Myth Busters – Soil Fertility

Myth #1: Some people still believe soil must have a certain ratio of calcium, magnesium and potassium to produce high yields? Some of the most productive soils in the world are located in the Red River Valley of North Dakota, Minnesota and Manitoba. Most of these soils have high levels of calcium, magnesium and potassium. People who believe in this myth, would say these soils have cation ratios that are “Out of Whack”! If these soils are so “Out of Whack”, how can they produce some of the highest yields in the world! The fact is that if there is a sufficient level of each of these nutrients in the soil to supply the crops needs, it doesn’t matter what the ratio of one nutrient to another nutrient is. Soils can produce very high yields with a very wide range of cation levels or ratios (see table). If you want to look at a ton of additional research both from the U.S. and around the world, do a “Google” search of “Soil Cation Ratios” ( I hope you have a whole day to look at research).

Myth #2: The people who tell you it is important to “fix” the cation ratios in your soil, have your best interest at heart? People who tell you they can help you “fix” the cation ratio in your soil are looking for one thing. They want to sell products that will “fix” this so called problem. The products are usually gypsum or extra potassium the soil does not need. The only problem this “fixes” is the need of an unscrupulous salesman to sell some products! You can easily bust this myth by using a yield monitor. Apply the materials in a few strips across the field and let the yield monitor do the talking! Hard facts from a yield monitor are very difficult to argue with.

Affect of Ca/Mg Ration on Alfalfa Yield
University of Wisconsin 1979
Soil Ca/Mg Ratio % Ca % Mg Yield Ton/A
2.64 32 20 4.14
2.92 35 20 4.28
3.48 38 18 4.35
4.81 43 15 4.12
8.13 68 15 4.35
Ratios adjusted by applying gypsum (CaSO4) Loamy sand soil texture