Renewable Farming

“Top Growers” aims to make sap analysis of corn and soybeans more cost-effective

Iowa farmer Mike Holst and his son Tyler are offering a group purchasing service for other corn and soybean growers who want to save money on the new sap analysis technology.  

Called “Top Growers,” the group pools their buying power to purchase a bulk quantity of sap analysis reports from Crop Health Labs of Bellville, Ohio. This firm currently uses the lab facility of Nova Crop Control in the Netherlands.

Instead of paying $75 for a set of two sap tests, an individual grower can pay $55 per set of two tests because Top Growers pre-paid for a quantity discount.  The $55 includes shipping from the Ohio collection point to the Netherlands lab where the analysis is made. 

The $55 gives you separate analytical reports from two samples taken from the same plants. The two samples are called a set. One sample is pulled from older leaves near the bottom of your crop. Another sample is pulled from newer leaves close to the top of the crop. Together, that’s a “set” which tells you much more than you’d get from a single tissue analysis of the same plants.

Differences between old and young leaf tissue provides signals of what to apply.  If a growing plant can’t extract the right balance of nutrients from the soil fast enough, it cannibalizes older leaves to nourish new growth.

Learning how to read these tests takes a bit of a learning curve, but it’s worth it. Knowing what to foliar feed and when enables you to escape the “shotgun” approach of applying a broad-spectrum foliar package.

Each analytical report shows 21 measurements.  You’ll see any deficiency in important trace elements. Also, the nitrogen report subdivides total N readings into the ammonium form and the nitrate form, which is valuable to show you the plant’s nitrogen source.

Sap testing offers growers early signals as to what the crop will need during its next several weeks of growth. You learn what nutrients to foliar feed before the crop loses growing time caused by deficiencies of trace elements or basic NPK. Tissue tests and visual scouting for deficiencies are helpful, but they don’t reveal problems until yield potential is lost.

Mike says, “The sap analysis is like a blood test of the plant. It detects deficiencies or imbalances before they impact the plant’s growth.”

Even if your basic fertility program as shown by a soil test should provide an abundance of micronutrients, sometimes a crop can’t extract those elements because of a deficiency of another linked element. A shortage of manganese, for example, could restrain potassium uptake. And a manganese shortage is likely to occur, at least temporarily, where glyphosate is part of the program.  Soybean grower Kip Cullers recommends as a “no brainer” the application of a pint per acre of Conklin’s manganese solution if glyphosate is sprayed. He told us at a grower meeting, “In a non-GMO, non-Roundup program, you might not need it.”

But deficiencies can be surprising. Mike says, “My sap test revealed imbalances in micronutrients which I would not have expected, because my fertility program should have supplied them. However, the sap analysis showed these elements weren’t being taken up. By knowing what the plant needs, I can respond with a specific foliar application and not lose growing time or yield.”

By participating in the Top Growers purchasing group, members also qualify for lower rates on educational sessions teaching growers how to interpret lab results.

For more information on Top Growers, you can e-mail Mike Holst ( or phone him at 563-320-3004.

For a full background on sap testing services offered by Crop Health Labs,  visit this website:

The image below shows a sample of a sap analysis report.


Typical sap analysis report