Abstract: At the Beijing experimental base of the Sino-German cooperative project, optimized and conventional irrigation fertilization systems were carried out in 1999-2000. Total 318 mm water with seven times and 60 kg/ha nitrogen with two t imes. were applied in the optimized system. Total 329 mm water with four irrgatio n times and 300 kg/ha nitrogen with base and top-dressing fertilization comprised the conventional system. The results were as follow. The root size of the optim ized system was larger and integrated root system age (IRSA) at flowering stage was younger than that of the conventional system, and the ratio of root in the 30-60 cm soil layer was also increased. There were no significant difference in both grain yield and water use efficiency between the two systems, although the opt imized system increa sed nitrogen use efficiency 4 times comparing with conventional one.

Key words: Waternitrogen system, Winter wheat, Root system