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Weeds are especially problematic in highbush blueberry which has a long establishment period, shallow-fibrous roots, and poor competitive ability in obtaining water, nutrients and sunlight. Commercial approaches in certified organic blueberry fields compared horticultural management methods in two New Jersey sites. The trials utilized both new and established blueberry blocks having trickle or overhead irrigation. Commercial methods investigated included rotary cultivation, mowing, propane flaming, cover crops, landscape fabric, and various mulches. Mulch comparisons included pine bark mulch, hardwood mulch, coffee grinds, cocoa grinds, municipal leaf mulch, and composted tea leaves. 3' × 12' plots were replicated 4 times in 4 adjoining rows. Applications of 3-4 inches of these mulches within the crop row to a new planting of Duke highbush blueberry have provided a combined weed control level of ca. 95% without landscape fabric and ≈98% with landscape fabric during 2003. Walkway weed suppression in new plantings was achieved with the establishment of two types of fine leafed turf fescues and monthly mowings. Bare ground percentage decreased from 80% to <2% within one year's time as these fine fescues gradually out-competed annual weeds for space. These fescue cover crops increased ground coverage from 8% to >95% over the seven month growing season. Such varieties were selected because they have good germination, require little water, use limited nitrogen and can squeeze out weeds through allelopathy. Applied research studies indicate that several suitable methods can be utilized for effective weed management in organic highbush blueberry production systems.

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In a previous study to determine the feasibility of using herbicide desiccated cover crops for weed suppression during vineyard establishment, we found that weed suppression is excellent for about 6 to 8 weeks after desiccation in fall-planted rye. By the end of the season, however, weed growth in rye plots was similar to weedy control plots. Vine growth was reduced in rye plots compared to weed-free bare ground plots. Because of the experimental design, no follow-up weed control was performed in the rye plots and weeds eventually became well-established. So, it was impossible to determine if reduced vine growth was due to weed competition or allelopathy from the rye residues. A second study was conducted to determine the effects of follow-up weed control (with glyphosate) in fall-planted rye plots and weedfree bare ground plots. Results indicate that vine shoot number, shoot length, leaf area, and top growth dry weight was greatest in weedfree bare ground, less, but not significantly so in rye with follow-up weed control, and significantly less in rye without follow-up weed control. Root dry weight was reduced in rye with and without follow-up weed control compared to weedfree bare ground. Root dry weight was reduced 37% in rye with follow-up weed control and 63% in rye without follow-up weed control compared to weedfree bare ground. These results suggest that weed competition is not the primary cause of vine growth reduction in herbicide desiccated rye cover crops, so there is likely allelopathic effects of the rye residues on grapevines, which would limit using rye as a desiccated cover crop during vineyard establishment. However, there may be some value in using rye in established vineyards to reduce vigor.

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species greatly impacts transition, ryegrass allelopathy has been proposed as another contributing factor. Allelopathy, the suppression of growth of one plant species by another through the release of chemicals into the environment, has been implicated as

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seed germination and growth through chemical interference (allelopathy). Various types and amounts of allelochemicals are produced and can be released from the plant through leaching, volatilization, root exudation, death, and decay of plant parts

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source plants (autotoxicity) or the other species grown in the vicinity of source plants (heterotoxicity). This autotoxicity or heterotoxicity can be treated as allelopathy and the autotoxicity was found to be increased if the plants were cultivated

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content of asparagus spears is similar to that of buckwheat. Buckwheat has strong growth-inhibitory activity ( Zahida et al., 2002 ) and rutin contained in buckwheat is a causative agent for allelopathy ( Golisz et al., 2007 ; Kalinova and Vrchotava, 2009

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and Díaz-Pérez, 2007 ; Teasdale, 1998 ). In some cases, weed suppression has been attributed to production of allelopathic chemicals by cover crops ( Putnam and Duke, 1978 ; Putnam and Tang, 1986 ). Allelopathy is a trait that could be beneficial in

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Authors: , , , , , and

., 1998 ). It is now believed that grafting not only modifies the root system directly, but also induces metabolic alterations in scion growth. It is recognized that allelopathy plays an important role in agriculture and ecological systems. Inhibition of

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plant could otherwise access ( Keddy, 2001 ). Direct competition only occurs through relatively rare mechanisms such as allelopathy ( Williamson, 1990 ). Even resource competition is complex because in natural systems, multiple resources are often

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Al-Khatib, K. Boydston, R.A. 1999 Weed control with Brassica green manure crops 255 270 Narwal S.S. Allelopathy update, volume 2, basic and applied aspects New Delhi, India Oxford & IBH Publishing Co. Pvt. Ltd

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