Blog Posts‎ > ‎Bob's Notes‎ > ‎

Lowering Soil pH - Things to Do....

posted Dec 7, 2010, 2:25 PM by Bob Whitney   [ updated Dec 7, 2010, 2:28 PM ]
Lowering pH is tough because it is so hard to keep it lower.  Typically we still have water deeper down in our soils that will come up and bring elements to raise our lowered topsoil pH and also we use irrigation waters that are higher in pH with lots of dissolved minerals that raise our soil pH.  In some parts of the world the soils are typically high mainly because you don't get the leaching acid rains to move out the minerals that are causing high pH.

Lowering soil pH:
  1. use lots of organic matter in the soil and on top of the soil.  Organic matter decomposes forming organic acids which will help lower pH but more importantly will help buffer or keep pH down.  Peat moss is the lowest pH organic matter we have but compost and tree mulch are cheaper and can be as effective over time.  You need 4-6 inches to do good and add twice per year.
  2. Add sulphur to the soil and incorporate if you can.  Sulphur that is 90-99% elemental will be gobbled up by bacteria and form sulphuric acid H2SO4 which will lower pH.  10 lbs per 1000 sq ft or about 1 ton per acre.  You need to add this in the  rooting zone.  Add this once per year every year.
  3. Use Ammonium Sulphate as a fertilizer source.  It is very acid and will add to the other steps.
  4. You can plant on raised beds.  This will help keep roots in your defined area and this area would be the place to add the amendments.  A raised bed can be as simple as throwing up soil into a raised terrace.
  5. You can add sulphur acid into the water source.  This is a little tricky but the best way is to add acid to water in a tank or pond.  Basically you test the water and then start pumping acid into the tank until it get to the right pH.  Sounds bad but the large body of water is a buffer for you against doing too much.  A second way is to inject acid into the water as it is being pumped into a mixing chamber and then pumped to the crop.  You need really good injectors and sensors so that this doesnt get messed up.  Usually the water is around 6 pH and so is like rainwater that over time begins to lower pH.   A third way is to inject straight something like acetic acid, vinegar, straight into the water system at high concentrations.  The roots can take vinegar straight but this is very expensive if you have a large area.  We do this in greenhouses sometimes.