Isolation Of Highly Effective Phosphate Solubilizing Bacterial Strains And Their Biological Effect On Application

Phosphate solubilizing microorganisms which can transform unsoluble phosphate into available forms, and thus improve the phosphorus nutrition of plants take an important part in phosphorus cycling in calcareous soil.This reseach begins with isolating and screening phosphate solubilizing bacteria(PSB), by using modified PVK plate method. A total of forty-four strains of phosphate solubilizing bacteria were isolated from the root surface of wild plants grown well in calcareous soil. In a liquid medium (NBRIP), total P concentration in the culture of the isolate K3 reached 643.2μg·mL^-1, including available P of 584.8μg·mL^-1. It was found that 12.9% of tricalcium phosphate was dissolved after 7-day incubation with the inoculum of the K3 bacterium, which was 10.5 times higher than that in CK. The total P concentration in the culture of the strain K9 was observed as 608.5μg·mL^-1 with available P reaching 606.4μg·mL^-1. Strains K3 and K9 were sorted to Pseudomonas and Enterobacter, respectively, through biochemical and 16S rDNA analysis. Other strains also have good ability to dissolve unsoluble phosphate, Such as K4, Total P concentration in the culture of K4 reached 638.27μg·mL^-1, including available P of 597.01μg·mL^-1. It was found that 12.75% of tdcalcium phosphate was dissolved after 7-day incubation with the inoculum of the K4. Strain Y10, Total P concentration in the culture of Y10 reached 632.48μg·mL^-1, including available P of 564.26μg·mL^-1. It was found that 12.62% of tricalcium phosphate was dissolved after 7-day incubation with the inoculum of the Y10. Statistic result showed that there are no significants among these strains, thus choose K3 with high total P concentration and K9 with high available P as materials to do the next job.In pot experiments, the height, diameter and dry weight of corn seedlings had significant difference between CK and the treatments with the addition of PSB strains. When the soil was inoculated with PSB-inclusive organic fertilizers, the corn seedlings showed significant differences in dry weight among three treatments including PSB-inclusive organic fertilizer, organic fertilizer and CK. But the difference of soil available P were not significant in the three treatments. Both the manure with treatment and PSBs' treatment, The number of PSB in corn rhizosphere added with either PSBs plus organic fertilizer or PSBs are significantly higher than in bulk soil. Culture solution of PSB could promote germination energy and germination percentage of corn. The pH value of the culture solution with PSB dropped quickly in the culture of NBRIP medium, but the pH went up slowly in LB medium.In order to apply and extend the achievements, some experiments about PSBs storage were done. Quantities and activities of PSBs during the storage period differed a lot in different organic absorbents. The number of PSB in lees processing by-product compost was 10⁷ g^-1 after 45 days storage in room temperature. The cultural product of K3+K9 was tested in JiangSu Center for Diseases Prevention and Control and the results shoewed they belonged to low toxicity and could be released to the environment.