Why dolomite aglime is key to farming in Butler & surrounding counties
For generations, farmers in Butler and surrounding counties have worked the land, battling the natural tendencies of Pennsylvania soil.
While modern fertilizers and high-tech equipment get much of the attention, some of the most critical agricultural work is done by a simple, often overlooked material: dolomite aglime.
In regions where heavy clay, high rainfall and decades of cropping have created acidic soil, dolomitic limestone is not just an additive, it is a vital, strategic tool for ensuring high yields and long-term soil sustainability.
The problem: Acidic soils and low magnesium throughout Western Pennsylvania, particularly in areas like Slippery Rock, New Castle and the surrounding townships. Rainfall leaches essential nutrients, including calcium and magnesium, deep into the ground, while the persistent use of nitrogen-based fertilizers increases acidity further.
When soil pH drops below 6.0, phosphorus and other nutrients become “locked up” and unavailable to plants. Furthermore, low pH increases the solubility of aluminum, which is toxic to root development. Fertilizer without lime is about as effective as a tractor without fuel.
The solution: dolomite's dual action. While traditional, "aglime" (calcitic) brings up the pH, it often lacks magnesium. This is where dolomite — or magnesian limestone—shines. Dolomite, a carbonate rock containing both calcium and magnesium, offers two critical benefits in one application. It neutralizes acidity and raises the soil pH to the optimal 6.5–7.0 range, unlocking nutrients and improving fertilizer efficiency. It also supplies magnesium, providing a crucial, often missing ingredient that is essential for chlorophyll production in plants.
Butler and surrounding counties need it because the soil in these counties often suffers from a "double-whammy" of high acidity and low magnesium.
For corn, soybean, and particularly, alfalfa farmers, the magnesium from dolomite is critical. Farmers can improve crop yields by optimizing the pH and adding magnesium and see stronger stem stiffness, greener foliage and higher yields.
It can also improve forage quality. For local dairy and livestock farms, magnesium-rich forage grown with dolomite can help prevent diseases like grass tetany.
Dolomite also helps break up hard, compact clay soils, improving water penetration and reducing erosion — a major concern in sloped areas.
Other types of lime that can be spread on farmers’ fields are high magnesium lime and high calcium lime. What should be used in fields all depends on what soil tests would say you need or don’t need. If your soil test shows that you are below optimum in magnesium or calcium, then you use the different lime accordingly.
There are a lot of variables when it comes to spreading lime. Most of it depends on what your long-term goals are, depending on if your growing row crops, vegetables or pastures for cattle. There is no “one size fits all” approach to spreading lime and it’s something that you should do research on on your own soils to determine what is best for your operation.
Agronomist John Thompson of Thompson Farm Volant, LLC, who has 45-plus years of agronomic experience and an agronomy degree from Penn State University, emphasizes a few things about aglime. First, the best time to act is now and have soil test pulled and analyzed. Second, the geology of the limestone in Western Pennsylvania is calcitic and lacks magnesium. This requires dolomite aglime to be acquired from Eastern PA and/or Western Ohio. Third, the effective neutralizing power (ENP) is what does the work of the aglime and neutralizes the acid in the soil.
When researching your aglime, ensure that the ENP is a minimum of 1,500 pounds per ton to maximize the value of your lime. Look for 60-100 mesh screen size to see results quickly.
Lastly, if your aglime's ENP is less than 1,500 pounds per ton and lower than 60 mesh screen you will need to apply more per acre and wait longer to see the effects.
As agricultural sustainability becomes more challenging, utilizing local resources like dolomite aglime remains a cornerstone of productive, sustainable farming in Butler and surrounding counties.
William Thiele is a Butler County dairy farmer and director of Pennsylvania Farm Bureau District 15. John Thompson is a Butler County Farm Bureau member.
