QUESTION: The client wanted to know whether she can plant grass seed and use lime and preemergent weed control at the same time.
DIAGNOSIS / RECOMMENDATION: Generally, weeds present in the lawn are an indication of poor quality turf. The best weed control is a thick, healthy turf. To figure out why there are weeds in the turf, the following questions should be answered: Are there soil-related problems such as pH, fertility, poor drainage, or compaction? Could the limiting factor be shade? Was the turf previously damaged by an environmental extreme or pest attack? “Weeds possess incredible capacities to occupy and dominate environments where other plants cannot survive.” 
The only way to clearly understand the health of the soil and what additional modifications might be needed to optimize turf performance is to test the soil “for levels of pH (a measure of soil acidity), phosphorus (P), and potassium (K).” The results of the soil test will indicate whether the soil’s acidity, as measured by pH, is appropriate for good turf growth. Additionally, the analysis will report the level of phosphorous and potassium present, as well as micronutrients. Based on this analysis, the soil test report will recommend fertilizer and/or lime if needed. The level of phosphorous is especially important because “[M]any of Virginia’s soils that have been regularly fertilized over the years have more than adequate P …and no further applications of P are required and/or desired. … When P is needed, the soil test will recommend an appropriate fertilizer and application level, but the use of traditional complete garden-type fertilizers (e.g. 10-10-10) without the benefit of a soil test is not representative of environmental stewardship.”  It should also be remembered that application of lime on a routine basis, without the benefit of a soil test, is also not recommended.
Without knowing the specifics of the client’s existing lawn’s soil health, grass type (cool or warm season), and weeds trying to be controlled, only general information can be given.
It is important to know what weeds are present to “understand control alternatives. For instance, many winter annual weeds (hen bit, chickweed, bittercress, annual bluegrass, etc.,) … will die as temperatures warm.”  A better way to control them is by treating winter annual broadleaf weeds in the fall, with either preemergent or postemergent applications.
“Cool-season perennial weeds such as dandelion, clover, and plantains can be controlled in the spring with appropriately selected and timed herbicide applications. The key to success is knowing the weed and its life cycle to make an appropriate herbicide choice and application.”  Herbicide labels provide a wealth of information on specific chemicals in the product, how to properly and safely apply them, and what weeds will be controlled. All labels should be read carefully and strictly followed.
With respect to the advisability of combining cool-season grass seed with a preemergent herbicide, generally it is not recommended. “[A] preemergent (PRE) herbicide can be used to control germinating weed seed, but consider that most of these products will also control any grass seed that has (or is) to be applied. If a PRE is not used, be prepared to apply POST emergent herbicides later this spring after you get the turf actively growing and before the weed gets very large.”  Be mindful, however, “many standard POST broadleaf herbicides will seriously damage warm-season grasses if applied during spring transition.” 
An exception to the general recommendation to avoid combining preemergent applications with seeding is as follows: If crabgrass control is desired along with seeding for coolseason grasses, “[T]wo herbicides that have unique uses in spring and summer establishments are siduron and quinclorac. Siduron is a preemergent crabgrass herbicide that can be safely applied just prior to or at seeding of cool-season turf grasses only. The other option is quinclorac, an herbicide that can be applied just before or at seeding of most cool-season and warm-season turf grasses, or after emergence of both turf and weedy grasses. As a postemergent herbicide, quinclorac requires a proper adjuvant such as a crop-oil concentrate or methylated seed oil. Follow label directions very carefully with either of these chemicals in order to maximize crabgrass control without damaging or killing turf seedlings.” 
From The Bedford Extension MG Help Desk
Editors: Betsy B. and Linda E., Bedford Extension Master Gardener
All references accessed (February 5, 2017)
*Photo credits given in source link
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Answers provided herein were based on specific situations and growing conditions.These recommendations may or may not be appropriate for all circumstances.For specific recommendations for your particular situation please contact your local Cooperative Extension Office.
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–A Bedford Area Master Gardeners Association (BAMGA) Publication–