ALLELOPATHY
• The word allelopathy is derived from greek words
Allelo = mutual or each other
Patho = suffering or to suffer
• The term allelopathy was coined by Molish in 1937.
• Allelopathy refers to the inhibitive or detrimental effect of one plant species on the germination, growth and metabolism of another plant species due to release of allelochemicals.
• According to Rice allelopathy refers to any direct or indirect inhibitory effect by one plant including microorganisms on another plant through the production of chemical compounds that escape into the environment.
• Allelochemicals includes aliphatic compounds like oxalic acid, succinic acid, butyric acid. It also includes terpenoids, cynogenic glucosides like alkaloids, phenolic compounds, HCN.
• Source of allelochemicals are leaf leachates and leaf litter, crop residue decomposition and root exudation.
• One crop against other crop allelopathy is likely to operate in multiple cropping systems like intercropping, mixed cropping and agroforestry.
• Sorghum is allelopathic against Amaranthus hybridus and Setaria viridis.
• Sweet potatoes have allelopathic effect on weeds like Cyperus sps.
• Cucumber is allelopathic against Echinocloa crusgalli and Amaranthus sps.
• Maize is allelopathic against Chenopodium album.
• Parthenium is having allelopathic interactions on several crops.
• Euphorbia is having allelopathic interactions on flax.
• Chenopodium album is having allelopathic interactions on alfalfa, maize and cucumber.
• Parthenium is allelopathic to many weeds.
• Parthenium invades and forms a territoty of its own replacing all the existing weed flora because of allelopathic effect.
• Amaranthus spinosus, Cassia seracia etc. pose a strong allelopathic effect on parthenium.
• Weed against weeds allelopathy has enough importance and could be exploited to control some of the poisonous and problematic weeds.
• Parthenium is suppressed moderately (26-50%) by Cassia auriculata, Sida spinosa and Hyptis Suaveolens.
• High suppression (51-75%) of parthenium by Croton bonplandianum, Cassia oxidentalis and Cassia tora.
• Very high suppression (76-100%) of parthenium by Cassia sericea and Tephrosia purpurea.
• Adoption of crops/crop cultivars more allelopathic to weeds may reduce the cost of weed control.
• Sorghum residue is incorporated to control weeds in sequence rotational crops.
• Application of residues of allelopathic crop plants as mulch or adoption of allelopathic crop in rotational sequence and allowing the residues to remain in field has enough importance to bring down weed population.
• Selection of companion crop that is selectively allelopathic to weeds has enough bearing towards weed control.
Ex: Sorghum + cowpea, Maize + cowpea, Agroforestry, Agrisilvipasture system
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