University of Maryland Extension

Fall Soil Sampling and Lime

It’s hard to believe that fall has arrived and it’s time for soil sampling and possibly time to lime.

No, I haven’t done my soil sampling yet nor my dad’s (as promised). But I want to do it soon because I am always excited to see the results. I am guessing that lime will be needed this fall, that we’ll need a cover to increase organic matter, and that soil fertility is down. Still, I can’t wait to get soil samples and see if I am right. Nothing will be done until the soil sample results are here because all decisions will be based on that report. Yes, it is that important!

Lime is my biggest concern. Lime is so important because it adjust the soil acidity or alkalinity. The soil pH affects the availability of nutrients to the plants, and the ideal pH is based on the desired crop. Most agronomic crops grow best in slightly acidic soil with pH between 6.0 and 6.5. Alfalfa likes soil pH to be between 6.6 and 7.0. However, potato and sweet potato yields are best at a pH of 5.2.

Did you know that the soil pH level may also regulate the breakdown of herbicides? Certain herbicides do not break down in the soil if the pH is too high or too low. However, when the pH is right, they will breakdown and become active. This is yet another reason to monitor pH closely.

There are a number of liming materials used to neutralize acids in soils. Liming materials usually contain oxides or carbonates of calcium and magnesium. It is the oxide, hydroxide, or carbonate contained in the liming material that acts to neutralize soil acidity. Different liming materials have different acid-neutralizing capabilities. Most folks use calcite limestone, which contains calcium carbonate, or dolomitic limestone, which contains both calcium and magnesium.

Liming materials are most effective when they are thoroughly incorporated and mixed with the soil at a depth of eight inches. When lime is applied without mixing – as in a no-till situation, a pasture, or hay ground – liming is still effective, but the application should never exceed 1,500 pounds oxides per acre.

Fall lime application is popular because it allows reaction time correcting soil pH before the next growing season. I plan on getting my soil analyzed soon so I can lime this fall and be better prepared for spring 2015.

There is a lot to consider when planning a lime application. Fortunately, the University has two publications to fully explain and assist you with these decisions. They are “Soil Fertility Management” (SFM- 5, May 1997) and “Nutrient Manager; Focus on pH and Lime” (Volume 3, Issue 2, fall 1996). 

Pick one of our beautiful, brisk fall days to enjoy gathering your soil samples. Perhaps you can guess what the results will be. You may be able to get pretty close by evaluating the growth, color, density, and vigor of the crop currently in the field. In just a week or two you will receive the lab results and be able to compare it to your expectations. 

Don’t forget we offer Fall Soil Nitrate Testing (FSNT) for anyone who plans on a fall nitrogen or manure application on winter wheat and barley grain. Call the office for availability. 


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