Variation of Yield and Quality in Early Maturing Rice Cultivars by Transplanting Date in Chungnam Plain Area in Korea

Studies were initiated for two consecutive years to examine the effects of transplanting date on the yield and quality of early maturing rice cultivars and to select rice cultivars capable of adapting to early transplanting in the middle plain area. The experiment was laid out in a split-plot design with 3 replications. The main plots consisted of two transplanting dates viz. early (25th of April) and ordinary (25th of May), with sub-plots containing eight cultivars. For early transplanting the mean temperature at the grain filling stage was lower than for ordinary transplanting, while the rice grain quality traits and palatability values were improved. Early transplanting results in 11 days earlier heading, higher head rice yield and lower milled rice yield than ordinary transplanting. Significant differences among the eight cultivars tested in this study were observed for most traits. Among cultivars, ‘Joami’ demonstrated the highest palatability. ‘Joami’ also performed better in head rice ratio and head rice yield than ‘Unkwang’, which is widely cultivated in the middle plain area. Palatability value (PV) showed significant positive correlations with head rice ratio (HR) and amylose content (AC), and negative correlations with chalky rice ratio (CR) and protein content (PC). Mean temperature (MT) was positively correlated with CR and PC, and negatively correlated with HR and AC. The highest positive and negative correlations among the rice quality traits were observed between HR and AC (r = 0.734), and HR and CR (r = -0.944), respectively. Based on the research findings, ‘Joami’ is suitable for early transplanting for cultivation in the Chungnam plain area.