Comparison of yield and yield components of native and improved rice cultivars in transplanting and direct seeding cultivation methods

Rice (Oryza sativa L.) is the most important crop in Gilan and Mazandaran provinces, which is transplanted in puddled soil. This method of planting requires a lot of labor and its production cost is very high. Researches has been shown that rice direct seeding can be a low-cost alternative to transplanting method. Therefore, in this study, the effect of direct seeding on the yield and yield components of different native and improved rice cultivars has been investigated.

This experiment was carried out during 2019 and 2020 in the research farms of the Rice Research Institute of Iran-Rasht. The experiment was a split block based on randomized complete block design with three replications. The main plots included cultivation method in two levels (transplanting and direct seeding) and the sub-plots included rice cultivars in five levels (Hashemi, Anam, Gilaneh, Shiroodi and Taher). Rice density in transplanting method was 25 hills per square meter (each hill contains three seedlings) and seed rate in direct seeding was considered for all cultivars 100 kg / ha.

The results showed that the cultivation method had no significant effect on paddy yield, while the effect of cultivar and interaction of cultivar in cultivation method in the first year of the experiment was significant in this regard. In 2019, the range of paddy yield varied from 4152 kg / ha for Hashemi cultivar in transplanting to 7531 kg / ha for Shiroodi cultivar in direct seeding. In 2020, the lowest (4473 kg / ha) and highest (7842 kg / ha) paddy yield belonged to Hashemi and Shiroodi cultivars in direct seeding, respectively. The effect of cultivation method (in the first year), cultivar and the interaction effect of cultivation method and cultivar on the number of panicle per unit area were significant. In both years (except Anam cultivar in 2020), the number of cultivars panicle in direct seeding was more than transplanting. In 2019, Anam cultivar had the highest (444 panicles) number of panicles in transplanting method, while the number of panicles of this cultivar in direct seeding was 517. In this year, the highest panicle number (626 panicles) in direct seeding method belonged to Shiroodi cultivar, while this cultivar had 332 panicles/m2. In 2020, Hashemi and Taher cultivars had the highest number of panicles per unit area (456 and 397 panicles, respectively), while the number of panicles of these two cultivars in direct seeding was 606 and 536 panicles, respectively. The effect of cultivation method on the number of filled grains per panicle was not significant. However, in both experimental years, the number of filled grains in transplanting method was 26% and 22% higher than direct seeding method, respectively. This was while the effect of cultivar and the interaction effect of cultivation method and cultivar on the number of filled grains per panicle were significant. The results showed that, biological yield, harvest index and number of filled and empty grains in both years of the study had the highest positive correlation with paddy yield.

The results of this study showed that there was no significant difference between direct seeding and transplanting methods in terms of paddy yield. In direct seeding, increasing the number of panicle per unit area led to a decrease in the number of filled grains per panicle, while in transplanting, reducing the number of panicle per unit area led to an increase in the number of filled grains per panicle and thousand grains weight. In fact, significant changes in these yield components in the two cultivation methods led to similar paddy yield in them.