Agronomy Update  04/18/19 11:33:06 AM


Iron Chlorosis Deficiency (IDC) has been a hot topic this growing season & for good reason! While yellow beans scatter the countryside, members of the Colfax Chlorosis Club, along with Chandra Langseth (Richland Co Extension), Dr. Goos (NDSU Soil Science), and myself (Chelsey Pizel, CFE) are doing our part to determine what we can do in our fields to combat this yellow soybean issue!

Colfax Chlorosis Club's First Annual Field Tour. Throughout the tour we visited fields with Soygreen, row spacing, population, and cover crop trials to see what worked in battling IDC.

Here's what I can tell you about IDC and what we learned through Dr. Goos on our field tour!
For starters, Iron Chlorosis Deficiency in soybeans commonly takes place when two variables are present: High pH soils and moist/wet conditions. According to Dr. Goos, "Colfax is ground zero for IDC"!

I am by no means a soil scientist, so I am going to try to break down what's happening in the soil & soybean plant when IDC symptons are occuring, and put it simply! When a high pH soil gets wet, the carbonates in the soil start to dissolve and form bicarbonates. The bicarbonate nuetralizes acidity in the root zone, thus "inactivates" the Iron that is in the topsoil. The soybean plant responds by trying to reduce the pH in the root zone, using up all of its energy when its already low on Iron = Yellow Soybeans!

Basically, because the Iron in the soil is not available for uptake, the plant tires itself out and turns yellow. Now, when you couple this already tuckered out plant with other stressors (high salts, "burner" herbicides, chemical carryover, etc) we are essentially "kicking the plant while its down" and causing more injury, making the symptoms worse.


So what can growers do to battle IDC?!
  1. Most importantly, Variety selection! When dealing with soils that are prone to IDC, it is crucial to plant soybean varieties that are defensive. Even when using a Chelated Iron product like Soygreen, we cannot turn a weak IDC variety into a strong one! Keep in mind however, even when planting a strong IDC defensive variety, no plant is Immune to IDC. If conditions are bad enough, a good IDC variety will still turn yellow, but it could be the difference between yellow beans & brown/dying beans. 
  2. Soygreen (Chelated Iron) in furrow at planting. Placing Soygreen in the rootzone makes the Iron instantly available for the soybean plant from the start. Some testing has been done comparing Soygreen vs Competing products. What researchers have found is Soygreen has the highest percentage of ortho-ortho EDDHA Chelated Iron (the "good" Iron) therefore creating the best response. This isn't saying not to try Iron products other than Soygreen, just maybe we need to look at using the higher rate of other products.
  3. Row Spacing - 30" Rows seem to be less susceptible to IDC than 15" or solid seeded row spacings. 
  4. Cover crops - we've been seeing a lot of trials dealing with establishing a rye cover crop in the fall, and no-till seeding soybeans into it the following spring. The idea behind the cover crops is to dry out the topsoil; keep something growing to obtain cover over the dirt which in turn prevents evaporation that brings salts to the topsoil.

Lastly, a frequently asked question regarding IDC: Are there any rescue treatments a grower can do in-season?
My answer: Usually rescue treatments are ineffective in regards to yield. The reason why foliar applications of Iron are usually not yield bumping is because of Iron's lack of mobility in the plant. Foliar applied Iron cannot systemcatically move throughout the plant. This means the Iron sprayed over the top may turn the existing leaves green, but new growth will be yellow again. If a grower is wishing to try some foliar applied chelated Iron, I would recommend spraying very early, at the first sign of yellowing soybeans, and apply Iron in split applications to "spoon-feed" the plant. Ideally, a band sprayer would work best to centralize the Iron to directly on top of the soybean plant. 




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