hope each of you have fared well this year as another growing season seems to be mostly behind us and things are finally settling down. Fall is one of my favorite times of year, right behind the first frost! Courses are usually still in good shape and cooler temperatures make playing a little more bearable for a sub-par golfer such as myself. The start of college football definitely helps too.
This year’s Turfgrass Field Day is coming soon (September 19th), and I hope each of you can make it to learn a little for your own benefit and show support to the sponsors, vendors, and research teams! And it isn’t long until the Deep South Turf Expo, at which we will have our annual business meeting on October 16th. At this meeting we will elect officers for the following year and take a vote to increase MTA dues from the current $75 to the proposed $100. This change seems inevitable given how long since it was last changed, and with increasing costs and all.
It has been a privilege to serve as your President. I want to say thank you to all that made this year a success!
Levi Jumper
2024 MTA President
Mississippi Turfgrass Association Box 9555
MS State, MS 39762
Office: (662) 325-0517
Fax: (662) 325-2705
www.msturfassociation.org
Published by:
Leading Edge Communications, LLC 206 Bridge Street Franklin, TN 37064 Office: (615) 790-3718 Fax: (615) 794-4524 info@leadingedgecommunications.com
MISSISSIPPI TURFGRASS EDITOR
VICE-PRESIDENT / PRESIDENT ELECT
Hampton
Country Club (601) 467-2718
SECRETARY-TREASURER Dr. Barry Stewart Mississippi State University
OCTOBER 15 – 17, 2024 MISSISSIPPI COAST CONVENTION CENTER
A PREVIEW OF THE 2024 DSTE GENERAL SESSION SPEAKERS
We are really excited about our education program this year! Let me introduce you to our general session speakers listed below. In addition to the program on Wednesday, we have a full house on Thursday with our outstanding array of Breakout Session speakers.
Registration for exhibitors and attendees is open on-line at DeepSouthTurfExpo.org. Make plans now to attend. Getting together with friends and colleagues in Biloxi in the Fall is always a special time for our industry. And remember, the sessions are approved for continuing education and pesticide points. Don’t miss the 2024 Deep South Turf Expo!
Becky Grubbs Bowling, Ph.D.
Dr. Becky Grubbs Bowling is an Assistant Professor and Extension Specialist with the University of Tennessee Institute of Agriculture (UTIA) specializing in Turfgrass Science and Management. She completed her B.S. and M.S. in Horticulture at Texas Tech University in 2010 and 2013 respectively, before completing her Ph.D. in Crop and Soil Sciences at the University of Georgia in 2017. Bowling works in partnership with other faculty/scientists, professional organizations, county extension agents, and others to conduct applied research and provide resources and programmatic support to the Tennessee turfgrass industry and beyond. Dr. Bowling’s program focuses on environmental turfgrass science with an emphasis on optimizing resource-use efficiency to promote environmentally and economically sustainable management practices for the turfgrass industry.
Nathan Crace, ASGCA
Nathan Crace, ASGCA, PLA, is the principal of The Watermark Golf Companies. He is a member of the American Society of Golf Course Architects and in 2020 was elected to a seat on the ASGCSA Board of Governors. For more than 25 years, Nathan has been working with clients in all sectors of the golf industry from PGA Tour stops, private clubs and resorts to public courses, municipalities, Division I university and even the US Air Force. While Nathan has garnered numerous awards for this work over the quarter century, his primary objective is to exceed client expectations by over-delivering and working to promote the game of golf for future generations.
Derek Kaye
Derek Kaye is Founder of Whispr Innovations. Founded in January of 2020, WHISPR Innovations is a for-profit venture aimed at eliminating 1% of US air pollution. WHISPR’s first project is WHISPR Lawn, an initiative to revolutionize the landscaping industry with RaaS (robots as a service) model and battery-electric equipment. Derek is equipped with proficiency as a leader, automation consultant, public speaker, business developer, robotics enthusiast, and conflict resolution specialist.
Tony Mancuso, CGCS
Tony is the Director of Agronomy at Escondido Golf and Lake Club in Horseshoe Bay, Texas. He is a former graduate of Mississippi State University and has had an exceptional career at various courses all over the world including Belmont Country Club, Nine Bridges/Haesley Golf Club in South Korea, Cherokee Town and Country Club, Bellerive Country Club and New Albany Country Club.
Pawel Petelewicz, Ph.D.
Dr. Pawel Petelewicz is an Assistant Professor of Weed Science at the University of Florida where he evaluates new chemistries for their potential use in turfgrass crops. He tests novel products in combination with currently available herbicides to ensure their best utility and longevity. He evaluates the integration of chemical and non-chemical practices to enhance the efficacy and safety of weed control measures and the capacity of turf to withstand competition with weeds. His ultimate goal is to develop comprehensive weed control programs that are effective, safe and reduce the occurrence of herbicide-resistant weed populations.
Amy Wilber
Amy holds a B.S. in turfgrass science from The Ohio State University and a M.S. in weed science from Mississippi State University. She is currently an Extension Associate and Ph.D. student at Mississippi State University. Her research focuses on the evaluation of new herbicides, practical applications of herbicides for turfgrass producers, and remote sensing for turfgrass and weed detection.
Educational sessions for warm-season turf managers
Over 20 Educational sessions on the latest Turfgrass management topics
Tradeshow with over 100 exhibitors featuring products and services for the Turfgrass industry
Business Meetings for ATA, ATRF, MTA, LMGCSA
Networking opportunities with industry peers and friends
CEUs and Pesticide Recertification Points
THIS REGIONAL SHOW IS DESIGNED EXCLUSIVELY FOR THE TURF MANAGER INCLUDING
Golf Course Superintendents, Sports Field Managers (Institutions, Universities, Park and Recreation), Lawn Care Operators, Landscapers, Sod Producers, Grounds Managers and Right of Way Professionals
Better Built. Quality Results. Period.
2024 SCHEDULE OF EVENTS
8
8
7
3
3 pm New Tools in the Poa Management Toolbox • Dr. Becky Bowling, University of Tennessee
3:30 pm Trends in Bunker Renovation, Re-Design, and Restoration • Nathan Crace, ASGCA, PLA, The Watermark Golf Companies
4 pm High Tech Meets Turfgrass Management: Trends to Watch For • Amy Wilbur, Mississippi State University
4:30 pm Hasta La Vista, Weeds: Terminating Weed Control Issues with AI-Based Targeted Applications: Achievements, Aspirations, Anticipations (and Roadblocks Ahead) • Dr. Pawel Petelewicz, University of
4 – 6 pm Tradeshow Closing & Exhibitor Move Out Dinner on your own
Winter Management of Ultradwarf Bermudagrass Putting Greens
Dr. Eric DeBoer, Louisiana State University
Managing Ultradwarf Greens
Tony Mancuso, Escondido Golf and Lake Club
What to Choose From and What to Wait For: Trends in WarmSeason Turfgrass Breeding
Dr. Marta Pudzianowska, Mississippi State University
Traffic Tolerance of New Bermudagrass Cultivars
Dr. Dave Han, Auburn University
Overseeded and Non-Overseeded Sports Fields
Dr. Scott McElroy, Auburn University
Dr. Jay McCurdy, Mississippi State University and Dr. Pawel Petelewicz, University of Florida
Cultivating Sustainable Landscapes with Integrated Pest Management
Dr. Eric DeBoer, Louisiana State University
Robotic Lawn Mowing & Battery Electric Landscaping –Pushing for Change Derek Kaye, Whispr Innovations
Herbicide Headaches: Understanding Possible Reasons for Herbicide Failures
Dr. Pawel Petelewicz, University of Florida
Potential Strategies for Reducing Fertilizer and Irrigation Inputs
Dr. AJ Lindsey, University of Florida
Mowing Technology for Sod Farmers
Dr. Scott McElroy, Auburn University
Optimal Nitrogen Rates and Compost Utilization for Sod Production
Dr. AJ Lindsey, University of Florida
Soil Health Characteristics in Sod Production
Jason Eberhard, Mississippi State University
Landscapes are Changing: Are Sod Producers Prepared?
Dr. J. Bryan Unruh, University of Florida
12
ACTIVITIES & ACCOMMODATIONS
TAILGATE CELEBRATION
Kick off the Expo with your peers at Tailgate Celebration at The Preserve Golf Club, opening night, Tuesday, October 15th. Sponsors will be cooking up some tailgate favorites for you to enjoy while mingling and networking with attendees from all over the southeast. This event is free and open to all attendees, exhibitors, and guests. Pre-registration is required to help plan food. Directions: 8901 Highway 57, Vancleave, MS 39565. Just 17 miles from Biloxi, travel east on I-10 and take exit 57 / MS-57. Turn north and the golf club will be two miles on the left.
SCRAMBLE GOLF TOURNAMENT
The scramble golf tournament will be held on Tuesday, October 15th at The Preserve Golf Club. The Preserve is an 18-hole course which has been integrated within an 1800-acre native preserve full of live oaks, cypress swamps, long leaf pines and native grass prairies and designed by Jerry Pate. Bring your clubs and prepare yourself for a wonderful afternoon of golf with your peers. Lunch, two drink tickets and two mulligans will be included in your registration (and the Tailgate Celebration will follow immediately after play). Pre-registration is required. Directions: 8901 Highway 57, Vancleave, MS 39565. Just 17 miles from Biloxi, travel east on I-10 and take exit 57 / MS-57. Turn north and the golf club will be two miles on the left.
CORNHOLE TOURNAMENT
We are bringing back the Cornhole Tournament again this year. Register in advance for this fun competition on the tradeshow floor. Registration is $25 per person and you can request to be paired with your favorite cornhole buddy. The tournament will be conducted on Wednesday, October 16th between 11am – 3pm on the tradeshow floor in the MCCC.
SOFTBALL GAME
Interested in a friendly game of softball with your peers? We are hosting a softball game where anyone who registers can play a fun game of softball at the Gulfport Sports Complex on Tuesday, October 15th. Teams will be randomly assigned and provided with team T-shirts. Must register in advance and bring your glove. Directions: 17200 16th Street, Gulfport, MS 39503. From the MCCC, travel west on Highway 90 for 3.2 miles and turn right on Cowan Road (MS 605). Travel 4.4 miles to I-10 and travel west for 3.5 miles. Take exit 34B onto US-49N for .6 miles. Turn left onto Landon Road for 1.3 miles and turn left into 16th Street. Travel .4 miles, the complex will be on the left.
ACCOMMODATIONS
Our host hotel is the Beau Rivage, a Four-Diamond development by MGM Resorts International that sits directly on the Gulf of Mexico in Biloxi. The Deep South Turf Expo has secured a discounted room rate of $109 for Expo attendees. Make your reservations directly by using our exclusive link found by clicking the red button at www.DeepSouthTurfExpo.org. It is important that you DO NOT use a third party provider/discounter to make your reservation; only use our link. Don’t delay—our room rate is only available until September 23, 2024.
The Mississippi Coast Convention Center is our home for the educational sessions and tradeshow at the Deep South Turf Expo. It is a multi-purpose, state-of-the-art facility that sits directly across the Gulf of Mexico just 5 miles west of The Beau Rivage at 2350 Beach Blvd., Biloxi, MS 39531.
With over 20 educational sessions to choose from, plus a tradeshow with more than 100 exhibitors, this regional event is designed to benefit every turfgrass manager. Learn the latest and greatest research and management practices for growing the best southern turf. We welcome all sod producers, lawn care operators, landscapers, golf course superintendents an d sports field managers to Biloxi, Mississippi for our seventh annual Deep South Turf Expo. Look inside for more details and registration information.
MTA ANNUAL BUSINESS MEETING
The annual business meeting of your Association will be Wednesday, October 16, 2024, at 1:00 p.m. in Room MCCC-D4. It is held during the Deep South Turf Expo in Biloxi at the Mississippi Coast Convention Center.
Your attendance is vital in helping maintain all the business necessary to keep the MTA in good order. At this time, we will review events from our last meeting in October 2023 and elect the Officers & Directors of your board for the 2025 session.
At Right: Will Arnett, outgoing MTA 2023 President, receives the President’s Plaque from incoming 2024 President, Levi Jumper.
The Mississippi Turfgrass Association (MTA) wanted to refine its image as a professional association for turfgrass professionals, since to many people outside of the industry, turfgrass may not appear to be the thriving segment of the agricultural economy it has grown to become in recent years. Therefore, the first step in this process was the creation of a new, more contemporary logo to reflect the MTA’s commitment to environmental sensitivity and cutting-edge technology. The following logo was created—which incorporates the “A” in the acronym MTA by transforming it into a blade of grass spiraling around the proper name of the organization.
The logo was created by Nathan Creative Services Group LLC (Nathan Crace) and first appeared in the January 2001 MTA Newsletter.
The MTA logo can be used by active members in good standing on business cards, letterheads, etc. to denote their membership and affiliation with their professional organization (MTA).
If you would like to use the MTA logo on your correspondence, please contact
Linda Wells lmw218@pss.msstate.edu (662) 769-7558
As a member in good standing, you may use the MTA logo on any/all of your business transactions. •
By Jay McCurdy
C Centipedegrass REVISITED
entipedegrass has become perhaps the most common lowmaintenance turfgrass species in the southeast. We can think of no other that has the breadth of utility in poor soils and areas with infrequent care. Unfortunately, its finicky response to routine maintenance means it sometimes gets “loved to death” by those responsible for its care.
Centipedegrass was first introduced in 1916 from Southeastern Asia. Seed were collected by the plant explorer Frank Nicholas Meyer (the namesake of ‘Meyer’ zoysiagrass and the ‘Meyer’ lemon) who was employed by the USDA’s Office of Seed and Plant Introduction. He drowned somewhat mysteriously near Shanghai in 1918 while exploring southeastern China via the Yangtze River.
There are at least eight species within the genus Eremochloa. Centipedegrass (Eremochloa ophiuroides) is the only one cultivated as a turfgrass species. Centipedegrass has many other common names. Chinese lawngrass or China grass denotes its origins. It is called cemetery grass due to its prevalence within cemeteries and poor man’s or lazy man’s grass because of its low maintenance requirements.
Centipedegrass is a warm-season, lime-green, medium-textured, slow-growing grass found throughout the southeastern United States as low-maintenance turf. It persists in humid-subtropical and tropical climates. Centipedegrass persists as far north as Tennessee and coastal Virginia; although, it is easiest to maintain where winter-time temperatures are mild. Centipedegrass is one of the least drought-tolerant warm-season turf species. For this
reason, it tends to do well in gulf-coastal environments due to timely rainfall during peak summertime temperatures.
Centipedegrass varieties include ‘common,’ ‘TifBlair,’ ‘Oaklawn,’ and ‘Tennessee Hardy.’ Centipedegrass spreads by aboveground stems called stolons, as well as by seed. Seed take roughly three weeks to germinate and require adequate soil temperature to do so (approximately 80 degrees). Centipedegrass is commonly propagated vegetatively as sod but may also be established by sprigs or plugs.
Centipedegrass thrives in soils of moderate to low pH (between 5.0 and 6.0). Prior to establishing any turfgrass, a soil test should be performed in order to determine soil pH. Other site considerations should include shade, wear, and expectations. Centipedegrass persists in moderate shade better than bermudagrass but not nearly as well as St. Augustinegrass. Centipedegrass has poor wear tolerance and is slow to recover from injury because of its slow growth rate. Low fertility requirements and short-statured growth make centipedegrass well suited for low to no mow scenarios, but property owners expecting thoroughbred performance will be unhappy with a plow-horse trod.
Once established, nitrogen inputs should be limited to less than 2 lbs nitrogen per 1,000 ft² per year. By contrast, this is roughly half that recommended on low-maintenance bermuda and zoysia grass lawns. When using controlled-release nitrogen sources, I recommend even less. In some environments, nitrogen input may not even be needed every year.
A prior article, The Centipedegrass Conundrum – Holistic Approaches to Weed Control by Jay McCurdy and Michael Richard was published in 2018 and has been updated here with new information.
Mississippi State University
FIGURE 1. Centipedegrass injury due to drought conditions in the fall of 2016.
Some of the most experienced centipedegrass gurus suggest a potassium supplement in the spring and fall. Some folks use foliar apps of iron to correct the bleached appearance of grass grown in soils where pH is above optimal. The darker color lasts until the leaf tissue grows enough to be mown. Humic and fulvic acids, as well as various other soil amendments, are frequently suggested though research is scant in centipedegrass.
Centipedegrass does not have underground rhizomes like bermuda and zoysia grasses. When over-fertilized, it becomes thatchy and prone to stress-related decline. To prevent thatch, only fertilize when grass is actively growing, which in most southeastern lawns is after the third or fourth mowing event. Centipedegrass does well at a range of mowing heights (1 to 4 inches), but it does not recover well from scalping. Mowing low according to the 1/3rd rule during growing months helps promote lateral growth. Bag clippings if they accumulate or clump together and add them to your compost.
New Insights in Weed Control and Fertilization
Lawn care professionals have made significant improvements in managing centipedegrass by softening their chemical weed management approach. They are using less harsh herbicide chemistry and have moved towards a lower reliance on preemergence herbicides. This is in contrast to the way we think about managing bermuda and zoysia grasses.
One approach that has improved centipedegrass quality on home lawns is the use of slow-release fertilizers, usually applied in the early spring green-up phase. Despite inadequate temperature for release, some of these formulations provide an earlier green color and generally more competitive lawn.
Without a doubt, some of the best centipede lawns are those that are mown relatively high in height of cut (approximately 2.5 to 3 inches) and relatively infrequently (usually no more than weekly during the growing season). This practice promotes healthier, denser turf, which is more resistant to weeds and other stresses.
Holistic Weed Control
Unfortunately, centipedegrass does not conform to conventional herbicide applications as well as bermuda and zoysia grasses. Lawn care professionals who manage centipedegrass well are less governed by routine schedules and make decisions based upon concern for plant health rather than pest control. They scout and spot treat problematic areas. They run routes that are focused on sensitive species—centipede, St. Augustine, and carpet grasses. And most importantly, they educate consumers about expectations and appropriate cultural practices.
The essence of weed-free centipedegrass is dense, healthy turf. Centipedegrass is highly susceptible to herbicide injury during fall and spring transition periods, regardless of labeling. For instance, auxin-mimicking herbicides (2,4-D, MCPA, dicamba, and others) are tolerated well enough when turf is actively growing,
FIGURE 2. Herbicides applied in Biloxi, Mississippi on May 4, 2015. Spray volume was 40 gallons per acre. A non-ionic surfactant was included. Photos were taken 2 weeks after treatment. Notice slight turfgrass injury results from all treatments.
Tenacity, 8 fl oz
Princep 4FL, 32 fl oz
MSM Turf, 0.5 oz
Tenacity + Princep
Figure 3. A centipedegrass lawn that has thinned due to poorly drained soil. The grass in the foreground is actually carpetgrass, which tolerates standing water and wet soils.
but during fall and spring transition, centipedegrass is susceptible to injury and slowed growth. Likewise, metsulfuron is labeled, but when applied during transition or even during mostly dormant winter conditions, injury and thinned stands are fairly common. When actively growing, phytotoxicity is transient, but during fall and spring dormancy or summer drought stress, even the slightest injury may push it over the edge.
Best Management Practices for Centipedegrass Weed Control:
• Prioritize plant health. Manage fertility, soil pH, cultural practices, and especially thatch if you want a resilient centipedegrass lawn.
• Mow at a height that allows infrequent mowing. The higher the height of cut, generally the less frequent mowing.
• Rely upon fall preemergence herbicide applications for control of annual bluegrass and cool-season broadleaf weeds rather than winter/spring postemergence treatments. It is fairly typical to apply low rates of mitotic-inhibiting herbicides (e.g., Barricade, Pendulum, Dimension) in conjunction with simazine at a fall timing. Some practitioners apply reduced rates of Specticle in the fall, but this is not advised unless dealing with extremely healthy centipedegrass. Ultimately, simazine and atrazine are the safest preemergence treatments for centipedegrass, but they lack the same spectrum of weeds controlled as many other preemergence options.
• With the exception of simazine or atrazine, avoid the use of preemergence herbicides in the spring. Fly-away or looping stolons in lawns treated with mitotic-inhibiting herbicides or Specticle are typical. Gallery (isoxaben) might be another exception, as it tends to be very safe on grasses. Unfortunately, Gallery lacks control of grassy weeds.
• Reduced rates of simazine and atrazine are standard recommendations for spring broadleaf/Poa control with the added benefit of some preemergence activity. For new customer accounts, a round-1 “clean-up” option is atrazine. Atrazine on a granular fertilizer carrier (e.g., Scotts Bonus S) in spring is a standard that homeowners can do themselves, but this application timing is arguably too early for application of the fertilizer carrier.
• Avoid postemergence herbicides during spring and fall periods of static growth. Even though they’re labeled, products containing auxin-mimicking herbicides (e.g., 2,4-D, dicamba, mecoprop, clopyralid, and others) can be particularly problematic during periods of transition or slow growth. Herbicides are rarely the only cause of decline, but when combined with stress, such as drought or slowed recovery from winter, they too frequently result in thinned turf or stunted growth.
• When possible, spot treat postemergence herbicides rather than broadcast applying. This can be impractical but so is resodding an entire yard.
Preemergence Herbicides
Labeled for Centipedegrass:
• Barricade and others (prodiamine)
• Coastal (prodiamine, simazine, imazaquin)
• Dimension and others (dithiopyr)
• Gallery (isoxaben)
• Gemini (prodiamine, isoxaben)
• Echelon (prodiamine, sulfentrazone)
• Freehand (dimethenamid, pendimethalin)
• Kerb (pronamide)
• Pendulum and others (pendimethalin)
• Pennant Magnum (metolachlor)
• Specticle Flo (indaziflam) – Not for use in sod
• Surflan (oryzalin)
Postemergence Herbicides
Commonly Used on Centipedegrass
A bulleted list fails to show the general trends in use. These postemergence herbicides are safe when applied to actively growing, non-stressed centipedegrass. Ones that are particularly safe include halosulfuron and sulfosulfuron—both of which provide good to excellent control of most sedges. Sulfosulfuron has some additional benefits in that it can suppress buttonweed and bahiagrass. But for broad spectrum weed control, we routinely include the standard of sulfosulfuron with a low rate of metsulfuron (0.25 oz/A or less of the 60 WG product) with Change Up (1 pt/A). There are lots of similar options that we hear of folks using. Just be certain you are not applying to drought stricken or diseased turfgrass during the growing season.
This may disappoint some readers, but there are no truly safe AND effective herbicide applications for broadleaf weed control during periods of transition (into and out of dormancy) and winter dormancy. We see centipedegrass death/decline for many reasons, but it is noticeably higher in professionally managed lawns than in lawns that are “mow-what-grows”. A balance must be struck in order to provide the best centipedegrass. 100% weed control should not be the sole objective. •
FIGURE 4. From left to right: bermudagrass, centipedegrass, St. Augustinegrass, and zoysiagrass stolons.
FEATURE IN THE BEGINNING…
FERTILIZER COATING TECHNOLOGY STATE OF MATTERS
By Max Schlossberg, PhD.
No more than zero artificial intelligence resources participated in the composition of the following chronicle.
By the time NASA successfully landed their unmanned ‘Surveyor 1’ spacecraft on the moon (1965), numerous slow-release, granular N fertilizers were available in the US. Natural organic fertilizers derived from sewage sludge or livestock manure/litter were the original slow-release N carriers. Next came the urea-formaldehyde reaction products; e.g., methylene urea, isobutylidene diurea, and the eponymous ureaform, all characterized as synthetic organic carriers. However, neither these natural nor synthetic organic N sources completely satisfied the Green Industry’s need for a dependably long-lasting, controlled-release, N fertilizer.
But by the time Jacobsen released the original ‘Greens King’ triplex putting green mower (1968), agricultural and material scientists had developed coated fertilizers. Their purpose was to improve the utilization efficiency of nitrogen fertilizer, most notably urea (46-0-0). This effort improved the granular fertilizer at its core by adding one (or more) layer(s) of a persistent coating that limited nutrient diffusion from inside to outside the coating/membrane.
Alkyd resins, synthetic polymers derived by reacting polyhydric alcohols with polybasic acids or anhydrides, were the original fertilizer coatings. Yet the high cost of this added value precluded widescale adoption of the urea fertilizer featuring it. Subsequently, scientists of the Tennessee Valley Authority patented a more economical process of coating urea with elemental sulfur. In 1970, sulfur-coated urea (SCU) became the first, mass-produced, controlled-release fertilizer by which plant-availability of urea-N was initiated by physical rupture or ‘failure’ of the sulfur coating.
The prolific marriage of urea and sulfur was hardly a proverbial crapshoot, given sulfur’s already established role as a plant essential macronutrient, fungicide, and additive mitigating the caking tendency of many fertilizers. Moreover, elemental sulfur comprises a biodegradable and inexpensive acidulent that facilitates plant recovery of urea-N in neutral to alkaline soil. Relative to granular urea and confirming all coatings remained intact through application, numerous University studies showed SCU to significantly improve fertilizer N recovery by treated turfgrass.
This is likely why the next generation of coated fertilizer built upon, rather than replaced, the sulfur component. While the controlled release of urea N from SCU is governed by the sulfur-coat thickness, the addition of a thin thermoplastic or resin envelope around the SCU prill improved the coating integrity without further N dilution. These polymer-sulfurcoated urea (PSCU) or polymer-coated/sulfur-coated urea (PC/SCU) hybrids featured a more linear release rate than SCU and were widely adopted in the late 1980’s.
Yet the 21st century ushered in a new era of reduced polyurethane / polyolefin cost and a specialty fertilizer marketplace heralding granules coated by a thin layer of polymer as the preferred technology ( Figure 1 ).
FIGURE 1. Courtesy of Allied Nutrients
POLYMER COAT
Aerate and Play Right Away!
Decreased down time, increased revenue.
The surface is very “puttable.”
The dots are sand that is level with the turf.
DryJect® is a high-pressure, water based injection system that blasts holes through the root zone and fractures the soil profile. Plus, it automatically fills holes as it aerates.
DryJect® makes a big difference in playability … right away!
Owing to their thinner coat, synthetic polymer-coated fertilizers possess a higher grade than their sulfur coated counterparts. Polymer-coated urea (PCU) is minimally affected by microbial activity and remains a highly popular blending source within the turfgrass, landscaping, and horticultural production industries.
While polymers proved aptly supportive of the original, impermeable coating mechanism; newer synthetic polymers marked the advent of semi-permeable coatings. In contrast to the physical rupture or coating ‘failure’ release mechanism exhibited by first- and second-generation coated fertilizers, semi-permeable coatings facilitate a multi-stage diffusion release mechanism governed by an osmotic nutrient transfer from the fertilizer–polymer interface to the polymer–soil interface. Progression through the following sequence; (i) diffusion/swelling; (ii) degradation of the polymer coating, and (iii) fracture or dissolution, is governed by coating thickness, soil temperature, soil moisture, and soil N concentration gradient; all ideally falling in synchrony with vegetative growth and nutrient requirements.
OVER THE LAST TWENTY YEARS…
I have had the honor of evaluating numerous slow- and controlled-release N fertilizers, at the very facility where the first experimentally-coated fertilizers were evaluated by Drs. Duich and Waddington almost sixty years ago. These recent results from the Joseph Valentine Turfgrass Research Center confirm improved plant recovery of urea-N to be a benefit of ongoing technological refinement by polymer-coated granular fertilizer manufacturers.
While different granular fertilizers may share a common 100% polymer-coated urea (PCU) attribute and support equivalent cumulative recovery by Kentucky bluegrass or similar turfgrass species, significantly varied patterns of N release have been shown to manifest over 17-week experimental periods ( Figure 2 ).
FIGURE 2
The duration of polymer-coated urea (PCU) fertilizer N release is controlled by impermeable coating thickness and its mass ratio to semi-permeably-coated prills (specific to the blended product). Figure 3 depicts data collected the last 10 years in numerous PSU field trials illustrating the relation of fertilizer N content (%N in grade) to release duration (days until assimilation of 50% of fertilizer N; higher number=slower release). The scatter plot shows little relation between these two parameters when all coated, natural organic, and synthetic urea formaldehyde reaction product fertilizers are considered. Yet regarding PCUs (blue circles), containing only urea and whose N content is diluted by polymer coating thickness, the inverse relationship between PCU fertilizer N content and duration of N release becomes apparent (Figure 3).
Perhaps of greater interest to our readership is that recent PSU research shows under typical Mid-Atlantic US conditions, a single 1.8 lbs N / 1000 ft2 application of 100% PCU fertilizer to a mature Kentucky bluegrass lawn poses no greater environmental risk than conventional urea applied at a 0.9 lbs N / 1000 ft2 rate.
THE CURRENT STATE OF AFFAIRS…
It wasn’t long before the fertilizer industry branched out from urea to diversify coated fertilizers and appeal to additional commodity markets. Polymer-coated ammonium nitrate and ammonium sulfate are currently available in select regions of the US. If compound fertilizers are more your thing, then you’re encouraged to contact one of the numerous commercial vendors with polymer-coated potassium nitrate or diammonium phosphate available for delivery. There are even polymer-coated complete fertilizers that feature all the primary nutrients in a single bag of controlled-release splendor.
The coating materials currently used in synthesis of PCU, PSCU, or alternative N source fertilizers are polyolefins, polyvinylidene chloride, acrylic resin, and polysulfone synthetic polymers. And despite years of woeful commitment to collecting and sorting used plastic containers in support of recycling, these polymeric materials continue to be sourced from non-renewable resources. Furthermore, the very properties of polymers that make them such effective barriers to nutrient diffusion contribute to their persistence in nature and resulting microplastic pollution.
Which all begs the following question: ‘Do the negative environmental impacts associated with the manufacture and application of PCU fertilizers outweigh their proven agronomic benefits?’ This is sure to spawn an extraordinary complex answer... one I’d certainly open with ‘It depends.’ But that’s as far as I can currently go with this apples to oranges comparison, perhaps better posed as: ‘How many grams of legacy microplastic is offset by a pound of urea not volatilized as NH3 or N2O?’ Once I am notified this article is off to press, perhaps I’ll ask ChatGPT.
Like some scientists, I appreciate objectivity and have been reading up on experimental fertilizer coatings accordingly. Which seems understated considering the last Web of Science search I queried using ‘fert*’ and ‘coat*’ as keywords returned 1,511 papers published since 2018! I’ll be honest, I didn’t read the whole lot. But please... I’m an author on two of them anyhow.
To summarize, the majority of material scientists currently developing and evaluating innovative
FIGURE 3
To Our 2023 Advertisers
urea coatings do not believe the agronomic benefits of polymer coatings outweigh the negatives. Rather, they’re hellbent on preserving humanity by replacing synthetic polymer coatings with biodegradable membranes. But in the spirit of objectivity, they may not be hellbent, perhaps just allergic to plastic. Deathly allergic, like the Wicked Witch of the West to water kind of allergic. Ding Dong!
Nevertheless, recent advancements in nanotechnology and material science afford us a wide array of encapsulation technologies and unlimited possibilities. Most research has focused on renewable and biodegradable chemistries, and/or efficient coating processes. Compounds that have recently been investigated as a fertilizer coating and described in a peer-reviewed publication include (among others): alginate, biochar (of course biochar, as if there is anything it can’t improve), cassava (Manihot esculenta) starch composite film, castor oil, cellulose, chitin/chitosan, graphene oxide, humus, lignin, natural rubber, pectin, phasetransitioned whey protein, xanthan gum, and zeolite.
THE FUTURE OF COATED FERTILIZERS…
In one recent paper, scientists polymerized castor oil and magnetite (Fe3O4) nanoparticles into a cross-linked membrane with high thermal stability. This is an intriguing approach that checks both the ‘recycles waste oil’ and ‘contains nanoparticles’ boxes, while relieving current industry reliance on nonrenewable fossil fuels.
Lignin also comprises an organic fiber of great potential, primarily due to its high carbon content, biodegradability, tensile strength, and oxidation resistance. As a component of slow-release fertilizer coatings, lignin is shown to delay the release of fertilizer nutrients and subsequently improve water holding capacity and quality of treated soils.
The above are a few of the more promising results my literature review revealed. It seems the most likely progression in coating
technology will be avoiding non-renewable resources and incorporating agronomically advantageous compounds. Such additives may include biological agents; e.g., beneficial microbes, NBPT (urease inhibitor), dicyandimide and nitrapyrin (nitrification inhibitors), biostimulants; and/or surfactants, micronutrients, zeolite, etc.
Further along the innovation pipeline await ‘smart coatings.’ A given name I hope will do as much for coatings as phones. The only thing I love more than my smart phone is keeping it encased in acrylic, charged, dry, financed, and continuously updating its operating software and 37 apps I can’t open. But smart coatings will ultimately have to earn that lofty title by filing tax forms, graphing your caloric intake by week, and releasing nutrients in response to environmental stimuli like temperature, moisture, and/or turfgrass uptake. I hope I am around long enough to evaluate that last responsibility in the field.
Which seems like a decent segue to my take-home point: an important and final aspect of fertilizer innovation is unbiased, third-party evaluation in the field. Perhaps the most entertaining parts of those 1,511 papers, or less (that I read), were the agronomic validation efforts directed by the very material scientist(s) who engineered the experimental coatings. Many of which I would characterize as somewhere between marginally critical and straight-up flimsy; i.e., conducted in a glasshouse over short duration, limited to 2 or 3 replications, and offset by peculiar positive controls.
As you assimilate new fertilizer, amendments, and/or pesticide promotions; please remind vendors and technical reps of your insistence on impartial, University-grade field research results when making purchasing decisions. Field trials capture highlyvariable growing conditions that may exacerbate limitations, or advantages, of new or experimental products. Likewise, University personnel will include appropriate positive controls; i.e., respected industry bellwethers that support practical new product assessment. •
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