The University of Missouri soil test lab handles from 35,000 to 40,000 samples per year from producers, homeowners and industry. The lab also conducts soil, plant, water, manure, compost, environmental and nutrient fertilizer tests.

The primary functions of soil testing are to determine if soil pH is in the range for best crop growth and if phosphorus and potassium are at adequate levels for growth.

Research calibration data is used to determine adequate soil test levels of phosphorus and potassium for crop and forages.  Soil testing identifies nutrient levels and is used to make recommendations on the amount of nutrients removed when crops are harvested along with applying nutrients to build soil test levels over time. University of Missouri uses eight-year build program; however, recommendations are also made for shorter build programs for variable rate nutrient applications.

Crop and forage yields are maximized when applying nutrients and then maintaining them at the adequate levels. Applying phosphorus and potassium at low rates never build soil test values to adequate levels, thereby do not maximize yields.

Furthermore, research has shown that phosphorus and potassium fertilizers can be top-dressed with no-till farming and row crops can obtain these nutrients. Just like in pastures.

Nitrogen needs for crops and forages are estimated or amounts calculated to grow various crops. Yield goals are used to determine the yield objective of the grower fertilizing their crop.

Adjusting the soil pH typically is by a one-time application of an agricultural lime. Liming is adjusting the soil pH and is not a nutrient. Our soils have high levels of calcium, so this is not a limiting nutrient.

Agricultural limes contain different sizes of particles which react to reduce soil acidity. Larger particles react for years whereas small particles react quickly. The value in a good agricultural lime is a mix of different particles sizes. Calcium carbonate reacts with soil acidity and adjust the soil pH, adding calcium does not.

Liming materials are purchased by a guarantee called Effective Neutralizable Material (ENM). State testing of liming materials allows growers to have the guarantee of a number which can be used to calculate the amount of lime that is required to be applied to a crop field to adjust the soil pH to that for the specific crop.

For more information, contact Wayne Flanary, Field Specialist in Agronomy, University of Missouri Extension at 816-279-1691.