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will need to adopt non-chemical weed control options," said Kao-Kniffin. Culture saves us The first study involving cultural methods for weed control uses repetitive overseeding, which is not a new concept, and is routinely used on golf courses in the South, but hasn't been implemented as a routine strategy on school playing fields in the North. "In overseeding, grass seed is sown in the late summer or early fall and sometimes in the spring to mimic the natural ecosystems of grasslands," said Kao-Kniffin. "It replenishes the density of the turf, which suppresses weeds by shading out competitors, and it increases the field's playability. When you have a dense cover of turf, weed seeds don't have the opportunity to germinate, so it's a natural weed-suppression strategy." Kao-Kniffin's study will use perennial ryegrass — a grass spe- cies that germinates rapidly, often within three days with enough moisture. The next study involves using fertilizer at the proper rate and calibration so that nitrogen works its magic to encourage greater turf density, which crowds out weeds. "Some contractors go overboard with adding fertilizers," said Kao-Kniffin. "This can result in excessive phosphorus applica- tion, whereas nitrogen should really be the focus when it comes to turf density in most sites." Furthermore, in New York and many other states, phos- phorus bans apply because of their damaging effects on aquatic ecosystems. A third study involves topdressing sod for school grounds and playing fields with organic amendments such as vermicompost (worm-composted farm waste) and composted yard waste. Kao- Kniffin said that several sod farms in New York have agreed to collaborate with Cornell researchers on the project if the scientists obtain research funds for the initial work. Already, a sod farm has started a trial evaluation of vermicompost, applying 20 pounds of the compost per 1,000 square feet of sod. That translates into an application rate that is economical if the grower is saving in the costs of production (mowing, irrigation, and fertilizer and pesticide applications). This year, they dug up/sampled some of the vermicompost- enriched sod and found a significant enhancement of root growth compared to sod that was not grown with vermicompost. "One of the sod growers said that at this rate of growth, they might be able to harvest sod earlier, which means turning over the product faster, which saves on labor costs and inputs," said Kao-Kniffin. "This could make turf more economical to produce; compost manufacturers are very interested in the findings of this research." Kao-Kniffin's colleague at the New York State Agricultural Experiment Station in Geneva, N.Y., entomologist Karl Wickings, has submitted a proposal to the USDA seeking fund- ing to get researchers and industry stakeholders like turf managers, compost manufacturers, and sod farmers together to talk about how to create sod that is more sustainable. They are hoping to get funded for that next year. Kao-Kniffin also does research at the microbial level, looking for beneficial microorganisms including fungi and bacteria that could be introduced to turfgrass and work symbiotically with it. "That research is fundamental — i.e., not practical yet," she said. "But the ideal situation is that in 10 years we might have some commercially available inoculants and/or promising genotypes of turf and ornamentals that can attract beneficial microbiota to the roots." Healthy turf is dense, and more resistant to pests. Kao-Kniffin said that as pesticide restrictions multiply in the U.S., there will be a demand for this kind of "superturf" — one that doesn't require so many chemical inputs. Once her lab isolates these microbiota and exceptional genotypes, they will bring this information to the landscape industry. As above, so below Grant Thompson is a graduate student working on his mas- ter's and doctoral degrees with advisor Kao-Kniffin. In his research at Cornell, Thompson has looked at urban grasslands and turfgrass systems through the lens of biodiversity and eco- system functioning (BEF). BEF theory has been applied to many ecosystems, such Industry Insights 24 Landscape and Irrigation September 2014 www.landscapeirrigation.com