Investigation of the effect of plant density on different characteristics of promising forage sorghum cultivars

Three forage sorghum cultivars named KFS 1, KFS2 and KFS3 were studied for determination of the most suitable plant density, in factoril experiment based on a randomized complete block design in three replications at Karaj in 2001-2002. Plant densities were 167, 208, 278 and 417 thousands plants per hectare. Ammonium phosphate on the base of P2O5 Was applied at 115 kgha-1 and total nitrogen used was 183 kgha-1 at four times. Four traits including green fodder, dry matter, plant height and tiller number were measured in each cuting. Harvesting was conducted from 7.8 m2 area. Two years data were analyzed in combined analysis and the means were compared with Duncan's multiple range test (DMRT) method. Results showed significant differences between years (except for plant height), cultivars (except for tiller No.), year x cultivar interaction (except for tiller No.), plant density ,year x Plant density interaction (except for dry matter), cultivar x plant density interaction (except for plant height at 5% level probability) and year x cultivar x plant density interaction (except for plant height)at 1% level of probability. By means comparison with DMRT showed, all of studied traits ranked in the first group at first year. The cultivars KFS1 and KFS3 with 126.7, 124.5 tha-1 of green fodder, 24.38, 23.05 tha-1of dry matter, 186 and 187 cm of plant height ranked in the first group. KFS2 produced the lowest dry matter yield with an average of 20.18 tha-1. Plant densities of 278 and 417 thousands plant ha-1 had the highest and lowest dry matter yield, respectively. The tiller number differed significantly in the first and second cuts, but there were not significant difference in the means of tiller number among the studied cultivars.