Drought and turfgrass
Editor’s note: This article is from the archives of the MSU Crop Advisory Team Alerts. Check the label of any pesticide referenced to ensure your use is included.
What is drought? I’m making no attempts to become a climatologist, but I always find it interesting to see how the term drought is thrown about. So let’s go to the source, the National Drought Mitigation Center to find out how they define drought.
“Drought is a normal, recurrent feature of climate. It occurs almost everywhere, although its features vary from region to region. Defining drought is therefore difficult; it depends on differences in regions, needs, and disciplinary perspectives. Based on the many definitions that have appeared in the literature, for example, we might define drought in Libya as occurring when annual rainfall is less than 180 mm, but in Bali, drought might be considered to occur after a period of only 6 days without rain! In the most general sense, drought originates from a deficiency of precipitation over an extended period of time, resulting in a water shortage for some activity, group, or environmental sector.”
I’ve come to realize in Michigan that there is a time almost every summer when people consider that we are in a drought. For many urban/suburban residents drought is easily defined by the lawn turning brown. Once the lawn turns brown initially the response is often glee as the realization hits that the weekend will be free of mowing. After two weekends or maybe even three weekends of idle mowers and no rain, the concern starts to form about whether or not the lawn will be alive by the time the rain returns. Usually at this time various media outlets, especially astute weather forecasters on TV, start including lawn references in their daily forecasts. For example, this weekend has a good chance of showers that should provide some relief for that Sahara desert that was once your lawn. Just from my simple observations, it seems that precipitation patterns in Michigan have been very sporadic this year. Areas that are separated by less than 10 miles might differ dramatically in precipitation totals in the last month. Based on the weather data collected at the Hancock Turfgrass Research Center it has been over a month since we’ve had any significant rain and the un-irrigated turfgrass areas are really showing it!
For Kentucky bluegrass lawns, which are the majority of lawns in Michigan, there is usually no danger that the lawn is going to die unless water is lacking for six to eight weeks. However, there are really no hard fast numbers for predicting whether the turf will die as many other factors will come into play such as high temperatures and traffic. Even if you are not an irrigator, it might be a good idea to give the turf a little water if it hasn’t received any water for a month. Apply about a one half to one inch of water just to make sure the lawn survives this dry period. The goal of this irrigation is not to turn the turf green, but to prevent it from completely desiccating (severely drying out) and possibly death. If we continue in this dry spell, I would continue to give the turf a drink every three to four weeks.
Helpful tips for dry turf
Don’t worry about trying to control weeds right now in drought stressed turf, however if the turf is irrigated or has had rainfall, weeds can certainly be controlled. In drought stressed turf, many weeds are slowing down their growth, and trying to control them now would be more difficult, besides they might be the only green color in your yard. For those who have irrigated and still have some green turf, avoid mowing during the heat of the afternoon. This can result in tire tracks or foot printing on the lawn that may not go away for quite a while. Mow during the cooler times of the day, early morning or in the evening after dinner. Also, maintain the highest mowing height possible. Don’t think that by mowing lower you’ll help the turf by reducing the amount of leaf area the roots have to support. Remember if the turf doesn’t have any leaves it can’t harvest light for photosynthesis and the result is that more energy will be spent to produce new leaf tissue. Mow high and mow in the coolest part of the day.
Unfortunately, the dry conditions are not going to help any fall establishment projects. We are currently in the optimum time for seeding turfgrass, at least we would be if there was some soil moisture. Fall is usually the best time for seeding because of cooler temperatures, which are scheduled for next week, less evaporative demand due to both cooler temperatures and shorter day length, and hopefully some timely rain showers. This is still the perfect time to think about reseeding or establishing new turfgrass areas, but it is going to be critical that irrigation is available to maintain a moist seed bed during establishment. Any mulch cover that can be used on a new seeding will help retain moisture and reduce the drying throughout the day.
Dr. Frank's work is funded in part by MSU's AgBioResearch.