Q&A on Soil Sampling

Aug 02, 2021

You are busy attending fairs or going on vacation, which means the fall soil sampling season will be here soon.  Higher than average input cost and higher projected commodity prices are just two factors that support the benefits of fall soil testing.  Properly identifying nutrient levels with a soil sample can help you make the best management decisions available.  Soil testing is the single most important guide to the profitable use of fertilizer and lime.

The purpose of soil testing is to identify the soil fertility that the plants or crops, in a given area will experience.  The most difficult step in soil testing is accurately representing the desired area of soil.  A laboratory cannot improve the accuracy of a sample that does not represent the area.  In most soils, it takes more than one year to make significant changes to the soil test levels.  As the soil improves with better fertility programs presented by your SFG agronomist, subsequent crops or plant growth should show increasing rates of improvement.

Q: Should I grid sample my field?

A: Grid soil sampling is a method of intensively sampling your field, typically obtaining a sample for every 2.5 acres.  This method of sampling is typically used when you use variable rate technology to apply fertilizers or lime.  Grid sampling is most justified on high value and high yielding soils, particularly when you anticipate significant variation in soil test levels including low testing area within a field.  It can also be useful the first time you sample the soil in a field with an unknown history.

Q: When is the best time to take soil samples?

A: Anytime that your need them!  In the fall, just after harvest is usually the preferred time.  A key to proper soil sampling is to be consistent.  It is important to try to always sample a give field at the same time of year.

Q: How frequently should I resample a field?

A: It Depends.  With a straight corn bean rotation samples are usually good for 4 years.  If the crop is corn on corn, or other special rotation sampling more often is recommended.  Also, sample every year when there is an aggressive soil build up program, or when there is a significantly low fertilizer rate applied.

SFG is here to help you, we are a family business here to help your family.  Please call us anytime that you have questions about any aspect or soil sampling, understanding the results, or any area of agronomics.