Effects of Azolla Incorporation Timing on Growth and Yield Performance of Spring Rice (Oryza sativa L.)

Spring rice in Nepal often faces nitrogen shortages during peak crop demand, limiting yield potential. Azolla, a nitrogen-fixing aquatic fern, offers an eco-friendly alternative, but its effectiveness depends on inoculation and incorporation timing. A field experiment was conducted in Sapahi, Bara, Nepal (March–June, 2023) using a Randomized Complete Block Design with seven treatments and three replications. Plots measured 2 × 3 m (6 m²). Treatments comprised Azolla inoculated at 25, 35, 45, 55, and 65 days after transplanting (DAT) with recommended P & K, a recommended NPK dose (RDF), and a control. Data on growth, yield, and yield components were recorded and analyzed using ANOVA in RStudio. Treatment means were separated using Duncan’s Multiple Range Test (DMRT) at the 5% significance level. RDF recorded the highest grain yield (4.25 t/ha) and effective tillers (302.67 m-2), significantly higher than all other treatments (p < 0.001; LSD = 0.050). The best Azolla treatment, 25 DAT + P & K (4.02 t/ha), outperformed later Azolla applications and the control (1.87 t/ha). T1 also achieved more effective tillers (259.67m-²), longer panicles (23.72 cm), and lower sterility (25.44%) than other Azolla timings (p < 0.001). Azolla application at 25 DAT with P & K improves yield and reduces reliance on synthetic nitrogen fertilizers, making it a sustainable option for spring rice production in Nepal.