broccoli (Brassica oleracea L.) crop [61]. Similarly, sunflower residues and surface
mulches have potential to control various weed species in the field crops [62]. In
another study, application of barely mulch in maize provided up to 80% weed control
and 45% increase in maize grain yield over control [63]. Abbas et al. [50] reported
that the mulches of allelopathic crops including rice, maize, sorghum, and sunflower
at 12 t ha
À1 provided effective control of herbicide-resistant P. minor in wheat.
Mulches and residues of various crops including rye, clover, rice, maize, and canola
have been reported for their potential as weed control [1, 7, 11–18].
Combined use of different allelopathic mulches can enhance their weed control
potential due to the availability of diverse allelochemicals. Furthermore,
allelochemicals have been known for their synergistic effect [6]. For example,
combined use of canola, sunflower, and sorghum mulches provided more efficient
weed control in maize as compared to the sole use of individual mulch material [64].
Therefore, residues of allelopathic crops can be used either as surface mulch or soil
residue incorporation to control weeds in different crops.
3.5
Development of Herbicides from Allelochemicals and Their
Derivatives
Herbicides with new modes of actions are badly needed due to fast-increasing
herbicide resistance in weeds against all the major herbicide groups [65]. In addition,
weed management in organic production systems is a great challenge [66]. Various
natural herbicidal compounds have been identified from different microbes and crop
species [1, 3, 4, 11]. These herbicidal compounds can be categorized in two major
groups: phenolics and terpenoids [67]. These natural phytotoxins offer a great
opportunity to be directly used as natural herbicides and to develop novel herbicide
mode of actions [5]. The toxicity of allelopathic compounds depends on various
factors including cultivar, plant part, concentration of extract, donor plant growth
stage, and environmental conditions [68]. In this regard, several crop and weed
species are now getting importance as a potential weed-controlling agent because of
having various allelochemicals [1, 11–18].
In conclusion, allelochemicals from various crop and weed species can be directly
used as herbicides or can provide basis for development of herbicides with new
modes of actions.
3.6
Utilizing Hormetic Potential of Allelochemicals to Enhance
Crop Competitiveness
The phytotoxic response of allelochemicals is dose dependent; allelochemicals
cause growth enhancement (hormesis) at their low concentrations. The growthpromoting response of allelochemicals can be used to enhance crop growth. It will
provide crop plants a competitive advantage over weeds. Allelochemicals
can cause up to 50% and 42% increase crop growth under laboratory and
21 Allelopathy for Weed Management
511
mulches have potential to control various weed species in the field crops [62]. In
another study, application of barely mulch in maize provided up to 80% weed control
and 45% increase in maize grain yield over control [63]. Abbas et al. [50] reported
that the mulches of allelopathic crops including rice, maize, sorghum, and sunflower
at 12 t ha
À1 provided effective control of herbicide-resistant P. minor in wheat.
Mulches and residues of various crops including rye, clover, rice, maize, and canola
have been reported for their potential as weed control [1, 7, 11–18].
Combined use of different allelopathic mulches can enhance their weed control
potential due to the availability of diverse allelochemicals. Furthermore,
allelochemicals have been known for their synergistic effect [6]. For example,
combined use of canola, sunflower, and sorghum mulches provided more efficient
weed control in maize as compared to the sole use of individual mulch material [64].
Therefore, residues of allelopathic crops can be used either as surface mulch or soil
residue incorporation to control weeds in different crops.
3.5
Development of Herbicides from Allelochemicals and Their
Derivatives
Herbicides with new modes of actions are badly needed due to fast-increasing
herbicide resistance in weeds against all the major herbicide groups [65]. In addition,
weed management in organic production systems is a great challenge [66]. Various
natural herbicidal compounds have been identified from different microbes and crop
species [1, 3, 4, 11]. These herbicidal compounds can be categorized in two major
groups: phenolics and terpenoids [67]. These natural phytotoxins offer a great
opportunity to be directly used as natural herbicides and to develop novel herbicide
mode of actions [5]. The toxicity of allelopathic compounds depends on various
factors including cultivar, plant part, concentration of extract, donor plant growth
stage, and environmental conditions [68]. In this regard, several crop and weed
species are now getting importance as a potential weed-controlling agent because of
having various allelochemicals [1, 11–18].
In conclusion, allelochemicals from various crop and weed species can be directly
used as herbicides or can provide basis for development of herbicides with new
modes of actions.
3.6
Utilizing Hormetic Potential of Allelochemicals to Enhance
Crop Competitiveness
The phytotoxic response of allelochemicals is dose dependent; allelochemicals
cause growth enhancement (hormesis) at their low concentrations. The growthpromoting response of allelochemicals can be used to enhance crop growth. It will
provide crop plants a competitive advantage over weeds. Allelochemicals
can cause up to 50% and 42% increase crop growth under laboratory and
21 Allelopathy for Weed Management
511