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Corn Illustrated: Add lime to raise soil pH levels where soil tests indicate it's needed.

Dave Nanda

January 28, 2020

2 Min Read
2 piles of lime
LIME WHERE NEEDED: Lime can still be applied this spring if soil tests indicate low soil pH.

Proper soil pH is one of the most important factors for maximizing crop growth and potential yields.

What soil pH levels are needed by different crops? The pH values required by corn, soybeans, wheat and alfalfa are somewhat different for optimum performance. However, farmers grow different crops on the same ground and need a range of pH values that is suitable for most of the crops they grow. They can’t have constantly fluctuating levels of acidity or alkalinity to match different crops.

A pH neutral environment is suitable for most plants. However, corn likes soil pH values of 6.2 to 6.8, whereas soybeans can tolerate more acidic soils of 5.8 to 6.2. For uptake of nutrients by the roots of most crop plants, a proper balance of 6.0 to 6.8 pH value is essential. The Purdue University Corn and Soybean Field Guide recommends a pH of 6.0 to 6.8 for corn and soybeans on mineral soils. The pH for alfalfa should be 6.5 or higher.

Adjust pH levels

How can you adjust the pH values of soils on your farm? Most soils tend to become acidic over time due to weathering of soil minerals and release of acidifying metals, and leaching of calcium, potassium, magnesium and sodium. Decomposition of organic matter and application of ammonia-based fertilizers and their nutrification also contributes to acidic soils.

To maximize yields, you must balance soil pH depending on the crops you intend to grow. Balanced pH is so critical because it can affect nutrient availability, soil-applied herbicides and their degradation, potential for aluminum or iron toxicity, as well as nitrogen fixation by legumes.

For example, according to the Purdue field guide, phosphorus becomes less available at pH levels below 6.0. Manganese begins to be less available as soil pH rises above 6.5.

For effective soil pH management, soil testing every two to three years for every field is important. Soil samples should be collected at the same time every year.

Soil testing is even more important this spring since lower-yielding fields last year could not use all available nutrients. We can’t estimate what is left over after the leaching caused by rains last fall and this winter.

Liming factors

Liming to increase soil pH of acidic soils is based on soil type, tillage depth and lime quality. Clay soils with lots of organic matter require larger amounts of lime than sandy soils with low organic content to correct a pH deficiency.

Fine lime with smaller particles dissolves faster and neutralizes soil acidity more quickly than coarse lime. There are many types of liming materials available.

Soil type, level of acidity, crop to be grown, and type and depth of tillage would determine the amount of lime you need to apply. Please check with your local supplier.

Nanda is director of genetics for Seed Genetics Direct, Jeffersonville, Ohio. Email him at [email protected] or call 317-910-9876.

About the Author(s)

Dave Nanda

Dave Nanda is director of genetics for Seed Genetics Direct, Jeffersonville, Ohio. Email [email protected] or call 317-910-9876. Please leave a message.

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