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Jim Murphy

Good Time to Assess Drainage

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The soil that supports our lawns, sports fields, golf courses, and other land uses begins to recharge (store) with water as the evapotranspiration rate drops off during autumn and continues to decline to a very low rate during winter. Water storage in soil is good since that provides the water needed to support green-up and re-initiation of plant growth in the spring. However, an excessive accumulation of water is an indicator that one or more conditions in the landscape are restricting drainage.

Poor drainage in a softball field
A depression in the grade of an outfield causing ponding of water on a softball field.

Observing the drainage capacity of landscapes during late winter and early spring 2024 should be highly effective at determining whether corrective action is needed to improved drainage. We have experienced above normal precipitation In New Jersey during three of the last six months. September 2023 precipitation averaged 7.55” across the state, which was 3.39” above normal and ranks as the 9th wettest September. December 2023 precipitation was the wettest 12th month on record dating back to 1895. Statewide, precipitation averaged 8.20”, which was 3.93” above the 1991–2020 normal and was 0.33” above the previous wettest December in 1996. January 2024 was 6th on record dating back to 1895. The statewide 6.39” of rain and melted snow was 2.90” above the 1991–2020 normal. See https://www.njweather.org/news for more weather details.

Thus, autumn and winter precipitation has certainly recharged our soils to be at or very near field capacity, Field capacity refers to the water remaining in a soil after it has been thoroughly saturated and allowed to drain freely, usually for one to two days.

With our soils essentially full of water, any additional precipitation during the remainder of the winter and into early spring will provide us a good assessment of drainage. Soil that is freely drained will be wetted after precipitation but will return to a well drained condition (field capacity) within one to two days. Slow to drain areas will become soggy and possibly pond water for more than two days. The longer excess water lingers beyond 2 days within or above the soil, the poorer the drainage.

It is a good practice to scout your landscapes during this time of year and watch for areas that remain soggy or ponded well beyond 2 days after rain. Once you find poorly drained areas the key to improving drainage is to identify where the excess water is coming from and to intercept it before impacting the turf and other landscape plants. The two essential concepts behind good drainage designs are to protect soils from becoming ponded and/or the root zone from becoming waterlogged. Drainage solutions range from re-contouring the landscape (shed excess water through surface drainage) to installing a network of below-ground pipe drainage (intercept excess subsurface water).

Spring Green-up

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Rain late last week combined with rising soil temperatures has initiated green-up of some cool-season grasses in central New Jersey.

Spring green-up initiated on a tall fescue lawn.
Spring green-up of a tall fescue turf seeded in the fall of 2022.

Soil temperatures have been slowing increasing over the last few weeks. Currently, the 24-hour and 5-day rolling averages for soil temperature are 47 degrees F at Hort Farm 2 in North Brunswick, New Jersey.

Keep in mind that exposure will influence green-up. Turf grown in shaded locations will remain cooler and hence be much slower to green-up than turf grown in full sun locations. Growth of cool-season grasses will become more vigorous once soil temperatures are consistently above 50 degrees F.

Now is a good time to remove winter debris like branches, twigs, and leaves to avoid smothering damage during green-up of turfed landscapes.

The decision to fertilize a turf/lawn depends on its function and whether vigor or growth needs to be encouraged. For example, a lawn with a full turf cover that is rapidly greening-up should not be fertilized until later this spring; whereas, a lawn that hasn’t fully recovered from last year’s stress damage will likely benefit from a well-timed fertilization with nitrogen. See Rutgers Cooperative Extension bulletin E327, Best Management Practices for Nutrient Management of Turf in New Jersey for more information on fertilization of turf.

Be aware that green-up will vary with the species of grass. Among the cool-season turfgrasses, perennial ryegrass will be the earliest to green-up. Tall fescue will be slower than perennial ryegrass. Green-up of Kentucky bluegrass will depend on the cultivar (variety) being grown; older, common types of Kentucky bluegrass can green-up relatively early in the spring. Whereas, many of the newer, darker green, and lowing-growing types of Kentucky bluegrass can be very slow to green-up. Green-up of a fine-leaf fescue turf will depend on the species; strong creeping red fesuce and Chewings fescue will be faster to green-up than hard fescue.

Zoysiagrass, which is a warm-season grass, will be the slowest to green-up and is not likely to exhibit substantial signs of growth (green-up) until late-May. See Rutgers Cooperative Extension fact sheet FS521, Zoysiagrass Lawns in New Jersey for more information on advantages and disadvantages of growing zoysiagrass.

Property owners with lawns needing repair this spring should select seed blends or mixtures based on site conditions, intended use, expected level of maintenance, and the potential turf quality that can be achieved. See Rutgers Cooperative Extension fact sheet FS684, Turfgrass Seed Selection for Home Lawns for more information.

Mild winter, what does it mean for overseeding of turf or dormant seeding?

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Typically, turf management isn’t on top of the to-do list in mid-February. But winter in New Jersey isn’t typical typical this year. The statewide average temperature in January 2023 was 41.0°, which was 9.3° above the 1991–2020 normal and ties with 1932 as the mildest January since records commenced in 1895. For more details on a winter weather recap see the Rutger NJ Weather Network at https://www.njweather.org/.

Some may be asking, what does this mean for the overseeding I did last fall to renovate my turf? The answer depends, in part, on what seed mix or blend was used and when was it seeded. The minimum temperatures for seed germination are poorly defined because of the extreme slowness of germination at low temperatures. But observations of late-fall seedings clearly indicate that tall fescue and Kentucky bluegrass seed does not effectively develop a seedling turf once soil temperatures drop to 50° F. Late-fall seedings with fine fescue will also be slow but greater seedling development may be seen with the red fescues (strong creeping red and Chewings). Among the cool season grasses used for turf, perennial ryegrass has the greatest chance for development of turf cover from a late-fall seeding since the species has been observed to germinate at temperatures below 40° F but above freezing.

Because of the mild winter weather, it would be useful to scout any areas of turf that were overseeded last fall to identify and document the extent of seedling emergence and development. This will serve as a benchmark for future assessments and indicators of progress for turf renovation during the approaching spring.

Small seedling plants.
Although difficult to see, the small seedling plants in this image during February indicate germination and emergence of a late-fall overseeding of Chewings fescue on a lawn that suffered damage from summer stress.

Mild weather may be encouraging some to consider dormant seeding, which is the process of applying seed with the knowledge that it will not germinate (remains dormant) until environmental conditions are favorable for germination later in the spring. For cool-season grasses, that generally means seed will not germinate until soil temperatures are consistently above 50° F. And it is important to understand that air temperature will probably need to be 60° F or above before soil temperatures will be consistently above 50° F. Soil temperature at the 2-inch depth is currently averaging above 40° F at the turfgrass research farm in North Brunswick, NJ.

Dormant seedings have greater risks associated with higher seedling mortality and loss from wash-outs, bird feeding, etc. Mortality can occur if the seed germinates and then a hard frost occurs and kills the seedlings. Losses due to wash-out and bird feeding are greater because proper soil preparation during the winter is limited by excessive soil moisture or frozen conditions dictating that dormant seeding are reliant on frost-action to incorporate seed into the soil. As a result, seed rates for dormant seeding are often increased by 30 to 50 percent as an attempt to offset these possible losses.

When attempting dormant seeding, consider using walk-behind spreaders and other equipment that won’t cause soil damage and compaction. If the soil is dry and firm enough, heavier equipment may be used but dry, firm conditions are often not the case, especially when the soil has frost heaved or rains have saturated the soil. Also, do not add a fertilizer product during winter dormant seeding operations in accordance with sound environmental stewardship. Fertilizers should never be applied to snow-covered or frozen soils as there is a high risk of fertilizer runoff.

If rapid ground cover is a primary goal for dormant seeding, perennial ryegrass will provide the fastest rate of establishment. Also, covering a dormant seeding with a growth blanket will be a great aid to germination and establishment. Growth blankets protect the seed from wash-outs, wind blowing, and bird feeding and retain moisture and heat, thereby accelerating the establishment rate and extending the growing season. Growth blankets also discourage people from trafficking and disturbing the area.
In summary, dormant seedings are much riskier than seeding at more ideal times. This doesn’t mean dormant seeding aren’t or shouldn’t be done, but it does mean expectations need to be tempered based on the associated risks. And it would be wise to have alternate plan ready should the dormant seeding not achieve the expected outcome.

Tropical Storm Brings Rain But What About Gray Leaf Spot?

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The passing of tropical storm, Fay brought some needed precipitation to the region, albeit too much at once in many places. Relatively dry soils (assumes not being over-irrigated) and the long, warm days of summer should allow turfs to dry out reasonably fast.

But what about gray leaf spot? Spores of the pathogen are thought to be blown up from southern regions to the north on the winds of tropical systems. With the recent passing of Fay, Dr. Bruce Clarke recommends being on the watch for early symptoms and signs of gray leaf spot outbreaks. Gray leaf spot can be severe on older, non-tolerant cultivars of perennial ryegrass while new, improved cultivars will be much less sensitive although not immune. Over the last couple years, we have also experienced some strong outbreaks of gray leaf spot on tall fescue across the region. So don’t ignore the tall fescue turfs if you have some.

For more information, see the fact sheet, Integrated Control of Gray Leaf Spot on Perennial Ryegrass.

Gray leaf spot control with fungicides on perennial ryegrass.
Fungicide plots on a perennial ryegrass cultivar that is highly susceptible to gray leaf spot.

Green-up Started

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Soil temperatures have been warming and reached the mid-40s °F last week at Rutgers Hort Farm No. 2 in North Brunswick NJ and are creeping into the upper-40s °F early this week. Dr. Clarke recommends that treatment of turf with a history of take-all patch be initiated when soil temperature averages 40 to 60 °F. Treatment of fairy ring should be initiated when average temperature is in the range of 50 to 55 °F. Waiting to treat beyond these soil temperature thresholds will increase the risk that control strategies are not as effective.

Table 1. Soil Temperature Data under Bentgrass Turf Mowed at 0.375-inch in North Brunswick, NJ on 17 March 2020 at 2:00 PM.

 3-inch DepthThatch-Soil Interface
Current48 °F50 °F
24-hour Average45 °F44 °F
5-day Average47 °F47 °F

Additionally, the Forsythia bloom started last week in central New Jersey, which Dr. Matthew Elmore recommends as a traditional phenological indicator for preemergence herbicide programs on turf.

Initial forsythia bloom in a home lawn.
Initial forsythia bloom in a home lawn in central NJ last week.

Glyphosate Alternatives

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Recent news about glyphosate has many thinking about alternatives.

Joe Neal (Professor of Weed Science, Extension Specialist & Department Extension Leader Horticultural Science) and Andrew Senesac (Extension Weed Scientist Cornell Cooperative Extension, Suffolk Co., NY) have published a thorough summary of alternatives and the associated pros and cons through NC State Extension at https://content.ces.ncsu.edu/are-there-alternatives-to-glyphosate-for-weed-control-in-landscapes

Green-up Transitioning to Growth: Ready to Mow?

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Three weeks ago, many turfgrasses began greening up as surface soil temperatures warmed into the 50s °F during the day. Currently, surface soil temperatures are reaching into the 60s °F during the day, which stimulates vertical leaf growth especially after a rain. Any early spring N fertilization will also encourage vertical leaf growth.

Accordingly, mowing equipment should be reconditioned and ready for routine use. Setup of mowing height should not be overlooked; an incorrect mowing height will lead to problems. Generally, lawn grasses will be easier to maintained at a mowing height of 3-inches or higher.

Grasses will be healthier when there are more leaves (leaf area) to capture sunlight for photosynthesis and shade the soil surface. More photosynthesis helps the grass grow more roots and a shaded soil surface remains cooler. Shade also blocks the exposure of weed seed to light, which is an environmental trigger for weed germination.

Uneven ground is another reason to recommend relatively high mowing. Many lawns are relatively uneven. A lack of smoothness in a lawn contributes to poor mowing.  A mower set 3-inches helps protect high spots in a lawn from being severely scalped. For example, a high spot in a lawn that ends up being cut at 2-inches with a mower set at 3-inches would be cut at 1-inch if the mower were set at 2-inches.

Mower scalp caused by mower deck being set too low on a lawn with uneven ground.

 

Soil Health

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Soil that has been severely compacted often breaks into large massive plates.

For those interested in soil health – we all should be – the Soil Health Institute has release a 60-minute documentary featuring innovative farmers and soil health experts from throughout the U.S.

You can view the film at https://livingsoilfilm.com/

 

Dog Days and Cool-Season Grass

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Cool-season lawn struggling to grow in shallow soil on a south-facing slope during dog days.

According to Merriam-Webster, dog days is the period between early July and early September when the hot sultry weather of summer usually occurs in the northern hemisphere; a period of stagnation or inactivity.

The dog is actually the Dog Star – also called Sirius – which rises simultaneously with the sun during the hottest days of summer in the northern hemisphere. Plutarch (Greek writer, 46-120 AD) referred to the hot days of summer as hēmerai kynades (literally, “dog days”); the Latin translation dies caniculares is the source of our English phrase. But I digress…

You most likely have noticed that cool-season grasses have recently entered a period of stagnation or inactivity (dog days) and, in some cases, are spent. The hot summer days have steadily increased soil temperatures to the point that the soil is now warmer than air temperature for much of the daylight hours and all of the night. During the last 10 days at Hort Farm No. 2, soil temperature at 3-inches has oscillated between 76 and 90 °F and at 2-inches 78 and 92 °F. These soil temperatures are well above the optimum temperatures for root growth and clearly explain why cool-season grasses are lethargic at this time.

What to do? Be patient and do not “push” the grass. This is not the time of year to stress out turf – the grass has very little resiliency and will not tolerate much abuse or recovery quickly. I recently witnessed utility vehicle traffic on subtly drought stressed turf during the hottest part of the day result in classic tire-track damage. Root systems of cool-season grasses are weakest and shallowest at this time of year. Thus, localized drought stress can develop rapidly – within a couple hot, sunny days – during the dog days.

These cultural practices can be helpful in getting high value turf to survive dog days. Once the turf has drained after drenching thunderstorms (2-3 days), program daily, very-light (50-65% of reference ET), deficit irrigation using a rainhold setting (such as 0.2-inch rain) to stop irrigation from adding to over-wetting from storms. Deficit irrigation assures that thunderstorms will be the reason for excess wetness, not the irrigation schedule. This irrigation plan should encourage the turf the dry without over-drying between irrigations (or thunderstorms). If excess drying does occur with this irrigation plan, it probably will start in highly localized (small) areas, which can be effectively managed with well-timed syringing to re-hydrate dry leaves and prevent crispy thatch during the heat of the day. Crispy thatch means that surface adventitious roots either are or will soon be crispy as well. Moist to dry thatch is good, whereas crispy and crunchy thatch in the heat is bad. Weekly, low-rate fertilization (N and possibly P, K and micronutrients) is crucial on sand-topdressed and sand-based rootzones commonly found on golf course putting greens and some sports turfs. These rootzones have very little mineralization capacity to supply essential nutrients during dog days. Weekly low-rate fertilization provides a steady, consistent slow-growth and avoids the “surge-crash” cycle of growth that results from less-frequent and higher application rates. Typically, low-rate N is no more than a 0.1-lbs. per 1,000-sq. ft.