Abstract: As the main cotton-producing area and an important production base of food in China, Xinjiang is facing the dual pressures of ensuring national food security and achieving low-carbon agriculture. A comprehensive accounting of carbon footprint of major crops can contribute to decision-making in agricultural structure adjustment and the environmental management in Xinjiang from the perspective of carbon emission reduction. Based on data of the planting area, yield, and agricultural input of wheat, maize, and cotton in Xinjiang from 2005 to 2021, we used the life cycle assessment method to calculate the production carbon footprint of the aforementioned three major crops and used the grey relational analysis to analyze their influencing factors. Results showed that during 2005-2021, the planting areas of wheat and maize varied with the planting area of cotton. The average annual carbon footprint per unit area of wheat, maize, and cotton were 2.21, 2.67, and 3.61 t CE·hm^-2, and the average annual carbon footprint per unit yield were 0.41, 0.35, and 1.91 t CE·t^-1 respectively. The carbon ecological efficiency of the three crops was in an order of wheat (10.99 t CE·t CE^-1) > maize (9.68 t CE·t CE^-1) > cotton (2.96 t CE·t CE^-1), the carbon production efficiency was maize (2.88 t·t CE^-1) > wheat (2.48 t·t CE^-1) > cotton (0.53 t·t CE^-1), and the carbon economic efficiency was cotton (7148.74×10³ yuan·t CE^-1) > maize (6094.32×10³ yuan·t CE^-1) > wheat (5904.23×10³ yuan·t CE^-1). As for carbon input structure, farmland N₂O emission and chemical fertilizer input were the main sources of the production carbon footprint. Total mechanical power, crop planting area, effective irrigation area, agricultural film usage, compound fertilizer and nitrogen fertilizer input were the main driving factors. Based on our analysis of carbon footprint of wheat, maize, and cotton in Xinjiang in 2022 and 2023, we found that this area need to moderately adjust the planting structure in the future. At the same time, it should develop science and technology to improve the utilization efficiencies of chemical fertilizers, agricultural films, irrigation and mechanical operations to achieve the low-carbon production of crops while ensuring the national food security strategy.

Key words: carbon footprint, life cycle assessment, carbon efficiency, grey relation analysis