The Research Of Screening And Identification Of Three Affinity For Purplish Soil Of PGPR And Its Application

PGPR (nitrogen-fixing bacteria, phosphate-solubilizing bacteria and potassium-solubilizing bacteria) were isolated on selective medium from the purplish soil of Beibei, Chongqing in the research. Target strains which had the corresponding abilities were screened out. Then PGPR strains were identified by a serious of morphological, physiological and biochemical and 16s rDNA analysis, respectively. Pot experiment by a single vaccination was applied to study whether the PGPR could promote the growth of Chinese cabbage. PGPR complex microbial inoculants which were mixed by PGPR and sterilized peat were developed to study the reduction of fertilizing amount during growth process of Actinidia seedlings. Then, added the PGPR to the cow fermented dung to research the influence of the growth and quality of ginger seedlings.This research provided a theoretical basis for developing the potential of purple soil, furthur studying on the classification of microorganisms of purple soil, and tapping the high affinity microbial fertilizer.(1) Six nitrogen-fixing bacteria, six phosphate-solubilizing bacteria and five potassium-solubilizing bacteria strains were screened from purple soil through Ashby nitrogen-free medium, phosphate-solubilizing selective medium and potassium-solubilizing selected medium, respectively. Among these strains, N3, P1 and K2 were proved to possess a strong ability to fix nitrogen, dissove phosphorus and decompose potassium. And the amount were reached at 91.5 mg/L,128.7 mg/L and 23.2 mg/L after seven days later through liquid cultivation, respectively. Through morphological, physiological and biochemical, and molecular biology analysis, N3, PI and K2 were identified as B.amyloliquefaciens sp. (named as XD-N-3), B. pumilus sp. (named as B. pumilus XD-P-1) and B. circulans sp. (named as B. circulans XD-K-2).(2) The results of the growth-promoting effect of PGPR on Chinese cabbage showed that these treatments that inoculated with XD-N-3, XD-P-1 and XD-K-2 can significantly promote the growth of Chinese cabbage. Comparing with the CK5, the treatment that vaccinated with XD-N-3 can significantly improve the stem diameter, total root length of Chinese cabbage, and remarkably improve the total nitrogen nutrient content of purple soil, which increased by 15.54%,166.73% and 12.02%, respectively. XD-P-1 can remarkably enhance the plant height and leaf area of Chinese cabbage, and improve the content of soluble phosphorus of purple soil, which increased by 25.36%、 83.50% and 36.69% respectively. XD-K-2 can significantly enhance the plant height and leaf area of Chinese cabbage, and improve the content of soluble potassium of purple soil, which increased by 22.61%、72.32% and 34.06%, respectively. The results indicated that the efect of XD-N-3, XD-P-1 and XD-K-2 were as well as nitrogen fertilizer, phosphatic fertilizer and potash fertilizer. Above all, the isolated PGPR showed a high affinity to purple soil and promoting effection, and could be used as candidate strains of microbial fertilizer.(3) Compared with the treatment that with non-inoculants, two treatments that inoculated with PGPR compound inoculants can significantly promote the growth of Actinidia seedlings, and increase the number of culturable microorganisms. Under the condition that fertilized with half amount of fertilizer and PGPR compound, the leaf area of Actinidia and the number of culturable bacteria were remarkably higher than the treatment that only fertilized with PGPR compound inoculants, which were as much as 24.28% and 59.65% respectively. Furthermore,50%NPK+PGPR treatment can significantly improve the nitrogen content of the overground part, and the phosphorus of the underground part of,Actinidia seedlings, and increase the content of soil organic matter and effective phosphorus, which were as much as 34.55%,21.99% and 13.09%, 7.69% respectively. The results indicated that PGPR colonized largely and showed high affinity to purple soils under low fertilit. Through its own life activity and a variety of metabolism, PGPR could promote the growth of Actinidia and reduce the use of fertilizer. Therefore, our findings can provide some theoretical basis for application of practical production.(4) PGPR biological fertilizer treatment can significantly improve the leaf area of ginger seedlings, gingerol content, the number of culturable bacteria and phosphate-solubilizing bacteria of root soil than the normal biological treatment, which increaced by 45.92%,15.38%,192.24%,246.48% respectively. It is showed that PGPR biological fertilizer not only can promote the growth and increase gingerol content of ginger seedlings, but also can significantly increase the number of culturable microorganisms of root soils. While the effect depends on the types of biological fertilizer, and PGPR showed higher affinity to the purple soil than others. Comparing to the normal biological treatment, PGPR biological fertilizer treatment can remarkably improve the potassium content of the overground part, phosphorus content of the underground part of ginger seedlings, and available phosphorus of the root soils, which increased by 22.22%,16.67% and 91.08%, respectively. The results indicated that PGPR biological fertilizer can promote the ginger seedlings to absorb nutrient content, as well as to improve the utilization of soil nutrients.