Cation Exchange Capacity of your soil

 in a positively charged mineral, like calcium, it must release a positively charged mineral to maintain electrical balance. There is no gain in releasing another nutrient so the plant releases the mineral, hydrogen, which has no nutritional value. Hydrogen is an acid element that determines the pH of your soil. As the cation (plant food) are removed from the clay colloid and exchanged for hydrogen, your fuel tank is emptied and the acidity of your soil increases

If you have medium clay soil with a CEC of 20 to 30, then you have much higher storage capacity and less need to spoon feed. As long as fuel tank is not empty, these soils can deliver nutrition for extended periods. These are the soils that respond well to cation balancing strategies, where we try to achieve a cation balance involving 68% Calcium, 12% Magnesium, 3-5% potassium and less that 1.5% sodium on the clay colloid. The original research conducted by Dr. William Albrecht applied specifically to these types of soil.

However, we often find that playing the precise numbers game in very heavy soils is not always productive. These soils (with a CEC of 30-70) have such a large storage capacity that their need for extra inputs should always be confirmed with a leaf test. For example if you have 7000 ppm of Calcium on your soil test, that often can be enough. Always leaf test to see if the plant is accessing enough calcium before embarking on liming or Gypsum program that may not be necessary. If the leaf levels of calcium are good there is simply no need to play number game.