Proper Foliar Feeding and Water Considerations
Welcome to our annual foliar feeding methodology article! This year we would like to share with you some of our own research results that speak to the importance of foliar feeding and using proper water.
ARE ALL WATERS EQUAL WHEN IT COMES TO FOLIAR FEEDING?
In the Summer 2022 Growers Solution, we looked at the effect of foliar feeding on top and root mass. This year we would like to highlight the observed difference in 4 kinds of water used to spay GMS on a cucumber leaf. In this experiment, Matt placed a drop of solution (10% GMS) on four different spots of the same cucumber leaf. The types of water used were city water (treated by the municipality of Tiffin, Ohio); his own well water (untreated in any way); softened well water, and rainwater. Four hours after the application, once the water had been absorbed/dried, there was residue left where each drop had been. He re-moistened the leaf surface to simulate dew, and then took the photo shown in Photograph A three days later. Please note that the 4 close-up pictures in Photograph A were taken through a microscope. You can see that the only drop that has largely not resolubilized is the drop with city water. However, if you look closely, you will see that there is either some material or damage left where the softened water was. Interestingly, the well water seems to have been resolubilized and absorbed almost as well as the rainwater drop.
We are showing this experiment because we have mostly compared the differences between hard water (untreated) and either R.O. or rainwater. However, there are many people who will treat their water with a softener or, especially in gardens and if they are on municipal water, will use city water. We will go into more depth with this experiment in a future Solution, but for now, let Photograph A provide you with some food for thought!
DOES FOLIAR FEEDING EFFECT SOIL MICROBES?
We often talk about the benefits of foliar feeding to the plant, but only recently have we started considering the effects of it on microbes in the soil. In the foliar experiment highlighted in the Summer 2022 foliar feeding methodology article, Matt also took microBIOMETER readings of the soil supporting the plants he was spraying. Remember that these plants were sprayed once or twice (two experiments were done) with a 2 gallon per acre equivalent of GMS mixed in pure water. You can see the microBIOMETER results in Table 1 and Table 2.
A few things to note:
1. It is clear that foliar feeding does have an effect on the soil microbe biomass (amount of living material).
2. Regular GMS (with trace elements) provided the best results in both experiments, including doing better vs. GMS without trace elements.
3. There isa discrepancy between the single and double spray experiments where the GMS without trace elements did better than other treatments in the single, but was outclassed by both molasses and the check vial in the double.
4. In both experiments, both 28% and 9-18-9 appeared to have a detrimental effect on the biomass.
WASHING AND MIXING PRECAUTIONS
Since many people's sprayers are used for multiple products-including fertility and various pest and weed control products-it is important to remember to wash out your sprayer of old product before going out to spray GMS. This is for two reasons: 1. Even residual amounts of herbicides, such as that left in the lines or lining the inside of the tank, are strong enough to seriously damage or kill non-resistant crops if accidentally sprayed onto them. This is especially important with newer technologies, including glyphosphate, dicamba, and 2-4D mixtures. Please follow proper protocols in order to avoid crop damage. 2. GMS is unpredictable in how it will react to or affect herbicides when they are mixed. Just as when mixing with some hard water, there may be a precipitate that will cause efficiency and equipment problems. Also, some operators have noticed an increase in herbicide potency when mixed with GMS, causing even resistant crops some problems. It is not advisable to tank mix GMS with any other product.
FINE MIST
Foliar feeding with fertility products is most successful when as much of the plant as possible is coated in as fine a mist as possible. The pores in leaves' cuticles are very small and so will absorb small water particles much better than large ones. Spray pressures over 40 psi tend to produce the smallest particles. In addition, if spray drift is a concern, tend towards higher spray pressures for the anti-drift type of nozzle you are using. Remember, plants can absorb nutrition through their leaves and through smooth bark/stalks, so getting as much coverage as possible is in your best interest.
SPRAY TIMING
Foliar spraying should not be done in the heat of the day or in direct sunlight. This is because foliar nutrition must be absorbed through pores in the leaf surfaces which will close in high heat or sunlight to prevent water loss from the plant, thereby preventing them from absorbing anything on their surface. Furthermore, since foliar nutrition must be absorbed with water through the plant surface, we advise that you spray when there is or will shortly be dew on it. Taking these together, the best times to spray are early morning, late evening, on overcast or foggy days, or anytime the leaves will have dew on them. If you do spray in high heat or direct sunlight, the risks of leaf burn and bad fertilizer efficiency are high.
SPRAYING GMS STRAIGHT OR DILUTED
GMS can be sprayed straight or be diluted in water. In the early days of the company, when low-volume sprayers were more commonplace, spraying GMS straight was by far the most popular choice. Since the use of foliar-applied herbicides and fungicides has become widespread, higher volume sprayers have become more the norm. In such a case, GMS can be mixed with water to meet volume requirements. Spraying straight or diluted does not affect the effectiveness of GMS, barring if water of poor quality is used.
If you are going to mix GMS with water, it is best to use R.O., distilled, or rainwater because they contain little to no dissolved solids. The phosphorus in GMS can react poorly with the various elements in hard water, creating a white precipitate that reduces efficiency and can plug up sprayer screens and nozzles. However, if you keep the amount of water added under the amount of GMS, this should not be a problem.
WATER QUALITY CONSIDERATIONS
In the past, we recommended that, if you were going to mix GMS with hard water, you acidify the water first to ensure it wouldn't react with the GMS and produce a precipitate. Acidifying the water will prevent the phosphorus and various elements from bonding together and precipitating out. While this will ensure that the mixture makes it through your screens and nozzles, research done over the past year and a half has shown that, even if the water and GMS don't react, there is still a detrimental effect on the leaf from using hard water. The mineral left on the leaf surface from the hard water can impair photosynthetic potential, so it is important to use clean, low dissolved solid water to ensure no harm comes to the plant and you get the most out of GMS. We are finding that even water sources that have been treated either by a municipality or in a water softener and other in-home treatment equipment (excluding an R.O. system) may have detrimental effects on the leaf surface. This is for the same reason hard water can harm leaf surfaces: Whatever mineral is in the water that is not absorbed by the plant will remain on the leaf surface.
This is an excerpt from the Summer Growers Solution (2023) written by Zach Smith, Product and Training Specialist.
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