The objective of this study is to explore the effects of different amount of drip irrigation on carbon metabolism and photosynthetic nitrogen use efficiency of maize after anthesis under shallow buried drip irrigation. Three treatments of irrigation amount 40% (W1: 1600 m3 hm-2), 50% (W2: 2000 m3 hm-2), and 60% (W3: 2400 m3 hm-2) of traditional border irrigation (4000 m3 hm-2) were set to study dynamic characteristics of leaf source, photosynthesis, activities of photosynthetic carbon metabolism enzyme, photosynthetic nitrogen use efficiency, content of non-structural carbohydrate after anthesis, and yield of different amount drip irrigation under shallow buried drip irrigation. The results showed that there was no significant difference on mean yield between CK and W3, while W2 and W1 were both significantly lower than CK and the annual average yield of W2 and W1 respectively decreased by 3.91% and 11.18% compared with that of CK from 2018 to 2020. There was also no significant difference on yield W3 and W2, while W3 was significantly higher than W1. Compared with W1, the annual yield of W3 increased by 17.56%, 9.06%, and 9.56%, respectively. The instantaneous photosynthetic efficiency, instantaneous water use efficiency, and instantaneous carboxylation rate of W3 and CK were both higher at flowering stage and was the lowest in W1, while the performance of stomatal limit was the opposite. The leaf source characteristics and activities of photosynthetic carbon metabolism enzyme of W2 and W1 were both lower than W3 from 30 days after anthesis to maturity, in which the leaf area, specific leaf quality, content of chlorophyll, and LAD of W3 increased by 20.29%, 3.03%, 14.80%, and 21.37%, respectively. Compared with CK, the activities of 1,5-diphosphate ribulose carboxylase, pyruvate phosphate double kinase, malase, malate dehydrogenase, and phosphoenolpyruvate carboxylase of W3 increased by 19.66%, 12.53%, 10.67%, 21.17%, and 11.72%, respectively. There was no significant difference between the photosynthetic nitrogen use efficiency of CK and W3, which were both higher than W1 from 20 to 50 days after anthesis. Compared with W2, W1, and CK from 50th day after anthesis to maturity, the photosynthetic nitrogen use efficiency of W3 increased by 3.24%, 3.29%, and 7.40%, respectively. Compared with W2, CK, and W1, the sucrose content of W3 were the highest from the 50th day after anthesis to maturity of which increased by 11.31%, 14.02%, and 43.48% respectively. Compared with W2, CK and W1 from the 30th day after anthesis to maturity, the soluble sugar content of W3 was the highest from the 30th day after anthesis to maturity and W3 increased by 14.06%, 17.78%, and 34.20%, respectively. Compared with CK, W2, and W1, the starch content of CK had no significant difference with W3, which was the highest from the 50th day after anthesis to maturity, increased by 3.35%, 7.58%, and 24.93%, respectively. Consequently, when irrigation amount reached to 60% of normal irrigation amount of traditional border irrigation, maize under the shallow buried drip irrigation had better leaf source characteristics, strong activities of photosynthetic carbon metabolism enzyme, photosynthetic nitrogen use efficiency, non-structural carbohydrate content and yield, which could provide theoretical guide for rational irrigation, water saving and yield stability of maize.
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