Interactive effect of planting date and variety on agronomical characterestics and incidence of blast disease in rice replanting (Oryza sativa L.)

In recent years, two times cultiviation in year, or rice replanting, has gained popularity in Haraz watershed basin. In order to determine the interactive effect of planting date and variety on growth index, yield, yield components, and percent of blast desease in Tarom Mahali, Binam and Koohsar varieties in replanting cultivation, a field experiment was carried out at the Deputy of the Rice Research Institute of Iran, Mazadaran branch (Amol), in 2015 and 2017.Experiment was laid out as a split plot base complety random block design with three replications, where planting dates, as main plot, included 24 July, 2 and 12 AugustandTarom Mahali, Binam and Koohsar varietieswere put in sub-plots.Plot size was 3×4 m2 with a plant spacing of 20×20 cm2, and 2-3 seedlings per hill.Agronomical characterestics were measured at three growth stages, namely maximum tillering, flowering and physiological maturity. Results showed that tiller and panicle number per hill was higher in third planting date. SPAD value was affected by variety and Koohsar had highest SPAD value in all planting dates. Highest crop growth and net assimilation rate was obtained in Koohsar variety at flowering satge. The Highest yield was obtained in the second planting date for Koohsar and Binam varieties, though percent of blast disease incidence was higher as well. The higher yield of Koohsar variety could be attributed to having higher grain weight and harvest index compared to Tarom Mahali variety. Based on the results, best planting date would be from 2 to 12 August of in Haraz watershed basin.