farm hunter that was a great explaination.

To get a handle on buffer pH think about the surface area of the soil. A 1" square rock has 6 sq. inches of surface area. If you split the rock into pieces 1/2" square you now has 8 pieces each with 3 sq. inches of surface area each or 24 sq. in. total. Sand has large particles with little surface area. Clay is very fine with a huge surface area.

The soil particle surface contains the active chemical sites that hold fertilizer and other materials including the materials that have excess hydrogen or OH- groups. That' s why clay soils need more lime to neutralize the acidity.

Then there' s buffer solutions. Some chemicals don' t follow the straight acid-base titration curves. They undergo chemical conversions at certain pH' s and hold the pH of the solution at that level until they' re fully converted. If you have a large amount of a material that acts this way and combine it with a clay soil with many active chemical sites (large surface area) it can take a very large amount of lime to change the pH to where you want it.

The good thing is that it should also take more crop extraction and leaching to lower the pH back to where it was.

Dan O.