Straw returning and one-time application of a mixture of controlled release and solid granular urea to reduce carbon footprint of plastic film mulching spring maize

For a long time, nitrogen (N) management for high-yielding maize (Zea mays L.) has been a severe challenge. The N supply must maximize yield while minimizing environmental impact. In response to the above problems, we evaluated different approaches to nitrogen fertilizer management based on grain yield, economic benefits and environmental benefits of spring maize systems from 2017 to 2019 in a semiarid area of northwestern China. The four treatments included solid granular urea with a split application (UR), one-time application of a mixture of controlled release and solid granular urea (CU), straw return with the combination of controlled release and solid granular urea (CUS) and control (CK). From the perspective of agricultural production, compared with the CK, high yields (>15 Mg ha−1) were guaranteed in the other treatments. Considering both the environment and the economy, compared with the UR treatment, the CU treatment not only improved the economic efficiency of maize cultivation (increased by 4.9%–12.1%) but also significantly decreased the net global warming potential (NGWP) and carbon footprint (CF) (decreased by 21.1–21.7% and 17.8–23.1%, respectively). At the same time, the CU treatment optimized the proportions of N2O emissions at different growth stages and reduced the risk of emissions caused by high temperatures and rainfall in the middle and late stages of maize growth. Compared to the CU treatment, although the CUS treatment increased CO2 and N2O emissions (increased by 35% and 51%, respectively), the accumulation of soil organic carbon (SOC) was enhanced by straw return, which offset the negative impact of the increase in greenhouse gas emissions and significantly reduced the NGWP and CF compared to values for the other three treatments (decreased by 51% and 50%, respectively). With a comprehensive consideration of environmental impacts and economic benefits, the combination of solid granular urea (SGU) and controlled release urea (CRU) with the straw return is an environmentally friendly, high-yielding, high-economic benefit and low-emissions production technology for arid and semiarid areas.