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Agriculture is facing great challenges toward increasing crop productivity per unit area but also reducing the global warming intensity, especially in context of the need for a higher future food supply under changing and uncertain climate. Based on 45 site-year field experimental data in rainfed areas of Northeastern China supplemented with results from the DNDC model and combined with life cycle assessment (LCA), the study reported herein evaluated the grain yield and global warming effects of optimized maize (Zea mays) agronomic management systems. In comparison with farmers' practices (FM), the improved agronomic management (OM-1), including dense planting, reduced N fertilizer rate, split fertilizer application, and subsoiling, significantly increased grain yield, nitrogen use efficiency, and net energy ratio by 23.7%, 80.9%, and 58.1%, respectively. In contrast, the global warming potential (GWP) and global warming potential intensity (GWPI) decreased by 18.8% and 34.3% based on average of research sites. Adoption of additionally improved management system (OM-2), involving OM-1 system plus denser planting and use of organic amendments, achieved even higher grain yield while further decreasing GWP and GWPI by 31.6%, 24.9%, and 42.8% relative to FM system. In addition, OM-2 system had positive effects on soil carbon sequestration at the annual rate of 250.6kg CO2-eqha−1on a 20-year prospective, which is pertinent to mitigating global warming and improving soil fertility. Furthermore, negative correlation between grain yield and GWP and GWPI indicates a double-win option of obtaining higher maize productivity and reducing global warming intensity by optimizing agronomic management system.

Subsoil tillage (∼30 cm) reduced compaction and increased moisture and N availability on Mollisols.Subsoiling increased the vertical and horizontal distribution of maize roots between rows rather than in row.Grain and dry matter yield were 6.3 and 3.7% greater under subsoiling than conventional tillage.Subsoiling increased maize yield due to improved soil conditions and roots distribution. Soil compaction creates unfavorable soil physical and nutrient conditions, restrains root penetration and distribution, and reduces crop yield. A field experiment was established to assess the effects of tillage treatments on soil properties, root distribution, and grain yield of maize (Zea maysL.) on some Mollisols of Northeastern China. The two treatments included in rotary tillage (RT) and subsoiling tillage (ST). The results showed that soil bulk density, penetration resistance, soil moisture, available nitrogen content, root distribution of maize, and grain yield were significantly affected by tillage systems. Compared with RT, ST had lower soil bulk density and penetration resistance, but greater soil moisture and available nitrogen contents, especially in subsoil layer (i.e., 15‐ to 45‐ cm). The ST practice significantly increased the average root length density by 13.0% than that of RT mainly due to better vertical and horizontal distribution between the rows. Average grain yield and dry matter weight of maize increased by 693 kg ha−1(6.3%) and 933 kg ha−1(3.7%), respectively, under ST compared with those under RT. These data show that subsoiling tillage can loosen the soil, fracture the plow pan, increase the availability and infiltration of soil moisture and nitrogen in subsoil layers, improve the vertical and horizontal extension of maize root system in the soil, and increase grain yield on Mollisols of Northeastern China.

The objective of this study was to identify the response of grain yield to plant density and nitrogen rate in spring maize hybrids released from 1970 to 2010 and grown extensively in Northeast China. Twenty-one hybrids were grown for 2years in Northeast China at densities of 30,000, 52,500, 75,000, and 97,500plantsha−1and N application levels of 0, 150, 300, and 450kgNha−1. Irrespective of density or nitrogen application rate, grain yields both per plant and per unit area were significantly higher for newer than older hybrids. As plant density increased from 30,000 to 97,500plantha−1, yield per plant of 1970s, 1980s, 1990s, and 2000s hybrids decreased by 50%, 45%, 46%, and 52%, respectively. The response of grain yield per unit area to plant density was curvilinear. The estimated optimum plant densities were about 58,000, 49,000, 65,000, and 65,000plantsha−1for hybrids released in the 1970s, 1980s, 1990s, and 2000s, respectively. The theoretical optimum densities for the hybrids released from the 1970s to the 2000s increased by 1750plantsha−1decade−1. Nitrogen fertilization significantly increased grain yields per plant and per unit area for all hybrids. The theoretical optimum N application rates for high yield for hybrids released in the 1970s and 1980s were about 280 and 360kgha−1, and the hybrids from the 1990s and 2000s showed highest yield at 330kgha−1N. No significant difference in the grain yields of 2000s hybrids between the N levels of 150 to 450kgha−1was found. Significant yield gains per plant and per unit area were found, with average increases of 17.9g plant−1decade−1and 936kgha−1decade−1over the period 1970–2010, respectively. Yield gains were attributed mainly to increased yield per plant, contributed by increases in kernel number per ear and 1000-kernel weight. The rates of lodging and barren plants of newer hybrids were significantly lower than those of older ones, especially at high plant density.