Agricultural lime, also known as ground limestone, is a compound of calcium or calcium and magnesium. The main purpose of lime is to increase the pH level of garden soil (making it more alkaline or "sweet"), ultimately correcting the acidity of soil. And, since plants are not able to get the nutrients from soil that is too acid, lime helps vegetables get needed nutrients and grow.
What is pH Level?
PH level is a scale which describes how acidic or alkaline a soil is. This is used to figure out the amount of lime needed to reduce soil acidity. The pH scale ranges from 0 to 14 with the mid-point of 7 being neutral. This means the range of acidity is from 0 to 7 and that of alkaline is from 7 to 14.
Check your soil pH before adding lime to your vegetable garden to see how much, if any, you need to add. A simple soil pH test checks the acidity of the soil. You can buy a do-it-yourself test or electric meter available at most garden centers or send a sample in to a laboratory for more in-depth analysis. Vegetable gardens produce best at a pH between 6 and 7.
When and How to Lime
If your test shows that the soil needs liming, it is best to lime your soil in the autumn. This allows the lime to work its way into the soil over the winter and ready for the spring planting. Apply the lime after you clean up the vegetable garden and always follow the directions printed on the bag. Apply with a lawn or hand spreader and release like you are fertilizing. Never mix fertilizer with lime.
Additional Benefits of Lime
In addition to increasing the pH level of garden soil, lime also reduces the toxicity of some elements in the soil such as iron, aluminum and manganese, all of which could reduce plant growth. Adding lime to soil over winter also provides essential nutrients including calcium and magnesium, which helps keep it healthy through the cold weather. Some gardeners also say that lime helps improve the soil structure and keeps weeds down.