nitrogen absorption and may reduce the potassium and phosphorus uptake. However, a higher concentration of this allelochemical reduces the absorption of potassium, phosphorus, and nitrogen. Likewise, low concentration of an allelochemical
“diphenylamine” encourages the nitrogen absorption and discourages the phosphorus absorption of phosphorus in tomato roots [71].
3
Role of Allelopathy in Weed Management
The weeds are believed to be the most important competitors of the crop plants
causing substantial yield reduction through competition for nutrients, space, light,
and water. In different cropping systems, allelopathic weed management may
provide an effective strategy with no or less resilience on synthetic herbicides.
The phenomenon of allelopathy may be used in weed management through
crop rotation [72], use of smother or cover crops [73, 74], intercropping, crop residue
incorporation, [10, 73, 75], mulching [10, 76], and use of allelopathic aqueous
extracts alone [7, 77] or in combination with reduced doses of herbicides [78–82].
As described above, the allelochemicals affect cell division, biosynthesis of hormones, uptake/transportation of nutrients [83], permeability of membrane [84],
oscillations of stomata, photosynthetic pigments [85], respiration process, protein
metabolisms [8], and plant water relation [5], when being applied at higher concentration, which may cause significant growth decline in weed plants. The application
of allelopathy for weed control in field crops has been discussed in the following
section.
3.1
Intercropping
In intercropping, the compatible crops are grown together in order to get high yield
and economic profits. Further, intercropping increases the resource use efficiency
and helps controlling the weeds (Table 1; [99]). In particular, weed population can
be reduced, and the crop yield may be increased if the allelopathic crops are used in
intercropping. For instance, weed density of jungle rice (Echinochloa colona (L.)
Link.), jute mallow (Corchorus olitorius L.), common purslane (Portulaca oleracea L.),
and crowfoot grass (Dactyloctenium aegyptium (L.) Willd.) was decreased when
maize and cowpea (Vigna unguiculata [L.] Walp.) were intercropped [100]. The
weed infestation in wheat crop can be reduced by intercropping legumes in wheat as
compared to sole wheat crop [101]. In a study, the growth of Orobanche spp. was
decreased by introducing berseem (Trifolium alexandrinum L.) as intercrop in
legumes [102].
In cotton (Gossypium hirsutum L.), intercropping of sorghum and sunflower
crops reduced the weed density by 60–62% and enhanced the cotton
production by 17–22% [103]. In another study, the intercropping of pea with barley
decreased the population of wild mustard and common lamb’s quarters
(Chenopodium album L.) than the sole crops. Furthermore, the weeds also extracted
23 Ecological Management of Agricultural Pests Through Allelopathy
549
“diphenylamine” encourages the nitrogen absorption and discourages the phosphorus absorption of phosphorus in tomato roots [71].
3
Role of Allelopathy in Weed Management
The weeds are believed to be the most important competitors of the crop plants
causing substantial yield reduction through competition for nutrients, space, light,
and water. In different cropping systems, allelopathic weed management may
provide an effective strategy with no or less resilience on synthetic herbicides.
The phenomenon of allelopathy may be used in weed management through
crop rotation [72], use of smother or cover crops [73, 74], intercropping, crop residue
incorporation, [10, 73, 75], mulching [10, 76], and use of allelopathic aqueous
extracts alone [7, 77] or in combination with reduced doses of herbicides [78–82].
As described above, the allelochemicals affect cell division, biosynthesis of hormones, uptake/transportation of nutrients [83], permeability of membrane [84],
oscillations of stomata, photosynthetic pigments [85], respiration process, protein
metabolisms [8], and plant water relation [5], when being applied at higher concentration, which may cause significant growth decline in weed plants. The application
of allelopathy for weed control in field crops has been discussed in the following
section.
3.1
Intercropping
In intercropping, the compatible crops are grown together in order to get high yield
and economic profits. Further, intercropping increases the resource use efficiency
and helps controlling the weeds (Table 1; [99]). In particular, weed population can
be reduced, and the crop yield may be increased if the allelopathic crops are used in
intercropping. For instance, weed density of jungle rice (Echinochloa colona (L.)
Link.), jute mallow (Corchorus olitorius L.), common purslane (Portulaca oleracea L.),
and crowfoot grass (Dactyloctenium aegyptium (L.) Willd.) was decreased when
maize and cowpea (Vigna unguiculata [L.] Walp.) were intercropped [100]. The
weed infestation in wheat crop can be reduced by intercropping legumes in wheat as
compared to sole wheat crop [101]. In a study, the growth of Orobanche spp. was
decreased by introducing berseem (Trifolium alexandrinum L.) as intercrop in
legumes [102].
In cotton (Gossypium hirsutum L.), intercropping of sorghum and sunflower
crops reduced the weed density by 60–62% and enhanced the cotton
production by 17–22% [103]. In another study, the intercropping of pea with barley
decreased the population of wild mustard and common lamb’s quarters
(Chenopodium album L.) than the sole crops. Furthermore, the weeds also extracted
23 Ecological Management of Agricultural Pests Through Allelopathy
549