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To obtain soundly based scientific evidences for rational choice of N fertilizer rate and application frequency under SDI system in P.tomentosa plantation.A field experiment was conducted to evaluate the effect of different fertigation regimes on Triploid P.tomentosa growth,biomass accumulation and annual N uptake,as well as analyze the seasonal DBH growth patterns to improved fertigation scheduling according to tree phonological stages requirements.The experiment include 6 fertigation treatments,which were a factorial combination of three nitrogen rates(115,230,345 kg·hm-2·yr-1 ) and two application frequencies(2 or 4 times through the growing season),and an control (0 N,irrigated only) also include.Results showed that: fetigation treatments have significant effects on tree growth.Compared with control,fertigation treatments increased DBH and volume increments ranging from 21-36% and 16-43% in 2011,16-38% and 13-49% in 2012(p<0.05),respectively; Aboveground and total Biomass of fertigated trees responded more positively than tree growth,total biomass of trees receiving fertigation ranged from 26.51 to 34.03 t·hm-2 in 2011,35.17 to 43.62 t·hm-2 in 2012,average biomass was 21% in 2011 and 35% in 2012 greater in fertilized trees than in control trees.Biomass of 115 kg·hm-2 was significantly greater than the higher N rates (230 and 345 kg·hm-2); Whole-plot N uptake differed among treatments,with fertigatied trees having greater N uptake than the control trees.N115F4 had the highest N uptake both in 2011 and 2012.Which were 93.4% and 44% higher than that in control and other treatments,respectively; Fertigation treatments continued to grow at a greater rate later in the growing season,i.e.,July through August in 2011,Tree receiving N fertgation exhibited 75% higher than control,but this effect was failed in 2012.It is conclude that: 1) fertigation treatment did not altered seasonal growth patterns both in 2011 and 2012,but it significant increased the proportion of August DBH growth.2) Under SDI fertigation,N application rate had a greater positive effect than did application frequency on growth and productivity of P.tomentosa.Trees in the 115N kg·hm-2 and application 4 times through the growing season treatments achieved near-maximum growth potential; 3) the aboveground biomass of trees significant affected by N fertigation while there was no effect on root biomass.And N uptake under fertigation treatment is more sensitive to variation in N rate rather than application frequencies.