What We Learned From 7.5 Million Soil Samples

A hand holding a small pile of soil
The International Plant Nutrition Institute announced it has completed and released the results of its 2015 North American Soil Test Summary. The most recent survey was the most extensive to-date, comprised of lab-submitted results of more than 7.5 million samples.

What insights can a farmer pull from these results? You’ll be able to view, compare and contrast soil fertility data from 2001, 2005, 2010 and 2015 through a series of charts, maps and tables.

IPNI admits general soil test summaries cannot reflect specific needs of individual farms.

“Its value lies in calling attention to broad nutrient needs, trends, and challenges, and in motivating educational and action programs that are in turn relevant to growers and their advisers,” note the study’s authors.

Users can look at soil test data for several properties, including phosphorus, potassium, magnesium, sulfur, zinc, pH and chloride. The “Percent Below” maps, which quantify how many of the samples tested  below critical levels of P and K, are especially telling. For example, 13 U.S. states and four Canadian provinces had more than half of their soil samples testing below critical levels for P in 2015.


Percentage of samples testing below critical levels of K in 2015 was somewhat less severe, although large portions of the Southeast, plus Ohio and Michigan, had a majority of soil samples deficient in K.

To view the complete data, visit http://soiltest.ipni.net/

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