Lime After Crabgrass Control - Knowledgebase Question

Newtown, PA
Avatar for michaeldwo
Question by michaeldwo
March 18, 1999
I recently bought an 18 year old house, and had the soil tested. The lawn area is 6.4, and lime was recommended. I already put down a crabgrass preemergent-fertilizer combination. Do I need to wait any period of time before I apply the lime, or can I do it immediately? How much lime per 1000 square feet should I start with, and what is the ideal pH for the lawn? The soil is a fairly heavy clay.

Answer from NGA
March 18, 1999
Most turf types prefer a pH range from 6.5-7.0, so you don't have to raise the pH too much to make your grass happier. As for it's reaction with the herbicide-fertilizer, consult with the manufacturer of that product for details, if the information isn't listed on the product label.

Several types of lime are available, and which you should use depends on the soil's magnesium content. If a soil test indicates low to medium magnesium levels, use dolomitic limestone, which contains 46 to 51 percent calcium carbonate and 38 to 40 percent magnesium carbonate. Where magnesium levels are high, use a calcitic or oyster shell limestone. These products contain 65 to 80 percent calcium, but only 3 to 15 percent magnesium. On clay soil, it takes 10.5 lbs/1000 sq ft to raise pH a full number (that is from 5.5 to 6.5). If you use dolomitic lime, increase the lime amount by a third. Keep in mind that it takes several months for the effects of limestone to show effects, unless you use a very fine dust or a liquid form. On the flip side, the treatment should keep the pH steady for 3-4 years; then you should test pH again, and make necessary adjustments. Hope this helps!

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