Sept. 24, 2010

You’ve seen the TV ads promoting new medications and at the end, asking the question, “Are they right for you?”

We should probably place the same slogan on many of our agricultural products, especially the numerous combinations of standard fertilizers, organic acids, biologicals, growth regulators. and enzymes.

New EEF Fertilizers

Slow release fertilizers have been available for over 25 years, but only a few have moved into large scale commercial use. New formulations that control fertilizer release or alter reactions that lead to nutrient losses are being identified as enhanced efficiency fertilizers (EEF). The mechanisms or products in these EEF fertilizers may include fertilizer additives, physical barriers, or different chemical formulations and are similar to earlier versions.

Fertilizer additives claim to improve fertilizer availability by reducing N losses from volatilization, denitrification, leaching, and immobilization. They may temporarily block bacterial or enzymatic processes in the conversion of urea to ammonium or ammonium to nitrate. Most of the product development has been for N compounds, although some has been for phosphorus (Table 1). The phosphorus products can be either polymer coatings or a technology that shields P from reactions that create less soluble phosphates.

Most of the products are considerably higher in cost per pound of nutrient than conventional fertilizers and although some are being actively marketed, many are still in their research phase. There are numerous testimonials on company web sites and in some cases, selected results of replicated research trials are presented. For some of the products, the soil chemical and biochemical pathways and reactions are known and predictions can be made as to whether the product has any potential to improve fertilizer efficiency. Some products and their soil chemical reactions have not been studied or they are proprietary and have not undergone unbiased third-party research testing.

Product Benefits and Unknowns

The N products are likely to be of value for fields of high risk for N loss. The slow release products and nitrification inhibitors are more likely to be beneficial if there is a high risk of N loss from leaching or denitrification. If fertilizer N is surface applied, especially with heavy crop residue cover and on high soil pH, the N release products and N volatilization inhibitors are more likely to be beneficial.

Many of the products have been researched by land grant universities, including the University of Nebraska-Lincoln, but many have not. Often similar products will be marketed with different trade names, making it difficult for consumers to compare products. Producers are encouraged to gather information from university research studies and Extension publications, or to contact their local Extension Educator or specialist if they have questions.

Figure 1 shows chlorophyll meter results from current research with several EEF N products this year. This site in Merrick County is on a sandy soil and conditions favored N loss. One of the products maintained greener leaves than UAN solution alone, whereas others did not show much difference. Grain yields will be determined this fall to determine treatment effects.

Before Buying, Test

In addition, we encourage producers to do their own research strip trials, for example, with a split-planter using several replications in a field or on more than one field. Well-calibrated yield monitors can be used to obtain the harvest data. Local extension educators or staff at one of UNL’s Research and Extension centers may be able to assist with experiment design and data analysis to ensure reliable results.

Our best advice is that producers do their own research strip trials using a split-planter with several replications in a field or on more than one field to generate their own numbers. Well-calibrated yield monitors can be used to obtain the harvest data. Local ag experiment station personnel or Extension Educators can assist with design of the experiment and data analysis.

Years ago a senior soil scientist suggested how producers should approach new or questionable products:

1. Have the salesman leave a sample which you to use on a field and pay him out of the increased profits of the treated versus non-treated area.
2. Only buy enough the first year to run your test comparison strips.
3. Ask others who have had experience with the product.
4. Remember, it’s your money.

Summary

It remains to be seen whether these products can match the N uptake demand for the different crops grown across the different agro-ecozones in Nebraska and be cost-effective. Enhanced efficiencies usually improve use by 10% to 30%, not 2X or 3X (200% to 300%). Remember, a pound of nitrogen is a pound of nitrogen, regardless of the chemical form. For the phosphorus products, definitive lab work on phosphorus chemistry needs to be done to determine enhanced availability in addition to field testing.

In some instances, these products may not be an improvement over conventional sources, timing or placement combinations. That’s why asking the question “Are they right for you?” is important. The enhanced efficiencies must be coupled with accurate rate recommendations to attain improvement. Again, if soil and climatic conditions are not conducive to N loss or phosphorus fixation, EEFs will be no better than standard fertilizers but will cost the producer more. They may simply be needed as insurance of yield potential by reducing N losses as opposed to a guarantee of increased yield. As the old Latin adage "Caveat emptor" tells, “Let the buyer beware.”

Gary Hergert, Charles Wortmann, Charles Shapiro, Richard Ferguson, and Tim Shaver
Extension Soils Specialists