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Abstract

Interactive effects of plant growth-promoting rhizobacteria and manuring on the phosphorus supply of Zea mays L. and Brassica napus L.

The organic matter supply can promote the dispersal and activity of applied plant growth–promoting
rhizobacteria (PGPR), but the complementary effect of organic fertilization and PGPR
application on the turnover of P is scarcely known. The effects of the application of two PGPR
strains (Pseudomonas fluorescens strain DR54 and Enterobacter radicincitans sp. nov. strain
DSM 16656) alone and in combination with organic fertilization (cattle manure and biowaste
compost) on growth and P uptake of maize (Zea mays L.) and oilseed rape (Brassica napus L.)
were investigated under semi–field conditions. Furthermore, P pools and phosphatase activities
in soil and the arbuscular mycorrhizal–fungi colonization of maize roots were examined. The
organic-fertilizer amendments increased the growth and P uptake of both plant species and the
soil P pools. The application of the E. radicincitans strain increased P uptake of oilseed rape
when no organic fertilizer was added. Furthermore, the application of both bacterial strains increased
the activities of phosphatases under both plant species. Here, the effect of the PGPR
application even exceeded the effect of organic fertilization. The magnitude of this effect varied
between the different fertilizing treatments and between the two bacterial strains. Phosphatase
activities were increased to the greatest extent after application of P. fluorescens in the unfertilized
soil. Under rape increases of 52% for acid phosphatase activities (ACP), 103% for alkaline
phosphatase activities (ALP), and 133% for phosphodiesterase (PDE) were observed therewith.
In the unfertilized soil, the application of P. fluorescens also resulted in a strong increase of the
arbuscular mycorrhizal colonization of maize. We conclude that application of PGPR can promote
the P mobilization and supply of crops in P-deficient soils, however, in combination with
organic fertilization these effects might be masked by a general improved P supply of the crops.
Interactive effects of applied bacterial strains and organic fertilization depend on the sort of
organic fertilizer and crop species used.



Krey, T.; Caus, M.; Baum, C.; Ruppel, S.; Eichler-Löbermann, B. 2011. Interactive effects of plant growth-promoting rhizobacteria and manuring on the phosphorus supply of Zea mays L. and Brassica napus L. Journal of Plant Nutrition and Soil Science 174 (4), 602-613.