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Effects of nitrogen application rates on forage production, nitrogen use efficiency, and greenhouse gas emission intensity in a silage maize-lablab intercropping system

Zhang Yi-Yin1,Wang Hai-Xia1,Zhao Meng-Yu2,Wang Teng-Fei1,Ma Jiang-Ping1,Wang Bin1,3,Lan Jian1,*   

  1. 1 School of Forestry and Grassland Science, Ningxia University / Ningxia Grassland and Rangeland Engineering Research Center / Key Laboratory of Innovation of Forage Efficient Production Model, Ministry of Agriculture and Rural Affairs, Yinchuan 750021, Ningxia, China; 2 Ningxia Huinong District Rural Economic Operation and Management Station, Shizuishan 753600, Ningxia, China; 3 College of Ecology, Lanzhou University, Lanzhou 730000, Gansu, China
  • Received:2026-05-21 Revised:2026-08-21 Accepted:2026-08-21 Published:2026-09-01
  • Supported by:
    This study was supported by the Ningxia Higher Education Institution First-Class Discipline Construction Project (Grassland Science Discipline) (NXYLXK2017A01) and the Research and Demonstration Project on the Sustainable Development Model of “Two Crops per Year” Artificial Grasslands (2021BBF02001).

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Abstract: To clarify the response characteristics of forage yield, nutritional quality, nitrogen utilization, and greenhouse gas emissions in silage maize-lablab intercropping under different nitrogen application rates, and to provide a theoretical basis for high-yield, high-efficiency, and green production of high-quality forage in irrigated areas of Northwest China, a split-plot experiment was conducted in the oasis irrigation area of Northwest China from 2023 to 2024. The main plots consisted of two planting patterns: silage maize monocropping (SM) and silage maize-lablab intercropping (ML). The subplots consisted of five nitrogen application rates: N0 (0 kg hm?2), N75 (75 kg hm–2), N150 (150 kg hm–2), N225 (225 kg hm–2), and N300 (300 kg hm–2). System dry matter yield, nutritional quality, nitrogen uptake and use efficiency, and greenhouse gas emission intensity were measured, and structural equation modeling was used to analyze the relationships among these factors. The results showed that both nitrogen application and intercropping significantly improved forage yield and nutritional quality. Compared with monocropping under the same nitrogen application rate, intercropping increased system dry matter yield and crude protein yield by 18.68% and 30.85%, respectively, and increased crude protein content, total digestible nutrients, and relative feeding value by 19.81%, 8.47%, and 11.35%, respectively. Yield in the monocropping system peaked under N300, whereas that in the intercropping system peaked under N225. In addition, under the N75–N300 treatments, compared with monocropping, intercropping increased crude protein content, total digestible nutrients, and relative feeding value by 18.30%–24.51%, 7.02%–10.61%, and 9.49%–12.70%, respectively. Under the same nitrogen application rate, greenhouse gas emission intensities based on dry matter yield and crude protein yield were reduced by 8.51%–20.03% and 13.87%–29.08%, respectively, in the intercropping system compared with monocropping. Structural equation modeling revealed that nitrogen application and planting pattern promoted yield formation and forage quality improvement mainly by increasing LAI and nitrogen uptake. Nitrogen uptake was the key factor driving dry matter yield improvement. Greenhouse gas emission intensity per unit yield increased significantly under excessive nitrogen application, whereas appropriate nitrogen application achieved relatively low emissions while increasing yield. Overall, silage maize-lablab intercropping combined with a nitrogen application rate of 225 kg hm–2 significantly improved forage yield, nutritional quality, and nitrogen use efficiency, while effectively reducing greenhouse gas emission intensity. Therefore, it can be recommended as a suitable production pattern for high-yield, high-efficiency, and green production of high-quality forage in irrigated areas of Northwest China.

Key words: intercropping, nitrogen application rate, forage yield, forage quality, nitrogen use efficiency, greenhouse gas emission intensity

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