The effect of nitrogen fertilizer treatments on root traits and nitrogen use efficiency in Indica rice varieties with high nitrogen absorption efficiency

To investigate the effect of nitrogen management practices on root traits,the amount of nitrogen absorption at grain maturity,nitrogen fertilizer use efficiency,and to analysis the main root traits of rice responsible for high nitrogen absorption efficiency,a total of 15 conventional Indica rice varieties with marked differences in nitrogen absorption efficiency were pot-cultured in 2011 and 2012.( 1) The amount of nitrogen absorption( ANA) at grain maturity was differed significantly among rice varieties and nitrogen fertilizer treatments. Among varieties,nitrogen absorption efficiencywas positively correlated with ANA at grain maturity in all nitrogen treatments. In rice varieties with high nitrogen absorption efficiency ANA was greater than that in rice varieties with intermediate and low nitrogen absorption efficiency. In rice varieties with high nitrogen efficiency ANA was increased by increasing nitrogen fertilizer application rates or by using the base + promoting-spikelet fertilizer treatment.( 2) Ric