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Saving Water for a Rainless Day

By Don Comis
March 19, 2003

Drought-stricken farmers in western North and South Dakota and Montana could lose significant income if they don't take into account how much water various crops use.

Steve Merrill, a soil scientist at the Agricultural Research Service's Northern Great Plains Research Laboratory in Mandan, N.D., has measured the water needs of 16 major crops. His findings apply to farmers from central North Dakota south and west into South Dakota and Montana and to the northwest into Canada.

But the basic concept applies to farmers everywhere: Measure how much soil moisture you have coming into the growing season and use that as a guide to select a crop based on its water needs. Start the spring with soil moisture scarce, as farmers in parts of the West are likely to do this year, and you would choose a crop on the low end of water needs, like dry peas, the lowest water user Merrill measured. If farmers in drought-stricken areas of the West had the abundance of rainfall found in eastern North Dakota and Minnesota, they might have such soggy lowland soils that they would welcome sunflower's ranking as the highest water user.

Making the right soil moisture-crop match this spring not only gives a greater chance of a successful harvest next fall, but can also have a great effect on how much soil moisture will be available in spring 2004. For example, Merrill's studies showed that dry peas can leave up to four extra inches of moisture in the soil, compared to sunflowers.

Merrill measured each crop's water use with no-till, a soil- and water-conserving practice that is common in a region so dry that fields used to be periodically left idle for a year to recharge soil moisture.

Merrill presented his most recent results at the National Sunflower Association's 2003 Research Forum. The paper is posted at:

A paper on crop water use he presented at the 2002 forum is online at that site as well.

ARS is the U.S. Department of Agriculture's chief scientific research agency.