High yields remove large amounts of nutrients

Growers are often concerned about the money they spend for phosphorus and potassium fertilizers. Sometimes growers will not replace the amount of crop nutrients removed by the crop. If this continues for many years, eventually crop yields will drop as soil test levels decline. Once the growing crop shows nutrient deficiencies, low rates of fertilizers will not maximize crop yields.

Crop removal does not take into account the building of soil test values to maximize yields. A build and maintenance soil test philosophy is the principle where nutrients are applied to the soil so the availability of nutrients is great enough that they do not reduce crop yields. This is often a build plan. Often build plans may be four to eight years. The fertilizer recommendation combines the crop removal and the build rates together.

Blindly applying nutrients without any recognition of existing soil test nutrient levels may reduced crop yields without one realizing it. Soil test values are important to understand so dollars can be used in the most efficient manner to improve and maintain crop yields.

Growers generally apply phosphorus and potassium fertilizer to the corn crop and consider that the nutrients applied to corn will carry-over to soybean. If soil test values are high, this philosophy is correct, however, if low soil test values exist, then one should make annual applications to build soil test levels to maximize yields.

Fertilizing is one of the most important operations in growing crops. Time spent in understanding and interpreting soil tests are extremely valuable. Take time to visit and go over your results.

For more information, contact Wayne Flanary at 660-446-3724 or Heather Benedict at 660-425-6434, Regional Agronomists, University of Missouri Extension.