The effect of planting method on grain yield and quality characteristics of some rice genotypes in Guilan province

Introduction
Transplanting in puddled soil is the dominant method of rice cultivation in the world, which requires high labor and cost. Therefore, in recent years, this method is being replaced by direct seeding system. Although direct seeding system has many advantages, this method may change various aspects of rice plant cultivation. In this experiment, it was tried to determine the effect of changing the rice cultivation method from transplanting to direct seeding on the grain quality of some rice genotype.
Material and methods
This research was carried out in the 2019 crop season in the Rice Research Institute of Iran based on a factorial experiment with three repetitions. The main factor includes; Cultivation method in two levels of transplanting and direct seeding and sub factor includes; Rice genotypes in five levels of Hashemi, Kian, Anam, Gilaneh and Shirodi. Land preparation included the first plowing in the late of March, the second plowing in the first of May, and the third plowing (pudlling) seven days before direct seeding and two days before transplanting.
Research findings
The results showed that the effect of genotype on paddy yield was significant, but the effect of cultivation method and interaction between cultivation method × variety was not significant. Shirodi genotype had the highest yield with 7820 kg/ha, while there was no significant difference between other genotypes in this regard. The highest milled rice yield was related to Shirodi genotype in direct seeding system (71%), which had no significant difference with Gilaneh in direct seeding system (70%) and Shirodi in transplanting system (70%). The percentage of head rice in direct seeding system (57.06%) was lower than that of transplanting system (65.86%). Among the genotypes, Shirodi and Kian had the highest and lowest amount of head rice with 84.33 and 37.5%, respectively. The amount of grain amylose of all genotypes increased in direct seeding system compared to transplanting cultivation, but this increase was significant in three genotypes Anam, Gilaneh and Kian and non-significant in Shirodi and Hashemi genotypes. The highest amount of amylose with 27.45 belonged to the Shirodi genotype in direct seeding system and the lowest to the Kian genotype with 21.27 in the transplanting system. Changing the cultivation method from transplanting to direct seeding system led to a significant increase in the Alkali spreading value of Gilaneh, Shirodi and Kian genotypes, while this change had no significant effect on the Alkali spreading value of Anam and Hashemi genotypes. The highest amount of grain protein was related to Anam genotype (11.08%) in the transplanting system, which was not significantly different from direct seeding system (10.76%).
Conclusion
The results of this research showed that changing the method of rice cultivation from transplanting to direct seeding does not lead to a decrease in paddy yield, but it can affect the quality characteristics of rice grains. One of the most important factors affecting the cooking quality of rice is the low percentage of grain amylose. In this research, the amylose percentage of two Hashemi and Shirodi genotypes, which have the largest cultivated area among the native and improved genotypes in the northern rice-growing provinces, did not increase due to the change of planting method from transplanting to direct seeding system, which this point can be effective in the acceptance of this cultivation system by farmers in addition to not reducing the yield of paddy.