Agricultural Research Service (ARS) soil scientists Douglas Karlen and John Kovar argue that while "no-till" farming offers benefits such as lower energy costs and reduced soil erosion, the practice may also 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.
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 plant nutrient.
US corn production appears to be healthy. US government figures project 2004/05 global wheat production to be up 1.3 million tons to a 'record' 622 million tons, up 13 per cent from last year.
But despite such 'record' stocks, world grain production has fallen short of consumption in each of the last four years, forcing a draw-down of global stocks for wheat, rice, corn and soybeans to 30-year lows.
However, a recent report issued by the UN-backed Food and Agriculture Organization (FAO) predicted that world cereal production should hit record levels, with US production increasing.
Achieving greater production efficiency will help the ingredients sector realize lower prices. 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.