You pour your heart and soul, labor and sweat into your garden, so the last thing you want to do is kill it with kindness. Excessive fertilizer application can decrease plant health and can lead to decline and death. Limestone, a type of fertilizer used to adjust soil pH, can be a useful additive -- or much of a good thing. Diagnose your plant's underlying problem to decide if limestone is needed, and how much is enough.
Soil pH measures the acid and alkaline levels in the soil on a scale of one to 14, 7 being neutral or in equal concentration. A reading below 7 indicates higher acidity, while over 7 means you have alkaline soil. Most commonly grown plants prefer a pH between 5.5 and 7. If your soil pH falls below 5.5, applying limestone as a soil amendment can help raise the levels to the neutral or alkaline range for best growth.
Function of Limestone
Limestone reduces toxic levels of soil acidity, which interferes with plant growth. It enriches the soil with calcium, which regulates the free flow of necessary nutrients such as zinc, copper and phosphorous. It also improves soil structure, making it more porous, aerated and able to hold moisture. It does not create the nutrients, but it sets up the conditions that allow a plant to better absorb the nutrients in the soil. However, too much limestone will raise the pH too high, which can interfere with the plant's ability to absorb nutrients from the soil and eventually kill it.
Many factors affect the soil pH, and it can change throughout the year and from one year to the next. Therefore, the only reliable way to gauge whether your garden needs a limestone treatment to correct a low pH is to administer a soil test. Simple home test kits are available from your garden center, or you may get assistance from a cooperative extension service. Armed with the most current soil data on your planting area, you can avoid unnecessary limestone applications that cause malnourishment and kill your plants.
If your soil test indicates the need for limestone, the best time to apply lime is during soil preparation. Work it deep into the subsoil for best effect from fall to early spring when the soil is somewhat dry to get a better distribution. Spread it over the entire area, using a spreader if possible. The Alabama Cooperative Extension Service warns against applying limestone and fertilizer at the same time, recommending that you space these soil treatments two weeks or more apart to avoid injuring and killing your plants.