Growth and Yield Responses of Tomato ( Lycopersicon esculentum ) Grown under Soilless Cultivation to Application of Azospirillum, Azotobacter and Nitrogen

THIS STUDY was undertaken to investigate the possibility of .using Azospirillum brasilense and Azotobacter chroococcum applied with inorganic nitrogen to enhance tomato (Lycopersicon esculentum, Mill) production in soilless systems.The effect of inoculation with A. brasilense and / or Azoto. chroococcum with the application of 75 % (of the recommended dose) of N2 on certain tomato growth parameters (shoot height, number of leaves, and fresh and dry weights of plants) after 30, 60 and 90 days of transplanting were determined. In addition, total yield, mean fruit weight, and the number of fruits per plant were evaluated in plants inoculated with the two bacteria (separately or in combination) with 75 % N2, and plants inoculated with 75 % N2 (control 1) and 100 % N2 (control 2). Plants inoculated with a mixed inoculum of A. brasilense and Azoto. chroococcum with 75 % N2 gave the highest values of the growth parameters tested while plants inoculated with 75 % N2 (control 1) gave the lowest. The same treatment also resulted in the highest tomato yield, mean weight and number of fruits per plant followed by plants treated with A. brasilense and 75 % N2. The responses to the tested biofertilizers on nitrogen, phosphorous and potassium (NPK) uptake, the population of diazotrophic bacteria and nitrogenase and dehydrogenase activity of the tested bacteria on the rhizosphere of tomato showed that the mixed inoculum of A.brasilense and Azoto. chroococcum with 75 % N2 gave the highest NPK uptake levels after 30, 60 and 90 days of transplanting. The same treatment gave the highest population of diazotrophic bacteria and dehydrogenase and nitrogenase activity of the tested bacteria compared with the plants inoculated with a single organism or controls. In contrast, control 1 gave the least values among all treatments. This study shows that inoculation of tomato plants with Azospirillum brasilense and Azotobacter chroccocum have a significantly beneficial effect on tomato yield under soilless cultivation.