Evaluating soil amendments, fertilizer enhancers and plant growth stimulators

Editor’s note: This article is from the archives of the MSU Crop Advisory Team Alerts. Check the label of any pesticide referenced to ensure your use is included.

A new growing season brings lots of opportunities for farmers to purchase products with many exciting claims.

Michigan’s fertilizer law requires that when the nutrient content of a material is stated on the label, the company is guaranteeing that is the minimum amount of the nutrient mentioned. Fertilizer materials are licensed and closely monitored. However, the law associated with regulation of soil amendments or growth enhancers is much less defined. There is very little regulation. It is somewhat of a “truth in labeling” or “buyer beware” approach.

Each year farmers are presented with many materials or products with claims that range from improving soil conditions to enhancing nutrient availability to improving plant root growth and nourishment to improving drought tolerance to increasing crop yield, etc. Some products may provide some benefit and some may have no benefit for crop production at all. Farmers need to approach purchase and use of these non-traditional products with caution. The old adage that “if it sounds too good to be true, it probably is” has merit. Ask lots of questions. What is the mode of action of the material? Are the claims realistic? Are the claims supported by independent or University replicated field research results done with the crop and under the conditions on your farm? Results from greenhouse studies may or may not translate to what will happen in the field. Materials and products that work in other regions of the United States may not be effective under conditions in Michigan. The climate and soil conditions in southern and western states are different than in Michigan. Ask your local MSU Extension educator what they may know about the product of interest.

There are a number of humic acid and humate products in the market place with claims of improving soil organic matter, nutrient availability, nutrient uptake, microbial activity, soil aggregation, drainage or plant growth. The suggested application rate for many of these products is rather small. A recent article by Crozier, Gehl and Osmond in the March-April issue of the Crop & Soil periodical published by the American Society of Agronomy showed that adding 70 lbs of a humic acid product per acre incorporated to a depth of 6.7 inches in a sandy soil with one percent organic matter increased the soil humate concentration from 0.600 percent to 0.603 percent. Similarly, 1 lb a.i./acre of a seed-placed organic polymer will increase the soil CEC(cation exchange capacity) in the zone around placement by only 0.12 meq/100 g. in comparison with soils that have CECs of 4 to 20 meq/100g.

The North Central Regional Committee (NCR 103) has compiled a compendium of information about a large number of non-traditional products along with unbiased science based research information. This information may be used to help evaluate the effectiveness of products. The large number of products on the market makes it difficult to evaluate all of these types of products. Information on the products that have been tested is available at: http://extension.agron.iastate.edu/compendium/index.aspx.

The authors of the Crop and Soils article suggest three steps to evaluate any product.

  1. Document the validity of the mechanism,
  2.  Document yield response in appropriate field trials.
  3.  Evaluate suitability of the product based on cost, application rate, yield limitations in a specific cropping system, region product was tested in, and expected agronomic benefit. Some of this information may not be rapidly available or apparent. This again is where MSU Extension educators and specialist can help.

Lastly, when trying new materials or products, do so cautiously. Use them on a small acreage and leave untreated check strips for comparison of results. Don’t judge results based solely on plant appearance, but on crop yield and quality. Bottom line, come harvest time; has the product put only more money in your pocket?

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