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January 26, 2010

Use soil testing as a management tool

by Doug Toburen

When it comes to making plans for the upcoming growing season there are few things more important for producers than knowing the fertility of their soils.

According to Doug Shoup, Kansas State University southeast area agronomy specialist, with volatile input prices knowing soil test levels is the key for success.

“Soil testing is going to help you determine how much fertilizer to apply by seeing what the available nutrients in the soil are,” Shoup told producers at the recent Soil Basics 101 meeting in Overbrook, Kan.

According to him, these tests are not a waste of money—they’re Kansas-tested and Kansas-approved.

“Soil tests offer a lot of information and you need to use the information correctly,” he explained.

He used phosphorous as an example.

“You can reduce your yield potential by not having enough phosphorous in the soil. But, on the other hand, if you have more available than you think and add more, you aren’t going to get much of a response out of it,” Shoup said.

Therein lies the importance of testing soils accurately.

Some basic tools necessary when soil testing include a soil probe, a bucket and a bag.

“In order to sample soil properly make sure there is consistency in the depth of the sample, an appropriate number of sub-samples and that the proper care of collected samples is taken,” he said.

When it comes to depth of soil samples, zero to six inches is the target.

“In this part of the country our soils are eight to 10 inches deep before you hit the clay pan and sub-soil layer so zero to six inches is all the deeper you need to go,” he explained. “If you go beyond that you are going to be in the clay layer.”

On the flip-side, if you go too deep, according to Shoup, you are going to get high test results that over-estimate the nutrient supply and pH levels.

After the tools are all gathered and it is time to start sampling, Shoup feels that producers benefit from taking a number of samples throughout the entire field.

“Go throughout the field and collect your samples, stay out of low spots and terrace channels, though,” he explained. “About 10-20 sub-samples per field should be taken and submitted.”

Although there is no rule for the number of acres to include in a single sample, he feels 40 acres is ideal.

Soil samples can be taken any time of year but, according to Shoup, for corn and sorghum, late winter or early spring is ideal. For wheat, before planting in the fall is a good time.

“It is best to sample a field at about the same time of year each time samples are taken,” he explained.

Like there is no magic number for field size sampling, regimens can vary.

According to Shoup, if samples are taken every three to five years producers can easily monitor nutrient levels.

When it is all said and done, soil sampling, Shoup feels, is an economical way to manage high fertilizer costs.

“You can utilize soil testing as a way to monitor potential nutrient deficiencies and production problems,” he concluded.

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Use soil testing as a management tool
by by Doug Toburen , , Tue Jan 26, 2010, 09:47 AM CST
Crops