Effects of Nitrogen Application and Film Mulching on Yield Performance Parameters and Nitrogen Use Efficiency of Spring Maize in the Middle Reaches of Yangtze River Yield Performance Characteristics and Regulation Effects of Plant Density and Sub-Soiling Tillage System for High Yield Population of Summer Maize Productivity Performance of High-Yield Spring Maize and Approaches to Increase Grain Yield (above 15 t ha-1) in Irrigated Plain of Inner Mongolia Yield Performance and Resource Efficiency of Double-Cropping Maize in the Yellow, Huai and Hai River Valleys Region Yield Performance and Resources Used Efficiency of Winter Wheat and Summer Maize in Double Late-Cropping System