The relationship between available P and selected biological properties in the rhizosphere of ten crop species under glasshouse conditions

The aim of the present study was to evaluate the effect of cultivation of 10 agronomic plant species on selected biological activities and bioavailability of phosphorus (P) in different sampling zones. The lowest available P was measured in the planted soil with Solanum lycopersicum. Helianthus annuus, Zea mays and Phasaeolous vulgaris had a relatively larger effect on the decrease of available P in the rhizosphere soil and in the soil adhering to the root mats. S. lycopersicum and P. vulgaris had the highest P concentration (> 980 mg kg-1) and H. annuus and Z. mays had the highest P uptake (17.62 mg pot-1 and 13.13 mg pot-1, respectively). The mean soil microbial biomass P (MBP) was significantly high in the rhizophere soil and in the soil adhering to root mats of T. aestivum, Z. mays, S. tuberosum and S. lycopersicum (> 16 mg kg-1). The mean spore numbers of glumales (SNG) were significantly high in the rhizophere soil and in the soil adhering to root mats of P. vulgaris, S. lycopersicum, T. aestivum and Z. mays (> 167 N/10 g soil). The negative correlations of available P and soluble P with soil biological properties like SNG and alkaline phosphatase activity and the positive correlation with soil pH shows the importance of rhizomicroorganisms and glumales on P nutrition by plants in calcareous soil. Thus rhizosphere acidification of calcareous soil may not be as important as the improvement of biological properties in P uptake and acquisition by plants.