Effects of Different Irrigation and Nitrogen Application Methods on Photosynthetic Characteristics,Agronomic Traits and Nitrogen Use of Rice
"Longqing No.3"rice was used as material,two irrigation methods were set up:controlled irrigation and flood irrigation.Nitrogen application levels were 0,60,85,110,135 and 160 kg/hm2,respectively.The effects of different irrigation methods and nitrogen application levels on photosyn-thesis,fluorescence and agronomic traits of rice were studied.The results showed that nitrogen fertil-izer was the main factor affecting photosynthetic characteristics compared with irrigation.Under con-trolled irrigation,net photosynthetic rate(Pn),stomatal conductivity(Gs)and transpiration rate(Tr)were increased by 6.70%-31.74%,18.39%-49.04%and 16.91%-38.48%,respectively(P＜0.05).Under flood irrigation,net photosynthetic rate(Pn),stomatal conductance(Gs)and transpiration rate(Tr)were increased by 12.13%-28.20%,14.40%-18.35%and 0.40%-8.18%,respectively(P＜0.05).The intercellular carbon dioxide concentration(Ci)between the two irrigation methods was 150-350 µmol/mol,and no significant difference was found between the two irrigation methods(P＞0.05).Fo,Fm and Fs of 110 kg/hm2 and 135 kg/hm2 nitrogen fertilization treatments were better than other treatments,and radiation utilization efficiency(RUE)was also better than other treatments.Compared to flood irrigation,RUE value of the control irrigation was higher(1.60a＞1.52c).In agronomic traits,stem diameter and leaf area had a reasonable critical value(135 kg/hm2)for nitrogen uptake and uti-lization,and exceeding the optimal nitrogen application rate was not conducive to growth.Plant height increased with the increase of N application,with the maximum of 160 kg/hm2.Further analy-sis by the semi-variance function model showed that stem diameter and leaf area had moderate spa-tial autocorrelation,with a high degree of spatial heterogeneity caused by spatial autocorrelation,indi-cating that spatial heterogeneity caused by random components was relatively large,while spatial cor-relation of plant height was weak.Therefore,controlled irrigation had better nitrogen utilization than flood irrigation,with the optimal nitrogen application of 110 kg/hm2.
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