Journal of Experimental Agriculture International

Sunflower productivity is influenced by nitrogen management, whereas the contribution of foliar nano urea under irrigated black-soil conditions requires assessment. A field experiment was conducted during the rabi season of 2023–24 on black soil at the Regional Agricultural Research Station (RARS), Nandyal, under irrigated conditions to evaluate the efficacy of foliar-applied nano urea in combination with different nitrogen management practices in sunflower (Helianthus annuus L.). The experiment was laid out in a randomised block design with seven treatments and three replications, using the sunflower variety NDSH-1012. The treatments included a control (T₁), foliar application of nano urea at 4 ml l⁻^{1 of} water twice at 30 and 55 DAS (T₂), 25% RDN through urea as basal + foliar spray of nano urea at 4 ml l⁻^{1 of} water twice at 30 and 55 DAS (T₃), 50% RDN through urea as basal + foliar spray of nano urea at 4 ml l⁻^{1 of} water twice at 30 and 55 DAS (T₄), 75% RDN through urea as basal + foliar spray of nano urea at 4 ml l⁻^{1 of} water twice at 30 and 55 DAS (T₅), 100% RDN through urea as basal + foliar spray of nano urea at 4 ml l⁻^{1 of} water twice at 30 and 55 DAS (T₆) and 100% RDN through urea in three splits as basal, 30 and 55 DAS (T₇). Nitrogen management significantly influenced SPAD chlorophyll readings, head diameter, number of seeds head⁻¹ and seed yield. The highest SPAD reading at 60 DAS (49.7) was recorded with 100% RDN through urea in three splits (T₇), followed by 100% RDN through urea as basal + foliar spray of nano urea at 4 ml l⁻^{1 of} water twice at 30 and 55 DAS (T₆) (48.1). The same treatment recorded the highest head diameter (17.6 cm), number of seeds head⁻¹ (905) and seed yield (2084 kg ha⁻¹). Application of 100% RDN as basal along with two foliar sprays of nano urea (T₆) also recorded high values for head diameter (16.25 cm), seeds head⁻¹ (856) and seed yield (1892 kg ha⁻¹). Foliar application of nano urea alone resulted in only a modest improvement in seed yield over the control. Plant height was not significantly influenced by the treatments, whereas the major yield attributes and seed yield showed significant differences among treatments. The results indicated that adequate and timely nitrogen supply is essential for maintaining chlorophyll status, improving head development and enhancing seed yield of rabi sunflower. Under the conditions of the present study, application of 100% RDN through urea in three splits proved effective, while foliar nano urea showed potential as a supplementary nitrogen-management practice.