Wisconsin Corn Starter Fertilizer Trials

During 1995 and 1996, UW-Madison researchers in cooperation with crop consultants and county extension agents have been involved in a statewide corn starter fertilizer study. These trials were performed on farm fields that usually had soil tests for phosphorus and potassium in the high to excessively high categories. Data was collected from 43 fields in 1995 and 31 fields in 1996. Grain yields were measured from replicated field strips where corn was planted with and without starter fertilizer.

1995 results

When yield data from all sites were considered, starter fertilizer significantly increased yield by an average of 4 bu/acre (132 vs. 128). The average economic effect of using starter fertilizer was about break even considering the value of the average yield increase and cost of the starter fertilizer material. On an individual site basis, 40 percent of the fields showed a positive response to starter fertilizer and 60 percent did not.

1996 results

Again in 1996, the average overall yield response to starter fertilizer was about 4 bu/acre (137.5 vs. 141.8) and the average return to actual dollars spent on the fertilizer was a -$2.76. On an individual site basis, 22 of the 31 sites had a positive yield response to starter fertilizer, however, only 5 of the sites had statistically significant positive yield increases. Forty percent of the fields showed a positive economic response to starter fertilizer.

What it all means

Where soil test P is greater than about 25 ppm (average soil test P in Fond du Lac County is 53 ppm), there is no need to apply more than 20 lbs./acre of fertilizer phosphorus. Applying more than this will most likely result in no yield increase and a negative economic return to fertilizer dollars. The same would be true when soil test K exceeds about 140 ppm where applying more than 20 lbs./acre would most often result in a negative return. Where substantial amounts of manure are applied to meet part or all of the corn nitrogen requirement, P and K additions in the manure will often meet or exceed the corn P and K needs. In these cases, starter fertilizer application rates should not exceed the minimum 10-20-20/acre application.