Though some soils in the West are inherently alkaline, meaning the pH is above 7.0, many gardeners in other parts of the country have acidic soil and they put pulverized dolomitic limestone on their lawns as a matter of course each fall.
The product is recognizable by the heavy, white paper 40-pound bags. With acid rain increasing in much of the nation, that might seem like a good thing to do. If you’re concerned about weeds, however, the dolomitic lime can be a problem.
In ideal lawn soil, the ratio of calcium to magnesium should be 7:1; in dolomitic limestone, the ratio of those two key nutrients is 3:2. The high level of magnesium compacts the soil and actually promotes weed growth.
A better source of calcium for lawns is a product known as high-calcium limestone. It’s also a good idea to have a soil test if you haven’t for a while prior to putting down any limestone or soil additives; most Cooperative Extension offices in the nation still offer basic soil tests, or you can contact the Soil Foodweb laboratory on Long Island in New York for a more comprehensive test. A good source for the limestone is Mag-I-Cal from jonathangreen.com. ($17.90-$30.50 at amazon.com)