Effects Of Nitrogen Application Rate On Tiller Occurrence And Spike Formation And Nitrogen Utilization Of Wheat Under Water-Saving Supplementary Irrigation

In order to determine the physiological mechanism of wheat tiller formation,grain yield of different tillers and nitrogen utilization in response to nitrogen application rate under water-saving supplementary irrigation,the medium-ear type wheat variety Ji Mai 22 was selected as the test material.The wheat growing season from 2020-2021 was conducted in Wenyang field Modern Agricultural Industrial Park,Shandong Agricultural University,Tai’an City,Shandong Province.Field tests were conducted in the experimental farm of Shandong Agricultural University and Wenyang field Modern Agriculture Industrial Park during the2021-2022 wheat growing season in Tai’an City,Shandong Province.Four nitrogen application rates of 0 kg（N0）,130 kg（N1）,180 kg（N2）and 230 kg（N3）per hectare were set at each test site in each growing season to study the effects of nitrogen application rate on panicle formation of tillers at different tiller positions,photosynthesis and senescence characteristics of flag leaves of different tillers,grain yield and nitrogen utilization of wheat.The main results are as follows:1 Effect of nitrogen application rate on tiller occurrence and spike formation of wheat under water-saving irrigationCompared with N0 and N1 treatments,N2 treatment significantly increased the cross-section area of tiller nodes,trans-zeatin content,net photosynthetic rate,stomatal conductance and transpiration rate of the topmost spreading leaves of main stem at overwintering stage and regreening stage,and increased the number of tiller occurrence at different tiller positions at overwintering stage and joint stage.The number of tillers per plant at the overwintering stage of Wenyang field wheat in 2020-2021 growing season was 17.96%and 12.24%higher than that at N0 and N1 treatments,and 50.59%and 10.93%higher at jointing stage,respectively.The number of tillers per plant at the overwintering stage of N2was 42.68%and 13.29%higher than that at the overwintering stage of N0 and N1,and94.22%and 26.79%higher at the jointing stage,respectively.The number of tillers per plant in wintering stage of Wenyang field was 44.05%and 17.20%higher than that in N0 and N1treatments,and 98.79%and 28.13%higher than that in jointing stage,respectively.Compared with N2 treatment,the number of tillers in overwintering and jointing stages of wheat at each test site in two growing seasons did not increase significantly when nitrogen application rate was increased to N3 level.The dry matter weight and ¹³C assimilate allocation of wheat treated with N2 were higher than those treated with N0,7 days after ¹³C labeling at jointing stage and at maturity stage.Ear number per plant treated with N2 was 43.61%and 7.30%higher than that treated with N0 and N1 in 2020-2021 growing season.Ear number per plant of N2 treatment was 30.29%and 19.37%higher than that of N0 and N1 in 2021-2022growing season experimental farm,and 27.49%and 15.34%higher than that of N0 and N1 in Wenyang field,respectively.Compared with N2 treatment,the number of tillering and panicle formation of wheat at each test site in two growing seasons did not increase significantly when nitrogen application rate was increased to N3 level.2 Effects of nitrogen application rate on photosynthetic,senescence charactor and vied of flag leaves of different stems,tillers and leaves of wheat under water-saving irrigationThe relative content of chlorophyll,photosynthetic and fluorescence parameters,sucrose content,phosphosucrose synthetase activity,soluble protein content and superoxide dismutase activity of flag leaves treated with N2 were significantly higher than those treated with N0and N1,but had no significant difference from those treated with N3.The panicle weight and grain yield of main stem,I,II and III tillers treated with N2 were higher than those treated with N0 and N1,but there was no significant difference between N2 and N3.3 Effects of nitrogen application rate on wheat grain yield,water use efficiency and nitrogen fertilizer agronomic efficiency under water-saving irrigationIn 2020-2021 growing season,the grain yield of Wenyang field treated with N2 was45.14%and 17.43%higher than that treated with N0 and N1,respectively,and the nitrogen agronomic efficiency and partial productivity were significantly higher than those treated with N1.In the 2021-2022 growing season,the grain yield of N2 treatment was 50.78%and19.24%higher than that of N0 and N1 treatments,and that of Wenyang field N2 treatment was 47.95%and 20.98%higher than that of N0 and N1 treatments,respectively.Nitrogen agronomic efficiency and nitrogen partial productivity were significantly higher than those of N1 treatment.When nitrogen application rate increased to the N3 level,wheat grain yield at each test site in two growing seasons did not increase significantly compared with N3treatment,while nitrogen agronomic efficiency and nitrogen partial productivity decreased significantly.Considering the grain yield and nitrogen utilization,N2 treatment was the best treatment under the experimental conditions.