In order to study the high-yield

high-efficiency and high-quality nitrogen application rate under drip irrigation in the Huang-Huai-Hai Plain

a field trial was conducted using two high-yield varieties Jimai-22 and Yannong-1212 with 4 nitrogen levels

0

150

210 and 270 kg/hm2

under field drip irrigation during 2018-2020. The photosynthetic physiological characteristics

grain filling characteristics and grain yield were studied. The results showed that nitrogen application could significantly increase the SPAD value of the upper three leaves of winter wheat. Appropriate nitrogen application could significantly increase the relative chlorophyll content and flag leaf net photosynthetic rate (Pn) in the middle and late stages of grain filling. The SOD activity of wheat flag leaves showed a single peak curve. The SOD activity of each nitrogen treatment reached the maximum at 14 days after anthesis

and the SOD activity of N0 treatment reached the maximum at 7 days after anthesis. Under N2 nitrogen level

the flag leaf SOD activity of the two varieties was the highest in the middle and late filling stages. An appropriate rate of nitrogen application could reduce leaf membrane lipid peroxidation in late growth period and leaf MDA content

prolong leaf function period

and improve photosynthetic performance in late growth period. With the increases of nitrogen application rates

the grain filling rate and maximum theoretical 1000-grain weight of the two varieties increased first and then decreased. The Tm of the non-nitrogen treatments was relatively earlier than that of the various nitrogen treatments. For the maximum grain filling rate and maximum theoretical 1000-grain weight

Jimai-22 and Yannong-1212 appeared as the largest under N1 and N2 treatments

respectively. The yields of the two varieties first increased and then decreased with the increases of nitrogen application rates

and both were the largest at N2 treatment. The yield of Jimai-22 was higher than that of Yannong-1212 under N0 and N1 levels

but lower than that of Yannong-1212 under N2 and N3 levels

indicating that Yannong-1212 was more sensitive to nitrogen fertilizer and had a higher yield potential under high fertility and water conditions while Jimai 22 had a strong adaptability with a better performance under the low and medium fertilization. There were differences in the nitrogen responses on the yield components of the two varieties. The yield of Jimai-22 mainly depended on the number of ears and grains per ear

while the yield of Yannong-1212 was of a synergistic effect of the number of ears

grains per ear

and 1 000-grain weight. Nitrogen application significantly increased the protein

wet gluten

and sedimentation value of the two varieties. The quality of Yannong-1212 increased with the increases of nitrogen application in the range of 0~150 kg/hm2

while Jimai-22 increased with the increases of nitrogen application in the range of 0~210 kg/hm2. In summary

under this experimental conditions

the 210 kg/hm2 of nitrogen applied under drip irrigation resulted in better photosynthetic characteristics

enzyme activity

grain filling characteristics

yield and quality of both cultivars and therefore should be the optimal nitrogen application rate.