The effect of combining flood and drip irrigation methods in different levels of nitrogen fertilizer and number of seedlings on yield and water productivity of rice

In order to investigate the effect of combining irrigation methods and nitrogen fertilizer levels in single and multiple seedling cultivation system on yield and water productivity of Tarom Roshan rice (Oryza sativa L.) cultivar, an experiment was conducted as split split plots based on randomized complete blocks with six irrigation treatments. The irrigation treatments include permanent flood irrigation method during the growing season (T1, control), strip drip irrigation method after the refilling of missing hills stage (T2), tillering (T3), clustering (T4), flowering (T5) and pasting (T6) with 50% of the amount of permanent flood irrigation water for each irrigation treatments. Two treatments of 90 (N1) and 180 (N2) kg/ha nitrogen fertilizer from urea source and two treatments of single (S1) and multiple (S2) seedlings was applied in three replications in 2019 in the rice research farm of Guilan University. The results showed that the highest grain yield with 6730.7 kg/ha was obtained in the treatment of T5 irrigation method with single seedling system and there was no significant difference with the treatments of T3 irrigation method with single planting and T1 with multi-seedlings systems. Additionally, the highest water productivity based on grain yield with 0.844 kg/m3 was obtained in the treatment of T2 irrigation method with multi-seedling system and there was no significant difference with the treatments of T2 and T3 irrigation methods with single seedling system. Also, the highest water productivity based on grain yield in all irrigation treatments was associated with N2 fertilizer treatment. Therefore, for higher grain yield with higher water productivity, N2 fertilizer level can be applied and in water restriction conditions, T3 irrigation method with S1 cultivation system can be applied in Rasht region.