Integrated management improves spring maize yield and resources use efficiency, and reduces the carbon footprint in Northeast China

Northeast China is the largest maize production region in the country, but the long-term management approach of production aiming at high yield has led to the cropping system becoming a major source of greenhouse gas emissions. Effective measures to improve resource efficiency and reduce environmental costs based on guaranteed yields have become an urgent need for industrial agricultural development. In this study, an integrated management mode (IM), including wide- and narrow-row alternative planting (90 cm for wide rows and 40 cm for narrow rows), high planting density (90 000 plants∙hm⁻²), application of chemical regulation agents at the 15-leaf spread of maize, and reduction of nitrogen fertilizer (28.0% and 9.1% in semi-humid and semi-arid areas, respectively) was selected in the semi-arid and semi-humid areas of the central Northeast Plain, while sub-membrane drip irrigation was applied in the semi-arid area, in 2019 and 2020. The differences between IM and farmers’ mode (FM: 65 cm equal row spacing and planting density 60 000 plants∙hm⁻² without chemical regulation) in different ecological areas in Northeast China were comparatively analyzed in terms of maize grain yield, and use efficiencies of accumulated temperature and light energy, economic benefits, and carbon footprints. The results showed that, compared with FM, maize yield of IM in the semi-humid and semi-arid areas averagely increased by 24.2% and 25.6%, respectively, mainly because of a 50% increase in planting density resulting in 48.5% and 57.0% increases in the number of harvested ears; whereas the number of ears and thousand-kernel weight only decreased by 8.5% and 11.0% averagely in two areas for two years, respectively. The cumulated temperature production efficiency in the semi-humid area increased by 21.1%, the light energy use efficiency increased by 21.0%; in the semi-arid area, the cumulated temperature production efficiency and light energy use efficiency improved by 20.7% and 22.0%, respectively. Therefore, the annual net returns of IM in the semi-humid and semi-arid areas increased averagely by 32.9% and 24.4%, respectively, compared with FM. Meanwhile, the total carbon emission of IM in the semi-humid area was 2860.1 kg (CO₂-eq)·hm⁻², which was 18.7% lower than that of FM; while the total carbon emission of IM in the semi-arid area was 8.9% higher than that of FM, at 2729.6 kg (CO₂-eq)·hm⁻². The carbon footprint per unit grain yield of IM in the semi-humid and semi-arid areas was 0.20 kg (CO₂-eq)·kg⁻¹ and 0.22 kg(CO₂-eq)·kg⁻¹, respectively, which was 39.4% and 15.4% lower than that of FM. In summary, the IM in Northeast China was able to achieve synergistic improvements in grain yield, accumulated temperature production efficiency, light energy utilization efficiency, and economic benefits, and significantly reduce the carbon footprint, especially in the semi-humid area; the semi-arid area showed increased carbon emissions but had a higher yield increase than the semi-humid area, which ultimately also significantly reduced the carbon footprint. Therefore, an integrated management mode is recommended for maize production in Northeast China.