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Foliar Feeding Organic Herbicides & Pesticides for Soybeans

By Dr. Harold Willis

Foliar feeding is a complex subject that cannot be covered thoroughly here, but in general it allows you to supply small amounts of deficient elements to plants (through their leaves, primarily) at the time they need them.


Fertilizers applied to the soil before planting may not be available to the plants when they need them most—during peak growth and pod fill. Foliar spraying is not an effective way to deliver large amounts of major nutrients (so it is best to have them in your soil already), but it can help pull your crop through a difficult period and produce a good yield. Foliar spraying will often stimulate the plant to take up more of the soil’s nutrients.

soybean symptoms

Ordinary field sprayers do not produce a very fine spray, so they waste a lot of material. Better sprayers homogenize or atomize the spray, allowing you to spray a field for only cents per acre in some cases. You can mix your own tailor-made spray mixture with a little experience, depending on what your plants need at that time.

A good “all-purpose” spray is a mixture of about 6 quarts liquid (emulsified) fish and 2 quarts seaweed, diluted in 100 gallons of water (deionized or soft water is best). The fish and seaweed mixture should be acid (pH 5-6.5); this can be done by first adding from 1 pint to 2 quarts of liquid phosphoric acid to the 100 gallons of water. The liquid fish should be strained to keep from plugging your sprayer. Spray at the rate of 1 quart of the mixture per acre if you have a homogenizing sprayer, or until plants are wet.

Another spray mixture for young soybeans when soil fertility is low (low calcium and phosphorus, especially) is as follows: add in this order to 100 gallons water, (1) up to 2 gallons of 9% ammonia solution (or household ammonia); (2) up to 2 quarts liquid phosphoric acid (available from feed dealers or pharmacies); (3) 1-2 pounds of iron sulfate (dissolve first in warm water); (4) 5 pounds of soft rock phosphate (stir into a container of water and skim off and use the white, milky water above the mineral); and (5) 1 pound potassium sulfate (or 8 ounces potassium hydroxide). Spray at a rate of 7 gallons per acre, or until plants are wet.

If older soybeans have blossoms falling off and failing to set seeds (some will do this anyway), a spray mixture that may help contains the following in 100 gallons of water: (1) up to 2 quarts liquid phosphoric acid; (2) 1-2 gallons ammonia solution; (3) 1-2 pounds iron sulfate (dissolve first in warm water); (4) up to 8 ounces manganese sulfate; (5) 5 pounds soft rock phosphate (stir into a container of water and use milky water); and (6) 1 quart emulsified oil (crop oil, dormant oil). Spray at 7 gallons per acre, or until plants are wet. Additional sprayings may be needed at one-week intervals; if so, use ingredients at one-half strength and eliminate the emulsified oil.

Even after soybeans are older and filling seeds, yield can sometimes be increased by using a fish emulsion spray (2 gallons fish per 100 gallons water; spray until plants are wet). Do not use fish sprays after two weeks before cutting if the crop is for hay or forage, since animals do not like the taste.

Many proprietary brands of biologicals suitable for spraying are now on the market, and are advertised in Acres U.S.A.

Drone spraying soybeans
New technology offers farmers even more ways to effectively care for their crops!

Researchers at Iowa State University developed a foliar spray mixture that increased yield substantially when sprayed after pod set, since at that time root nodules begin to die and disintegrate. Their spray contained nitrogen, phosphorus, potassium and sulfur in the ratio 10:1:3:0.5. The fertilizer source materials they used were urea, a 3-20-18 formulation containing polyphosphate, and potassium sulfate or ammonium sulfate. Some sprays also contained 5% sugar. When tested by researchers in other states, results were disappointing, possibly because of soil imbalances. Most observers expected the Iowa State program to fail because it cost too much, and because the preparations were in danger of burning the plants.

Feeding foliar sprays through an irrigation system is an effective method of application if you are able to do this.

The best times to spray are in foggy weather or in the early morning (4:00 to 6:00 a.m.), since this is when the plants take in nutrients best. The evening (after 7:00 p.m.) is another good time to spray. Be certain your sprayer has no traces of herbicides or pesticides. Clean thoroughly with baking soda solution. You can test to see whether the spray mixture is going to help your crop if you spray several plants with a small hand sprayer (such as used with window-cleaning products). Wait a half hour and then test the sugar content of sprayed plants with a refractometer compared to unsprayed plants. If the sugar content increased, the mixture is beneficial.

Spray with Hydrogen Peroxide

An interesting development on the eco-agriculture scene is the use of hydrogen peroxide, H2O2, in a variety of ways. When added to animals’ drinking water in diluted amounts (about 30 parts hydrogen peroxide per one million parts water; or about 8-10 oz. of 35% hydrogen peroxide [or 3 quarts of 3% hydrogen peroxide] in 1000 gallons of water), the incidence of disease and sickness drops dramatically, from pneumonia to mastitis. Meat and milk production rise. Hydrogen peroxide solution can also be used to drench animals, as an udder wash, and to rinse dairy pipelines and bulk tanks. In animal (or human) use, it appears to act by providing more oxygen to internal tissues (hydrogen peroxide is basically water, H2O, with an extra oxygen atom, H2O2). Externally it also acts as a disinfectant, killing germs.
But hydrogen peroxide also helps plants grow better, although the mechanism is not clear. If seeds are soaked in a hydrogen peroxide solution (1 to 5 oz. of 3% hydrogen peroxide in 1 pint water or ½ to 2 oz. of 35% hydrogen peroxide in 2 quarts water) for about 8 hours, the percent germination should increase (germinating seeds need oxygen).

For a foliar spray to perk up growing plants, use 1 pint of 35% hydrogen peroxide (or 11 pints of 3% hydrogen peroxide) in 20 gallons of water to spray one acre.

Hydrogen peroxide also makes an effective insect spray. Use at a rate of about ½ pint of 3% hydrogen peroxide (or 1 oz. of 35% hydrogen peroxide) along with ½ pint of molasses per gallon of
water (equal to about 6 gallons of 3% hydrogen peroxide [or 5 pints of 35% hydrogen peroxide] and 6 gallons of molasses per 100 gallons water). The molasses helps the solution stick to the plants and also gums up small insects. What drips onto the ground will help the plants grow better, too.

The preferred form of hydrogen peroxide is 35%, or food grade. It is harder to get than the 3% solution sold in grocery and drug stores. The latter has small amounts of preservative chemicals added, but they may not be harmful when used on plants.

Source: How to Grow Super Soybeans