Effects of long-term phosphorus application and plant-growth promoting rhizobacteria on maize phosphorus nutrition under field conditions

Bacteria are capable to increase the plant availability of phosphorus (P) in soil. This study investigates the impact of a ten-year continuous application of organic and inorganic P fertilizers on P nutrition of maize and whether there occur beneficial interactions with plant-growth promoting rhizobacteria (PGPR) under field conditions.The experiment, established in 1998, included three fertilizer treatments (biowaste compost, cattle manure, and triple superphosphate-TSP) and a control (no P) as main plots. In 2007 and 2008 all main plots were divided into three sub-plots (no PGPR, Pseudomonas fluorescens, Enterobacter radicincitans). The impact of periodically applied organic fertilizers on plant traits and soil P pools was within the same range or higher than that of the annually applied TSP. The organic fertilizers also increased the activity of alkaline phosphatases in the soil considerably. The fertilizers impact was greater on the soil P pools than on the plant P uptake. Application of PGPR also affected soil and plant characteristics, whereas the P. fluorescens strain increased the easily available P in the soil and the mycorrhiza colonization of maize roots to a greater extent than the E. radicincitans strain. The P. fluorescens strain also promoted maize growth, however, more effectively in the non-amended control. We conclude that P fertilizers and PGPR should be applied separately rather than in combination.

► We examined the effect of compost, manure, and TSP and two bacteria strains (PGPR).
► The impact of organic fertilizers was larger or similar than that of TSP.
► The impact of the fertilizers was more pronounced on soil properties.
► Organic fertilizers had a similar impact on soil P as Pi fertilizers.
►  Effects of PGPR applications were smaller than those of P application.