Under further review

While the jury remains out as to the extent of its impact on the industry, seed coating technology has shown some beneficial attributes, especially in areas where water usage can be a challenge during grow-in and early stages of turf development.

“The technology has the potential to help improve seed performance, including fast germination, good uniformity and high stress tolerance,” says Qi (Chee) Zhang, assistant professor in the department of plant sciences at North Dakota State University. “However, research results are not consistent most likely because the efficacy of seed coating is affected by other factors, such as plant genotype, soil type, temperature, irrigation, etc., alone or in combination, which varied in research situations.”

Zhang has worked with ZEBA-coated tall fescue and Kentucky bluegrass seeds. He found that coated seeds had better germination to some extent under moderate environmental stresses than non-coated seeds. But under optimal conditions, there were no differences between the two types of seeds.

Dr. Mike Richardson, a professor in the University of Arkansas’ department of horticulture, has conducted “a few trials” with coating on turfgrass seeds and has studied literature on the technology. He believes there are some “significant benefits” of fungicide coating techniques as it relates to damping off diseases of cool-season grasses. “This is an important technique when seeding during warm, humid periods,” he says.

A benefit of coating techniques that add bulk to the seed are improved handling characteristics of the seed, Richardson says. “This is especially true on small-seeded crops like Bermudagrass or Kentucky bluegrass,” he adds. “It makes the seed easier to see, easier to calibrate the spreader and easier for the seed to flow through the spreader.”

Barenbrug USA, one of the companies at the forefront of seed coating, claims that seeds with Yellow Jacket coating enhance moisture holding during germination, thus slowing the loss of moisture from the seed; improve germ and establishment in conditions of reduced water availability and low humidity; prolong the availability of fungicide coating, allow for planting in less than optimum conditions; and take up available soil nutrients and releases them to the seedling. Other benefits, according to the company, include smaller seed products that are easier to spread and more visible for improved distribution; higher bulk density, which means the seed is more easily sown in windy conditions and quickly settled through existing turf for improved soil contact; no increase in normal seeding rates; improved stability of seed germination storage; and compatibility with most seeders, including hydroseeding; and it does not take up salt.

John Rector, Barenbrug USA turf product manager, says aside from these benefits, a significant impact of seed coating is on the early development of a strong, healthy root system. “This not only allows for fast establishment, but represents a positive factor on overall turf quality months after seeding,” he says. Rector calls the long-term benefit on plant health and establishment one of the “pleasant unexpected benefits” associated with enhanced coated seed.

“For golf, the ability to repair and improve greens, tees, landing areas and literally any area of the course without significantly impacting play is huge,” he adds. “Often a superintendent is limited to only light syringes of seeded areas in order to keep the course ‘in play.’ This plays right into one of the strongest benefits of a coated seed with a strong absorbent package, readily retaining and releasing moisture to the seed, while quickly re-absorbing moisture when applied.”

Treated seed establishes faster and better in harsher environments. “In tests, grass seed with nitrogen fertilizer coating averages 30 percent more plants emerging,” says Keith Walters, president-sales, marketing and production for Pogue Agri Products. “Treated seed gives better root shoot extension. Other advantages include seed placement accuracy, ease of planting, the placed seed attracts more moisture to the seed. Fungicide helps with damping off issues.”

Coated seed has been used for several years on certain species like Bermudagrass and bentgrass in the golf market, according to Aaron Kuenzi, vice president of marketing for Mountain View Seeds. “The benefit of the coating is easier handling and distribution due to their small seed size,” he says. “The coating also holds the seed in place with the soil and reduces floating and puddling of the seed for a more uniform stand. Just like all technology, seed coatings have changed a lot in the past few years.”

Coatings now can also include value-added products such has hydration polymers, micronutrients, mychorizza and biologicals. Kuenzi says that some studies indicate these products aid in germination, root density and enhanced growth. “Certain studies show that the additional and more robust rooting helps the plant to be more water efficient and can maintain turf quality with 15 to 25 percent less water,” he adds. The water savings are crucial in areas where superintendents face challenges because of drought and water use restrictions.

Dan Billette, the superintendent of Bloomfield Hills (Mich.) Country Club, is convinced coated seeds offer benefits. Billette used coated seed to establish new greens, which was a “gas and grass” project on bare soil last July. The seed was Pure Distinction with Yellow Jacket coating, and the seeding method was Gandy drop spreaders to bare soil. “The yellow color made the seed easy to see at application,” Billette says. “When considering seeding options, coated seed made the most sense. It retained moisture and promoted early germination. The bentgrass germinated in three days, which was critical because seven days after seeding we had a tremendous, 2 ½-inch rain and 75-mile-an-hour winds. The seedlings had enough of a foothold and were fine thanks to the early germination.”

Billette says he may have had to re-seed the greens if they hadn't been mature enough to withstand the rain event. “The coating also contains fungicide to fight off several of the Pythium diseases, which seedlings are prone to if the right conditions persist,” he adds. “Personally, I wouldn't even consider seeding a project such as this without using coated seed.”

Kuenzi points to “a lot of variables” that affect the overall benefit superintendents will see by using coated seeds. “Soil conditions and types play a big role, as does the specific seed coating technology used,” he says. “Not all seed coatings or treatments are created equal.” Mountain View Seeds offers WaterGard QS seed coating as an "insurance package" for application in less than ideal soil or climate conditions.

Zhang says, “There are different types of seed coating, coatings to improve water absorption, coatings with fertilizers, fungicides or herbicides. Depending on different situations, turf managers may or may not use coated seeds. It is probably going to vary case by case.”
 

Handle with care

At present, Rector says, coated seed needs to be cared for like raw seed. The seed must be kept in a dry situation with moderate temperatures. In terms of coating, should a superintendent require a custom mixture to be coated, there is an element of time for coating and handling. Also, quantity effects pricing. In this situation, planning is important to ensure the coated product is at the course when it’s time to plant.

The cost comparison benefit between coated and non-coated seed is greatest on smaller and more expensive seed species like bentgrass, Kentucky bluegrass and Bermudagrass, according to Kuenzi. “The increased survival of seedlings easily outweighs the cost of the coating,” he says. “Coatings have also been used on a limited basis for overseeding perennial ryegrass with mixed results. It is harder to confirm consistent cost benefits. Seed coating in general shows the most benefit in the first 60 days during establishment. This also carries forward if you have healthier plant.” Kuenzi adds that fungicides can be included as aids to turf in dampening off Pythium diseases for healthier plants and greater plant survival.

Kuenzi says there “are a few things to be aware of” with coated seeds. “The coating process is critical to the seed germination and longevity,” he says. “So, knowing your vendor and their process is crucial to the products performance.”

Walters says, “The only downsides we have seen are that sometimes coated seed can create some dusting issues or flaking.”

Richardson, though, is still not sold on the overall benefits of seed coating. “My experience is that seed coating has not been shown to enhance germination speed or germination percentage of turfgrass seeds,” he says. “We have occasionally seen a one-day improvement in germination speed with small-seeded crops such as bluegrass, but I’m not sure you can expect much more than that. With larger seeds, such as perennial ryegrass and tall fescue, I have not seen a benefit.” He adds that “in many cases,” seed coatings are “nothing more than clay.” He says this can improve the handling of the seed, “but I doubt that clay will have any biological benefit when seed is placed in a soil that will likely have more than enough clay already.”

Richardson adds he’s “very optimistic” that some of the polymer coating technologies might improve germination of turfgrasses in limited water environments, but he had thus far not seen any “hard evidence” they really provide a significant advantage in those environments. “I know that companies are looking at different polymers, surfactants and even biological additives, such as mycorrhizae,” he says. “But I have not seen any experimental evidence that these coating techniques will allow grass seed to germinate with less water.” Still, the technology holds promise. “It is certainly an increasingly common practice for seed companies to coat turfgrass seeds, so I think it is going to be very prevalent moving forward,” Richardson says.

Zhang agrees. "It is going to continue to be part of the turf industry,” he says. “But its efficacy is affected by so many factors. Therefore, the technology is probably not going to be applied on all seeds.”

John Torsiello is a Torrington, Conn.-based writer and a frequent GCI contributor.