Nitrogen Fertilizer Requirement and Use Efficiency in Sunflower at Ganges Delta Coastal Salt-Affected Soils

Sunflower, third most important oil seed crop having high potential to grow in the coastal salt-affected seasonal fallow lands of the Ganges river delta, its nitrogen fertilizer requirement, and use efficiency yet not defined for the region. The main objective of the experiment was to determine optimum rate of nitrogen (N), which maximizes yield and N use efficiency. The field experiment was carried out in dry-season of two consecutive years (2020 and 2021). The randomized complete block design model was employed to prepare the layout of the experiment where all the treatments were replicated thrice. Eight rates of N comprising 0, 21, 42, 63, 84, 105, 126 and 147 kilogram N per hectare (kg N ha(-1)) were the treatments in the experiment. Statistically higher grain yield (3.49 ton per hectare; t ha(-1)), straw yield (7.47 t ha(-1)), number of seeds head(-1) (1195), 1000-seed weight (74.4 gram; g) and total N uptake (197 kg ha(-1)) was found in 126 kg N ha(-1) rate. This rate had partial factor productivity of 26 kg grain kg(-1) added N, agronomic use efficiency of 14.2 kg grain kg(-1) added N, physiological use efficiency of 13.9 kg grain kg(-1) N uptake and recovery efficiency of 1.04 kg N uptake kg(-1) added N. The 126 kg N ha(-1) was therefore recommended to grow sunflower in the seasonal fallow coastal salt-affected lands of the Ganges river delta.