| Sugarcane is the most important sugar crop in China.However,excessive nitrogen fertilizer input in sugarcane planting seriously restricts the sustainable development of the sugarcane industry.A large number of studies have shown that nitrogen-fixing bacteria in sugarcane could associate with sugarcane to fix nitrogen and promote sugarcane growth through various mechanisms.Therefore,it is of great significance to reduce nitrogen fertilizer application in sugarcane production if the associated nitrogen fixation role of the strains can be fully utilized.In this study,the effects of the combined application of nitrogen-fixing bacteria and different nitrogen fertilizer levels on sugarcane growth were investigated.Meanwhile,the potential applications of microbial fertilizer combined with nitrogen fertilizer were discussed according to the experimental conclusion.The results could provide references for optimizing the fertilization application method in the sugarcane industry.The main conclusions are as follows:(1)Under different nitrogen fertilizer levels,the effects of inoculation of two nitrogen-fixing bacteria on the agronomic characters of two sugarcane varieties were investigated.The results showed that the treatment of reducing nitrogen by 25% and inoculated with nitrogen-fixing bacteria DX120 E had the most significant promotion effect on plant height and biomass of sugarcane,compared with 300kg/ha fertilization without bacteria treatment.Under the same nitrogen level,the brix of inoculation treatment was higher than that of control treatment,and the effect of DX120 E inoculation was better than XD20 and XD20+DX120E treatment.Compared with the two varieties,the effects of inoculation strain on sugarcane variety GT42 were better than ROC22.(2)Under different nitrogen levels,the effects of inoculation with two nitrogen-fixing bacteria on the physiological characteristics of two sugarcane varieties were investigated.The results showed that DX120 E or XD20 inoculation could significantly improve leaf area,leaf nitrogen content,chlorophyll content,and photosynthetic parameters of two sugarcane varieties when nitrogen was reduced by 25% or 50%.The effect of DX120 E inoculation on chlorophyll content in sugarcane variety GT42 was significantly better than ROC22 when nitrogen application was reduced by 50%.The net photosynthetic rate,transpiration rate,stomatal conductance,and intercellular carbon dioxide concentration were significantly improved by treatments with a 25% reduction of nitrogen,respectively combination inoculation with strain DX120 E or XD20,while co-treatments with both strains had a weakened effect on photosynthesis.(3)Compared with 300 kg/ha fertilization without bacteria treatment,nitrogen reduction by 50% or 25%,and inoculation of two nitrogen-fixing bacteria both improved the physiological characteristics of two sugarcane varieties,especially promoting the photosynthesis of sugarcane.Based on the results of this experiment,from the perspective of sustainable development,it is suggested to reduce nitrogen by 50% and combine it with inoculating nitrogen-fixing bacteria in sugarcane production management.But considering the economic benefits to farmers,it is suggested to reduce nitrogen by 25% and combine it with inoculating nitrogen-fixing bacteria.(4)The combination application of nitrogen-fixing bacteria and nitrogen fertilizer is promising in sugarcane production.Reducing nitrogen by 25% can save urea investment of 174 million yuan per extraction season and reduce carbon footprint by 33.26%,which has economic and ecological benefits.Based on the analysis of the development status of microbial fertilizer,some suggestions were put forward for its development trend in sugarcane planting.First,it is necessary to increase capital input.Second,strengthening scientific and technological research is also needed;Third,it is necessary to standardize fertilizer production;In the end,it was needed to offer some chance to train the farmer.Through the establishment of the "Internet + Agriculture" platform to efficiently connect information,the use of Guangxi Improved Seed Breeding Base to establish demonstration,with the help of Fusui Science and Technology Academy to guide production,promote the vigorous development of microbial fertilizer in Guangxi sugarcane industry according to local conditions. |
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