Effects Of Phosphate-solubilizing Bacteria And Controlled Release Fertilizer On Phosphorus Actives Of Soil

Phosphorus (P) is one of three major nutrients in crop productivity for its involvement inmany essential processes. Most of the soils, phosphate was present in unavailable forms dueto complex formation with Ca, Mg, Fe, Al or Mn. The continuing application of large amountof soluble P fertilizer to soil results in accumulation of phosphorus in most of cultivated soils.Controlled release fertilizer can release phosphate nutrient slowly, making P more available toplant. Phosphate-solubilizing bacteria can release special matters to make fixed phosphateavailable for plants. Controlled released fertilizer and phosphate-solubilizing bacteria shouldbe used together to reduce the costs of fertilization. The research results were as follows:1) In Tai Lake Zhihugang Region, organic matters of soil samples were as high as20-69.5g/kg (97.8%of93samples) with great fertilities; The total nitrogen contents of89.5%of95soil samples were as high as1.5-4.4g/kg; Olsen-P contents were30-719mg/kg (92.5%,n=94); The main values of pH were4.5-5.5with54%of92samples.2) There was no significant difference in pH values of leachate in different treatmentsafter late stage of experiment, but the pH value in leachate of two organic fertilizer (madefrom digested livestock manure) treatments were lower than other treatments during prophase.The peaks of electrical conductivity (EC), total nitrogen, and water-soluble phosphorusconcentration in leachate were occurred on the simulated irrigation period, and that oftreatments treated by controlled release fertilizer (CRF) were lower than other treatments. Therate of N loss of farmers’ fertilization practice (FFP) was highest among other treatments as68.98%, and that of treatments treated with controlled released fertilizer were significantlylower than other treatments, the lowest of that was24.46%, respectively. The forms of N inleachate were mainly nitrate for CRF and common fertilizer (CF) treatment, and amide-nitrogen or organic nitrogen for other treatments. Compared with other no-organic fertilizertreatments, adding organic fertilizer significantly increased the total phosphorus leachingamount and water-soluble phosphorus concentration. Total phosphorus loss from thetreatment of farmer’s traditional fertilization was16.73times of that from the CRF treatment.The promotion of CRF in Zhihugang Region of Tai Lake could decrease leaching loss of Nand P, and reduce pollution of ground water. 3) There were significantly differences on the release of nitrogen and phosphorus fromcontrolled release fertilizer in the field compared with laboratory conditions (water as matrix;25℃). Nutrient release in water at the temperature of field is more comparable than25℃.4) Twenty phosphate-solubilizing bacteria (PSB) were isolated from rhizospheres ofcalcareous soils. These isolates were identified by sequence analysis of16S rRNA genes asbacterial species of Bacillus megaterium (B. aryabhattai), Bacillus subtilis, Pseudomonasaeruginosa, Rhizobium sp., Acinetobacter sp., and Pseudomonas oryzihabitans.5) Seven of these isolates were evaluated with the National Botanical ResearchInstitute’s Phosphate (NBRIP) plate culture, NBRIP liquid culture, and real soil incubation.Results showed that halo zone formation by PSB on NBRIP plates was a good indicator forscreening PSB, but not good enough to quantify capability of P solubilization because of poorcorrelation between sizes of halo zone and water soluble P (WS-P). The NBRIP liquidmedium culture showed four PSB strains lowered medium pH (<4.3) and released WS-P up to523.69mg/l with three days incubation and Pseudomonas aeruginosa Krome3straindissolved95.3%tricalcium phosphate added after35days incubation. Incubation of PSB in asandy soil showed that PSB increased WS-P, but no Mehlich-3P (M3-P). Therefore, each ofthree culture practices has strength and weakness for charactering PSB and performing allthree tests provide the better understanding of PSB.6) Soil samples from the Pineland and nearby farmlands (vegetable fields and tropicalfruit groves) were sequentially extracted for water soluble P; exchangeable P; Al-and Fe-bound P; Ca-and Mg-bound P; NaOH-extractable organic P; and residual P. Phosphorusconcentrations were higher in each fraction of the farmed soils than in corresponding fractionsof the unfarmed soils. The unfarmed sites contained96.72%residual P. In the farmed sites,the Ca-and Mg-bound P fraction was the largest, ranging from63.70to75.60%of total P,and the residual P fraction was the second largest.7) We didn’t find any differences on plant growth conditions and Olsen-P content in soils,during tomato growing, even the phosphate-solubilizing bacterial strains were inoculated torhizosphere soils every week.