| Our country is short of potassium resources. The overall potassium fertilizer input in agricultural production is deficiency and the areas of farmlands which are lack of potassium are increasing. Simultaneously, due to potassium’s own characteristics and the unreasonable application in agricultural production, potash is easily leaked with water or fixed by soil, potassium utilization is low. Studying how the plant growth-promoting bacteria, which have growth-promoting characteristics and produce extracellular polysaccharides, affect plant’s efficient use of potassium fertilizer is of great significance to alleviate the pressure of shortage of China’s potassium resources and reduce the harm effect on environment of excessive application of chemical fertilizer.Firstly, the three plant growth-promoting bacteria (Q32, W33, Y1-3-9) chosen as the strains tested were preserved in our laboratory and could produce extracellular polysaccharide. We found the three bacteria can all produce acid and reduce the pH of the fermentation broth in potassium absorbing experiment. The difference was that the growth of Y1-3-9in K3(100%K) medium whose potassium ion concentration was higher had a certain degree of inhibition, however, the changes of external potassium ion concentrations had little effect on the growth of Q32and W33. And in the three concentrations of the fermentation broth, Q32and W33’s capabilities to absorb the potassium ions in the supernatant were much better than Y1-3-9’s.Through the soil-column experiment, the effect of strains Q32and W33on potassium leaching in different time periods was studied. The results showed that, after the10th day, the strain W33can reduce the leaching loss of the potassium. Inoculation of the strains tested could increase the total cultured bacteria number to some extent within the first10days. In addition, inoculation of the strains tested could significantly increase the content of soil water-soluble potassium between the10th day and the20th day. About soil available K, the treatment of W33was significantly higher than control on the10th day and then dropped to a level that was lower than control on the20th day; the treatment of Q32’s soil available potassium is higher than control from the10th day to the20th day. Strain W33could increase soil’s invertase activity on the10th day, while Q32could increase soil’s urease activity on the0th day and the30th day. Strain W33could increase the content of the soil polysaccharide from the0th day to the30th day. The two strains tested could reduce the pH of the soil on the10th day.After evaluating the results of the potassium absorbing experiment and the soil-column experiment comprehensively, that W33had the strong capability to adsorp potassium ions and reduce the leaching loss of potash was found eventually. This study continued to combine W33and the different gradients of potassium fertilizer to study the impact of plant growth-promoting bacteria producing extracellular polysaccharide on wheat’s efficient use of potash in pot experiment. The results showed that the strain tested could promote the wheat growth especially the root growth. W33could significantly promote the absorption of potassium and phosphorus of the wheat under higher potassium application rate too. It could improve the water-soluble potassium content in wheat rhizosphere soil under80%K application rate and non-rhizosphere soil under0%,60%,80%and100%K application rates. Inoculation with the strain was found to improve the wheat rhizosphere soil available potassium content under0%,60%and100%K application rates and available phosphorus content under100%K application rate. The activities of invertase and urease in the wheat rhizosphere soil had increased after inoculation with W33under100%and0%,80%,100%K application rates respectively. W33could significantly increase the content of rhizosphere soil’s polysaccharide under different rates of potassium fertilizer. Finally, the tested strain could significantly increase the number of cultured bacteria in rhizosphere soil under all K application rates but60%. The impact of inoculation on soil bacterial community structure was less than the plant root exudates.. |
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