Effects of intercropping with soybean on nitrogenase activity of endophytic nitrogen-fixing bacteria,nitrogen accumulation and cane yield of stubble cane under low nitrogen condition

ObjectiveThe effects of sugarcane-soybean intercropping on characters of endophytic nitrogen-fixation and growth in stubble cane under low nitrogen condition were studied to provide theoretical references for the applica-tion of sugarcane-soybean intercropping. MethodA split plot experiment was conducted using cropping patterns (mono-culture and intercropping ) as principal factors and sugarcane cultivars ( B8 , ROC22 and GT21 ) as secondary factors , and the nitrogenase activity of endophytic nitrogen-fixing bacteria , nitrogen accumulation and cane yield of sugarcane under low nitrogen condition were analyzed among different treatments . ResultThe results showed that , compared with the monoculture treatment , stalk diameter , millable stalks and cane yield of stubble crop under low nitrogen con-dition in the intercropping treatment were increased by 5.1%-8.7%,7.9%-31.0% and 9.0%-40.5%,respectively,while the plant height showed no obvious difference between cropping patterns. Intercropping treatment significantly increased the nitrogenase activities of endogenous nitrogen-fixing bacteria in stalks and leaves ,and the increments were 59.35 nmol C2H4/gFW·h and 0.98-1.89 nmol C2H4/gFW·h in variety ROC22,respectively,which were higher than those in B8 and GT21. Except that nitrogen content in leaves of B8 and total nitrogen accumulaction in leaves of GT21 at tillering stageweresignificantlyincreasedby18.8% and 35.2%,respectively(P<0.05,the same below).Nosignificantdiffer-ences in nitrogen content and accumulation in leaves between different treatments were observed in others (P>0.05), while the nitrogen content and accumulation in stalks at elongating stage in intercropping treatment were increased and total nitrogen accumulation in stalks of ROC22 and GT21 was significantly increased by 35.0% and 81.1%, respectively.ConclusionSugarcane-soybean intercropping can significantly improve nitrogenase activity of endophytic nitrogen-fix-ing bacteria , nitrogen accumulation and cane yield in stubble crop under low nitrogen condition , and the positive effect on yield of intercropping is the highest in GT21 among 3 the three varieties.