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The Benefits of Agricultural Limestone for Soil Health and Gardening


You may take calcium supplements to strengthen your bones, but have you thought about giving a calcium supplement to your soil? Agricultural limestone is used on acidic soil to make it sweeter, more alkaline, effectively correcting the pH level in your garden soil.

The calcium in agricultural limestone helps to make the cells of your plants healthier by strengthening the cell walls. This improves their stems and leaves, as well as their root systems. It also helps them absorb and utilize sunlight more effectively. Blossom end rot in tomatoes is just one result of a calcium deficiency in your soil. Have you ever purchased poinsettias with what appears to be burnt edges? That is also a sign of calcium deficiency in the potting soil.

Besides being used to raise calcium levels in the soil for healthier and more productive crops, large-scale farmers and small-scale home-gardeners use agricultural limestone to break up hard-packed clay soil. This improves drainage and aeration, contributing to higher, healthier vegetable yields. It works because the calcium in the agricultural limestone interacts with the silicon in the clay on a molecular level, causing the clay to become less dense. Who knew?

What Tums Do for Your Stomach, Limestone Can Do for Your Soil

Though some plants are acid loving, soil that is too acidic usually spells trouble as the high acid levels cause nutrients to become locked up and unavailable to your vegetable plants. Additionally, fertilizer added to acidic soil is not well absorbed, resulting in valuable minerals, such as nitrogen, just washing away; it’s time and money down the drain.  It is also true that highly acidic soil kills beneficial bacteria, such as rhizobia, a bacteria that fixes nitrogen for legume growth. A number of healthy bacteria work to enrich your soil, though highly acidic soil destroys those invisible (to the naked eye) populations that balance nutrients in the soil and water, effectively reducing disease-causing organisms. 

Agricultural limestone is a time-tested solution to add calcium to the soil, used by generations of farmers and gardeners. Completely nontoxic, the calcium carbonate in limestone also happens to be the active ingredient in Tums. So, just as you might take an antacid made of calcium carbonate to neutralize stomach acid; when you add calcium carbonate, in the form of limestone, to your garden, it reduces the acid levels.

Soil Testing to Determine Acidity

Just as you take Tums when you have an acid stomach or as directed by your doctor in place of a calcium supplement, you don’t want to apply limestone if your soil doesn’t need it. That’s why it’s best to test your soil. Soil testing is quick, easy, and inexpensive. You can get an inexpensive mini-tester that you simply stick in the ground whenever you need a reading. Within seconds it will tell you your soil’s pH. If you want a more comprehensive soil test that will tell you the levels of the other minerals in your soil, take a soil sample to your local Extension office. They will usually conduct the test for free. You can also take a water sample there if you are concerned about the water quality from your well or processing plant.

What is pH?

The pH of your soil indicates how acidic or alkaline it is. Acidic soil has a pH lower than 5, while alkaline soil has a pH greater than 7. The ideal pH for most vegetable plants is somewhere in the middle, between 5.5 and 7.5. Master gardeners fine-tune the pH of their soil, based upon what they’re planning to grow. To do this, consult a chart  that shows the optimal pH for various plants; the Farmer’s Almanac has such a chart.

Limestone: Inexpensive and Effective

If a soil test indicates that your soil has a calcium deficiency, agricultural limestone is an easy and inexpensive fix; you don’t even have to till it in for it to work. If the soil test also reveals a magnesium deficiency, consider using dolomite limestone, a mixture of calcium and magnesium. The ideal way to amend your soil with limestone is to apply it 2 to 3 weeks before you plant your garden; however, it is also effective to add it after the garden is planted and growing. Both dolomitic limestone and agricultural limestone do the job, and do it well, with minimal cost and physical exertion.