Influence of Incorporation Rates of Sulfur on Reduction of the Bicarbonate Injury in Hydroponic Cultivation of 'Ssanta' Strawberry

This research was conducted to determine the influence of incorporation levels of sulfur into a coir dust+pine bark medium (1:1, v/v) on the changes in the bicarbonate (HCO3 - ) concentrations and pH of soil solution, crop growth, and nutrient uptake of 'Ssanta' strawberry. In the preparing of the mixed medium, sulfur powder was added with the rate of 0 (control), 0.23, 0.45, 0.90, and 1.80 g·L-1 and Hoagland nutrient solution containing 240 mg·L-1 HCO3 - was supplied during the crop cultivation. The growth measurements and tissue analysis for the determination of nutrient contents were carried out 140 days after solution application and the soil solution analysis was performed every two weeks. As the level of sulfur was elevated, the overall growth of mother plants became better showing that the growth indexes except chlorophyll contents were the lowest in control treatment but the statistical differences were not found among the three treatments of 0.45 g·L-1 or higher sulfur. The higher the levels of sulfur incorporation, the higher the occurrence of runners and the growth of daughter plants. The length of the runners and the number of daughter plants occurred per mother plants were higher in the treatments of 0.90 and 1.80 g·L-1 than the three treatments of 0, 0.23, and 0.45 g· L-1, but the statistical differences were not observed between the 0.90 and 1.80 g·L-1 treatments. The rose of pH and HCO3 - concentrations in soil solution of root media continued all the cropping period, but those decreased slightly in the treatments of 0.90 g·L-1 or higher. The soil solution concentrations of K+ and PO4 3- in the treatments of 0.90 and 1.80 g·L-1 was lower than those in other treatments and the statistical differences in the Ca2+ and Mg2+ concentrations were not observed among all treatments. The nutrient contents in tissue analyzed in this experiment were the lowest in the control treatments and those increased as incorporation rates of sulfur were elevated. Above results indicated that when 'Ssanta' strawberry is grown hydroponically and the root medium is coir dust and the pine bark (5:5, v/v) mix, the sulfur incorporation rate as pre-planting fertilizer has to be higher than 0.9 g·L-1 root medium to reduce the HCO3 injury.