Effects and use of lime
What is Lime?
Lime is a soil amendment made by grinding limestone, a naturally occurring type of rock that is very high in calcium. Two types of lime are commonly used in lawns and gardens, agricultural lime and dolomitic lime. Agricultural lime, also sold as garden lime, is made from calcium carbonate. Dolomitic lime is made from dolomite, a type of rock very similar to limestone except it also contains magnesium. Both types of lime provide calcium for plants, but dolomitic lime also supplies magnesium, a nutrient often low in soils. Other types of lime you may find for sale include hydrated or slaked lime and quick or burnt lime. These are not recommended for lawns and gardens.
What Does Lime Do?
In addition to supplying calcium, lime makes soils less acidic. Acidic soils, referred to by old timers as sour soils, have a low soil pH. Soil pH levels can range anywhere from 3.0, very acidic, to over 8.0, moderately basic, in our region. Most plants grow best when the pH is slightly acidic, between 5.5 and 6.5. At levels lower than this many nutrients become unavailable to plants even if they are present in the soil, while elements like aluminum become too available and can burn roots.
When soil pH is too high plants may develop iron chlorosis or yellowing between the veins.
If your soil pH is too low (below 5.5), most plants will not grow well no matter how much fertilizer you add. If your soil pH is already 6.5 or higher adding lime can harm plants by raising the pH too high. This makes nutrients unavailable, resulting in nutrient deficiency symptoms like yellow leaves and stunted growth.
How to Tell if Your Soil Needs Lime
The only accurate way to know if your lawn or garden needs lime is to have the soil tested. Soil test kits can be purchased at garden centers or online, but they do not provide accurate results or tell you how much lime you need to add.
I will add Dolomitic Lime lightly into my next soil grow as a source of Calcium and Magnesium, not to control pH, though I'm aware it may establish a weak buffer. I've been lucky that I'm using well water that needs no adjustment. Rock solid 6.5. Soil is excellent at maintaining pH and was a large reason I went this route, but the yields in hydro are eyepopping. I like 3 parts
OF to 1 part perlite and 1 cup guano, 1 cup bone meal, both organic, for a 5 gallon dirtpot. But if it turns into a pH war, I'll drop it from the mix. Keeping it simple with less variables to consider when problems pop up will make troubleshooting easier. Be proactive on the Cal/Mag indoors, start early before deficiencies appear. Good luck with your grow!
