IA DNR: Test Soils Before Spring Fertilizer or Manure Application

DES MOINES - Crop and confinement animal producers who use manure as fertilizer should schedule soil sampling this spring before applying commercial or manure fertilizer. Sampling after fertilizer or manure application may not give an accurate representation of the nutrient status of the field.

The soil sample test results for phosphorus and for acidity (pH) will be needed by many producers who need to update their plans with the phosphorus index starting in September. The phosphorus or P index takes into consideration the lay of the land, the distance from a stream and the phosphorus that is available in the soil.

"Producers have a narrow window this spring and next fall to get soil sampling done for the P index which many producers need to incorporate into their manure management plans in 2008 and 2009," said Jeremy Klatt, a DNR environmental specialist.

"This is the year that brings everyone on board," Klatt said. "The index has been phased in over the last four years, but this is the year that everyone who submitted manure management plans prior to April of 2002 must start using it."

Klatt advised producers to do the soil testing now and to allow plenty of time to run the P index and revise their manure management plans. That way if producers find that they need additional fields for manure application, they have time to find them.

Crop producers who accept manure from confinements may also want to talk to their manure provider about how the P index could affect manure application on their land and if they need to have soil samples taken.

"Take at least one sample for every 10 acres of the field," he said. "Generally, producers should follow Iowa State University's soil sampling recommendations or another credible method." Soil samples taken in the last four years can be used, if they meet the minimum requirements.

Producers may keep the soil test results on site, but must submit a complete MMP using the phosphorus index for each field once every four years. The complete MMP and soil loss calculations (detailed RUSLE2 report) and P Index calculations must be sent to the local DNR field office.

The DNR will not be granting exemptions or extensions of the deadlines for the P index-based plans. See the DNR Web site for more information about the P index: www.iowadnr.gov/afo/mmp.html#phosphorus. or www.iowadnr.gov/afo/files/pindex_fs.pdf.

Check the Iowa State University soil fertility Web site for information about soil sampling at extension.agron.iastate.edu/soilfertility/. Finally, more information about the P index can be found in back issues of Odor and Nutrient Management at the Iowa Manure Management Action Group's Web site at http://extension.agron.iastate.edu/immag/pubsnl.html.

Writer: Karen Grimes