Phosphorus Availability

The usefulness of Mehlich 3 (M3) reagent was evaluated as a method to extract numerous elements from coalmine soils in As Pontes (Spain) showing a wide range of physicochemical properties. Critical levels (deficiency and/or toxicity) were established for plant available elements extracted by this reagent. The M3 method was compared to 1M NH4Cl, Olsen, acid oxalate, and DTPA methods as extractants for exchangeable Ca, Mg and K, available P, non-crystalline aluminium, and available heavy metals, respectively. The M3 method correlated significantly to NH4Cl for Ca, Mg and K (r=0·76, 0·84 and 0·87, respectively), to Olsen P (r=0·77) and to oxalate Al (r=0·77). Significant correlations were found between Fe, Cu, Zn and Cd extracted by M3 and DTPA; for Mn, Ni, Co and Pb different relationship between methods were obtained for acid and alkaline samples, so that critical levels were established for M3 metals as a function of soil pH. Copyright © 1999 John Wiley & Sons, Ltd.

The use of phosphate solubilizing bacteria (PSB) is an ecological strategy that allows for increasing the availability of phosphorus (P) in soil. The objective of this study was to evaluate P availability in wheat, in soils derived from volcanic ash (Andisol and Ultisol,) and inoculated with phosphate-solubilizing Bacillus thuringiensis, the experiment was conducted in pots under greenhouse conditions using a completely randomized design. Wheat plants were inoculated and re-inoculated at 20 and 46 days after sowing (DAS), respectively, with B. thuringiensis; and, soil and plant sampling was performed after 46, 66, and 87 days based on the Zadoks growth scale (Z). The inoculation resulted in an 11% increase in P of the rhizosphere at Z46 (Ultisol), P also increased 34% and 67% in aerial tissues at Z46 (Andisol and Ultisol), respectively, while an increase of 75% was observed in root tissues at Z87 (Ultisol). Similarly, the inoculation resulted in increases in acid phosphatase activity (Andisol), soil microbial biomass (Andisol and Ultisol), and root biomass in plants (Ultisol), without achieving increase of the aerial biomass of the plants. The phosphate solubilizing B. thuringiensis strain showed some positive, but also negative effects in soils and plants, depending on the soil.

The use of phosphate solubilizing bacteria (PSB) is an ecological strategy that allows for increasing the availability of phosphorus (P) in soil. The objective of this study was to evaluate P availability in wheat, in soils derived from volcanic ash (Andisol and Ultisol,) and inoculated with phosphate-solubilizing Bacillus thuringiensis, the experiment was conducted in pots under greenhouse conditions using a completely randomized design. Wheat plants were inoculated and re-inoculated at 20 and 46 days after sowing (DAS), respectively, with B. thuringiensis; and, soil and plant sampling was performed after 46, 66, and 87 days based on the Zadoks growth scale (Z). The inoculation resulted in an 11% increase in P of the rhizosphere at Z46 (Ultisol), P also increased 34% and 67% in aerial tissues at Z46 (Andisol and Ultisol), respectively, while an increase of 75% was observed in root tissues at Z87 (Ultisol). Similarly, the inoculation resulted in increases in acid phosphatase activity (Andisol), soil microbial biomass (Andisol and Ultisol), and root biomass in plants (Ultisol), without achieving increase of the aerial biomass of the plants. The phosphate solubilizing B. thuringiensis strain showed some positive, but also negative effects in soils and plants, depending on the soil.