Introduction: Rice (Oryza sativa) is one of the most important staple foods in the world. Currently, it is the staple food of more than 3.5 billion people, i.e., about 50% of the world population (IRRI, 2012). Puddled transplanting is the major system of rice planting in many parts of the world. This method is labor -intensive and requires a large amount of water. The Dry direct-seeded rice method, which does not need puddling and transplanting and in which the seeds are directly sown in tilled or no-tilled soil, is a feasible alternative to save water and labor. Water scarcity is the biggest challenge facing the production of agricultural products in Isfahan province, and currently more than 5,000 hectares of agricultural land are under rice cultivation. this research was carried out to investigate the effects of irrigation management on yield and water productivity in different planting methods of rice in the Lanjan region of Isfahan.
Materials and Methods: In order to investigate three rice planting methods, a field study was conducted using a split plot design based on a randomized complete block with three replications in the Lenjan region of Isfahan during 2019. The main plots included three rice planting methods: Conventional flooding as a control (C₁), dry seeding with drip irrigation (C₂), and transplanting with integrated irrigation (C₃). Two rice genotypes, Sazandegi and line No. 2, were considered sub -plots. During plant growth, the amount of irrigation water was calculated and applied based on the cumulative evaporation from the Class A evaporation pan. Using class A pan evaporation at the project site, the amount of daily evaporation was calculated by considering the relevant coefficients. The amount of irrigation water was calculated. Statistical analyses and graphs were performed using SAS and Excel software, and comparisons of means were performed using the LSD test.
Results and Discussion: The results showed that there were significant differences (5%) between genotype and planting methods in terms of grain yield and water consumption. However, the interaction between planting methods and genotypes was not significant (5%). The conventional flooding method (C₁) by using 21008.3 m³.ha^-1 water, which was 70% more than dry seeded with drip irrigation (C₂) and 21% more than transplanting with integrated irrigation (C₃), had the highest grain yield (4709.7 kg ha^-1). This amount was 21% more than treatment (C₂) and 37% more than treatment (C₃). In treatment (C₂), physical water productivity was 0.314 kg/m3, which was 29% more than in treatment (C₁) and 11% more than in treatment (C₃). Sazandegi used 200 m³.ha^-1 water more than Line 2 and produced a higher grain yield (608 kg ha^-1), while the physical water productivity of both varieties was the same.
The results showed that the interaction between planting methods and genotype had a significant effect on  the number of tillers per square meter, the number of panicles per square meter, and plant height. The highest number of tillers (65) per square meter, panicle length (22.2 cm), and plant height (109.7 cm) were obtained in the conventional flooding method (C₁) in Sazandegi. Also, the lowest plant height (80.5 cm in rice line No. 2) and number of tillers per square meter (41.3 and 46) were obtained in the dry seeded method with drip irrigation (C₂) in Sazandegi and line No. 2, respectively, but the minimum panicle length (17.5 cm in line 2) was obtained in the transplanting method with integrated irrigation (C₃).
The effects of the interaction of planting methods × genotype on the number of panicles per square meter, number of grains per panicle, and 1000 grain weight were significant (1%). The means comparison showed that in the C₁ treatment, the number of grains per panicle and the grain weight were higher than in C₂ and C₃. While the lowest number of panicles per square meter, number of grains per panicle, and 1000 grain weight were observed in C₃, By reducing the amount of water consumed in the C₂ and C₃ treatments, the grain weight of the genotype increased compared to C₁. The higher grain yield in treatment C₁ can be attributed to the absence of drought stress, as well as the higher number of full grains per panicle and 1000 grain weight.
Conclusion: According to the results, the conventional flooding method is recommended with no water limitation. Despite the higher performance of the conventional flooding method, due to the water scarcity in Isfahan province, the dry -seeded method with drip irrigation and the Sazandegi cultivar is recommended and can be replaced in the future.