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Steven Vanek, H.C. Wien and Anu Rangarajan

Growing a main vegetable crop for harvest and a cover crop for residue return to soil in the same growing season is a promising strategy to sustain soil quality in vegetable rotations. Our research evaluated cover crop strips interseeded between pumpkins (Cucurbita pepo L.) as a way to implement such a strategy. Cover crop types were lana vetch (Vicia villosa ssp. dasycarpa Ten.) and a lana vetch–winter rye (Secale cereale L.) mix, interseeded before, at the same time, or after pumpkins. The competitive impact of different cover crop strips was assessed using pumpkin yield, cover strip biomass, crop nitrogen status, soil nitrate status, and soil water potential. Cover strips were also assessed for competitiveness with native weeds. Seeding date affected the competitiveness of cover strips with pumpkins, while cover type did not. Cover crops seeded before pumpkins or at the same time reduced pumpkin yield in proportion to biomass produced by the cover strips early in pumpkin growth. Cover strips seeded after pumpkins did not reduce yield. Tilling in a before-seeded cover strip at 30 days after pumpkin seeding gave higher pumpkin yield than before-seeded cover strips that were not tilled. At three of four sites, after-seeded cover strips had the lowest percent weed biomass in strips, and at two sites with moderate weed pressure vetch–rye strips were more effective than vetch alone in suppressing weeds. Cover strips seeded before or at the same time as pumpkins reduced pumpkin yield by taking up resources that were otherwise available to pumpkins. At a high-rainfall site, competition for soil nitrate by cover crop strips was the dominant factor in reducing pumpkin yield. At a low-rainfall site, the dominant factor was competition for water. Because of effective weed suppression and lack of pumpkin yield reduction, interseeding vetch–rye strips after pumpkins was a promising practice, as was tilling in preexistent cover strips at an interval <30 days after pumpkin seeding. Good previous weed management and rye–vetch mixes at high seeding rates are necessary to allow interseeded cover strips to outcompete weeds.

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Haley Rylander, Anusuya Rangarajan, Ryan M. Maher, Mark G. Hutton, Nicholas W. Rowley, Margaret T. McGrath and Zachary F. Sexton

Intensive tillage degrades soil structure, decreases soil organic matter, and can cause soil compaction and erosion over time. Organic vegetable farmers are often dependent on tillage to incorporate crop residue, control weeds, and prepare seedbeds. Black, impermeable, polyethylene tarps applied on the soil surface and removed at planting can help suppress weeds before planting and reduce farmers’ reliance on tillage. However, little is known about how black tarps affect planting conditions and how they can be used to advance reduced tillage production systems. This study investigated the effects of tarp use and tarp duration on the soil environment, surface cover crop residue, and weed suppression to assess the efficacy of using tarps to improve reduced- and no-till practices for organic vegetable production. Experiments were conducted at three sites in the northeastern United States (Freeville, NY; Riverhead, NY; and Monmouth, ME) for 2 years. Following the termination of an oat cover crop, tarps were applied over untilled soils and left in place for four time periods: untarped (control), 3 to 5 weeks (short), 6 to 8 weeks (mid), and 10 or more weeks (long) before two removal dates. Soil moisture and temperature, cover crop residue, soil inorganic nitrogen, weed seed survival, and weed percent cover were measured after tarp removal. Soil moisture and temperature were generally higher under tarps at the time of removal compared with untarped areas at 10% to 55% and 1 to 3 °C, respectively, but the effects were inconsistent. Tarps significantly increased soil nitrate concentrations by 2-times to 21-times with longer tarp durations, resulting in higher concentrations compared with untarped controls. Tarps did not affect the amount of soil covered by cover crop residue and had no consistent effects on weed seed survival of Amaranthus powellii S. Wats. or Chenopodium album L., two common annual weed species in the Northeast. Tarping for at least 3 weeks reduced the weed percent cover by 95% to 100% at the time of removal. Increasing tarp duration beyond 3 weeks did not affect any measures except soil nitrate concentrations. These results indicate that tarps can facilitate the use of reduced-till and no-till practices for organic vegetables by creating a nutrient-rich and moist soil environment free of emerged weeds before planting without soil disturbance.

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Husrev Mennan and Mathieu Ngouajio

modification; and weed control ( Haramoto and Gallandt, 2004 ; Mennan et al., 2006 ; Ngouajio and Mennan, 2005 ; Teasdale, 1996 ; Yenish et al., 1996 ). Many studies have reported positive effects of living cover crops on early season weed suppression and

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Alyssa H. Cho, Alan W. Hodges and Carlene A. Chase

populations could mean a decrease in labor costs associated with hand weeding. Although the importance of weed suppression by cover crops is well documented, economic data are lacking to support the monetary benefits growers might obtain by using a cover crop

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Mercy Olmstead, Timothy W. Miller, Callie S. Bolton and Carol A. Miles

( Delmas and Grant, 2010 ). Although there are many benefits to using cover crops, their primary use has been as an alternative weed suppression technique in organic and conventional vineyards worldwide ( Dastgheib and Frampton, 2000 ; Liebman and Davis

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-growth and that proper rootstock selection is critical. Summer Cover Crops for Weed Suppression Cover crops can be used as a sustainable weed management tool in vegetable production. Kruse and Nair (p. 407) investigated impacts of short-duration summer

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Michael J. Adler and Carlene A. Chase

be used during summer fallow periods to suppress weeds through resource competition ( Collins, 2004 ); however, it is likely that weed suppression by these cover crops may also be in part the result of allelopathy. Allelopathy in velvetbean has been

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Elsa Sánchez, William J. Lamont Jr and Michael D. Orzolek

have evaluated the effectiveness of newspaper mulches for weed suppression in various crops in field settings ( Calkins et al., 1996 ; Carter and Johnson, 1988 ; Grassbaugh et al., 2004 ; Monks et al., 1997 ; Munn, 1992 ; Warmund et al., 1995

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Sanjeev K. Bangarwa, Jason K. Norsworthy and Edward E. Gbur

) crop ( Boydston and Hang, 1995 ). ‘Caliente’ mustard has the capacity to produce a high amount of glucosinolates, the precursor of isothiocyanates, which makes it a promising cover crop for weed suppression ( Norsworthy et al., 2005 ). Chemical weed

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-chemical options. By choosing woodchips from trees with allelochemicals, woodchip mulches represent an environmentally friendly weed suppression method. Using container-grown dogwood and crape myrtle plants sown with large crabgrass and pigweed, Ferguson et al. (p