By Brian Hefty

Last fall on our farm, we identified some areas with phosphorus levels high enough that had we applied more P (like we originally planned), it likely would have HURT YIELD, not helped it.  Having an excess of almost any nutrient can be as detrimental as having a low level of that nutrient.  For example, excess phosphorus can prevent zinc from getting into the plant, so even if you shouldn’t have a zinc deficiency, you do because of the phosphorus excess.

I understand you are trying to cut costs going into 2017.  I also realize that an investment in soil testing isn’t technically a crop input, and you may not currently be a believer in soil testing, but here are my top 5 reasons why I recommend that every farmer use soil testing this fall.

  1. If you don’t know how many nutrients your soil has, how can you properly fertilize?  In some cases, you may need lots of fertilizer, but in other cases you may not.  Why spend $100 on fertilizer when $50 might be the right amount?
  2. N, P, and K may NOT be your yield-limiting factor.  Could it be sulfur?  Maybe it’s zinc or boron, iron or copper or even manganese.  You don’t know unless you test.  Just think if your issue was manganese.  You could possibly invest $10 more in manganese and get a big yield bump.  I know that N, P, and K are always top of mind, but are they top of mind because they are actually what your soil needs or are they top of mind because that’s what the fertilizer dealer has to sell?
  3. Soil pH is actually the most important thing I want to see on the soil test.  If your soil pH isn’t right, nutrients won’t be as available to your crop.  Your soil life (beneficial bacteria & fungi, earthworms, etc.) won’t be as abundant.  Herbicide injury or carryover may be more likely.  Plus, there could be many other negative consequences, too.  Crops like corn, soybeans, and wheat typically do best when the pH is between 6.3 to 6.8.  If your pH is low, add lime immediately.  If your pH is high, you likely need to improve drainage or build more topsoil.  If you want to quickly lower your pH, use elemental sulfur.
  4. I want to know your CEC (cation exchange capacity).  The higher the CEC, the heavier your soil is.  I know you can simply say, “I have heavy soil”, but “heavy” is a relative term.  If you know your CEC you have a better understanding of how much nitrogen you can apply, how much lime it will take to change pH, and how close together tile lines need to be, among other things.  I know you may not currently think about CEC, but whenever I’m making recommendations for a field, I ask the farmer what the CEC level is.
  5. Is your soil fertility in balance?  For this, we look at the base saturation test and the parts per million numbers for many nutrients.  Balance is incredibly important in soil if you want better nutrient availability and higher yields.

I want to challenge you to pull soil tests this fall on at least half your farm.  You want to cut costs, but what you actually need is to become more profitable.  Costs are no big deal if they are actually investments with a positive ROI.  Also, instead of having someone else pull your soil tests, save some money and do it yourself.  When you pull your own tests you know the samples were pulled in the right spots with the proper technique.  Speaking of technique, I recommend driving up to a grid point, pulling two soil cores in front, behind, and on each side of your vehicle for a total of eight.  When using a soil probe, always hold the probe straight up and down, go to exactly the same depth each time, and use WD-40 if you need to lubricate the probe so soil can be more easily removed.

If you need soil testing help, I recommend attending the free Ag PhD Soils Clinics this winter.  Also, use the free Ag PhD Soil Test app.  When you submit your tests, your cost works out to the same rate Midwest Labs would charge you, but you also get our recommendations, the use of the app, and the ability to look at all your data on agphdsoiltest.com.  One of the best ways to save money on fertilizer is to know your soils through soil testing and then fertilize accordingly.