Control of weeds by Azolla in rice.
Culture of A. pinnata in flooded rice fields before transplanting suppressed the growth of some weeds. Scirpus articulatus and Marsilea quadrifolia were less affected than Cyperus difformis, Polygonum punctatum, Cynodon dactylon, Ludwigia perviflora and Echinochloa crus-galli. Spirogyra sp. and Chara sp., on the other hand, remained unaffected. A. pinnata introduced after transplanting reduced the weed quantity by 50%, whereas introducing A. pinnata both before and after transplanting resulted in 60% control.