Growers Notes on Roundup

This spring we have been receiving many calls on mixing Growers Nutritional Solutions 10-20-10 with Roundup ® Ultra for Roundup Ready ® soybeans.

By Jim Halbeisen


This spring we have been receiving many calls on mixing Growers Nutritional Solutions 10-20-10 with Roundup ® Ultra for Roundup Ready ® soybeans.  Because this will be the third year some customers will be mixing GNS 10-20-10 with the popular post emergence herbicide we can pass on information learned from experience.

The rate of GNS 10-20-10 to be used on  soybeans depends to a great extent on their vegetative growth when the application is to happen.  If the soybeans are less than 10 inches tall the best economic approach would be to use 1 gallon per acre of GNS 10-20-10; whereas, if  soybeans are over 12 inches in height a 2 gallons per acre application is recommended.

Remember that drift control is very important when spraying Roundup ® Ultra.  If using the fine mist tips (smaller drops) Growers Nutritional Solutions normally recommends,  be sure to spray in very low wind speeds and use enough water to give adequate coverage to the plants and weeds.  When using the drift control tips (larger drops) designed for spraying in light breezes, use an amount of water that gives good coverage, but keep it to the minimum.

Also, it is important to remember that absorption by the plant of an organic molecule, (Roundup ® Ultra), occurs much easier than an  inorganic molecule, (GNS 10-20-10).  Therefore you will get absorption of Roundup ® Ultra in the heat of the day; but to get the inorganic elements in GNS 10-20-10 absorbed, you still must follow the Growers regular recommendation and spray in the evening, early morning, or on a foggy overcast day.

Some operators who normally spray straight Growers 10-20-10 (no dilution) have had trouble mixing Roundup ® Ultra because of the very high load of nutrients in Growers, and have found it necessary to add an equal amount of water in the mix.  Also, if you are using hard water when spraying GNS 10-20-10 continue to soften it as in the past before placing the GNS 10-20-10, ammonium sulfate, and Roundup ® Ultra in the spray tank.

According to Monsanto's latest recommendation guide, when using a clear liquid N-P-K foliar fertilizer (Growers) with Roundup ® Ultra it is best to use a clean ammonium sulfate as part of the spray mixture.  Their mixing order is:  #3, #4 and #5.  We are adding #1 and #2.
        1.  add water
        2.  add water softening agent (if necessary)
        3.  add ammonium sulfate
        4.  add GNS 10-20-10
        5.  add Roundup ® Ultra

Finally, Monsanto suggests that trace minerals could hinder the success of their herbicide on perennial weed control or even annual weed control, but Growers Nutritional Solutions customers have not found this to be the case in field usage of these products.  Actually, we do not recommend mixing any pesticide with Growers Nutritional Solutions 10-20-10.  (See "Growers Recommendations For Using" Book.)  However, over the years many people have done so, and successfully, to cut costs, but at their own risk.

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