Both at 60 and 75 DAS, Agrodhan-14 was the tallest cultivar which was followed by BRRI hybrid dhan3, and BRRI dhan28 was the shortest one which was at par with BRRI dhan59 and BRRI dhan50. At harvest, plant height ranged from 74.4 to 91.97 cm. Agrodhan-14 appeared as the tallest variety which was at par with Binadhan-6, and BRRIdhan50 was the shortest variety which was closely followed by BRRI dhan58.Weed infestation reduced plant height at all growth stages. The magnitude of reduction varied with growth phase, and reduction in plant height in weedy treatments followed a declining trend with advancement of crop growth. Presence of weeds markedly decreased plant height by 3, 16, 14, 3.5, 3.5 and 10% at15, 30, 45, 60, 75 DAS and harvesting time, respectively.
In case of interaction,dutch buckets for sale the tallest variety was Binadhan-6 which was followed by Agrodhan-14 in weed free condition at 60 DAS. The shortest variety was Binadhan-10 which was statistically similar with BRRI dhan50 in weedy condition and BRRI dhan28 and BRRI dhan59 in weed free condition . Relative yield loss is an excellent indicator of weed tolerance of a variety. Lower the relative yield loss, higher the degree of weed tolerance, since weed tolerance refers to the ability to maintain high yield in the presence of weed competition.The rice varieties showed wide diversity in relative yield loss, which ranged from43.4% to 82.1% . The relative yield loss was lowest in BRRI dhan59, followed by BRRI dhan67 and Binadhan-10 which exhibited high weed tolerance. The cultivars evaluated in this study varied not only in yield and weed suppressing ability, but also in all the agronomic traits measured.
Although a wide variation in traits was observed among cultivars, none of them gave satisfactory yield under aerobic conditions. Binadhan-5 emerged as the most productive, whereas BRRI dhan59 appeared as the most weed suppressive rice variety. The least productive cultivar was BRRI dhan55, which was closely followed by Binadhan-8and BRRI dhan58. Based on reports in earlier studies , the present study included a variety of commonly cited traits including plant height, tillering ability,early visual vigor, duration, and SPAD values. Significant variations among the varieties were recorded suggesting that selection based on those traits was practical.Plant height is considered as desirable characters for weed suppressive cultivars.Although plant height varied widely among the cultivars, early plant height i.e. height at 30DAS was strongly and negatively correlated with weed dry weight. Earlier and faster growth allowed the rice crop to compete with weeds for plant resources,hydroponic net pots and this was reflected in the crop yield. The results indicate that only early plant height can be considered as vital selection criteria for weed competitiveness under aerobic soil conditions. Similar type of results has also been reported by Gibson et al . , Caton et al . , Zhao et al . , Anwar etal . .Early visual vigor or vigor index, a reliable predictor of crop biomass integrating both height and tiller number, is an important selection criterion for weed competitiveness.
Yield and weed competitiveness are effectively predicted by early visual vigor. Vigor rating is rapid, non-destructive, less labor-intensive and reliable, and therefore a promising and feasible tool for making decisions on weed competitiveness. In this study, early visual vigor varied widely among varieties, and its strong correlation with other parameters confirms its acceptability.It has been reported previously that early season vigor is directly linked with the competitive ability of the crop and later in the crop growing season, it confers competition against weeds .The SPAD meter provides a very easy, swift and non-destructive method for estimating relative leaf chlorophyll content.Higher SPAD values indicate greener healthier plants. The results showed SPAD values varied among the varieties.Weed interference negatively and markedly affected all yield components which cumulatively impaired grain yield. The rice varieties used in the current research showed wide diversity in relative yield loss, which ranged from 43% to 82%. Weed biomass was strongly and negatively correlated with grain yield, indicating that weed suppressive ability can be combined with yield potential. Anwar et al. and McGregor et al. also observed a similar relationship.