Young corn plants stand tall above the soybean
residue from the previous year's crop.
(Image courtesy USDA-NRCS)
Potassium: The Overlooked Crop Nutrient?
By Luis Pons
June 15, 2005
Is potassium deficiency limiting corn
Agricultural Research Service (ARS)
Kovar think so, and they cite a shift by growers away from preplant tillage
as a possible cause.
"No-till" farming has become an important agricultural practice
because it offers such benefits as lower energy costs and reduced soil erosion.
But the practice may have a side effect in causing potassium--which is
naturally recycled as plants decompose--to accumulate in the surface soil where
new plant roots cannot capture it, according to Karlen and Kovar. They're based
in the ARS
and Water Quality Unit, part of the
Soil Tilth Laboratory at Ames, Iowa.
The scientists also question whether increased emphasis on nitrogen and
phosphorus management brought on by those nutrients' off-site effects may have
led growers and researchers to overlook potassium's importance as an essential
ARS scientists started investigating the potassium problem in 2000 at a
tillage research site initiated in 1971 at Iowa State University's Agronomy and
Agricultural Engineering Research Center in Boone County. They noticed that
corn and soybean plants grown in no-till plots were susceptible to slow
early-season growth and lower yields. The region's growers were experiencing
similar problems, according to Karlen. The scientists' goal was to find a way
to overcome the slow early-season growth and lower yields while maintaining
no-till usage because of no-till's other benefits.
According to Kovar, they found the cause through field tests in which dry
fertilizer was placed three inches below the surface, enhancing early-season
growth. Follow-up studies pinpointed potassium deficiency as the cause of the
growth and yield problems.
Now Karlen, Kovar and the Kansas-based
Fluid Fertilizer Foundation are
in the middle of a three-year exploration study in which they're directly
applying 30 gallons per acre of a liquid potassium solution during planting.
The solution penetrates the soil to the root level.
In the first year, the treatment helped boost corn yield by 8 bushels per
acre, and soybean yield by more than 2 bushels per acre.
ARS is the U.S. Department of
Agriculture's chief scientific research agency.