The effects of plant densities on LAI and dry matter of different parts of sweet sorghum cultivars

Sweet sorghum had favorite ability to grow well and produce high biomass under dry condition. Two sweet sorghum cultivars (Rio and Keller) and six plant densities (100000, 200000, 300000, 400000, 500000 and 600000 plants per ha), were evaluated in a split plot layout within a randomized complete block design with three replications at the Isfahan University Research Station, Isfahan, Iran in 2009. Plant density had significant effect on total dry matter of anthesis stage, hard dough stage and physiological ripening stage. No experimental characteristics significantly influences by cultivar and plant density interaction. Stem dry matter in soft dough stage, hard dough stage and physiological ripening significantly affected by cultivar. Panicle dry matter in anthesis stage, soft dough stage, hard dough stage and physiological ripening significantly influenced by plant density, but cultivar effect on panicle dry matter in these stages was not significant. LAI was significantly influenced by all growth stages, but cultivar and cultivar and plant density interaction had no significant effect on it. The highest LAI in stage that vegetative stage turn into reproductive stage was related to 600000 plants per ha. Keller had obtained the maximum stem, leaf and total dry matter in the stage that vegetative stage turn into reproductive stage. Keller also had obtained the maximum stem, leaf, panicle and total dry matter in both 50% of anthesis stage and soft dough stage. The maximum stem, leaf, panicle and total dry matter was achieved in 600000 plants per ha. After this treatment, 400000 plants per had obtained the highest these experimental characteristics. 600000 plants per ha also had obtained the highest stem, leaf, panicle and total dry matter in physiological ripening. On the basis of the result Keller and 600000 plants per ha are suitable to obtain the appropriate LAI and dry matter accumulation.