other materials
• Reduce amount of water to improve results.

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Foliar Feed For efficiency