4.1 Plant Allelopathins as a Source of Bioherbicides
Plant allelopathins can be positively used in integrated weed management. The plant
allelochemicals are not suitable under field conditions because the mode of action is
different and profitable also. To evade masking impacts of one allelopathin by
another plant allelochemical, researchers are interested in the isolation and application of a single, specific compound for weed elimination. The list of allelochemicals
isolated from various plants that may act as inhibitors of weed seed germination
and/or weed growth is summarized in Table 5.2.
4.2 Allelopathic Crops in Weed Suppression through
Intercropping and Crop Rotation Methods
4.2.1 Intercropping
Handling croplands bestowing to natural agroecological principles will restrain
weed infestations in all crops, and crop rotation has long been documented for its
competence to thwart weeds from evolving to cause severe yield reduction. Combining crops with allelopathic features into the rotation complements another component of weed control. The practice of allelopathic crops in agriculture is currently
being realized as a mechanism of crop rotation and intercropping, as cover crops or
as green manure (Farooq et al. 2014; Haider et al. 2015). Population density of
weeds and biomass production was significantly reduced using crop rotation and
intercropping systems (Jabran et al. 2015). Intercropping of sorghum (Sorghum
bicolor L.), sesame (Sesamum indicum L.), and soybean (Glycine max L.) as
intercrops in cotton (Gossypium hirsutum L.) crop showed a greater net profit and
a substantial reduction on purple nutsedge (Cyperus rotundus L.) growth when
compared with the cotton alone in a 2-year experiment (Iqbal et al. 2007). Several
allelopathic crop plants intercropped with maize tested the growth and development
of several narrow- and broad-leaved weed species (Nawaz et al. 2014).
4.2.2 Cover Crops
The cover crops with allelopathic features having added advantages, such as
safeguarding plants from soil erosion, maintaining soil fertility and structure, and
improving nitrogen fixation, are also effectively employed in weed control (Tursun
et al. 2018; Altieri et al. 2011). Some of the important cover crops comprise canola,
rapeseed, cereal rye, crimson clover, wheat, red clover, brown mustard, oats, cowpea, fodder radish, annual ryegrass, mustards, buckwheat, hairy vetch, and black
mustard. The strong allelopathic cover crops suppress weeds by physically
suppressing through shade effect, fall of temperature, and competition of cover
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105
Plant allelopathins can be positively used in integrated weed management. The plant
allelochemicals are not suitable under field conditions because the mode of action is
different and profitable also. To evade masking impacts of one allelopathin by
another plant allelochemical, researchers are interested in the isolation and application of a single, specific compound for weed elimination. The list of allelochemicals
isolated from various plants that may act as inhibitors of weed seed germination
and/or weed growth is summarized in Table 5.2.
4.2 Allelopathic Crops in Weed Suppression through
Intercropping and Crop Rotation Methods
4.2.1 Intercropping
Handling croplands bestowing to natural agroecological principles will restrain
weed infestations in all crops, and crop rotation has long been documented for its
competence to thwart weeds from evolving to cause severe yield reduction. Combining crops with allelopathic features into the rotation complements another component of weed control. The practice of allelopathic crops in agriculture is currently
being realized as a mechanism of crop rotation and intercropping, as cover crops or
as green manure (Farooq et al. 2014; Haider et al. 2015). Population density of
weeds and biomass production was significantly reduced using crop rotation and
intercropping systems (Jabran et al. 2015). Intercropping of sorghum (Sorghum
bicolor L.), sesame (Sesamum indicum L.), and soybean (Glycine max L.) as
intercrops in cotton (Gossypium hirsutum L.) crop showed a greater net profit and
a substantial reduction on purple nutsedge (Cyperus rotundus L.) growth when
compared with the cotton alone in a 2-year experiment (Iqbal et al. 2007). Several
allelopathic crop plants intercropped with maize tested the growth and development
of several narrow- and broad-leaved weed species (Nawaz et al. 2014).
4.2.2 Cover Crops
The cover crops with allelopathic features having added advantages, such as
safeguarding plants from soil erosion, maintaining soil fertility and structure, and
improving nitrogen fixation, are also effectively employed in weed control (Tursun
et al. 2018; Altieri et al. 2011). Some of the important cover crops comprise canola,
rapeseed, cereal rye, crimson clover, wheat, red clover, brown mustard, oats, cowpea, fodder radish, annual ryegrass, mustards, buckwheat, hairy vetch, and black
mustard. The strong allelopathic cover crops suppress weeds by physically
suppressing through shade effect, fall of temperature, and competition of cover
5 Allelochemicals as Natural Herbicides for Sustainable Agriculture to Promote. . .
105