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| the allelopathic effects of a wide variety of crops and cover crops have been investigated.
While often thought of as just negative effects, scientists studying allelopathy define it more broadly as both *postive* and negative effects of chemicals released by growing and dead plants on other organisms (not just other plants).
lots of lab studies have been done exposing seedlings to raw and purified plant extracts and specific modes of action have been identified for some specific compounds (just like for herbicides).
how allelopathic compounds effect crops and weeds in real fields and why these effects are less consistent than in the lab is much less well understood.
It is clear that in some situations, allelopathic compounds can be deactivated fairly quickly by processes such as microbial degradation, leaching and/or binding on soil surfaces and that crops and weeds vary widely in their production of and sensitivity to allelopathic compounds.
Negative allelopathic effects of cereal rye on corn are very widely reported yet some farmers have good success no-till planting corn into rye residues. An IA farmer recently sent me yield data from a corn hybrid trial in which all the corn had been no-till planted into rye. Yields ranged from 216-279 and averaged over 240 bu/ac.
The rye was sprayed when it was quite young (less than 12" as I recall) and the corn was not planted until weeks later. A fairly high rate of hog manure was applied and the field had been in continuous no-till for ~ 30 years.
This farmer regularly plants corn into rye without apparent negative effects.
This example does not make me think that allelopathy does not exist but rather that the negative effects can be avoided.
Anyone curious about the science of allelopathy might enjoy taking a look at some of the pages in a book titled Allelopathy: basic and applied aspects.
http://books.google.com/books?id=5-3AEm2erJIC&printsec=frontcover&s...
Joel
WIU Agriculture | |
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Alleopathy
