Optimization of sowing date and seeding rate for high winter wheat yield based on pre-winter plant development and soil water usage in the Loess Plateau, China oleh Ai-xia REN, Min SUN, Pei-ru WANG, Ling-zhu XUE, Miao-miao LEI, Jian-fu XUE, Zhi-qiang GAO, Zhen-ping YANG