Growth, Biomass Production and Phosphorus Relations of Sunflower under 4R Management Strategy

Phosphorus (P) is an essential macronutrient required for sunflower growth and development. Adopting a 4R phosphorus framework focusing on the use of P fertilizers in the best of method time, source and dose can foster sustainable sunflower production. A thrice replicated field experiment was conducted in sunflower (cv. Hysun-39) using a split-split plot design with two P application methods (main plots), i.e. banding near seed rows at sowing and broadcasting at land preparation, two P sources (sub plots), i.e. monoammonium phosphate (MAP) and diammonium phosphate (DAP), and five P doses (sub-sub plots), i.e. 0, 30, 60, 90, and 120 kg P2O5 ha⁻¹. The soil under experiment was sandy clay loam, alkaline, slightly saline, and marginal in organic matter and available P. The results revealed that banding was superior to broadcasting in improving shoot length, shoot dry biomass, leaf dry biomass, and P concentration in different plant parts. The growth parameters and P concentration of sunflower was non-significant between P sources (MAP and DAP). Increasing P doses significantly improved growth parameters, with the highest values recorded at 120 kg P₂O₅ ha⁻¹, followed by 90 kg P₂O₅ ha⁻¹, while the lowest values were observed where no P was applied (0 kg P2O5 ha-1). Significant two-way interactions were observed between P methods and doses for shoot length, shoot dry biomass, and root dry biomass, with the highest values at 120 kg P₂O₅ ha⁻¹ applied through banding near seed rows. The interaction between P sources and doses significantly influenced leaf dry biomass, with MAP at 120 kg P₂O₅ ha⁻¹. However, the three-way interaction among P methods, sources, and doses was non-significant for all growth traits and P concentration of sunflower. Phosphorus uptake was significantly influenced by P methods and doses, with the highest uptake recorded under banding near seed rows and 120 kg P₂O₅ ha⁻¹. However, both two-way and three-way interactive effects of P methods, sources, and doses for P uptake were non-significant. The findings suggest that banding near seed rows is the preferable method for P application in sunflower, with MAP being more efficient source. The application of 120 kg P₂O₅ ha⁻¹ is recommended for maximizing growth and P uptake. Future studies focusing on the same aspect under various crops, soil types and environmental conditions are suggested to validate these findings.