Effects of reduced nitrogen application on photosynthetic characteristics and yield of spring wheat in Hexi irrigation area
[Objective]This study aimed to investigate the effects of reducing nitrogen application on the photosynthetic characteristics and yield of wheat and explore the relationship between photosynthetic characteristics and yield under different nitrogen fertilizer levels.[Method]A field experiment was con-ducted in the Hexi irrigation area using spring wheat as the research subject.Four nitrogen levels were set:N1(conventional nitrogen rate,300 kg/hm2),N2(10%reduction,270 kg/hm2),N3(20%reduction,240 kg/hm2),N4(30%reduction,210 kg/hm2).The growth characteristics,chlorophyll content,photosyn-thetic characteristics,and yield of wheat were determined.[Result]The leaf area index(LAI)of wheat in N3 and N4 levels decreased by 6.69%and 7.14%respectively compared to the N1 level,but there was no significant difference between N1 and N2 levels.With the reduction of nitrogen application,the net photosyn-thetic rate(Pn)and transpiration rate(Tr)of wheat leaves initially increased and then decreased.The highest values were observed in the N2 level,which were 10.04%and 13.17%higher than those in the N3 and N4 levels,and 9.32%,15.37%,and 23.56%higher than those in the N1,N3,and N4 levels respectively.The in-tercellular CO2 concentration(Ci)of leaves also followed a similar trend,with the maximum observed in the N3 level.The SPAD value and stomatal conductance(Gs)of leaves in the N3 and N4 levels significantly de-creased by 8.08%,17.41%,and 10.32%,13.76%respectively compared to the N1 level,but there was no significant difference between N1 and N2 levels.The grain number per spike,spike number,and yield of wheat initially increased and then decreased with the decrease of nitrogen application.The highest yield was observed in the N2 level,which was 10.71%and 7.91%higher than those in the N1 and N4 levels,and 2.52%higher than that in the N3 level.Correlation analysis showed a positive relationship between photo-synthetic characteristics and yield,indicating that efficient photosynthetic characteristics were the basis for high wheat yield.[Conclusion]Under the experimental conditions,reducing nitrogen application by 10%,specifically 270 kg/hm2,was found to be the optimal nitrogen application rate for achieving high and stable yield of spring wheat in the Hexi irrigation area.
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