| The global food demand is likely to double by2050because of population growth and increased consumption of animal protein. However, the rates of yield growth have slowed since the1980s, and even stagnated in many areas. Meanwhile, agriculture has incured substantial environmental costs, such as emissions of greenhouse gases, loss of biodiversity, and degradation of land and freshwater. The agricultural intensification with substantial resource consumption and environmental costs has lead the push for management alterative meeting the dual goals of conserving natural resources, and environment while meeting increased demand for cereals. In this study, the dynamics of biomass accumulation and N uptake of the high yield maize were analysised based on large database from nine field experiments. We established the relation models between aboveground biomass accumulation and canopy leaf area index, leaf SPAD, plant N concentration and root-zone N content, finaly established the integrated soil-crop system management for high yield and high resource use efficiency in North China Plain, and demonstrated through cultivar and plant density interact with N management in field experiment. Finally, we comprehensively evaluated the productivity, resource use efficiency, environment effects, fanners’ income and sustainability of the cropping system in North China Plain.The main results were concluded as follows:1. Based on512measurements in9field experiments in8sites, aboveground biomass accumulation and N uptake increased as grain yield levels increased from<8Mg ha-1to8-10Mg ha-1and>10Mg ha-1, and this happens during the grain filling period. The post-flowering biomass accumulation increased from5.8kg ha-1to9.2and11.4kg ha-1, and N uptake increased from20.1kg ha-1to34.7and53.1kg ha-1This was related to the higher green canopy leaf area index during the grain filling period, the LAI of>10Mg ha-1yield levels could keep more than4until42days after flowering, while the LAI of the<8Mg ha-1to8-10Mg ha-1could only kept to14and28days after flowering.2. We established the relation models between aboveground biomass accumulation and canopy leaf area index, leaf SPAD, plant N concentration and root-zone N content, finaly establish the tegrated soil-crop system management for high yield and high resource use efficiency in North China Plain. Compared to farmers’ conventional treatment, the rate of N application could be dramaticly decreased from250kg ha-1to166kg ha-1, while grain yield could be increased from9.9Mg ha-1to10.3Mg ha-1, so the partial factor productivity of N increased from39.5kg kg-1to62.0kg kg-1.3. For the filed experiment research of cultivar interact with N management on improving grain yield and grain N concentration, the maximum grain yield averaged8.85and8.90Mg ha-1for ZD958and XY335, respectively, which was approximately45%higher than the yield of YD13(6.10Mg ha-1). GNC in XY335was highest among the three hybrids. The maximum GNC averaged1.62%for XY335,1.42%for ZD958, and1.48%for YD13. Compared to YD13, XY335and ZD958had higher biomass and N accumulation during the grain filling period and at harvest, and the apparent amount of N remobilization from stover (leaf plus stem) after silking was greater in XY335than in ZD958, which contributed to high yield and GNC in XY335. All maize hybrids achieved their maximum grain yield and>95%of their maximum GNC with ONR treatment. Selection of appropriate hybrids such as XY335in combination with optimal N management can increase grain yield and GNC btained on the North China Plain.4. A field experiment with five rates of N application and three plant densities (6.0,7.5and9.0plants m2) in Quzhou County on the North China Plain (NCP) was conducted to understand the physiological mechanisms of biomass accumulation and partitioning in the grain, and the nitrogen (N) uptake associated with different plant densities and N management strategies. The highest grain yield and NUE were achieved in the7.5plants m2treatment; both the suboptimal (6.0plants m2) and supra-optimal (9.0plants m2) plant densities resulted in diminished yield and NUE. Compared to6.0plants m2, the7.5plants m2treatment displayed higher biomass accumulation during the grain-filling period and also exhibited more biomass allocated to kernels with similar total biomass accumulation compared with the9.0plants m2treatment, which contributed to its higher grain yield. The N uptake in the7.5plants m2treatment was similar to that in the9.0plants m2treatment for pre-silking. However, the post-silking N uptake of the7.5plants m2treatment was66.4kg/ha, which was29.1%higher than that of the9.0plants m2treatment. Furthermore, the highest maize grain yield was achieved in the0.7xoptimal N rate (ONRx0.7), ONR and ONR×l.3treatments for6.0,7.5and9.0plants m2, respectively, which suggests that different N management strategies are needed for different plant densities.5. Compared to the conventional winter wheat/summer maize two harvests in one year cropping system, in the optimal winter wheat/summer maize two harvests in one year cropping system with optimize agriculture cultivation, water and N management, grain yield was increased by15.6%, and N fertilizer can be decreased by33.7%, irrigation water reduced by11.7%, the intensity of GHG emission reduced by16.7%simultaneously. However, it still need to use232mm groundwater per year, could not achieve groundwater sustainable use in future. When winter wheat planting was decreased in the three harvest in two years cropping system (first year winter wheat and summer maize, second year:spring maize), groundwater consumption was reduced and could achieve sustainable use for water balance, the lowest intensity of GHG emission and highest farmer income was achieved. However, the grain yield was lower than that of the optimal winter wheat/summer maize cropping system. |
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