Submitted by: Brett Harman, IFA Agronomy Purchasing Manager With permission and Information provided from: Cory Schurman, Agro Culture Liquid Fertilizers
Foliar feeding of nutrients is very successful when general application guidelines are followed.
Responsible Nutrient management utilizes products and application methods that give applied nutrients maximum efficiency.
For a nutrient solution to work when foliar-applied, it’s necessary to have a low salt index. When products have a salt index above 10, they usually cause leaf tissue damage or give a plasmolysis reaction that results in plant cell damage and cell collapse.
Making applications with high salt index products result in browning, burning or speckling on the leaves and stems. When these types of reactions happen, nutrients are not easily absorbed into the growing crop, offering little or no results.
IFA uses products that have low salt indexes. We can foliar feed a crop in season and achieve consistent and positive results.
A combination of nutrients are usually recommended after a review of tissue analysis, known soil deficiencies and crop uptake needs, as well as visual observations during the season.
The grower and IFA crop advisors take that information and develop a combination of nutrients that best address the crops requirements and give the best results.
For best results when foliar feeding, there are some basic rules that should be followed to provide the best opportunity for positive, consistent results.
1. Temperature — Plants will begin to close the stomatal openings or curl the leaf at 87 F. This is done naturally so a plant does not transpire as much water during the heat of the day.
Applying the nutrient solution before that temperature is reached gives the grower the best chance of overcoming the normal plant physiological functions. Plants can better absorb nutrients when the temperature is below 87F.
2. Salt Index — Whatever products are foliar fed, spray solutions should have a salt index of 10 or less. Application of IFA low salt index products will result in an osmotic absorption, which is quick, clean and complete absorption of nutrients into plant tissue without tissue damage. This gives the grower the best chance of achieving positive results.
3. Humidity — Humidity levels vary greatly across the United States. Utah has very low levels of humidity compared to the Midwest.
Higher humidity levels will help overcome leaf curling and stomatal closing, which also allows the nutrient solution to perform better and be more completely assimilated into the plant.
4. Sunlight — For best results when foliar feeding, plants need to be metabolizing and growing. This happens during photosynthesis.
For best results, applications should be made during the day so that the plant can absorb the nutrient solution, providing the best opportunity for positive results.
5. Droplet Size — Apply nutrient solutions with good atomization and small droplets. There are several spray tips available that will accomplish this. Whatever tip you choose, it’s best to have the pressure calibrated to at least 40 psi with the best results being achieved at more than 60 psi.
One thing to remember when foliar feeding is that a large percentage of stomatal openings are on the underside of the leaf. Applying solutions that coat both sides of the leaf will give the best chance of obtaining positive results.
When growers determine crop nutrient needs and make applications with the above guidelines, they will have the best chance to increase yields and overcome stress. Foliar feeding then becomes a valuable management tool that the grower can use to supply nutrients to a growing crop.
If you have questions about foliar feeding or need help putting together product mixes, talk with your local IFA certified crop advisor to determine the right combination and timing.
