Soil Tests and Yields
Since 1955, Growers Mineral, Corp. has told farmers that crop production is more complicated than fertilizer arithmetic. An article "How Much Fertilizer Does It Take" appeared in The Growers Solution, Volume 31, Issue 1, Winter, 2018 discussed how the agricultural establishment has had to change crop nutrient removal amounts after examining crop data. Work done at the University of Illinois showed that the numbers used for crop removal of elements was not the best way to predict what needs to be added to a soil to get profitable crop production.
In my travels interacting with GMS customers, real life examples of the problems with using the soil test to predict crop yields are always very interesting.
For example, a long time GMS customer had soil tests completed for nutrient management work. The nutrient management work only needed to see the volumes of the P (phosphorus) that were in the soil; however, the soil testing laboratory automatically made P and K (potassium) recommendations for a possible corn crop. On this particular field, the soil test values were such that the soil testing laboratory recommendation called for 188 pounds of P₂O and 232 pounds of K2O to achieve a corn yield of 200 bushels per acre.
This particular farmer made a serious technical error by applying only 10 gallons per acre of GMS for his P and K needs. Ten gallons of GMS only gave him 22.8 pounds of P₂O and 11.4 pounds of K2O. However, the agricultural establishment technology did not overrule the soil microbiology because the farmer harvested 325 dry bushels in a truck weighed small check plot. The entire 35 acres did not yield an average of 325 dry bushels; however, the entire field exceeded the 200 dry bushels per acre average.
The farmer's problem was that the soil test measured the soil pH at 7.6. The higher yield must have resulted from "trace element tie-up."
This is an excerpt from the Early Fall Growers Solution (2022) written by Jim Halbeisen, Director of Research.
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