Abstract
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 <em>Solanum lycopersicum</em>. <em>Helianthus annuus</em>, <em>Zea mays</em> and <em>Phasaeolous vulgaris</em> had a relatively larger effect on the decrease of available P in the rhizosphere soil and in the soil adhering to the root mats. <em>S. lycopersicum</em> and <em>P. vulgaris</em> had the highest P concentration (&gt; 980 mg kg<sup>-1</sup>) and <em>H. annuus</em> and <em>Z. mays </em>had the highest P uptake (17.62 mg pot<sup>-1</sup> and 13.13 mg pot<sup>-1</sup>, respectively). The mean soil microbial biomass P (MBP) was significantly high in the rhizophere soil and in the soil adhering to root mats of <em>T. aestivum</em>, <em>Z. mays</em>, <em>S. tuberosum</em> and <em>S. lycopersicum</em> (&gt; 16 mg kg<sup>-1</sup>). The mean spore numbers of glumales (SNG) were significantly high in the rhizophere soil and in the soil adhering to root mats of <em>P. vulgaris</em>, <em>S. lycopersicum</em>, <em>T. aestivum</em> and <em>Z. mays</em> (&gt; 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.
Highlights
Phosphorus deficiency is one of the major limiting nutrition problems for plants, in both acidic and calcareous soils where P retention and precipitation is greatest (Marschner 1995; Hinsinger 2001)
In order to determine which mechanism was more important in P acquisition by plants in calcareous soils, we examined the correlations between available P and soil pH, microbial biomass P (MBP), alkaline and acid phosphatase activities and spore numbers of glumales in the rhizospheric and nonrhizospheric soil of 10 different plant species under glasshouse condition for a better understanding of the importance of different mechanisms in P acquisition by plants with the use of thin slicing technique
The highest alkaline phosphatase activity was measured in the rhizosphere soil and in the soil adhering to root mats of P. vulgaris and L. sativum
Summary
Phosphorus deficiency is one of the major limiting nutrition problems for plants, in both acidic and calcareous soils where P retention and precipitation is greatest (Marschner 1995; Hinsinger 2001). Plant phosphorus absorption depends on its concentration gradient and diffusivity in the soil near the roots. Guo et al (2000) reported that continuous cropping of maize (Zea mays L.) and soybean (Glycine max [L.] Merr) on different tropical soils loaded with high dose of fertilizer P highly depleted the labile and moderately labile inorganic P (Pi) fractions. These authors stated that the organic P (Po) and stable P fractions remained almost constant at the end of 14 crop harvests except the labile Po in a Mollisol that was highly depleted. It was reported that growing alfalfa (Medicago sativa L.) for 66 days highly depleted the native labile Pi in the rhizosphere of different soil orders without affecting the Po fractions (Crews 1996)
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