Reduce the risk of IDC in your soybeans

It’s time to take proactive measures against IDC, before it shows up

Last year was one of the worst for Iron Deficiency Chlorosis (IDC) in soybeans that anyone has ever seen on the Canadian prairies. It was bad enough that we wrote this blog about it.

We outlined the three main causes of IDC: high soil pH, soluble salts, and carbonates. Now we can focus on how to reduce IDC risk – with proactive measures that must be taken before IDC symptoms emerge.

Select the right field

Testing your fields for calcium carbonate equivalent (CCE) and soluble salts will give you the information you need to select the right field for soybeans this fall. Always select fields with the lowest carbonates and soluble salts. If soils typically have a pH higher than 7.3, you need to test. Two fields with the same pH of 7.3 may have very different carbonate levels – one may be zero and the other 10%.

Once you’ve completed your soil tests, assess your risk level using the risk ratings in the table (Table courtesy of AGVISE Laboratories).

Risk of soybean IDC

CCE Soil Level (Carbonate) Salt Level (Routine 1:1 test) IDC Severity Risk 
% Mmhos/cm  Relative Risk
0-2.5% <0.5 Low
0-2.5% 0.5 - 1.0 Moderate
0-2.5% >1.0 Very High
2.6-5.0% 0-0.25 Low
2.6-5.0% 0.26-0.50 Moderate
2.6-5.0% >1.0 Very High
>5.0% 0-0.25 Moderate
>5.0% 0.26-0.50 High
>5.0% 0.51-1.0 Very high
>5.0% >1.0 Extreme

 

Choose the best variety

If you absolutely must put soybeans on a high risk field, choosing the right variety is the number one way to combat IDC. Not all varieties are created equal on the tolerance scale, and if you know you are at risk of developing IDC, choosing a high tolerance variety is of utmost importance. 

In Manitoba, one of the best tools we have for determining IDC tolerance is Seed Manitoba, a guide to various crop varieties in the province. Varieties receive a rating of 1-5, with 1 being the most tolerant. This is a good guide for selecting varieties, but nothing will beat the actual experiences you have on your own farm. Keep track of the varieties you grow, how well they hold up under high risk IDC conditions, and how they compare to each other.

While both of these choices can help reduce risk, field selection remains the number one priority. Further steps to reduce your risk are unnecessary if no risk exists, and there is no way to make an IDC-susceptible variety into a tolerant variety.

If you have questions about how to assess and reduce your IDC risk, or about field and soybean variety choice, contact your local Cargill agronomist. 

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