Effect of transplanting date on radiation interception and radiation use efficiency in rice (Oryza sativa L.) varieties

The formation of grain yield depends on fators such as available radiation and the genetic  characteristics of plant like radiation interception rate, radiation use efficiency and biomass contribution. In regard to climatic changes, for studying the effect of environmental conditions on this characteristics, a factorial experiment in randomized complete block design with three replications was conducted at Haraz Extension and Technology Development Center, Iran, in two crop seasons, 2013 and 2014. Three transplanting dates were used to encounter rice varieties under different environmental conditions. Treatments included rice cultivars (Tarom Samadi, Tarom Hashemi, Local Tarom, Shiroudi, Keshvari and Gohar) and transplanting dates (5th may, 20th may and 10th June). Results showed that grain yield, biomass, LAI at heading and 20 days after heading, harvest index, accumulated intercepted photosynthesis active radiation (PAR), radiation use efficiency, grain filling rate, grain filling period and panicle number.m2 varied significantly between rice varieties. Transplanting date had significant effect on all traits, except radiation use efficiency. Highest grain yield, biomass, harvest index, accumulated incident PAR, accumulated intercepted PAR, grain filling period and growth duration were obtained  in transplanting on 5th may ( 7204 kg.ha-1, 17229 kg.ha-1, 41.9%, 1050 MJ.m-2, 827 MJ.m-2, 20.6 and 105 days, respectively) and lowest in transplanting on 10th June. Results of this experiment showed that changing in transplanting date of rice varieties caused changing in mean temperature during growth period, accumulated incident PAR and accumulated intercepted PAR as fallow, but had non significant effect on radiation use efficiency.