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There are numerous questions about fertilizer recommendations at this time of year. These questions are frequently directed to personnel in the University of Minnesota Extension Service. In addition to specific questions, crop producers throughout the state always seem to have some general questions about the recommendations from the University of Minnesota.

Are the recommendations appropriate for the high yielding crops of today? Are these recommendations accurate? Are they out-of –date? They might save some money spent on fertilizer; but, will yield drop? The recommendations are based on research conducted in small plots; will they work on a whole field basis? These questions and others that are related are not out-of-line. They are perfectly logical.

Fertilizer recommendations from the University of Minnesota have been compared with those of other Soil Testing Laboratories at various locations for several years. The data collected strongly supported the conclusion that there were large differences in fertilizer costs. However, there was no reduction in yield when the University Recommendations are followed.

More recently, crop producers have started to question "other" recommendations. They have been comparing the "other" recommendations to those from the University of Minnesota. Two of those comparisons are described in the following paragraphs.

A father and son (a student at the University of Minnesota) in west-central Minnesota had, for several years, been concerned about the amount of money spent for fertilizer. They realized that they had been using rates that were substantially higher than those in the University of Minnesota recommendations. So, they made a comparison between U of MN recommendations and the U of MN recommendations plus 200% of those recommendations for phosphate and potash. When yields were calculated for several acres used in the test, the average yield for the U of MN recommendations was 155 bu. per acre. Using the U of MN recommendations and adding 200% for phosphate and potash (the usual recommendation) produced a yield of 151 bu. per acre. Yields were not lowered by using less fertilizer. Calculating the savings for all of the corn acres on their farm, they realized a savings of approximately $50,000 by using the lower rate of fertilizer.

Another situation involved a sugar beet grower. His soil test levels for P and K were high to very high in many fields. With soil test values in these ranges, no phosphate or potash was recommended. Again, these recommendations were questioned and some field comparisons were conducted by one grower for the sugar beet crop in the rotation. There was no reduction in sugar beet yields when the U of MN recommendations were used. When calculated for the entire sugar beet crop on this farm, the grower saved $77,000 in production costs for the crop.

The preceding paragraphs describe two situations when U of MN recommendations reduced fertilizer cost without reducing yield. There are probably many other stories to tell.

Crop producers frequently ask about the basis for the University of Minnesota fertilizer recommendations. It’s important to point out that these recommendations are the end result of a considerable amount of field research conducted over several years. These recommendations are reviewed and modified as new information is collected each year. They are not the same as they were in the past. They are appropriate for the high yields in modern crop production.

Results from trials conducted in small plots and large fields lead to the same conclusion. The fertilizer recommendations from the University of Minnesota will not harm the bottom line.