Does Your Lawn Need a “Do-Over”?

By C. Rae Hozer, Cumberland County Master Gardener

These articles on soil test results and late season lawn maintenance started with a yard which had originally been seeded with cool season turfgrass. Over the years weeds and moss  crowded out much of the good grass. (My observation is that this summer, crabgrass and other weedy grasses took over many a yard around here.) When asked by the homeowner to explain a University of Tennessee Soil Test Report for the area she plans to sod this month, it reminded me that many folks have questions about these tests Soil lab results as presented on the report can be pretty mystifying. Since this is the prime time (September and October) to put in a new lawn or to renovate one with cool season grass in the Upper Cumberland region of Tennessee, other Plateau Gardeners are probably starting or refurbishing a lawn and might appreciate the explanation, too.

Tennessee is in what is called a lawn grass “transition zone” between northerly states like Illinois and Michigan where cool season grasses do best and southern states like Louisiana and Mississippi where warm season grasses rule. Grasses which grow well at cooler times during the growing season include bentgrass, Kentucky bluegrass, perennial ryegrass, fine and tall fescues. Warm season grasses include common and hybrid Bermuda grass, Zoysia and centipedegrass. In general, cool season grasses are more successful in this transition zone than warm season varieties but factors like altitude, amount of sun or shade and how much water is used to irrigate, also influence which turf works best.

Whichever type grass you grow, cool season or warm season, the University of Tennessee publication ‘PB1038 Fertilization & Management of Home Lawns’ has helpful information. Pick up a copy at your local UT Extension office or download it at home using the link www.utextension.utk.edu/publications/pbfiles/PB1038.pdf on your computer web browser.

Soil at a pH level above 6.1 that is adequately fertilized will yield a lawn that looks greener, less weedy and more attractive than grass growing in soil at a lower pH (more acidic soil) with insufficient fertility. The soil lab report tells you how much fertilizer and lime to put down and when to apply it for the type of turf you have. Following directives of the soil test typically leads to the good looking, thicker growing turfgrass homeowners want.

The soil test results and ratings for available nutrients are presented near the top of the report front page. Beneath the heading ‘Sample Number’ is the number or name used to identify the area from which the soil was taken. This soil sample was submitted as ‘LAWN’. Under the heading ‘Water pH’ the result was ‘6.4’. While a pH of 7.0 is at the exact center of the 1 to 14 pH scale, the range of values from 6.5  to 7.4 are considered fairly neutral. Most landscape plants thrive in soil rated within that mid-range. Lower pH values indicate more acidic conditions and higher numbers more alkalinity. A pH of 6.4 is only slightly more acidic than 6.5 and well above the 6.1 minimum pH for turfgrass. As a result, in the recommendations for fertilizer/lime application rate and timing section below, after the heading ‘Limestone:’ it says ‘Lime is not needed at this time’. 

The fertilizer recommendations aren’t as easily interpreted. The nutrients P (phosphorus) and K (potassium) are rated ‘L’ (Low), ‘M’ (Medium), ‘H’ (High) or ‘V’ (Very High).

Topic continued next week.

Plateau Gardening is written by Master Gardeners for those tending home landscapes and gardens in Tennessee’s Upper Cumberland Region. Contact UT Extension Cumberland County, P.O. Box 483, Crossville, TN 38557, (phone 931-484-6743) for quick answers to specific questions, free publications, or to learn about becoming a Master Gardener. Email comments or yard and garden inquiries to Master Gardener Rae, mgardenerrae@frontiernet.net.