AGRI-BRIEFS   AGRONOMIC NEWS ITEMS

From Agronomists of the Potash & Phosphate Institute 655 Engineering Drive, Suite 110 Norcross, Georgia 30092-2837 Phone (770) 447-0335

Summer 1999, No. 4

Maybe our thinking is out of date. For example, though the central Midwest is often thought of as a mature market for fertilizer, there are many opportunities to increase fertilizer use within the region. Think about the last 25 years. Cropping systems have been mostly corn/soybean rotations, but the ratio of soybeans to corn has increased. This means more removal of potassium. If the fertilizing program hasn’t changed, there may not be enough potash applied to keep up with crop removal. Add to that the fact that yields of both corn and soybeans have continued to increase, while fertilizer use has been steady or declining, and there is a growing potential for potassium deficiency.

Soil test summaries confirm that potassium levels in Midwest soils have tended to decline over the last 25 years, with over 50 percent of the samples analyzed showing a need for build-up fertilizer applications. Summaries for phosphorus also show a growing need to add more phosphate in many areas, even though the more popular concern is related to reducing phosphate application in those areas where there is a potential water quality problem.

Reduced tillage has also added to the potential for increased phosphorus and potassium markets in the Midwest. Optimum soil test levels tend to be higher under reduced tillage, due to the early season growth response to higher concentrations of nutrients under cool, wet conditions commonly found with reduced tillage.

Site-specific management practices—including more intensive soil sampling and crop yield monitors—are helping identify areas, even in high-testing fields, that need build up fertilizer applications to reach optimum yields and profits. If a field has been managed under a field-average program, high testing areas often overshadow the low testing areas in computing the average recommendation. This means the low testing areas continue to get less fertilizer than they need, and the soil test level (and productivity) continues to fall. This is especially troubling when, as is often the case, the low test area of the field has the highest yield potential.

Managing such a field on a site-specific basis will help alleviate this imbalance and will at least for the short term lead to higher fertilizer use. It will often also lead to moving the average yield (productivity) to a higher level, so that maintenance fertilizer needs also increase. This produces a bigger market for the dealer and more profit for the farmer. With this approach to getting a higher yield system in place, farmers are protected against poor growing conditions and/ or low crop prices. More important, they are better positioned to take advantage of the times when growing conditions or price—or both—are above average.

Mature market? Maybe there is really no such thing—just mature thinking that keeps us from recognizing the potential market we have in front of us.