Sustainable SOD Production for the Northeast
Turfgrass sod production is emerging as one of the few agricultural commodities that remain economically viable in Rhode Island and in urbanized areas of surrounding states. Presently, this sod consists almost entirely of Kentucky bluegrass, a crop that requires high inputs of fertilizer, water and pesticides for production and for maintenance in the landscape. Some sod growers are experimenting with new sod consisting primarily of tall fescue blended with bluegrass and other rhizomatous species needed to produce a harvestable sod. This shift in grass species is a response to consumer demands for sods with reduced maintenance requirements. Tall fescue is more tolerant of wear, low fertility, low moisture and shade conditions than most cultivars of Kentucky bluegrass. Many new commercially available varieties of tall fescue also contain an endophytic fungus which grows within the grass plant, further improving the plant’s tolerance to many stresses, especially insects. Recent research indicates that some endophytic tall fescue cultivars might be resistant to all common insect pests of turfgrass, including the Japanese beetle.
This LISA project is intended to further the production and use of tall fescue and other low maintenance turfgrass sods. Specific research objectives address measuring the insect resistance of various mixtures of tall fescues and other grasses. Through another research objective, we are attempting to incorporate the endophyte-conferred resistance of tall fescue into other grasses which might also be useful in this project. Demonstration experiments are underway on the agronomic requirements for these new sod mixtures and we are working to describe the economic implications of this program of sod production vs. traditional bluegrass culture. In another research component we are studying nutrient dynamics under sods produced and maintained with minimal inputs of water and fertilizer.
Research results will be published in scientific journals and presented through several Cooperative Extension channels including CES publications, grower meetings, and growers’ field days. Demonstration plots will be planted, maintained and harvested by local commercial turf growers and will be toured during the annual turf field day and Sod Producers Field Days at URI (combined attendance over 1,000 from at least nine states).
We expect to meet most of the objectives of this proposal between 1990 and 1993. Clearly some aspects such as persistence in the landscape will require additional time, and some other components will likely continue past the grant termination. Most work will be conducted at the URI campus and in nearby commercial sod fields. Because the insect resistance research is central to determining turfgrass blends, this aspect was conducted at URI and at the University of Massachusetts at Amherst, MA during the 1990 season.
(1) Insect resistance.
A great deal of effort has already gone into this aspect of the project, much of it in field evaluation of insect response to grasses and grass responses to insect feeding. Growth chamber studies are underway to refine our understanding of this relationship, as are laboratory studies to transfer endophytes between grasses.
As specified in our proposal last February, a series of plots was planted last spring with endophytic and non-endophytic plots of tall fescue, hard fescue, chewings fescue, and perennial rye grass. Bluegrass plots and mixtures of bluegrass with tall fescue rounded out the total of nineteen treatments, each replicated five times. The entire set of 90 plots was repeated at the University of Massachusetts at Amherst. Into these plots were placed screen cylinders, enclosing a 6-inch-diameter plug of grass plants, including soil and roots to a depth of eight inches. These cylinders were in turn inoculated with seven densities of Japanese beetle grubs, ranging from 0 to 24 grubs per cylinder. Following grub inoculation, plots were visually rated for damage every other week. In November most of these cylinders were disassembled, grubs were counted, and roots were measured. In Rhode Island, where the grubs are expected to successfully overwinter in these cylinders, the cylinders will be examined next season to monitor grass damage in the spring and early summer and to determine winter survival of the insects.
Analysis of this very large and complex data set will require some time and these results will not be available until at least the first of the new year. However, a cursory review of these data indicates that there may not be any impact of endophytes, grass species, or grass varieties on Japanese beetle survival under the conditions of this experiment (near optimum growing conditions). An interesting observation was that grub densities measured in November tended to plateau around nine grubs per cylinder (45/sq.ft.), even when three times that many grubs were introduced. Perhaps intra-specific competition (cannibalism?, territoriality?) are important in limiting the upper densities of grubs that can be achieved.
A field survey of Japanese beetle grub densities in the 1987 Tall Fescue Variety Trial at URI tends to confirm these observations. Again, an incomplete analysis seems to indicate no relationship between endophyte content of the grass varieties and their associated grub densities. A very interesting observation made in these tall fescue plots was that there was no visible damage in any of the plots — even those with very high grub densities. Several of these densities approached the plateau densities in our confined studies. Perhaps, due to the competition noted above, grub densities rarely reach levels damaging to tall fescue which, because of its relatively greater heat and drought tolerance, can outgrow grub damage — even in midsummer.
At present we are measuring root and foliage samples from the cylinders and preparing to measure levels of loline alkaloids in these samples. All grubs collected in these samples have been saved to determine their size and weight. Data are being formatted for analysis. In the future we want to repeat aspects of this field-test under rain out conditions where moisture levels are carefully controlled. We hypothesize that under low moisture conditions, stressed plants will produce more loline alkaloids, perhaps impacting on Japanese beetle survival. Greenhouse experiments are now underway in which endophytic grasses are being grown under different moisture levels to measure the impact of moisture on loline alkaloid production. Results of these tests will determine the range of conditions for next summer’s rain out trials.
In growth-chamber studies, first-stage Japanese beetle grubs confined on germinating tall fescue seedlings experienced seventeen times more mortality on endophytic (e+) grasses than on non-endophytic (e-) varieties of tall fescues. When similar larvae were confined on plugs of field-grown mature tall fescue in the growth chambers, there was no apparent difference in survival on e+ versus e- tall fescue. Experiments are underway to determine the nature of this apparent resistance in germinating seedlings and these will be expanded in the future to determine whether this resistance exists with larger beetle grubs and in other species of endophytic grasses.
Efforts to transfer Acremonium coenophialum into other grass species that do not normally contain this endophyte are progressing quite well. Endophyte from tall fescue has been introduced into callus tissue from red fescue and Kentucky bluegrass. To date, we have regenerated whole plants from inoculated callus tissue of Dawson red fescue and Pennlawn red fescue. When large enough, these red fescue plants will be examined for endophytic content. Kentucky bluegrass tissues remain in the callus stage, but by visual examination it appears that at least some are successfully inoculated. Alternative approaches for transferring endophytes are underway including embryo inoculations and inoculations of imbibed seed. These latter approaches have resulted in some seedling plants on artificial media in petri dishes which will be transferred to the greenhouse and then examined for endophyte content. Other species of Acremonium are presently being isolated and cultured for additional transfer work.
As these synthetic endophytic cultivars mature, plants will be divided and increased in the greenhouse. Loline alkaloid levels will be measured in the roots of these plants and compared to naturally endophytic tall fescue under different levels of drought stress. Any plants that seem to offer potential for insect control will be further propagated and moved to the field for evaluation.
(2) Agronomic requirements.
Work on this objective is well underway, although slowed by the lack of available alternative sods. In 1989, there were two plantings: one at URI and one commercial planting of tall fescue mixed with bluegrass. In 1990, we made additional plantings at URI and 4 commercial growers also planted alternative sod mixtures.
In URI plots we are evaluating plots of tall fescue mixed with 2%, 5%, and 10% Kentucky bluegrass, concentrating upon the 5% mixtures which we think will be ideal. Cooperating LISA grower Sue Albert has two fields of 95.5% (tall fescue, bluegrass) and other fields planted to various blends of bluegrass mixed with endophytic perennial rye grass and fine fescues. Another LISA cooperator, John Partyka, has planted a 12-acre experimental field using two cultivars of highly endophytic tall fescue and five varieties of Kentucky bluegrass. These seven grasses are planted in various combinations at various seeding rates. Two other local growers have planted tall fescue sods (one with netting to hold it together) and two are also experimenting with other mixtures of fine fescue and Kentucky bluegrass in their sods. All are sharing results with URI, but it is too early to draw many conclusions for these plantings, most of which are only a few months old.
Seeding technique is one aspect on which we already have considerable data from last season’s work. It appears that because of segregation of the very different-sized seeds in the planter, it will be necessary to double-seed fields of tall fescue mixed with bluegrass. In fields that were planted first with one grass and then with the other, we find a uniform stand of mixed grasses. When seeds are mixed before planting, we do not find a uniform stand. It appears that 6-8 lbs. of seed per 1,000 square feed will be adequate for most turf-type tall fescues, but perhaps with the finest-leaved varieties 10 lbs. will be better. Seeding rate will get additional study next season.
Fertilization and irrigation.
Results to date indicate that fertilizer required for producing tall fescue sod will be in the range of 3-5 lbs. Nitrogen per 1,000 sq. ft. per year (130-220 lbs./acre) — somewhat less than Kentucky bluegrass sod. It appears that after establishment, no irrigation will normally be necessary to produce this sod which will result in a considerable savings over bluegrass sod. The relationship between fertilization, irrigation, and time to maturity is still under evaluation. Very early data indicate that 14-16 months will be required to grow harvestable tall fescue sod — about the same time required to grow Kentucky bluegrass to maturity. (Some growers have pushed bluegrass sods with high fertilizer rates and harvested in twelve months or less, but the economics and environmental consequences of this are questionable.)
(3) Nutrient dynamics.
The tall fescue sod under investigation and the other mixtures under consideration all require less water and fertilizer than conventional bluegrass sod. Work done to date at URI indicates that there is little or no loss of nitrogen to groundwater unless turf is overwatered and overfertilized and even bluegrass sod should not result in any groundwater contamination. We have instrumented plots of all the common cool season turfgrasses to measure nutrient dynamics. Preliminary data indicate that tall fescue is more efficient at capturing nutrients than bluegrass.
(4) Sod persistence.
Work toward this objective was necessarily delayed until the tall fescue/bluegrass sods matured enough for transplant. In November, we harvested the first of these sods from LISA cooperator Sue Albert. We sodded three athletic fields in a demonstration experiment, and we have transplanted some of the sod to URI to begin the fertilization/irrigation/wear experiments described in the grant proposal. We also anticipate another demonstration experiment next spring where we shall transplant more of this sod into a URI horticultural display garden and compare its performance to traditional bluegrass sod and some other alternative endophytic grass mixtures under a moderate wear, low maintenance regimen.
Last fall a URI graduate student in Resource Economics was assigned to the Sustainable Sod project to study the economic aspects of this program. At present, economic information is being gathered to establish a framework for evaluating the potential economic implications of producing alternative sod crops. A survey of economic literature is underway to locate recent articles on production and marketing implications of turfgrass sod. Specialists at state experiment stations in the northeast are being contacted to locate reports describing the farm-level economics of turfgrass sod production. Information gathered in these efforts will be used to develop baseline crop budget data for sod production. This budget will be modified later to describe the potential economic implications of growing the alternative sods under investigation.
From the limited experience of researchers and commercial growers of tall fescue sod in Rhode Island, it appears that relative to Kentucky bluegrass, this crop will be more expensive to seed, but cheaper to water and fertilize. Because end users will not need to irrigate tall fescue sod after establishment, they may save the cost of installing and using an irrigation system. If this tall fescue sod is endophytic, users will likely also experience a savings in pest control. The net result of these factors is that users may be willing to pay a premium for this sod. These aspects, among others, will be evaluated over the next several months and will require continued close cooperation among the academicians, farmers and landscapers under this LISA project