SURVIVAL OF PLANT-GROWTH PROMOTING RHIZOSPHERE BACTERIA IN THE RHIZOSPHERE OF DIFFERENT CROPS AND MIGRATION TO NONINOCULATED PLANTS UNDER FIELD CONDITIONS IN NORTHEAST GERMANY

Survival of two plant-growth-promoting bacteria, Pseudomonas fluoresce ns PsIA12 and Rhizobium trifolii R39 (rifampicin-resistant mutants), w as studied in the rhizosphere of different crops in field experiments on loamy sand in the years 1993 and 1994 (Muncheberg, Germany). After seed inoculation with a peat formulation the Rhizobium strain colonize d the rhizosphere of pea and white lupin as well as that of the non-le gumes maize, wheat and rape. While the Rhizobium strain established mo re or less stable populations during the whole vegetation time, the po pulation of the Pseudomonas strain increased with the vegetative plant development and declined with flowering and maturing of the legumes. In the maize rhizosphere this strain was reisolated only in numbers lo wer log 3 cfu g root(-1): Both strains were able to establish small po pulations up to log 4.8 cfu . g root(-1) in the rhizosphere of non-ino culated crops and weeds up to 0.6 m away from inoculated plants.