By Brian Hefty

For years, farmers with soil pH’s below 6.3 have been using lime to raise their pH, but lime offers more benefits than just that.

First of all, here’s why lime chemically changes your soil pH.  Lime is calcium carbonate or CaCO3.  Low pH soil has excess hydrogen.  Remove the hydrogen, and soil pH rises.  Here’s how that happens.  The hydrogen combines with the lime to form water, or H2O.  That leaves carbon dioxide (CO2) to go up in the air (by the way, while humans breathe in oxygen, plants breathe in carbon dioxide) and calcium.

In summary, by adding lime to low pH soil, you get water, carbon dioxide, and calcium.  Those are all good things.  With the calcium, you may not realize how good that actually is.  Here are 3 points I really like about calcium on our farm.

  1. Calcium molecules are big.  Relative to magnesium, for example, calcium is huge in size.  What that means in your soil is more pore space for roots to grow, less chance for soil compaction, and better water movement in the soil.
  2. Calcium is a secondary nutrient.  What that means is most crops need quite a bit of calcium in their diet.  Calcium helps strengthen cell walls and improves nitrogen efficiency in plants, as well as playing a key role in a host of other essential functions.
  3. By having a sufficient amount of calcium (65% to 80% in base saturation), that limits the relative amount of magnesium in the soil and reduces tie-up issues caused by magnesium.  Certainly, too much calcium can be a problem, too, but we have way more problems with too much magnesium in our area than too much calcium.  As we’ve worked to improve our calcium percentage, we’ve also found our soils to get a little softer.  This isn’t shocking, as soils high in magnesium are generally tight and poorly drained.

When you apply lime, just pay attention to what else you’re getting with that lime besides calcium carbonate.  You never want heavy metals.  They can damage your soils and your crops long-term, so have your lime tested.  Unless you have soils low in magnesium, you want your lime to have a lower magnesium content.  Finally, you’ll get quicker results from your lime if the ECCE (Effective Calcium Carbonate Equivalent) is high.  You can get a higher ECCE rating if the particle size of your lime is small and if the lime has close to the same effectiveness as straight calcium carbonate.

On our farm, we apply 6 tons of lime from a local water treatment facility (our tests on this lime have been good) about once every 3 or 4 years on any of our ground that has a pH of less than 6.3.  Also, we often find that our soil pH is good everywhere except the top 6 to 10 inches of our soil.  It’s great to have the subsoil in good shape, but you’ve got to make sure the top few inches are good, too.  I bring this up because some people believe that lime isn’t necessary if the subsoil’s pH is above 6.5.  Just like we try to treat different areas of fields separately, I believe we should treat the top few inches of soil differently than the next few inches, especially when it comes to soil pH.

In summary, we believe lime is a great thing if your soil pH is below 6.3 or if your base saturation of calcium is below 65%.  Just try to find lime with a high ECCE to get the most bang for your buck.