Cover crops, allelopathy

Keywords Allelopathy Cover crops Crop residues Intercropping Mulching Organic farming Weeds... 

Providing weed suppression through the use of allelopathic cover crops is an important method of weed control in organic farming and it is one of the best possibilities of allelopathy application (Sullivan 2003a). Besides, growing of cover... 

Except direct use of allelopathic crops as cover crops, smother crops, and intercrops, applications of allelopathy for weed control include the use of allelopathic residues as an herbicide agent, e.g., pellets flours, water extracts, etc. The most common example of crop residue utilization is application of straw on the soil surface (mulching), e.g., rice straw inhibited germination of field bindweed (Convolvulus arvensis L.), winter wild oat (Avena ludoviciana Durieu), and little-seed canarygrass (Phalaris minor Retz.) (Lee et al. 1991 Tamak et al. 1994 Young et al. 1989). 

Fisk JW, Hesterman OB, Shrestha A, Kells JJ, Harwood RR, Squire JM, Sheaffer CC (2001) Weed suppression by annual legume cover crops in no-tillage com. Agron J 93 319-325 Fujii Y (2003) Allelopathy in the natural and agricultural ecosystems and isolation of potent allelochemicals from velvet bean (Mucuna pruriens) and hairy vetch (Vicia villosa). Biol Sd Space 17 6-13... 

Rasmussen IA (2004) The effect of sowing date, stale seedbed, row width and mechanical control on weeds and yields of organic winter wheat. Weed Res 44 12-20 Reddy KC (2001) Effects of cereal and legume cover crop residues on weeds yield, and net return in soybean (Glycine max),. Weed Tech 15 660-668 Reynolds LB, Potter JW, Ball-Coelho BR (2000) Crop rotation with Tagetes sp. is an alternative to chemical fumigation for control of root-lesion nematodes. Agron J 92 957-966 Rice EL (1984) Allelopathy. Academic, New York, p 317... 

Additional benefits derived from cover cropping include weed and disease suppression. Approaches for managing weeds are discussed below however, the main mechanism of weed suppression by cover crops appears to be resource competition, rather than factors such as allelopathy (Bond and Grundy 2001). The different occurrence of the fungal pathogen... 

Nagabhushana, GG, Worsham, A.D., Yenish, J.P. Allelopathic cover crops to reduce herbicide use in sustainable agricultural systems. Allelopathy J 2001 8 133-146. 

Fig. 3.16 The effects of soil moisture, and wheat and crimson clover cover crop residues on percent pigweed seedling emergence in Cecil A soil, where C equals crimson. Wheat inhibitory, C-clover inhibitory, and C-clover non-inhibitory were collected 2,1, and 4 months after glyphosate desiccation, respectively. The absence of standard error bars indicates that the error bars are too small to be visible. Figures adapted from Lehman and Blum (1997). Figures used with permission of International Allelopathy Foundation...

LaveUe P, Spain AV (2001) Soil ecology. Kluwer Academic Publishers, Dordrecht Lehman ME (1993) Effects of allelopathy on plant emergence and growth as modified by physical factors and root distribution. North Carolina State University Thesis, Raleigh Lehman ME, Blum U (1997) Cover crop debris effects on weed emergence as modified by environmental factors. Allelopathy J 4 69-88... 

How weeds produce their effect is the subject of continuing research. As rather recently defined, the negative effect of weeds on crop plants includes both competition and allelopathy (1.) and has been termed interference. Previous weed science research considered the competition component foremost and, usually, solely (e.g. 2). Allelopathy, however, has received some attention recently, with a number of symposia and reviews devoted to allelopathic effects. Some of these cover the effects of weeds on crops (3, 4, 5). In this chapter, I review the possible role of allelopathy in weed interference in crop production in the Mid-South. A second objective of this review is to indicate where research is needed and to suggest potential lines of future research, especially with respect to the developing role of conservation tillage practices in this region. 

While allelopathy is not covered in this chapter, excellent weed control can be achieved at reduced herbicide rate when used in conjunction with allelopathic rice varieties. Therefore, selection of highly allelopathic crop varieties, either through traditional breeding or using genetic engineering techniques, may also provide novel and low input approaches to weed control. 

Putnam AR, DeFrank J, Barnes JP (1983) Exploitation of allelopathy for weed control in annual and perennial cropping systems. J Chem Ecol 9 1001-1010 Putnam AR, Tang CS (1986) The science of allelopathy. WUey, New York, NY Qasem IR, Hill TA (1989) On difficulties with allelopathy methodology. Weed Res 29 345-347 Reader RJ (1991) Control of seedling emergence by ground cover a potential mechanism involving seed predation. Can J Bot 69 2084-2087... 

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