April’s Ups & Downs: Spring Core Aerification, Abiotic Issues, and Rust in Greens?
After Easter, spring enters a higher gear. And so April’s second week advanced rapidly with 80s for highs, then it stopped — Mother Nature hit the breaks with 30s for lows again. It turned out to be a light to moderate frost with snow flurries! A majority of woody ornamentals are still just waking up and so just fine. But any freezing event IS TROUBLE for young transplant seedlings or tender sprouts unless conditioned. I had just transplanted cold-tolerant cole crops (broccoli, cabbage etc.) and romaine lettuce into a garden. I worried. I didn’t exactly know if my purchased plants were hardened off. “Hardening off is a simple process of gradually exposing tender plants to sunlight, wind and uneven temperatures.”
I mention because if a golf course green surface contains a mixed species we do have one species that is TROUBLE. We call it Poa, or Poa annua, or annual bluegrass. Poa is quick to green up = less cold tolerant. The other, creeping bentgrass is slower to green up and is more cold tolerant. So like gardeners, golf course superintendents are on edge each spring (usually March) if managing greens with Poa. Thankfully in 2023, little to no freezing injury occurring on golf greens, but this is not always the case. Spring continues and April’s third week saw a most colorful period begin. Outdoor hues shifted from yellow to red. For example, both redbud trees, Cercis canadensis, and tulips are in full bloom. Golf course superintendents and staff can shift to more aggressive cultivation practices given creeping bentgrass is no longer dormant and is growing. Ready or not, a higher gear!
Cultivation of Green Surfaces is Required
Aerify or verticut they’ll say. Simply said, it reduces compaction via heavy traffic (by foot or machine) and removes organic matter accumulation via thatch (by creeping bentgrass stolons or Kentucky bluegrass rhizomes). In the end, an optimized rhizosphere will result in more roots and longer roots when we need it most — July for example. The biggest enemy of creeping bentgrass is root-related. Two items rise above all others. 1) It suffers from chronic root rots and 2) midsummer physiological decline.
New CDGA Research. A new research project will focus on newer methods to cultivate greens and look at different sands for topdressing. Originally, sand topdressing was just a simple way to convert native soil-based greens to sand. It took off in the 1980s and today is a common practice. It has many beneficial characteristics. But sometimes, it can complicate things — infrequent sand topdressing can create layers. More to come.
Abiotic
About half the time when diagnosing problems of turfgrass the causal agent is biotic like a disease (fungal most common). The other half of the time? Not the case. But we are still able to learn something because we can rule out what didn’t do it. We then are looking at abiotic causes. It just means many other factors are also part of the story. Turfgrass physiology and environmental stress are critical things to know — especially if you are maintaining golf greens.
Recent Example. White bleaching of Poa annua in small spots on a green led me to look up information on turfgrass physiology. White leaf blades appeared to be a hormonal malfunction of Poa was most likely caused by cold temperature stress. A very cold period of two nights did occur about Mar 18–19 in the area and would have preceded symptoms observed.
“Plant hormone levels may also change during cold acclimation. However, little is known about the relationship between plant hormones and freezing tolerance in turfgrasses. In other species, absisic acid (ABA) increases and gibberellin decreases during cold accumulation. The growth-promoting effect of gibberelin is negatively associated with freezing tolerance, where as the quiescence or dormancy promoted by ABA is positively associated with tolerance.” Fry and Huang.
Turf Library Recommendation. Fry, Jack and Huang, Bingru. Applied Turfgrass Science and Physiology by Jack Fry and Bingru Huang. John Wiley & Sons Inc. 2004.
Recent Example. I would communicate, “Found nothing on the bleached turf…”
Weed of the Week — Common Chickweed, Stellaria media
Reference. Common Chickweed. Aaron Patton et al., Purdue University. Click link for more information.
Iron Oxide Layer Evaluation of Greens by Shehbaz Singh, MS
A root zone investigation was conducted this week on the sand-based greens at Bob Berry Sunshine Course. This was done to confirm the suspected location and presence of a iron-cemented layer (iron oxide layer) at the sand and gravel interface.
What is Iron-Cemented layer? Green constructed as per USGA specification has sand based rootzone of 12 inches above a bottom gravel layer needed for drainage. Sometimes, a hard brittle reddish-brown layer forms at the sand-gravel interface. It is a cemented iron-oxide mineral. More detailed information about iron-cemented layers can be found by reviewing scientific research published in Geoderma by Obear, Hartemink and Soldat. Soils with iron-cemented layers on golf courses in the USA
Greens at Bob Berry Sunshine Course There are total of four greens at Bob Berry Sunshine course in Lemont. All greens are creeping bentgrass. As part of renovation project in 2020, greens 1, 2 and 3: The upper mat layer was scraped off and then reseeded with newer bentgrass varieties, but the original root zone remained. However, the practice green was completely reconstructed as a variable depth green.
Age of Greens
- Greens 1, 2, 3 = 19 years. Built to USGA specifications in 2004.
- Practice putting green = 3 years. Built as a variable depth green in 2020.
Evaluation Procedure. A soil sampling probe was used to sample down to the gravel layer of each green. The probe was 1-inch in diameter. Four samples were systematically taken in parallel straight lines from the front, middle, and back sections of each green.
Presence of iron-oxide layer — Yes or No
Width (cm) — Measured iron-oxide layer within soil core column
Depth (in) — Where iron-oxide layer was found
Soil moisture (%) — Spectrum Technologies Inc. TDR350 with 3 inch tines
Surface Firmness — Spectrum Technologies Inc. TruFirm meter
Presence of Iron Oxide Layer. Iron-oxide layer was mostly observed in the lower, front sections of our greens. This was expected. It has been reported that wetter areas of older greens can be prone to a cement layer formation.
- Green 1 front = 75% presence (n=4 or four samples total)
- Green 2 front = 100% presence (n=4)
- Green 3 front = 50% presence (n=4)
- Practice Green A front = 0% presence (n=4)
- Practice Green B front = 0% presence (n=4)
Additionally, middle sections of green 1 and green 2 showed the presence of an iron-oxide layer with 25% (n=4) and 50% (n=4) incidence respectively.
Final Photo
