Much of the Northeast has seen below normal rainfall since April 2010 as well as unusually warm temperatures, especially during July. This has led to drought concerns throughout the region. However, the recent rains of the last week should be enough to bring the lawns out of dormancy. New green growth over 60% or more of the lawn area is a good sign that the lawn can recover. So what can you do to aid our lawns or athletic fields in the recovery process?
Insect Damage – in our travels we have seen evidence of some chinch bug damage. This can easily be confused with drought damage. With normal precipitation or irrigation the turf can generally outgrow damage caused by chinch bugs, but with the water restrictions and the lack of rainfall this is unlikely to have occurred. Unfortunately these areas will not recover on its own as dormant grass would. Aerating and over-seeding are necessary (discussed below).
It is also important to begin scouting for grubs. Given that this has been a dry year the best time to scout for grubs will likely be mid-September. In general they are found in sunny areas of the lawn with the poorest soil conditions in the top 3” of soil. Should you find more than 6 – 8 per square foot it is best to treat that area. We recommend an application of Heterorhabditis bacteriophora-Hb nematodes. Hb Nematodes have been proven effective on all grub varieties. They are a microscopic worm that actively seek out the grubs and infest them through natural body openings.
Aerate –to relieve soil compaction, allow grass roots to spread and improve air circulation in the root zone. For this reason it is best to perform core or deep tine aeration when the turf is actively growing. In the case of cool-season grasses this is in early fall when the turf is coming out of dormancy. Aeration is stressful to the turf as such it should be avoided when the turf is already under stress; during summer drought or going into winter dormancy. Dr. Nick Christians of Iowa State has found that if the turf is allowed to go into dormancy with open aerification holes, there is a greater risk of winter damage.
Over Seed – to introduce new grass seed on existing turf using either a mechanical seed slicer or broadcast spreader after core aeration. Fall is the best time to over-seed residential lawns (beginning as early as mid-August). The warm days and cool nights create morning dew providing the necessary moisture for seed germination. Athletic fields should also be over seeded after mid-August, as well as several more times throughout the growing seasons due to their heavy use. A good practice is to over seed when core aerating and/or topdressing. Over seeding when aerating and/or topdressing increases the seed-to-soil contact and increases germination. After core aerating you can broadcast the seed thus saving time over mechanical seed slicing. Over seeding at higher than recommended rates increases the number of new grass plants and helps to provide faster ground coverage and better weed competition.
Seed selection – it is important to make the appropriate seed selection for the turf use and the seeding window. On residential lawns seeded before the middle of September a seed mix containing Kentucky bluegrass, perennial ryegrass and fescue varieties would be appropriate. If seeding is to occur after the middle of September recognize that Kentucky bluegrass can take up to 20 days to germinate; as such a seed mixture higher in perennial ryegrass and fescue varieties would be more appropriate.
On athletic fields a combination of Kentucky bluegrass and perennial ryegrass is more appropriate. If seeding after mid-September or the athletic field has poor coverage, the recommendation would be to use only perennial ryegrass due to its faster germination.
Topdressing – caring for lawns and athletic fields is the ultimate exercise in no-till agriculture. As such the challenge is how to improve soil conditions when tilling up the lawn isn’t a viable approach. Topdressing when aerating is an accepted practice to improving soil conditions. Topdressing with compost provides the benefits of adding biology, as well as, adding organic matter and thus improving the Cation Exchange Capacity, CEC, of the soil. Disadvantages associated with compost topdressing include labor costs, potential for a large percentage of the material to oxidize and issues surrounding the quality of the compost including the potential to introduce additional weed seeds and utilizing compost that may not be completely finished. In cases where compost is not mature the bacteria in the compost will compete with the grass drawing the nitrogen from the soil to finish the job.
On athletic fields many topdress with sand to improve drainage. This is an acceptable approach on engineered sand based athletic fields, however most fields in the Northeast are actually organic based fields (native soil). Topdressing these fields with sand can actually result in fields that become more severely compacted and hold fewer nutrients than before the application of the sand topdress material.
A good alternative as a topdress material is the application of granular humates or raw leonardite. These inputs provide the benefit of improving CEC and encouraging the proliferation of indigenous soil biology without the introduction of weed seeds or requiring the handling of the volume of material associated with a compost topdress. Another topdress material that holds great promise is the use of vermicompost.
Fertilizing – now is the time to put down the early Fall application of organic fertilizer. Microbes in the soil have likely gone into dormancy to survive the environmental stresses of the summer. The presence of a ready food source, moisture and cooling temperatures will encourage the fungi and bacteria out of dormancy allowing them to cycle nutrients to the turf.