Using sorghum for organic weed management in conservation rice-wheatcropping system

Sorghum (Sorghum bicolor (L.) Moench) is one important allelopathic plant. Sorghum plant containsand releases several allelochemicals (viz. gallic acid, protocatechuic acid, syringic acid, vanillicacid, p-hydroxybenzoic acid, p coumaric acid, benzoic acid, ferulic acid, m-coumaric acid, caffeic acids,dhurrin, p-hydroxybenzaldehyde, sorgoleone, etc.,) in the rhizosphere soil. These allelochemicals,upon release in the rhizosphere plays multifarious roles including weed suppression. We evaluated thepotential of sorghum allelopathy for managing weeds in rice-wheat copping systems for five consecutiveyears in the same field. For rice crop, sorghum was planted in the last week of April and harvestedduring the second week of June. After the sorghum harvest, rice was direct seeded under aerobicconditions. Before wheat planting, sorghum was planted in third week of October, and was harvestedin late November. Wheat was planted in no till system. In addition, other allelopathic strategies wereincluded as treatments: (a) sorghum water extract (SWE) (۱۸ L ha–۱), (b) sorghum mulch (SM) (۸ tha–۱) and (c) SWE (۱۸ L ha–۱) + SM (۸ t ha–۱). In both rice and wheat, the combined use of SWEand SM in rice/wheat grown after sorghum significantly reduced the weed population and total weedcompared with the fallow–rice/wheat treatment. This weed suppression was translated into substantialincrease in grain yield of both crops. The weed suppression effect was more pronounced with time,and maximum weed suppression and yield grain was recorded in the ۵th year of experimentation.The improved weed management and grain yield by combining allelopathic approaches enhanced theprofitability of both rice and wheat crops. In conclusion, sorghum allelopathy has remarkable potentialfor reducing weed infestations and improving the yield and profitability in in conservation rice-wheatcropping system.