关键词: 西北地区, 生命周期评价, 玉米, 资源投入, 生态环境风险

Abstract: 【Objective】Northwest China is rich in land resources and is one of the four major maize production areas in China. It is critical to clarify the resource inputs and ecological environmental risks of maize production in this region.【Method】 Based on the life cycle assessment (LCA) method to evaluate resource inputs (fertilizer, pesticide, diesel, mulch, seed, and labor) and ecological environment risks (greenhouse gas emissions, soil acidification, water eutrophication and human toxicity) of maize production in six provinces (Xinjiang, Shaanxi, Shanxi, Ningxia, Inner Mongolia, Gansu) of Northwest China during the past 15 years (2004-2018), and quantitatively evaluate the resource inputs, ecological environmental risks and spatiotemporal variations of maize production per unit area (per hectare) in this resources.【Result】Resource inputs and ecological environment risks of maize production were high in Northwest China. The average fertilizer input in past 15 years was 233.1 kg N·hm^-2, 106.3 kg P₂O₅·hm^-2, 23.3 kg K₂O·hm^-2, the pesticide, diesel, mulch, seed and labor inputs were 6.5 kg ·hm^-2, 93.2 L·hm^-2, 13.7 kg·hm^-2, 38.8 kg·hm^-2 and 120.1 h·hm^-2, the average yield was 7.9 t·hm^-2. The averaged greenhouse gas emissions was 4188 kg CO₂-eq·hm^-2, the soil acidification potential was 155.3 kg SO₂-eq·hm^-2, the water eutrophication 52.6 kg PO₄-eq·hm^-2, and the human toxicity was 2.9 kg 1, 4-DCB-eq·hm^-2. Compared with 2004, the overall resource input for maize production of Northwest China in 2018 was increased, showing an overall increased trend. The rates of nitrogen fertilizer, phosphorus fertilizer and potassium fertilizer per unit area increased by 9.2%, 52.7% and 203.7%, respectively; and the rate of pesticide, diesel oil and mulch per unit area increased by 303%, 143% and 108%, respectively. The rates of seed and labor per unit area decreased by 38.6% and 50.8%, while the planting area and maize yield increased by 79% and 26.9%, respectively. On the whole, the multiple ecological environment risks showed a first increased and then decreased trend, in which the greenhouse gas emissions, soil acidification potential, water eutrophication potential and human toxicity per unit area increased by 13.6%, 15.8%, 2.6% and 302.5%, respectively. Among the 15 years of maize production in Northwest China, the highest nitrogen fertilizer input and greenhouse gas emissions per unit area were observed in 2016, and the lowest were observed in 2007. The resources inputs and ecological environment risks of maize production in different provinces of Northwest China were significantly different. In terms of unit area, the rate of nitrogen fertilizer, mulch and labor input was highest in Gansu, and lowest in Shanxi, Shaanxi and Inner Mongolia, respectively. The rate of phosphorus fertilizer and diesel was highest in Xinjiang, and the lowest was Shaanxi. The rate of potassium fertilizer was highest in Shanxi and lowest in Xinjiang. The rate of pesticides and seeds was highest in Ningxia and Xinjiang, and lowest in Shanxi. The planting area and maize grain yield were highest in Inner Mongolia and Xinjiang, and lowest in Ningxia and Shaanxi, respectively. Simultaneously, the greenhouse gas emission and soil acidification potential were highest in Gansu, the water eutrophication potential was highest in Shaanxi, and the human toxicity was highest in Ningxia and lowest in Shanxi. The comprehensive value of resources inputs and ecological environment risks for maize production in Northwest China was highest in Ningxia. Shanxi achieved the lowest comprehensive value of ecological environment risks for maize production in Northwest China. 【Conclusion】Maize production in Northwest China is characterized by "high input, high yield and high risk", the resource inputs and ecological environment risk are quite different in different spatiotemporal scale. During 2004 to 2018, the planting area, grain yield, and resources input were totally increased slightly, while the ecological environment risk showed a first increased and then decreased trend. Maize production can be considered to incline to high-yield and low-environmental risk areas in the future. Simultaneously, optimizing the fertilizers rate, applying enhanced efficiency fertilizers, and adopting systematic management strategies would lead to achieve high yields and low ecological environment risks.

Key words: Northwest China, life cycle assessment, maize, resource input, ecological environment risk