| Sugarcane is one of world’s most important sugar crops, more than70%v of world’s sugar supply comes from sugarcane. The sugarcane is C4plant and has highly efficient photosynthetic energy conversion. Currently, more and more nitrogen fertilization is applied and that makes the sugarcane planting costs become higher and higher in sugarcane plantations. Sugarcane biological nitrogen fixation is a good way to reduce the amount of nitrogen fertilizer costs in the plantation management. Sugarcane biological nitrogen fixation has important significance for the modern sugarcane industry in sustainable development, developing an resource-saving industries and environmental friendly ecological industry. In this study, in order to approach the effects of different nitrogen fixed bacteria on different sugarcane varieties, four sugarcane varieties (ROC22, B8, GT21and GT28) were planted in the barrel as experimental materials to study the effect of inoculated with the nitrogen-fixing bacteria Klebsiella DX120, Azospirillum, nitrogen-fixing bacteria strains98-296to the photosynthetic characteristics and the macroelement accumulated in sugarcane. These experiments aim to provide supplement for the further application of nitrogen-fixing bacteria in sugarcane planting. The major results as follows:1. Inoculated with nitrogen-fixing bacteria, the content of chlorophyll in the first leaf of ROC22, B8, GT21and GT28both have improved. Especially in August, the content of chlorophyll in treatments were higher than CK, but less than the fertilizer treatments. With the growth of sugarcane, the differences among the treatments were getting smaller and smaller.2. After the root of four sugarcane varieties watered with nitrogen-fixing bacteria, the photosynthetic rate increased in the growth stage of sugarcane. In August for example, for ROC22, the photosynthetic rate of single strain treatments (A, B, C) and mixed strains treatments (AB, AC, BC and ABC) were higher than CK, but lower than fertilizer treatments. For B8, the A, C, BC and ABC treatments had higher photosynthetic rate than CK, another treatments were no significant difference. For GT28, only the AC treatments had higher Pn than CK, others were no significant difference. As a whole, different sugarcane varieties had different Photo, Cond, Ci and Trmmol, and performance in different growth periods as well.Inoculated with nitrogen-fixing bacteria could improve the Ci and Trmmol of leaves.3. The content of nitrate in sugarcane leaves had increasing trend from August to November after inoculated nitrogen-fixing bacteria. The content of nitrate in the first leaf slightly higher than CK, but below the fertilizer treatments after inoculated with different nitrogen-fixing bacteria. From October to November, the content of nitrate in CK and fertilizer treatments had great decrease, while the nitrogen-fixing bacteria treatments were relatively stable.4.1noculated nitrogen-fixing bacteria was helpful to improve the accumulation of N, P and K in the sugarcane leaves. The content of nitrogen in the leaves of each treatments had gradually reduced from August to November in general, and the difference was greater in later growth. Inoculated nitrogen-fixing bacteria can improve the N content in leaves.The N content in treatments inoculated with azotobacters changed less than the CK and fertilizer treatments. Accumulation of P content in sugarcane leaves continued to improve during the sugarcane growth period. The P content of nitrogen-fixing bacteria treatments showed a higher growth rate compared with CK. There were no significant differences among the treatments during August to November on potassium content.5. Inoculation of azotobacter could increase the sugarcane single stem weight and sucrose content. There was no significant difference in the sucrose content among the nitrogen-fixing bacteria treatments, fertilizer applications and CK. After nitrogen-fixing bacteria inoculation, the brix of ROC22, B8, GT21, GT28improved on an average rate of1.50%,1.09%,1.42%and1.49%respectively, the single stem weight increased of4.26%,11.95%,6.04%and4.82%on average. |
