Fig. 6

The survival and available phosphorus content of different biochars-immobilized phosphorus-solubilizing bacteria Pseudomonas sp. NK2-GFPuv applied to soil for 1 and 30 days. A Bacterial population of NK2-GFPuv in soil after 1 and 30 days. Bars correspond to one standard deviation (SD) from the mean (n = 3). B The survival rate of NK2-GFPuv after 30 days of soil application, calculated as the ratio of bacteria population at 30 days to that at 1 day. Bars correspond to one standard deviation (SD) from the mean (n = 3), while different letters above columns indicate significant differences (P < 0.05) among samples under different treatments according to a one-way ANOVA in conjunction with Tukey’s multiple-comparison test. C Content of available phosphorus of biochar-immobilized NK2-GFPuv applied to soil after 1 and 30 days. CK indicates untreated soil. Bars indicate one standard deviation (SD) form the mean (n = 3), while asterisks indicate significant differences (P < 0.05) derived from a two-way ANOVA in conjunction with Dunnett’s multiple-comparison test in comparison with available phosphorus of CK at the same time points. ***P < 0.001; ****P < 0.0001; ns no significant differences. D Net increase of available phosphorus content at 30 days compared with 1 day. Bars indicate one standard deviation (SD) from the mean (n = 3), while asterisks indicate significant differences (P < 0.05) derived from a one-way ANOVA in conjunction with Dunnett’s multiple-comparison test in comparison with the net phosphorus increase of NK2-GFPuv. ***P < 0.001; ****P < 0.0001; ns no significant differences. E Correlation between net increase of available phosphorus and survival rate of strains in soil