Effects of combination use of N and Zn fertilizers on absorption,accumulation and distribution of zinc in rice crop

[Objectives]The aim of study was to provide a theoretical basis on zinc(Zn) absorption,accumulation and distribution of rice by combined application of nitrogen(N) and Zn fertilizers.[Methods]Field experiments were designed as three Zn levels(0,25,50kg·hm-2Zn SO4·7H2O) and two N fertilizer rates(200kg·hm-2,low N; 300kg·hm-2,high N).[Results]Results showed that the concentration and accumulation of Zn in different up-ground organs(leaf,stem,grain) of rice plants were increased with increased Zn application rate,and they were also significantly affected by N supply in different growth stages(tillering,flowering,harvest).The concentration of Zn in various up-ground organs of rice was between 20.1 to 50.6mg·kg-1at different growing stages.Zn concentrations in different organs of rice plants supplied with low N rate of Zn25 and Zn50 treatments were equal with those supplied with high N rate of Zn0 and Zn25 treatments,respectively,except Zn concentrations in the stem at flowering and harvest stages.Zn concentration in the same organ changed a lot at different growing stages and the highest Zn concentration was always found in stems.The accumulated Zn in stems was the highest among all organs during early growing period(tillering,flowering),and the distribution percentage of Zn in stems was more than 60%,higher than those in other organs.In late growing period(harvest),however,the accumulated Zn in the stems and grains were almost equal(40%).At harvest,the totally accumulated Zn in rice plants was 504.6 and 496.7g·hm-2,and the amount of Zn required for the formation of 100kg grain was 2.30 and 2.20g,and Zn in the grains coming from the redistribution of Zn in the rice plants(the transfer) was 43.2% and 46.7% under high N and low N application rates,respectively.The net accumulation and transportation of Zn,the contribution of Zn in plants to grain Zn and Zn harvest index which were higher in the stem than leaf,and also were higher to the high N rates than the low N rates.[Conclusions]High N application enhanced root uptake,root-toshoot translocation and remobilization of Zn,and the combined application of N and Zn fertilizers was necessary in rice production.