Earlier this fall we made recommendations on how to recuperate lawns after a drought; however, rain has not returned and now we must further adjust our maintenance practices in unirrigated turf areas.
The map on the left shows the lack of rainfall in Indiana over the past 90 days. The majority of Indiana has received 4-8 inches less than normal rainfall amounts during the last 90 days. The map on the right shows that all of Indiana is currently under drought from abnormally to extremely drought.
Below are some strategies on how to cope with the current situation in unirrigated turf areas.
The recommendations below pertain to unirrigated areas. Irrigated areas can be managed as normal.
Should I still fertilize in late November or early December?
There are three strategies that could be used. Option 1. First, applying 0.5-1.0 lbs N/1000 ft2 now with a quick-release nitrogen (N) source and anticipate that rains will return. Keep in mind that drought stressed plants will not take up nitrogen, and so a response to nitrogen fertilization will only occur after a rainfall occurs and the plant has a chance to take-up the nutrient. Additionally, this option will likely result in the loss of some nitrogen via volatilization. Volatilization losses could be minimal (<5%) if the fertilizer is watered in within a few days of fertilization or higher (approx. 5-30%) if rain does not water in the fertilizer within 10 days of application. Option 2. A second strategy would be to wait to fertilize until after the next rainfall. With either of these options the turf must still be green and photosynthesizing at the time of application and the soil temperatures should be >32 °F or ideally >40 °F. Option 3. Rains do not return and no fertilizer is applied.
Normally we would recommend fertilizing about 1.0 lb N/1000 ft2 in September and November in lawns. This year it may be that many areas receive only one fall application or none prior to winter due to drought. Weak turf that enters winter dormancy will emerge in the spring weak and be more susceptible to weed invasion next year.
Although aggressive fall fertilization is usually recommended to help our turf recover from drought, we may need to increase fertilizations next spring by 25% or more to help encourage growth and an improvement in turf density in order to help reduce weed pressure.
Should I apply a herbicide right now?
Herbicides are ineffective on drought-stressed weeds and can be damaging on drought-stressed turf, especially when temperatures are warm. If the lawn is >50% green, then herbicides can be applied.
Avoid the temptation to apply herbicides in a dormant (brown) lawn even though weedy species may be obvious.
It is better to hold off on applying fall broadleaf herbicides until rain returns and the turf and weeds being growing again. Although fall applications are better than spring applications for broadleaf control, spring applications can still be effective at controlling broadleaf weeds.
Broadleaf herbicides can be applied in Indiana through November and still provide effective control in many cases. Ester formulations are more effective at controlling weeds during cool-temperatures.
Read the herbicide label carefully if the area you want to treat has recently been seeded. Most herbicides require that newly seeded turf be mown 1-2 times prior to a herbicide application.
Should I seed right now?
Seed between December and February as a dormant seeding. The seed will lie there dormant (un-germinated) until warm temperatures return in the spring. This option can be effective for Kentucky bluegrass, perennial ryegrass, and tall fescue. For tall fescue and perennial ryegrass it may be worth waiting until late December to seed to ensure that soil temperatures are cool enough to prevent any immediate germination.
A slice- or slit-seeder will help incorporate the seed into the soil. This is especially needed in lawns that have a lot of dead crabgrass or other weed debris on the soil surface.
Can I aerify lawns right now?
Core aerification will provide many benefits to turf including decreased soil compaction and thatch and increased soil aeration and water infiltration.
Despite the benefits of aeration, it is only effective when the tines can penetrate the soil. Attempts to aerate dry soil will be ineffective.
Most soils in Indiana are too dry to aerate.
Athletic fields can be aerified through November as it is more crucial to relive compaction in these soils due to their higher need for compaction relief.
Unirrigated home lawns should be aerified in the spring instead of this fall.
Dr. Aaron Patton, Turfgrass Extension Specialist
Send corrections, suggestions, and comments to email@example.com