MISSISSIPPI STATE -- Experienced farmers know the importance of lime, but this is the first year growers could select from two grades depending on their price range and success expectations.

Larry Oldham, extension soils specialist at Mississippi State University, said acid soils limit production of every crop in Mississippi. These soils require lime to neutralize the soil acidity for maximum economic productions.

"Recent regulation changes allow two grades of lime to be sold: Grade A and Grade B," Oldham said. "Grade B is coarser and may not be as pure. Therefore, it will not help the soil as effectively as Grade A."

John Hall III of the Mississippi Department of Agriculture and Commerce said the state did not have any regulations on lime before 1993. This had resulted in inconsistent qualities.

"Grade A has a minimum standard it must reach for purity and particle size," said Hall, who is director of the Feed, Fertilizer, Soil/Plant Amendments and Lime Programs. "Now farmers can be sure of the quality of the lime they are purchasing."

Oldham said the size of individual particles determines how fast they react in the soil. Smaller particles will dissolve rapidly, larger particles take much longer.

"Research has shown lime reaction time increases from weeks for fine particles to more than 20 years for coarser particles," Oldham said. "When you want lime effective in the current growing season, Grade A is the only option."

The lower price of Grade B has appealed to some farmers.

"Grade B may store easier and be simpler to spread, but these properties have nothing to do with neutralizing soil acidity," Oldham said.

Farmers should apply lime three to six months before the crop is grown. If they base rates on soil test results, lime will only be needed about every three years.