Progress 05/15/06 to 05/14/07
Outputs
In Gainesville, suppression of purple nutsedge by summer fallow treatments in 2005 persisted into spring 2006, so that in summer squash, all treatments had significantly lower nutsedge infestations than the weedy control. Purple nutsedge densities in fallow treatments were not statistically different. In bell peppers, nutsedge density also was highest with the weedy control. With the fallow treatments, nutsedge densities were lowest with weekly tillage, intermediate with flaming and sunn hemp-mulched, and highest with sunn hemp-incorporated and soil solarization. In both squash and peppers, the use of infrared transmitting (IRT) film significantly reduced purple nutsedge infestation. The use of IRT also significantly increased squash yield except with the sunn hemp-incorporated treatment. In the bell pepper crop, fruit yields were highest with weekly tillage and lowest with the weedy control. Pepper yields increased by more than 20% with IRT film. In Tifton, all weeds,
including yellow nutsedge, were suppressed by IRT-film mulch. However, in bareground plots, only previously solarized plots resulted in effective yellow nutsedge control. Flaming, sunn hemp cover crop, and fallow-tillage the preceding summer did not effectively suppress yellow nutsedge and other weeds. Yields of squash and bell pepper responded similarly to treatments as yellow nutsedge densities. Yellow nutsedge was not present at significant densities in fall-seeded crops in 2005 and 2006, regardless of the treatment. Solarization effectively reduced weed populations in the upper portions of the soil profile. A sunn hemp cover crop suppressed annual weeds, but not yellow nutsedge. Sunn-hemp biomass impeded direct seeding of turnip green. At Clemson, the population dynamics of purple nutsedge was evaluated over two growing seasons with bell pepper as a fall crop. Initial viable tuber density in mid-Mar. 2005 was 907 total tubers/m2. Total tuber density increased to >5,500
tubers/m2 in fallow, nonweeded plots by Nov. 2006. Yearly tuber density remained relatively constant over the two years when the fallow period was followed by hand-weeding in the bell pepper crop. Mulched plots following the fallow period had tuber densities comparable to fallow, nonweeded plots at all sample times, except Nov. 2006 when densities were lower when mulched. Frequent tillage or use of a polyethylene film with or without an incorporated turnip cover crop generally caused tuber density to decline from mid-Mar. through Jul., but tuber densities then increased to levels higher than the initial density in late summer and fall when subplots were not weeded. A similar but lesser trend occurred in most mulched plots; however, densities were not different from hand-weeded plots. Season-long management was essential to prevent increases in purple nutsedge tuber production. Preliminary evaluation of costs of purple nutsedge management at Gainesville indicate direct
pre-harvest costs per acre of $2,888 for broccoli and $3,462 for peppers, including labor costs of $1,083 and $1,473 per acre, respectively. Soil solarization appears to be more economical than flaming.
Impacts
The effectiveness of control measures vary with nutsedge species, location, and cropping system. Although at no location will the measures employed eradicate nutsedges, at Gainesville and Tifton combinations of a summer fallow treatment with the use of IRT film in spring crops appears to have the potential to suppress and manage nutsedge. Information will be forthcoming on the cost of utilizing these measures. This will allow growers to decide whether the returns from a particular crop justify the costs of managing nutsedge. A workshop and field day on organic production was held on Sep. 20, 2006 in Citra, FL. The 237 attendees included beginning growers, experienced non-organic growers, established organic growers, administrators, faculty, students, and industry representatives. The field day focused on Nutsedge Control in Organic Production Systems and was led by Drs. Chase, Koenig, and Johnson. Participants were taught how to distinguish between purple and yellow
nutsedge. Plots demonstrating the cultural and physical techniques of soil solarization, sunn hemp, flame weeding, and tillage were used to explain how these practices were being used in our studies, which were proving to be most effective, and what short-comings had become apparent with some of the techniques. An evaluation instrument was used to evaluate whether learning had occurred during the field day. Statistical analysis to compare pre-test and post-test scores of participants resulted in a t-value of -5.56105 and a significant p-value of <0.0001, indicating that our training did in fact work.
Publications
- Chase, C.A., R.L. Koenig, and C.L. Brinton. 2007. Effect of tillage interval on purple nutsedge suppression. HortScience 42: 868. (abstract)
- Chase, C.A., R.L. Koenig, J.E. Pack, and C.L. Brinton. 2007. Integrating nonchemical options to manage purple nutsedge (Cyperus rotundus) in organic vegetable production. Weed Science Society of America Abstract #290. (abstract)
- Chase, C.A., R.L. Koenig, J.E. Pack, and C.L. Brinton. 2007. Effectiveness of cultural and physical measures in suppressing purple nutsedge in organic vegetables. Proc. Southern Weed Science Society 60: 240. (abstract)
- Norsworthy, J.K., S. Bangarwa, M. Malik, and P. Jha. 2007. Population dynamics of purple nutsedge in an organic production system. Proc. Southern Weed Science Society 60: 238. (abstract)
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Progress 05/15/05 to 05/14/06
Outputs
In Gainesville fallow treatments were initiated in July 2005 for purple nutsedge suppression. Clean fallow treatments accomplished with weekly tillage or weekly flaming and two sets of sunn hemp cover crop treatments were established. Cover crop residue was either incorporated prior to transplanting or retained as mulch for fall crops. The other treatments were soil solarization with clear polyethylene film and a weedy control. In October, cash crops of lettuce and broccoli were established in adjacent beds in each plot. During the winter fallow period, rye was planted as a cover crop on half of the plots and the other half was maintained weed-free using tillage. In March 2006, rye was incorporated prior to setting bell pepper and zucchini squash transplants. The halves of the plots maintained weed-free during winter fallow were mulched with a dark-green infra-red transmitting (IRT) film. Suppression of purple nutsedge by all summer fallow treatments persisted into
the subsequent fall cash crops, but solarization was the least effective. Highest lettuce yields were obtained with incorporated sunn hemp, solarization, and tillage. Highest broccoli yields occurred with flaming, solarization, and tillage. Squash harvests were completed in April and final pepper harvests will be completed in mid June. The experiment will be repeated in the same location to determine the cumulative effects of treatments over time. The same summer fallow treatments used in Gainesville also were also used in Tifton with yellow nutsedge as the target weed species. Although this particular site has a history of heavy yellow nutsedge infestation, the weed was present in 2005 at low densities. Crowfootgrass and southern crabgrass, which occurred at very high densities responded to treatments. Sunn hemp effectively suppressed weed emergence, but was difficult to shred prior to seeding fall crops. Turnip green stand was reduced in plots where pieces of sunn hemp stalk
physically inhibited turnip seed placement. Solarization with clear plastic mulch suppressed weed emergence during the summer months and this effect was extended to fall crops. Purple nutsedge was also the target weed species at Clemson where main plot treatments consisted of: 1) a green IRT film from mid-March through early August, 2) a clear film (solarization) from mid-March through early August, 3) turnip from mid-March to mid-June followed by (fb) a green film through early August, 4) turnip from mid-March to mid-June fb solarization through early August, 5) monthly tillage from mid-March through early-August, and 6) no nutsedge management (weedy control). Subplots were 1) hand hoed (weed free), 2) mulched with wheat straw, and 3) no nutsedge management. Results indicate that IRT film, solarization, or solarization following a turnip cover crop suppressed purple nutsedge tuber density before transplanting fall grown pepper, which lowered the shoot density of purple nutsedge at 3
weeks after transplanting pepper compared to no nutsedge management. The second year of the study was initiated in March and is ongoing to determine the long-term impact of each strategy on purple nutsedge tuber dynamics.
Impacts
Two graduate students, one in Gainesville and one in Clemson, are being trained in the conduct of systems research and organic production of vegetables by participating in the study. One student has plans for a career in crop consulting and this experience will provide him with knowledge and skills to serve an organic agriculture clientele. An undergraduate intern was trained over a 6-wk period during summer 2005 through his participation in the summer fallow treatments and scientific report writing based on his involvement with the project. Presentation of our results at conferences will allow us disseminate our results and broaden our impact to states not participating in the research, and to emphasize the need for more research in this area and that funds are being granted to undertake pest management research for organic crops. Three growers, one each from Florida, Georgia, and South Carolina are participating on the project evaluation committee. With their close
interaction with the project they are likely to adopt successful and economical measures identified by the study and help to promote more rapid adoption by other growers. A workshop/field-day is scheduled for Gainesville in September 2006 for organic growers and extension personnel. One session will include a presentation based on this work and other nonchemical measures for weed management that are applicable to organic production. A field visit to the research site will allow participants to see the results of the summer fallow treatments.
Publications
- Chase, C.A., R.L. Koenig, J.E. Pack, and C.C. Warren. 2006. Purple nutsedge management for organic vegetable production. HortScience 41:505. (abstract).
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