Most of the chatter this past 18 months about profit-sucking fertilizer prices continues to revolve around global demand and related energy prices. Little of it concerns how fruitless fertilizer applications can be if you’re assuming, rather than knowing, what the soil in question requires.

“Your soil is the foundation of your grazing system; it’s important to understand it and take care of it,” says Brad Carlson of the University of Minnesota (UM) Extension.

Carlson believes the first step to managing pasture soils begins with a soil survey to identify the different types of soil that comprise the acres in management.

“Many farmers know the soil types present on their farms, yet never take the time to fully understand the characteristics of each soil,” Carlson says. “The introductory portion of the soil survey contains valuable info for every soil found in your county. This includes: texture, depth of topsoil, drainage, slope, past erosion problems, and suitability for various uses (including pastureland).” He points out lots of that info is available via the Internet and USDA’s Natural Resources Conservation Service (NRCS) at websoilsurvey.nrcs.usda.gov.

But getting at the specifics requires effective soil testing, and that means collecting adequate samples.

In a recent edition of eHay Weekly, Doug Beegle, Penn State University Extension soil fertility specialist, offered these soil testing guidelines:

  • Sample uniform areas. While most fields are sampled individually, you might want to subdivide fields if there’s potential for significant differences across them. Examples include fields with significant soil differences, where parts of fields receive manure and other areas don’t, and where there are topographic variations (i.e., sidehills vs. low areas) within fields.
  • Collect at least 15-20 cores. “More is better,” Beegle says.
  • Sample to uniform depth. Inconsistent sampling depth is one of the biggest sources of error in soil sampling. “This is especially true in no-till and reduced-tillage systems where there’s often significant stratification of nutrients in the soil,” Beegle says.
  • Avoid atypical areas or sample them separately. “Odd” areas – dead furrows, old fence rows, lime or manure-stacking areas, wet spots, etc. – may be too small to manage separately. “Don’t sample them,” Beegle says. “One or two cores from these odd areas will just contaminate the sample for the rest of the field.” If these areas are large enough that you are able and willing to manage them separately, take separate samples.
To these recommendations, Carlson adds, “Take samples to a depth of 6 in. Avoid adding significant amounts of live plant and root tissue from the pasture sod. At least 20 soil cores taken randomly in the area that you’re testing are necessary to get a reliable sample. Sampled soil should be combined together, mixed and air-dried. Brown paper lunch bags work well, as they are inexpensive and dry easily.”

Next, it’s a matter of seeing the forest for all of the proverbial trees.

“When dealing with soils, it's easy to get wrapped up in numbers, management practices and potential increases in productivity,” Carlson explains. “Ultimately, it’s imperative to keep an eye on the big picture and plan thoroughly. Ensure that what you do maintains or improves profitability, and that you have the time and means to accomplish your objectives.

“The bottom line is you can't change the inherent properties of your soils, but by understanding them you can manage them to maximize their productivity.”

For more info, see the UM Extension publication “Managing Soils for Greater Grazing Productivity” at www.extension.umn.edu. Click on “agriculture.”