The difference of nitrogen uptake and utilization in waxy corn II.The genotypic differences in accumulation dynamics of nitrogen

In order to understand the regularity of nitrogen(N) accumulation dynamics,explain the genotypic differences of N accumulation at different growing stages and their effects on the yield formation,31 waxy corn(Zea mays L.ceratina Kulesh)varieties released in recent years in China were planted to analyze their N accumulation at the 4 th leaf age,the jointing stage,the 12 th leaf stage,the silking stage,the fresh ear stage and the maturity stage under same nitrogen fertilization conditions respectively.The results showed that the N content was decreased with the growth of waxy corn;N accumulation dynamics was a dissymmetrical S curve which could be fitted by Richards equation.There were significant differences in N content and N accumulation at different stages among different varieties.In addition,the increment of N uptake of high fresh ear yield varieties mainly occurred from the 12 th leaf stage to the silking stage,while for the high fresh grain yield varieties and high grain yield varieties,it mainly occurred from the 12 th leaf stage to the silking stage followed from the silking stage to the fresh ear stage.It was found that the N accumulation dynamics influenced on total N accumulation significantly,but it had minor effects on N utilization efficiency by path analysis.Moreover,there were significant differences in the parameters of the Richards equationfitted for N accumulation dynamics among different varieties.Higher maximum N accumulation rate,longer activity accumulative duration,higher N accumulation rate and longer duration in the middle stage in the process of growth of waxy corn had a beneficial effect on N accumulation of waxy maize.6 varieties of Feng nuo 2146,Jing ke nuo 267,Hu yu nuo 3,Jing ke nuo 218,Qian nuo 668 and Jing ke nuo 2000 were regarded as high yield and high N utilization efficiency in the 31waxy corn varieties,had mean N uptake 1.136(g/plant) from the 12 th leaf stage to the silking stage,and mean N uptake 0.554 g/plant from the silking stage to the fresh ear stage,which were 24.3% and 37.8% higher than that of other varieties,respectively.In addition,the average maximum N accumulation rate was 0.068 g/(dplant),and the average N accumulative rate of above six varieties in the middle stage was 0.059 g/(dplant),which were 15.8% and 15.9% higher than that of other varieties,respectively.Moreover,the average activity accumulative time was 63.4d,and the average last time in the middle stage was 29.5d,which were longer than that of other varieties by 1.9d and 0.9d,respectively.