Abstract: The influence of Anabaena spp.extract on the seedlings, yield and yield determining factors of rice and different combinations of treatments applicable to open field were investigared by plot tests and large area yield comparison.By pretreatment with algal extract the height of rice seedlings, number and length of roots, as well as tillering ability, were improved, duration in nursery shortened, leaf area increased.After maturity, the yield-determining factors of rice such as number and weight of ripened grains, number of productive tillers, weight per 1000 grains, length of ears,etc., apparently increased as compared to control.The weight of the aerial part of plant also increased in spite of the slight decrease of the plant height.The yield increment varied according to rice cultivars and different treatments.The efficiently and economically appropriate method for field use was seed presoaking plus foliar application at the stage of two and a half leaves with 1% algal extract.