Ohio Farm News
By Roger Bender

As soybean and corn fields are harvested, farmers plan for 2011 crops. Armed with yield data and valid soil tests, strategic fertility adjustments are targeted for fall application.

In lieu of higher fertilizer prices, many farms might benefit most from a lime investment, since the balanced soil is a first step towards an efficient crop nutrition program. Proper use of both lime and fertilizer is necessary for high crop yields. To optimize production, soil acidity should be corrected prior to fertilizer application.

Liming benefits soil in the following ways:

•Supplies calcium and magnesium

•Increases oil pH and the availability of phosphorus, molybdenum, and magnesium

•Increases favorable microbial activity, which results in an increased release of organically bound nitrogen, phosphorus, sulfur and other nutrients

Soil pH measures the active soil acidity or alkalinity. The lime requirement is determined using the buffer pH, or the lime test index, which measures potential soil acidity.

Finer-textured soils that have relatively high CEC (Cation Exchange Capacity) have the ability to buffer changes in soil pH by releasing adsorbed hydrogen; thus, more lime is required to affect soil pH. Coarser-textured soils have lower CEC values and have a diminished ability to provide hydrogen to replace that which is neutralized by liming; thus, less lime is required.

The lower the buffer pH is below 6.8, the greater the lime requirement. For organic soils, pH is used to determine lime requirement.

Agricultural liming materials used for correcting soil acidity include all calcium and magnesium oxides, hydroxides, carbonates, silicates or combinations sold for agricultural purposes. Commonly found liming materials include Ag lime superfine, Dolomitic hydrated ag lime, Calcitic ag lime, Dolomitic ag lime and water treatment lime.

The Total Neutralizing Power (TNP), Fineness, Moisture and Effective Neutralizing Power (ENP) of various liming materials are typically reflective of the fineness of the liming material.

Liming materials are labeled based on their effective neutralizing power (ENP). The ENP of a liming material considers the material equivalence, purity, fineness of grind and percentage of moisture. Particle size of liming materials impacts their effectiveness at neutralizing soil acidity and their speed of reaction.

Ag liming materials typically contain particles of differing sizes, which results in longer-term acid neutralization. Smaller particles react quicker, while larger particles dissolve slowly, affecting soil pH over a longer period.

This is why liming is typically not necessary every year. When comparing liming materials and their associated cost, ENP provides a good way to identify the most economical source.

Most farmers in west-central Ohio use ag lime for soil pH adjustment. We recently received a question about the value of water treatment lime. Such material can be economical in comparison to what farmers regard as a standard ag lime.

However, because of the fineness of the material, even application is even more critical to avoid extreme pH variations within a field. Extreme differences in soil pH can cause nutrient tie-up (especially with micronutrients), adverse effects of crop protection products and the like.

Want to learn more about liming? Check out the Ohio Agronomy Guide.

The views and opinions expressed in this column are those of the author and not necessarily those of Farm World. Readers with questions or comments for Roger Bender may write to him in care of this publication.