Characteristics of nitrogen accumulation and its relationship with root growth of rice after transplanting

To study the characteristics of nitrogen accumulation(NA) of root and shoot,and its relationship with root dry weight(DW) of rice,a split-plot design with three replications,was used with 3 tillage and cultivation methods as main plot treatments and 3 varieties as the subplot treatments.The tillage and cultivation method treatments included conventional tillage transplanting rice(CTT),conventional tillage broadcasted rice(CTB) and the broadcasted rice among high standing-stubbles under no-tillage condition(BSNT).The dry weight and nitrogen content of stem and sheath,leaf blades,rooting joint,root system and panicles were measured.The results showed that during 40 d after transplanting,NA dynamics of root system and top part were well fitted for the index model.The nitrogen content(NC) of stem and sheath,rooting joint and leaf blade were positively correlated with DW of root system,but NC of root system was negatively correlated with DW of root system.At the same time,the relationships between NA dynamics of all organs and DW of root system were consistent and their positive correlation coefficients were highly significant.NA dynamics of plant was well fitted for logistic y=a/(1+be-cx) equations and all of the coefficients of determination(R2) of the equations were above 0.988.Moreover,there were significantly positive correlation between NA and DW of root,with R2 being higher at early stage.Among different tillage and transplanting methods,CTT had the highest NA of different organs and NA of BSNT was the lowest from transplanting to booting.After booting,NA of BSNT surpassed CTB gradually due to its highest NC of each organ.In early stage,Gangyou 22 had the highest NA,but in late stage, Ⅱyou 162 had a higher rate of NA.The NA of K you 047 was the lowest during the whole growing season.