Allelopathy future research

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. 

Future research. Ample research has been conducted to demonstrate the allelopathic potential of numerous weedy species, and of their associated crops. Future research should be directed to discerning how much of this potential is realized in the field under humid, warm conditions such as that found in the Southeast United States. Newman (33), in a reflective article, concludes that "—it cannot be said with confidence that allelopathy has any significance for agriculture." The evidence so far certainly substantiates his conclusion. To get a better feel for allelopathy in the field, field studies should minimally include the weed and weed residues. 

Obviously these suggestions for future research in allelopathy are only a few of the large numbers that could be given. Hopefully, however, they may give some Impetus to progress in some vital areas of allelopathy. 

In summary, there is little reason to be concerned about allelopathy in mixed plantations where walnut is grown for timber as the harvested crop. Allelopathy does appear to be a factor to consider before planting European alder as a nurse crop with black walnut. Black walnut has had no apparent effect on the autumn-olive but is probably responsible for the decline and mortality of the European alder. These results present interesting possibilities for future research on the plant/soil/microbial relationships related to the metabolism of aromatics. 

---