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Soil nutrient extraction methods are not created equal

Diethylenetriaminepentaacetic acid (DTPA). Wow that’s a mouthful!  But we don’t need to know what it is, much less pronounce it, in order to know that’s the test we need when soil testing for micronutrients in Manitoba.

Different labs use different extraction methods, and some methods are more appropriate than others. Because of our high pH soils, the DTPA-extraction method is the most appropriate test to get an accurate reading of our soil micronutrient levels.

The need for accurate macro- and micronutrient level readings is universal, as it drives your fertility plan for the growing season. The cost of a soil sampling program is small when you look at the cost per acre over your whole farm. It’s money well spent – as long as you take good, representative soil samples and use appropriate soil tests for your land. 

A good soil test will tell you what nutrients should be available to your crop in the upcoming year. When testing for copper, zinc, iron and manganese, the wrong extraction methods can actually pull out too much of these key micronutrients, resulting in levels appearing two to three times higher than they really are. This will mask a true micronutrient deficiency and you could lose the opportunity get those micros to the crops this season. 

At Cargill, we use a soil lab that uses the DTPA extraction method for Manitoba tests. If your lab does too, take a look at your soil micronutrient levels. If you and your agronomist agree that it’s time to up your micronutrient ante, you can still book the fertilizer treatment that’s right for you. Call your Cargill team to learn about the products and services we offer to get those micros into your fertilizer program and to the crops that need them.