Turfgrass selection is perhaps the most important part in developing and maintaining a healthy and vigorous turf stand. There are many choices available to us today and the planning process cannot be underestimated. Over the years plant breeders have made significant advancements in the development of cultivars within cool-season species like Kentucky bluegrass, perennial ryegrass, fine fescue and tall fescue. During this time seed companies have consistently released varieties with improved growth characteristics, turf quality, resistance to drought, insect, disease and other important benefits. Today the turf manager faces the ever difficult task of making the decision of “Which variety or varieties are right for me?”
In going through the decision process for new construction, renovation or maintenance (overseeding), it is important to review all the elements in which turf has to perform. The following points should be a part of the planning and selection process of the appropriate species and cultivars for the intended use.
Species selection: environmental factors
· Type of sport or use: football, baseball, soccer
· Physical characteristics: soil or sand, climate and environmental stresses and concerns, drainage.
· Management issues: wear (goal mouth, center of field, sidelines)
· Repair and maintenance: time of repair and renovation (during difficult times, during play)
· Maintenance budget
· Maintenance: number of staff, type and number of equipment, cultural practices, irrigation system.
· Inputs: fertility, pesticides, irrigation, topdressing material, seed, etc.
· Other uses: concerts, events
Species selection: turf characteristics
· Growing environment: full sun or low light (stadium facilities)
· Wear tolerance, recovery period
· Establishment, turf density
· Turf strength, lateral stability, stable footing
· Disease resistance and winter persistence
· Heat and drought tolerance
· Other: salt tolerance, weed control, etc.
With ever increasing environmental, climatic and public demands while maintaining the need for high quality turfgrass athletic and recreational fields, seed varieties today offer the turf manager many benefits, agronomic stability and flexibility. Understanding the major and subtle differences between varieties within a species category is important in the selection process. For example Kentucky bluegrass is highly apomictic, meaning that plant alteration and variety improvement is a difficult and complex process, generally resulting in small differences in agronomic characteristics and range of genetic diversity within varieties categorized in the same ‘Type’ such as Midnight, Aggressive, America and Compact ,to name a few. Other major cool-season species such as perennial ryegrass and fescue (tall and fine) are also organized into types offering different characteristics for specific use.
When selecting a new seed variety from a proven seed company with a well-established development and breeding program, you can be sure that the varieties have been thoroughly field tested and evaluated to produce a broad genetic base. The National Turfgrass Evaluation Program (NTEP) testing conducted at multiple locations and through independent university sites across the US and Canada, data confirms the improved qualities needed for producing a high quality turf. If the variety has no traceable testing history then it is not worth looking at.
Most importantly, parent plants for new varieties have survived the test of time growing in different locations. Over the years well established breeding programs have selected turfgrass clones from hundreds of locations across North America and other regions around the globe. During a site visit the plant breeder will identify and collect desirable turf samples. Plants identified for collecting have noticeable characteristics that would be beneficial to incorporate into breeding project, leaf textured, density, vertical growing, specific disease and insect resistance, drought tolerance, salt tolerance etc. Specific areas are targeted for collecting where plants have been growing and surviving for generations under harsh conditions.
The collected plants are brought back to the research farm for evaluation. Collected plants, commonly referred to as “germplasm,” are added to the already established collection. After a few years of evaluation only the best 1-2% of all plants collected will be considered for use in breeding a new variety. Ninety eight to ninety nine percent of collected plants will be discarded. Only the best performing plants will be used for developing a new variety. Typically, it takes 10-12 years to breed and commercially release a new improved variety for use on professional turf surfaces.
For example, with the breeding and development of a new variety, existing plants from proven varieties are used. Additionally, new clones or germplasm are crossed with a selection of the new material that has been identified for improved agronomic qualities and characteristics (disease resistance, drought tolerance, vigorous growth, wear and recovery, uniformity, density etc.). This would mean that the new variety would have a broader genetic base developed using 20 parent plants and therefore be superior and less likely to suffer from catastrophic failure. This summary of the detail and investment that goes into the development of a variety give turf managers confidence that there are significant agronomic advantages and benefit in working with an improved seed variety. NTEP.org and private independent research data is a good reference point for identifying proven new varieties in the Kentucky bluegrass, perennial ryegrass and fescue species.
Understanding Kentucky bluegrass cultivars
Kentucky bluegrass is the primary species for athletic fields and recreational turfgrass use in North America. With proper management forms a fine-textured, high quality, long lasting turf stand. The rhizomes of Kentucky bluegrass increase stability, improve traction and provide good recovery to damaged and bare areas. Kentucky bluegrass can be used as a monostand, but to maximize the genetic base it is advantageous to select a polystand or blend of types.
It first must be understood that Kentucky bluegrass in contrast to all other cool-season turfgrasses, is highly apomictic. This means that almost every seed (usually over 95%) is an identical copy of the mother plant, which means that there is very little genetic diversity within a variety. This is because most varieties fall into similar groups or classifications. To maximize diversity it is best to blend together similar varieties from different categories. For example there is little agronomic benefit for an athletic field to be seeded containing five varieties similar to Midnight. The best approach would be to blend top varieties able to tolerate very low cutting heights from within the “Compact Elite,” the “America Elite,” the “Aggressive” type and possibly within the “Early Spring Greening” categories.
Improved drought tolerance of Texas hybrids
Recently much attention has been given to the development of heat and drought tolerance in Kentucky bluegrass. Known as hybrid bluegrass (Texas hybrids) these new cultivars have proven to perform equivalent to tall fescue varieties in a number of different trial locations. Other studies have also concluded that under limited irrigation cycles Texas hybrids perform better and maintained greater turf quality than tall fescue cultivars. In the same study tall fescue had higher water use. Along with improved heat and drought tolerance other benefits, extensive rhizomes for improved wear and recovery, lower water usage and good performance under lower maintenance.*
Ryegrass a good companion
Perennial ryegrass is a fine textures species with the potential to develop into a high quality, hardwearing turf stand. It’s fast establishing characteristics combined with high quality, color, texture and close mowing tolerance make perennial ryegrass ideal for athletic sports field use. These qualities are why perennial ryegrass is best used in a sports field seed mixture as a companion to Kentucky bluegrass. It is also important to remember that by blending the two species genetic diversity is increased maximizing each species strengths and weaknesses. Adding perennial ryegrass will speed up establishment assisting with natural weed control and importantly increases disease resistance and is resistant to different diseases than Kentucky bluegrass such as necrotic ring spot.
Perennial ryegrass is also endohpyte enhanced that improves tolerance to insects such a billbugs. Mix with Kentucky bluegrass the ryegrass component ranges form 10- 50% dependent on application. The percentage of perennial ryegrass used in a mixture should be based on the desired time period from time of seeding to planned use. If the establishment period is limited then a greater percent of ryegrass is recommended.
Intermediate ryegrass has been introduced over the past 8 years and offers some excellent benefits. Based on the principals of an annual plant Intermediate ryegrass has been develop to produce a high quality turf stand similar to perennial turf type ryegrass. Characteristics include germination under cool soil conditions, rapid establishment and improved turf quality over traditional annual ryegrass. Intermediate is an excellent overseeding tool for high traffic areas and is less competitive in a mixture with Kentucky bluegrass than perennial ryegrass.
Fescue offers alternatives
Turf-type tall fescue has traditionally been used on non-irrigated low-maintenance sports fields in transition zone and cooler climates. Tall fescue has two limiting factors that need to be considered; improved disease resistance and poor establishment. Generally speaking tall fescue is very wear tolerant once fully established, but getting tall fescue established before traffic and wear is introduced is an issue. This characteristic also affects the ability of tall fescue to recover quickly after heavy wear. Recent developments have seen the introduction of tall fescue cultivars with rhizomes improving establishment and wear tolerance. Tall fescue performs best when combined with 5-10% of Kentucky bluegrass.
Fine fescue cultivars offer some good alternatives for non-irrigated athletic fields and recreational turf areas. Specifically the Red fescue family Chewings fescue, Strong red fescue and Slender red fescue are examples of fescue groups that can be used in low-maintenance situations. Improved chewings and red fescue have seen recent advances in traffic tolerance, improved heat and drought tolerance, germinate more rapidly, have excellent cool temperature growth (spring and fall) and perform well in shady locations. Improved fine fescue cultivars also have the additional benefits of endophytes and should be seed in a blend with Kentucky bluegrass and perennial ryegrass for best performance.
Endophytes offer significant benefits
The availability of endophyte improved turfgrass cultivars is an important part of Integrated Pest Management (IPM) practices that can help reduce inputs. Endophytes are fungi that have a symbiotic relationship with some grasses, spreading through seed infection. The presence of endophytes in turfgrass has been demonstrated to provide many benefits including resistance to surface-feeding insects, increased disease resistance and increased stress tolerance. Currently the species of turfgrass with endophytes that are available on the market include perennial ryegrass, tall fescue, Chewings fescue, strong creeping red fescue, slender creeping red fescue and hard fescue. In some of these species, most cultivars available will have high levels of viable endophyte. Attempts have been made to find or introduce endophytes into other turf species such as Kentucky bluegrass but so far these associations have not been stable and have not led to marketable cultivars.
There are many factors to be considered in the construction and maintenance of an athletic or recreation field. Seed cultivar selection is one of many inputs that can impact the long-term success and quality of the turf stand. As outlined there are many different aspects that are critical in the selection of the proper turf grass species and cultivar for each specific turf site. Proper selection of turf cultivars can be the most important decision you have to make.
Paul Stevens is manager, professional turf, Pickseed Canada Inc., pstevens@pickseed.com.
*This chart is for general observation only. Individual performance of varieties within each classification may vary widely and require comprehensive regional test results to determine the best performance. To see chart in its entirety please visit www.pickseed.com.