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

Winter 2003, No. 3


In areas where adequate moisture is a concern, agronomists talk about how to get the most yield from each inch of water in the soil, a term called water-use efficiency. Imagine a field covered with a 24-in. sponge. A sponge this size could hold between 10 and 12 in. of rain and store it. The soil acts like a huge sponge, providing the nutrients and water to sustain crop growth. We can manage this topsoil to get the most from the stored water. Some common ways to make the most of this resource are to:
A look at wheat production in the Columbia Basin (Pendleton, Oregon) illustrates how water-use efficiency has increased over the last 35 years as a result of various practices.

Between 1967 and 1996, spring wheat yields increased an averaged of 1.2 bushels per acre each year in a wheat/fallow rotation. Although there are swings above and below this average annual increase, the upward trend remains consistent. Wheat yields in 1940 averaged 45 bu/A with a precipitation of 16.5 in., resulting in 2.7 bushels per inch of precipitation. Yields in the range of 85 bushels per acre in the 1990s with the same amount of rainfall reflect a water-use efficiency of 5.1 bushels per inch of rainfall—almost double the yield with the same amount of water!

While several factors (such as improved genetics and pest control) have contributed to this remarkable improvement, USDA scientists report that proper plant nutrition is one of the most important contributors to this yield boost. They report that this improvement reflects the “importance of having sufficient soil fertility to allow the wheat crop to take full advantage of additional soil moisture in favorable rainfall years.”

Careful attention to soil fertility and good soil management can go a long way towards converting every drop of available soil moisture into profitable yields.

For more information, contact Dr. Robert L. Mikkelsen, Western Director, PPI, 617 Oeste Drive, Davis, CA 95616. Phone: (530) 758-4237. E-mail:

A-B Winter 03-04 #3.pdf
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