If you’ve had Iron Deficiency Chlorosis (IDC) in the past few years, wouldn’t it be nice if you could find a way to permanently end your risk for having this issue on your farm? There is. If your soil pH drops below 7 and stays there, you will never see IDC again on your farm. Below, I will talk about how to get your soil pH down, but first, let’s discuss why we see this problem in high pH soils and all the other factors that can make it worse.
WHAT IS IDC?
IDC is not a lack of iron in the soil or in the plant. Instead, it’s simply a change in form of iron from the “good” ferrous form to the “bad”/unavailable ferric form. When you soil test, you will still find iron. When you tissue test, you will still find iron. The problem is simply your plant can’t properly use the iron when it’s in the ferric form. If IDC is severe, you will see interveinal yellowing on leaves like in the photo above, stunting, and yield loss. It is also possible to have yield loss without seeing visual symptoms.
WHAT MAKES IDC WORSE?
Once soil pH gets above 7, you are at risk for IDC. The higher the pH, the greater the risk. Additional factors that can make this problem worse include high nitrate levels in the soil, high carbonates and bicarbonates, high salt, excess moisture, and cold temperatures.
WHAT ARE THE “BAND-AID” SOLUTIONS?
While there is no true resistance in varieties, there is certainly a vast difference in tolerance. If you have a bad IDC problem, in the short-term our best advice is pick the most tolerant varieties you can find. The new Chloride Excluder Soybeans (or salt excluders as most people call them) can help to some degree, as well, if salt is a big problem for you. If you have a multi-variety planter or drill, put the good IDC bean in your high pH zones, and plant a better soybean in your other areas. Typically, the best IDC soybeans are not the highest-yielders when IDC is not present. In addition, use an in-furrow iron chelate (like Soygreen). We encourage you to make a variable rate map for your field and apply this only where needed. It will likely give you a fantastic return on investment in your IDC zones, but it is usually a waste of money where you don’t have IDC. Finally, believe it or not, compaction (or rolling your fields), wide rows, and high populations can help. This all comes back to concentration of organic acids released by plant roots. The more plants you have in close proximity, the more acid will be in that immediate soil area to reduce soil pH and convert the ferric iron back to the “good”/available ferrous iron.
HOW DO I END MY IDC PROBLEMS FOREVER?
Get your pH below 7. Yes, it’s possible in ANY soil and in ANY situation. Now, I’m not going to say it’s always economical in year one, but it certainly can be done if you want to do it. It begins with this question – why is your pH high in the first place? Common reasons include poor drainage, high pH water used in irrigation, excess magnesium, excess sodium, and farming subsoil due to erosion removing topsoil. If you address all these issues, your pH will likely come back to neutral over time. If you want fast results, use elemental sulfur, but only if you have great drainage. Also, elemental sulfur works better and faster if you apply a very fine grade. If the particle size is incredibly small and you can see it dissolve quickly in a glass of water, that’s best. If the particle size is big or the material is hard, it may take years before you see results, if ever. If you want specific advice on how to lower your pH based on YOUR soil tests, please send them to us at radio@agphd.com.
OTHERWISE, HERE ARE A FEW GENERAL TIPS.
⊲ POOR DRAINAGE – Add drain tile. The higher your CEC (the heavier your soil), the more tile you need. If your CEC is 40, don’t be surprised if you need tile every 20 feet, at least in the worst areas of your fields.
⊲ EXCESS MAGNESIUM – Use gypsum in most cases to raise soil calcium levels and flush out some of the excess magnesium. Before you do this, fix your drainage if it’s an issue.
⊲ EXCESS SODIUM – Again, fix your drainage first, but once you do, that alone may solve the problem if you also have adequate calcium and excess sulfur. If you don’t, you may need to add gypsum or elemental sulfur.
⊲ BUILDING TOPSOIL – If you have some eroded land like we do, you need to build new topsoil, and no, it doesn’t take 1000 years like some people will tell you. If you reduce tillage, plant crops with lots of roots (like corn), use lots of manure or compost, as well as biologicals, and raise cover crops whenever possible, you will actually see a fair amount of topsoil getting formed within 10 years. Yes, you may not reap all the benefits, but your kids and grandkids will.
In summary, IDC is a terrible issue that affects millions of high pH soil acres. In the short-term, plant tolerant varieties and use Soygreen. In the long-term, work on lowering your soil pH, and this problem will go away. Good luck!