Effect of transplanting time on grain yield, yield components and remobilization of three rice (Oryza sativa L.) varieties in Roudbar region

To evaluate the effect of transplanting time on grain yield and remobilization of dry matter of rice varieties, a field experiment carried out as split plot based on complete block design with three replications in Roudbar region, Guilan, Iran, in 2013. Three transplanting times (May 10 and 29 and June 17) were arranged in main plots and three rice varieties (Khazar, Gohar and Hashemi) in sub plots. The results showed that transplanting times and varieties had significant effects on plant height, panicle length, stem length, panicle weight, number of tillers, number of filled grains, 1000 grain weight, test weight and grain yield. The interaction effect of transplanting time and variety were also significant on plant height, panicle length, stem length, number of tillers and grain yield. The results of mean comparisons showed that the highest remobilization rates of dry matter was related to the second transplanting time and Gohar variety (277 and 235 g.m-2 , respectively). The results indicated that the delay in transplanting time decreased remobilization rate, contribution and efficiency, so that the lowest values of these traits were observed at the third transplanting time (51%, 31% and 26%, respectively ). The highest grain yield was belonged to Gohar variety during the first and second transplanting times (7653 and 7340 kg.ha-1, respectively) that may be due to the increasing 1000-grain weight, test weight and number of filled grains per panicle. According to results of the experiment, the second transplanting time was the best appropriate time for the climatic conditions of the experimental region and the highest grain yield in this time was belonged to the Gohar variety.