Dr. Dan Talks Agronomy

Give Me a Little Sugar

Can a dose of sugar kick start your crop? Yield contest growers swear by it, but the research is less conclusive. (DTN photo by Pamela Smith)

I'm still on a holiday sugar high, so it seems a good time to bring up the concept of adding a spoonful or more to a starter or foliar nutrient cocktail. Many of the winners of the yield contests and those who adopt biological practices add sugar as a "secret ingredient." The question is -- does it work?

We know that sugar is the energy of life. Almost all organisms break down sugar to support metabolic activities. In plants, photosynthesis produces sugar and cellular respiration burns sugar as energy.

When growers talk about adding sugar, they usually refer to corn syrup (fructose), granular table sugar (sucrose) or cane or sugar beet molasses (mixture of sucrose, glucose and fructose). The key to using sugar is that it has to be relatively inexpensive and easy to use.

Granulated sugar -- the same stuff that's in all those Christmas cookies we just consumed -- is easy to use, soluble and readily available. Molasses and blackstrap molasses are viscous liquids, inexpensive and readily available at feed mills or beet processing plants, but handling can be messy when poured by hand or transferred with a gear pump.

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Adding a little sugar to the soil stimulates microbes that need active carbon to thrive. Active carbons are always in short supply because microbes readily consume it and sugars are active carbon. In the soil, sugar supplies energy to microbes feeding on cellulose and humic materials and stimulate mineralization.

Sugar as a foliar application is less clear and most growers are adding sugar in this way. Sugar can't replace or substitute for the sugar produced by photosynthesis, so it doesn't influence yield. In other words, if the plant isn't producing enough sugar for itself, adding sugar as a foliar won't help. Nothing is absolute -- molasses products do contain vitamins, minerals and biostimulants or biochelators that when added to a foliar cocktail can improve performance and stimulate photosynthesis.

Kip Cullers, the Missouri farmer who has set soybean yield records, used sugar as one of his many inputs and included it in his post applications of herbicides and nutrients. In a DuPont Pioneer question-and-answer column, Cullers responded to the question of sugar by saying:

"I add sugar to the tank when spraying Roundup to help with yellow flash. I believe adding sugar also helps protect soybeans or "softens the blow" when applying Roundup. Overall, when I add sugar I'm trying to feed the microbes. Sugar or any other carbohydrate such as molasses found in calf feed can be used. I apply anywhere from 2 to 3 pounds of sugar per acre."

Read more here: https://www.pioneer.com/….

Another on-farm study on sugar was conducted in Nebraska. While they did not see a yield increase, the grower applied 3 pounds of sugar with 10 gallons of water on corn between V7 and V8 and noticed much better standability in the absence of fungicide. Read more here: (http://cropwatch.unl.edu/…).

Shawn Conley, University of Wisconsin agronomist, evaluated four sources of sugar applied at 3 pounds per acre in 15 to 20 gallons of water at locations from Wisconsin to Ohio in 2010. Products were applied foliar V4 to R1. There was no phytotoxicity observed, but they also did not see any yield benefit. Conley concluded: "While this study cannot conclusively prove foliar applications of sugar will not increase soybean yield, the authors [researchers] conclude that other management strategies to improve soybean yield should take precedence over applying sugar." The article was originally published in the University of Wisconsin Crop Manager, June 16, 2011, Volume 18 Number 14 and can be found at http://corn.osu.edu/….

If you have a sweet tooth and are determined to test sugar, do your own testing. My assessment is soil applications might make sense as they can stimulate soil microbes and can be healthy for the soil and crop. The information on foliar applications seems less palatable, and I recommend some testing to get a taste of what it might do.

Dan Davidson can be reached at AskDrDan@dtn.com

(PS/AG/BAS)

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