NUTRIENT SOLUTION BICARBONATE CONCENTRATION EFFECTS ON GROWTH MEDIA pH, ELECTRICAL CONDUCTIVITY, AND ON FLUE-CURED TOBACCO YIELD AND QUALITY FOR TRANSPLANTS PRODUCED IN A HEATED GREENHOUSE IN A DIRECT-SEEDED FLOAT SYSTEM

Abstract The effects of bicarbonate (HCO3−) concentrations on the production of flue-cured tobacco seedlings in a direct-seeded float greenhouse system were investigated and compared to seedlings produced in muck seedbeds over a three-year period. The HCO3− concentrations used (0, 100, 200, 400, and 800 mg/L) were created and maintained at the desired levels by acidification with H2SO4 or by addition of NaHCO3 to tanks containing 100 L of fertilized groundwater. Each 100 L tank (treatment) contained four 253-cell foam trays and was located in a heated and forced-air ventilated double-poly greenhouse maintained at 15° to 30°C. Excellent quality seedlings were produced in all treatments except the 800 mg/L HCO3−. Initial nutrient solution pH varied with HCO3− concentration and declined linearly with time for all treatments. Initial plug media pH also varied with HCO3− concentration; pH increased for about 25 d then declined to a level just above that of the nutrient solution pH. Changes in solution and plug...