allelopathic crops can provide eco-friendly alternative to chemical weed control [34]. Recent studies have explored the effectiveness of intercropping with
allelopathic crops as a good alternative to chemical weed control [6].
Intercropping of fodder legumes in maize helped to control the giant
witchweed (Striga hermonthica [Del.] Benth) invasion than the sole maize crop
[99]. Intercropping of various allelopathic crop species in maize was effective
to control different narrow- and broad-leaved weed species [35]. Infestation of
purple nutsedge (Cyperus rotundus L.) in cotton crop was significantly reduced
with intercropping of sesame (Sesamum indicum L.), soybean, and sorghum
on alternate rows [100]. In another field trail, the intercropping of white clover
(Trifolium repens L.), black medic (Medicago lupulina L.), alfalfa, and red clover
(Trifolium pratense L.) in wheat crop was effective to control various weed
species and to enhance wheat yield [101]. Similarly, intercropping of pea
(Pisum sativum L.) with barley (Hordeum vulgare L.) [102], sorghum with cowpea
(Vigna unguiculata (L.) Walp.) [36], wheat with canola [37], and wheat
with chickpea (Cicer arietinum L.) [38], reduced the weed infestation as compared
to sole crop and enhanced farm income. Therefore, intercropping of allelopathic
crops with the main crop has potential to control weeds through release of
allelochemicals.
3.2
Cover Crops
Cover crops with allelopathic properties can provide effective weed control
in addition to their other benefits including protection from soil erosion,
snow trapping, nitrogen fixations, and improvement of soil structure and
fertility [39]. The weed suppression potentials of cover crops including physical
suppression, shade effect, decrease in temperature, and competition with weeds
for inputs can be further increased through selection of strong allelopathic crops
as cover crops. Furthermore, the release of allelochemicals from cover
crops through root exudates, leaf shading, and washing by rain will help to
decay the weed seedbank. The weed control efficiency of cover crops depends
on its allelopathic potential and duration in the field; strong allelopathic
crop for long duration in the field will provide more efficient weed control
[40]. The weed control efficiency of cover crops also depends on weed species,
e.g., sorghum as cover crop provides effective control of broad-leaved weeds;
however narrow-leaved weeds were not controlled [41]. Environmental
factors also influence weed control potential of cover crops by changing
allelopathic potential, e.g., rye grown under nutrient stress conditions was more
phytotoxic as compared to rye grown under high fertility [42]. Herbicide-resistant
weeds, which are a major problem for sustainable weed management, may
be controlled with allelopathic cover crops. The allelopathic crops that can be
used as cover crops include rye, barley, sorghum, oat, wheat, canola, black
mustard, buckwheat, clover species, and hairy vetch [39, 2]. In a recent study,
allelopathic cover crops such as buckwheat and hairy vetch were effective in
controlling apricot weeds [39].
21 Allelopathy for Weed Management
509
allelopathic crops as a good alternative to chemical weed control [6].
Intercropping of fodder legumes in maize helped to control the giant
witchweed (Striga hermonthica [Del.] Benth) invasion than the sole maize crop
[99]. Intercropping of various allelopathic crop species in maize was effective
to control different narrow- and broad-leaved weed species [35]. Infestation of
purple nutsedge (Cyperus rotundus L.) in cotton crop was significantly reduced
with intercropping of sesame (Sesamum indicum L.), soybean, and sorghum
on alternate rows [100]. In another field trail, the intercropping of white clover
(Trifolium repens L.), black medic (Medicago lupulina L.), alfalfa, and red clover
(Trifolium pratense L.) in wheat crop was effective to control various weed
species and to enhance wheat yield [101]. Similarly, intercropping of pea
(Pisum sativum L.) with barley (Hordeum vulgare L.) [102], sorghum with cowpea
(Vigna unguiculata (L.) Walp.) [36], wheat with canola [37], and wheat
with chickpea (Cicer arietinum L.) [38], reduced the weed infestation as compared
to sole crop and enhanced farm income. Therefore, intercropping of allelopathic
crops with the main crop has potential to control weeds through release of
allelochemicals.
3.2
Cover Crops
Cover crops with allelopathic properties can provide effective weed control
in addition to their other benefits including protection from soil erosion,
snow trapping, nitrogen fixations, and improvement of soil structure and
fertility [39]. The weed suppression potentials of cover crops including physical
suppression, shade effect, decrease in temperature, and competition with weeds
for inputs can be further increased through selection of strong allelopathic crops
as cover crops. Furthermore, the release of allelochemicals from cover
crops through root exudates, leaf shading, and washing by rain will help to
decay the weed seedbank. The weed control efficiency of cover crops depends
on its allelopathic potential and duration in the field; strong allelopathic
crop for long duration in the field will provide more efficient weed control
[40]. The weed control efficiency of cover crops also depends on weed species,
e.g., sorghum as cover crop provides effective control of broad-leaved weeds;
however narrow-leaved weeds were not controlled [41]. Environmental
factors also influence weed control potential of cover crops by changing
allelopathic potential, e.g., rye grown under nutrient stress conditions was more
phytotoxic as compared to rye grown under high fertility [42]. Herbicide-resistant
weeds, which are a major problem for sustainable weed management, may
be controlled with allelopathic cover crops. The allelopathic crops that can be
used as cover crops include rye, barley, sorghum, oat, wheat, canola, black
mustard, buckwheat, clover species, and hairy vetch [39, 2]. In a recent study,
allelopathic cover crops such as buckwheat and hairy vetch were effective in
controlling apricot weeds [39].
21 Allelopathy for Weed Management
509