10/12/98

Contacts:
Randy Killorn, Agronomy, (515) 294-3433
Karen Bolluyt, Agriculture Information, (515) 294-3701

SAVINGS POSSIBLE WITH GOOD FERTILITY MANAGEMENT

AMES, Iowa -- Most Iowa cropland contains enough phosphorus and potassium for optimal crop yields, according to Iowa State University scientists. Given the economic pressure caused by low grain prices, avoiding unnecessary fertilizer applications is particularly important this year, they say.

Randy Killorn, ISU soil fertility specialist, said producers don't always see actual soil-test results. "Producers should request the results so they can evaluate their soils using information based on Iowa studies. They also can keep records of long-term trends on their land," he said.

According to an extension publication, "General Guide for Crop Nutrient Recommendations in Iowa," the most profitable long-term approach to P and K in soils is to maintain soil test values at the "optimum" level. "No phosphorus or potassium should be applied to soils that test 'very high' and no more than a normal starter is recommended for soils that test 'high,'" Killorn said.

Using soil-test results from a table in the nutrient-recommendation publication, producers can determine if soils contain enough phosphorus and potassium to optimize yields. Killorn said that 60 percent of Iowa soils tested at or above the optimal range for phosphorus in 1998, and 70 percent tested at or above the optimal range for potassium. Rising levels of P and K in Iowa soils are a long-term trend, he noted.

"At an average of $18.73 per acre for P and K replacement [for a 150-bushel-per-acre corn crop grown on soil testing "high" or "very high" in P and K], savings from good soil fertility management can make a big difference this year," Killorn said.

The nutrient-recommendation publication, PM-1688, is available for $1 (plus shipping and handling for out-of-state orders) from the Extension Distribution Center at (515)294-5247. The entire publication also can be downloaded from the Internet at http://www.exnet.iastate.edu/Publications/PM1688.pdf.

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