Ridge and Furrow Sowing Method with Close Spacing Reduces the Salinity Effect of Sunflower Production in the Ganges Delta

Coastal areas of the Ganges delta require optimization of agronomic practices to reduce the salinity effect on the crop production that can support the "Bangladesh Delta plan 2100". The present study was conducted in the Rabi seasons of 2018-19 and 2019-20 to determine the optimum sowing method and plant spacing of sunflower (variety Hysun 33) in the saline area of Bangladesh. Two sowing methods: flat bed sowing and ridge and furrow sowing and; three plant spacings: 40 cm × 25 cm, 50 cm × 25 cm and 60 cm × 25 cm were laid out in a randomized complete block design with three replications on a farmer's field at Dacope, Khulna. Results showed that although method of sowing had no significant effect on the yield of sunflower the ridge and furrow sowing method reduced the soil bulk density and soil salinity and increased the soil water holding capacity and solute potential significantly. Plant spacing and planting system (interaction of sowing method × plant spacing) had significant effects on growth and yield of sunflower. Plant spacing 50 cm × 25 cm produced the highest sunflower seed (2233 kg ha-1) by achieving optimum plant population to utilize the resource. Planting system: ridge and furrow sowing at 50 cm × 25 cm spacing had the lowest soil salinity (4.01 dS m−1) and soil bulk density (0.90 Mg m-3) which leads to highest solute potential (-380 KPa) and highest soil water holding capacity (21%, w/w) at 85 days after sowing of sunflower. This planting system had the highest crop growth rate (24.4 g m-2 day-1) that ultimately produced the highest grain weight per head (36 g) and seed yield (2274 kg ha-1) of sunflower. Ridge and furrow sowing at 50 cm × 25 cm can be effective for achieving maximum yield of sunflower in the Ganges tidal floodplain of Bangladesh.