Effects of Nitrogen Topdressing at Jointing Stage on Grain Yield,Benefit,Absorption and Utilization of Nitrogen in Winter Wheat

In order to obtain the reasonable nitrogen fertilization mode in north of Henan,the effects of nitrogen topdressing at jointing stage on grain yield,fertilizer benefit,absorption and utilization of nitrogen in winter wheat were studied.In this experiment,Zhoumai 18 and Jimai 22 were chosen as field experimental materials.The results showed that grain yield increased and then decreased with the amount adding of nitrogen topdressing under the base nitrogen 120 kg·hm-2.The relation between grain yield and nitrogen topdressing rate could be described as quadratic curve-fitting equation.Zhoumai 18 and Jimai 22 could reach higher grain yield and benefit under N260 treatment which nitrogen topdressing was 140 kg·hm-2.With the nitrogen topdressing increased,TNAA(total nitrogen accumulation amount) in plant increased slowly and sometimes decreased,and meanwhile NHI(nitrogen harvest index),NRE(nitrogen recovery efficiency) and NPFP(nitrogen partial factor productivity) reduced significantly,while NAE(nitrogen agronomic efficiency) increased at first and then decreased.Nitrogen topdressing at jointing stage could improve the nitrogen translocation amount to grain.Under the nitrogen topdressing treatments,81.53%-88.62% nitrogen in grain came from the nitrogen transportation of vegetative organs in Zhoumai 18,while 79.65%-89.10% in Jimai 22.Taken the above together,120 kg·hm-2 nitrogen as base fertilizer with 140-180 kg·hm-2 nitrogen as topdressing at joint stage was the appropriate nitrogen applying mode in northern Henan.