ISHS Acta Horticulturae 294: II Symposium on Horticultural Substrates and their Analysis, XXIII IHC
INFLUENCE OF NATURE AND PHYSICO-CHEMICAL PROPERTIES OF SUBSTRATES ON THE BACTERIZATION WITH PSEUDOMONAS FLUORESCENS |
| Authors: | B. DIGAT, F. LEMAIRE |
| Abstract:
In soilless cultures, most materials used as substrates are microorganisms-poor because of their making process. To avoid future contamination by pathogenic or deleterious microorganisms, it seems interesting to supply substrates with beneficial ones for example bacteria such as PGPR before and during the growing. Dynamics of a bacterial population of Pseudomonas fluorescens-putida, chosen because of its antagonistic effects on the pathogen microflora and its promoting effect on the plant growth, have been studied in different kinds of substrates : sphagnum peat, french brown peat, Hortifibre, pine barks, sand, vermiculite, perlite, rockwool in sterilized or non-sterilized conditions. Bacteria inoculum has been introduced in form of granules. The effects of pH, salinity, form and amount of nitrogen in the substrate have been tested on to the establishment of the bacteria without plant. Moreover, an experiment of bacterization of two substrates (Hortifibre and rockwool) has been made in conditions of cucumber soilless growing. In sterilized organic substrates, Pseudomonas population was higher than that of non-sterilized materials and the level of bacteria was keeping the same value from the day 60th except in the pine barks where it gradually decreased with the time. In the mineral substrates, higher bacterial population was in vermiculite. In the non sterilized mineral substrates, the kind of substrate acted on the dynamic of bacteria released from the granules : quick in vermiculite and perlite, slower in sand, none in rockwool during the first four days after inoculation. Then, the bacterial population increased in rockwool, became stable in vermiculite and perlite and decreased in sand. pH, salinity, nitrogen form and amount had little influence in the experiment conditions: ph 5 and 7 ; osmotic pressure, 1 and 10 bars ; nitric and urea nitrogen amounts (22 and 90 mg/1). During the Cucumber growing, the study of dynamics of Pseudomonas population pointed out that it was necessary to make several boosters to maintain a satisfactory level of bacterial inoculum. | |
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