N. Pruthviraj, V. Lakshmi
Background: Efficient boron and sulphur delivery is important for sunflower productivity, but the combined effects of green-synthesised nano formulations applied through seed priming and foliar spraying on nutrient-efficiency indices remain poorly defined. Objective: This study evaluated the individual and interactive effects of nano boron nitride and nano sulphur sources, concentrations and application methods on nutrient-use, agronomic and production efficiencies in sunflower. Methods: Two field experiments were conducted during the 2019 and 2020 rabi seasons at Bengaluru, India. A two-factor factorial design comprised four seed-priming treatments and six foliar treatments applied at the ray floret stage, together with recommended-fertiliser and recommended-package controls. Each response variable was analysed separately by factorial analysis of variance; after confirming the homogeneity of error variances, data were pooled across years. Year-wise and pooled means, standard error of the mean and critical difference at P = .05 are presented in Tables 1–2. Results: Seed priming, foliar treatment and their interaction significantly affected the evaluated efficiencies. Green-synthesised nano boron nitride seed priming at 1500 ppm combined with foliar green nano sulphur at 600 ppm plus green nano boron nitride at 1500 ppm (S₃F₅) produced the highest pooled partial factor productivity of N, P and K (39.9, 39.9 and 57.4 kg seed kg⁻¹ nutrient applied), approximately 115–116% higher than the recommended-fertiliser control. Green nano sulphur seed priming at 600 ppm produced the highest main-effect agronomic efficiency (3431 kg additional seed kg⁻¹ nutrient applied), while S₁F₅ produced the highest pooled production efficiency (186 kg ha⁻¹ day⁻¹). Discussion and Conclusion: The lower-dose green formulations generally outperformed their higher-dose commercial counterparts, indicating that formulation, concentration, timing and combined application influenced nutrient conversion into seed yield. The S₃F₅ strategy is promising for improving N, P and K partial factor productivity, whereas green nano sulphur contributed strongly to agronomic efficiency. Multi-location validation, environmental-safety assessment and economic analysis are recommended before field-scale adoption.