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NW Iowa | No it doesn't, but it makes a huge difference on what it holds.
high CEC reduces these losses by holding ammonium within the root zone.
Recommended liming and fertilization practices will vary for soils with widely differing cation exchange capacities. For instance, soils having a high CEC and high buffer capacity change pH much more slowly under normal management than low-CEC soils. Therefore, high-CEC soils generally do not need to be limed as frequently as low-CEC soils; but when they do become acid and require liming, higher lime rates are needed to reach optimum pH.
CEC can also influence when and how often nitrogen and potassium fertilizers can be applied. On low-CEC soils (less than 5 meg/20000g), for example, some leaching of cations can occur. Fall applications of ammonium N and potassium on these soils could result in some leaching below the root zone, particularly in the case of sandy soils with low-CEC subsoils. Thus, spring fertilizer application may mean improved production efficiency. Also, multi-year potash applications are not recommended on low-CEC soils.
Higher-CEC soils (greater than 10 meg/100g), on the other hand, experience little cation leaching, thus making fall application of N and K a realistic alternative. Applying potassium for two crops can also be done effectively on these soils. Thus, other factors such as drainage will have a greater effect on the fertility management practices used on high- CEC soils.
Hefty Brothers
How much of your nitrogen that you apply is being lost each year? How much of that N is ending up in someone’s water? I know you are busy, and you have a lot of things to think about on your farm, but unless each of us farmers learns how much N our soil can really hold, we will at some point be facing drastic nitrogen regulations on the farm.
Here’s the good news: it’s easy to figure this out. All you need to do is take a Cation Exchange Capacity (CEC) test of your soils. Then, multiply that number times 10 to learn APPROXIMATELY how much nitrogen your soil can hold at any one time. This isn’t an exact calculation, but it will get you close.
For example, let’s say your CEC is 12, meaning your soil can hold about 120 pounds of N. Let’s say it already has 20 pounds today, so you should limit your N application to just 100 pounds until your crop starts to use some of that N. However, if you have a big yield goal and want to apply 200 pounds, you can legally do that today. It’s just not very good stewardship because where do you think that excess nitrogen is going to go?
Now, “some” nitrogen in the water is no big deal. 10 parts per million of nitrate nitrogen is the drinking water standard. However, it would be easy to exceed that number if you got a big rain soon after over-applying N.
If you don’t think this is a big deal, let me tell you about Denmark. In 2011, Darren and I toured a few farms in over there. Did you know that Danish farmers are limited on how much nitrogen they can use on their farms? It’s true, and it’s now adversely affecting their yields. The problem started just like ours here in the U.S. Farmers were over-applying nitrogen BECAUSE THEY DIDN’T KNOW THEIR CECs. In addition to nitrogen limitations, Danish farmers are required to turn in an extensive and complete report each year to the government about EVERYTHING they plan to do on the farm, from tillage, to which crops they’ll plant, to their herbicide and fertilizer plan, and a whole lot more. We have a copy of a 25-page report that a 400-acre farm had to turn in prior to being allowed to do anything on their farm in 2011.
If we’re not careful, we’re going to end up in the same position as the Danish farmers, so here’s what I’m asking you to do TODAY:
Know your cation exchange capacity in every single field. It’s cheap and easy to test, and it doesn’t change much from year to year, so testing even once every 4 or 5 years is more than sufficient.
Don’t over-apply your nitrogen in any form, including manure. If your soil can only hold 150 pounds of nitrogen, subtract the amount that your soil already contains and only apply the difference.
If your crop needs more nitrogen, split-apply it. Put some on at sidedress, foliar, or some other way once your crop has used some of the early-applied N.
Use a nitrogen stabilizer like NutriSphere-N. Our studies have shown that nitrogen stabilizers help prevent loss and keep N in the ammonium (more stable) form longer. However, nitrogen stabilizers are not miracle products. If your soil can only hold 150 pounds of N, just because you add a nitrogen stabilizer doesn’t mean you can now apply 300 pounds of N safely.
In Denmark, it doesn’t matter now if a farmer wants to use a nitrogen stabilizer or split-apply nitrogen or any other method to reduce nitrate in the water. It’s too late. The law is in place, and a farmer simply cannot use more nitrogen. The same thing will happen here UNLESS we’re proactive, so please, get your Cation Exchange Capacity tests run now and follow the steps I’ve listed above! If our nitrogen use gets limited someday, it could be pretty tough to turn a profit on the farm. | |
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N-serve test result
