(December 2008) Provided you've finally gotten your crops out of the field, now is the ideal time to be applying lime to make sure your soil pH levels are adequate for next year's growing season. Soil pH decreases over time due to use of high rates of nitrogen fertilizer, crop nutrient removal, and leaching of basic cations, such as calcium. There can be significant yield loss or even crop failure when the need for lime isn't detected, or a good quality agricultural lime isn't applied at the correct rate.

"The best time to be liming is right before fall tillage, so you can work the lime into the soil profile," explains Steve Barnhart, AgriSolutions™ and CROPLAN GENETICS® brand regional agronomist. "Another benefit to liming prior to tillage is that the winter winds won't blow if off your fields. This is also a good time to treat no-till acres, and blowing won't be as much of a concern on these fields because it will adhere to the crop residue that's left over."

In the central and northern United States, the ideal soil pH level for corn and soybeans is 6.2 to 6.5. Alfalfa producers should have their pH levels closer to 6.9. Liming a bit before field averages drop ensures that areas of the field falling below the field average will be corrected before they can reach yield-limiting soil pH levels.

Symptoms of low pH include stunted plant development, uneven crop growth, faster aging of lower leaves, and yellowing between veins on upper leaves. Additionally, bacterial activity is reduced under low pH conditions, slowing the breakdown of soil organic matter, crop residues and organic fertilizer sources like manures. As a result, nutrient release from these sources is lessened.

Liming should be done every 3 to 5 years. Lime application will be slower in a dry soil, because water is required for lime to react with soil. Finer grades of limestone generally work faster, so producers should confirm with their dealer that they're getting the best product for the money. Pelletized lime is a good material for maintenance.

No-till fields should be treated more regularly so the soil pH does not drop too low, because these applications move slowly through the soil. Without tillage, the lime takes a long time to neutralize the acidity. In fact, according to a long-term Penn State study, it took nine years to raise the pH at a depth of 6 inches from 5.1 to 6.5 in a on a no-till field that had been left to become acidic.

To get the best value for their dollar, producers should annually grid test 25 to 33 percent of their field to ensure that they're applying the correct levels of nutrients to the right area of the field. At about $10 an acre, grid testing is a worthwhile investment as it ensures that excess fertilizer isn't being applied to acres that already possess adequate soil fertility.

For more customized information about liming your fields, your CROPLAN GENETICS® expert agronomist has you covered. Turn to your local seed specialist and check out your local Answer Plot® location as a third-party source to help sort out the other brands and find the answers for your toughest field.