Regulation of nitrogen topdressing stage and potassium fertilizer rate on absorption and translocation of nitrogen by wheat

【Objectives】 The objective is to explore the variation of nitrogen absorption, assimilation and distribution affected by nitrogen topdressing time and potassium fertilizer rate in winter wheat ‘Jimai 20’.【Methods】 Using high gluten wheat cultivar ‘Jimai 20’ as test meterial and the 15N tracer technique, a pot experiment was adopted with two nitrogen topdressing time (reviving and elongation stage) and three potassium basal application rate (K2O 0, 50 and 100 kg/hm2). Plant samples were collected at enthesis stage, and grain and plant samples at maturaity stage to determine the nitrogen contents, calculate the nitrogen absorption, utilization and distribution.【Results】 Although the interaction between N use stage and K rate had no significant effect on grain protein content of ‘Jimai 20’, the effects of K rate on nitrogen absorption, assimilation and distribution varied with N use stage. The nitrogen accumulation amount, translocation amount and contribution proportion of wheat all reached the maxima on the condition of K0 and nitrogen applied at reviving stage. Under K2O rate of 50 kg/hm2, nitrogen applied at elongation stage could effectively improve the nitrogen accumulation amount at the anthesis, nitrogen accumulation of plant and grain from soil, nitrogen translocation amount and contribution proportion of wheat at the maturity, and finally improve the grain yield significantly. The interaction between the nitrogen topdressing stage and potassium fertilizer rate has no significant effect on the grain protein content of Jimai 20. There are differences in effects of potassium fertilizer on the nitrogen absorption, assimilation and distribution among different nitrogen topdressing stages. Under the condition of nitrogen applied at the green-turning stage and without potassium fertilizer (K0), the nitrogen accumulation amount, nitrogen translocation amount and contribution proportion of wheat all reach the maxima. While under the condition of nitrogen applied at the elongation stage, proper potassium application rate (K1) could increase the nitrogen accumulation amount, nitrogen translocation amount, grain yield, nitrogen productive efficiency and nitrogen recovery index respectively. However, the excessive potassium fertilizer (K2) is not benefical to the improvement of the nitrogen use efficiency and grain yield. 【Conclusions】 It is beneficial to the nitrogen absorption, nitrogen utilization and formation of high yield for wheat(Jimai 20) under the condition of K2O rate of 50 kg/hm2 and nitrogen applied at the elongation stage.