Abstract
Sunflower (Helianthus annuus L.) has recently been identified as a promising crop for the seasonally-fallow lands of the coastal region of the eastern Ganges delta; but its fertilizer requirement especially phosphorus (P) for higher yield has not yet been determined. The objectives of the experiment were to find out the optimum P rate which maximizes yield and P use efficiency with minimum positive P balance in soil. Accordingly an experiment was conducted in 2020, 2021 and 2023 using eight P rates having 0, 7.2, 14.4, 21.6, 28.8, 36.0, 43.2 and 50.4 kg P ha−1 in sunflower. The significantly higher achene yield over the years was found in 21.6 to 36.0 kg P ha−1, and 28.8 kg P ha−1 on a pooled yield basis and this rate had a minimum positive P balance (5.9 kg P ha−1). At 28.8 kg P ha−1, the partial factor productivity varied from 90 to 127, and agronomic efficiency of 22 to 49 kg achene kg−1 added P over the years. The P requirement in the coastal ecosystem was lower compared to inland agricultural soils. The 28.8 to 36 kg P ha−1 rate could be sufficient to meet P requirements of sunflower while maintaining P status in salt-affected coastal soils of the eastern Ganges delta.
