Effects of the rhizosphere bacterium Pseudomonas fluorescens 20 and the endomycorrhizal fungus Glomus mosseae on the yield and growth of the radish, as a function of mineral nutrition.

摘要

Inoculation of radishes with Pseudomonas fluorescens 20 and Glomus mosseae was investigated with regard to applications of mineral fertilizers, crop yield, growth rate and intensity of photosynthesis, for radishes cultivated either in a controlled environment (RADC) or in field trials (RADF). RADC were grown in pots of air-dried floodplain soil from the River Oka (in the south of the Moscow oblast', Russia), under the following conditions: artificial illumination from 08.00 to 20.00 h; relative humidity of 70-80%; soil moisture content of 60-80%; and air temperatures of 18-20鳦 from sowing to the appearance of shoots, 10鳦 for 240 h after the appearance of shoots, and then 18-20 and 10鳦 for periods with and without illumination, respectively, prior to harvesting. Field trials were also carried out in which radishes were cultivated in pots (without bottoms) of grey forest soil. Activity of microorganisms (evaluated in terms of CO2 gas exchange) depended on the form of mineral N and quantity of NPK fertilizers applied. Inoculation of radishes with P. fluorescens 20 (against a background of nitrate fertilizers) resulted in higher yields than inoculation with G. mosseae. Mycorrhization of radishes was more effective in conjunction with ammonium fertilizers than with nitrate fertilizers. Inoculation with microorganisms in conjunction with increasing applications of NPK fertilizers did not increase yields. Inoculation with microorganisms allowed applications of NPK fertilizers to be reduced by 1.5 times without causing reductions in yields. The significance of the form of mineral N for effectiveness of mycorrhization was determined by levels of illumination experienced by plants.