Comparative Evaluation of Nano Urea Versus Conventional Urea for Nitrogen Management in Rainfed Sunflower (Helianthus annuus L.) Cultivation in Acid Sandy Loam Soils of Assam.

A field experiment was conducted during rabi, 2021-22 at the experimental plot of the Department of Agronomy, Biswanath College of Agriculture (BNCA), Assam Agricultural University (AAU), Biswanath Chariali, Assam having geographic coordinates 26°43'30'' N and 93°08'08'' E to assess nitrogen management in Sunflower (Helianthus annuus L.) with conventional and nano urea under rainfed farming situations in the North Bank Plain Zone of Assam. The experiment confined to 10 treatments in Randomized Block Design (RBD) viz., T1: Control (No Nitrogen), T2: Soil application of 50% N, T3: Soil application of 100% N (RD), T4: 3 foliar applications of 0.6% nano urea, T5: Soil application of 50% N + 2 foliar application of 1% conventional urea, T6: Soil application of 50% N + 2 foliar application of 2% conventional urea, T7: Soil application of 50% N + 2 foliar application of 3% conventional urea, T8: Soil application of 50% N + 2 foliar application of 0.2% nano urea, T9: Soil application of 50% N + 2 foliar application of 0.4% nano urea, T10: Soil application of 50% N + 2 foliar application of 0.6% nano urea. Results revealed that there was no significant effect on the seedling emergence percentage due to different nitrogen management treatments. The highest plant height (84 cm) and maximum number of leaves (33) were found in T10. T9 showed the maximum values of Relative Leaf Water Content (RLWC) (71%), leaf area index (LAI) (3.2 and 4.2 at 60 and 90 DAS), chlorophyll content index (30 DAS) and head diameter (16.70 cm). For most of the growth and phenological parameters, T9 and T10 were at par with each other. T1 (no nitrogen) was the earliest to complete its life cycle which is reflected in 50% heading (65 days) and days to maturity (97 days). Dry matter accumulation varied at different time intervals, initially, it was highest in T3 but later T9 and T10 showed the maximum values. In terms of seed yield, test weight and chaffy grain percentage (%), T9 showed the best results: (1505 kg/ha), (54 g/1000 seeds) and (20%) respectively, followed by T10. Whereas the highest stover yield was recorded in T10. The highest Benefit to Cost ratio (B:C ratio of 1.60) was obtained in the T9.