Abstract: Roots play an important role in water and nutrient uptake by crop. The investigation of root system development of winter wheat and the effect of nitrogen, phosphorus and soil moisture on its growth in the North Plain of China was made in 1990 and 1991. Roots were sampled by coring and the changes of root weight and length were determined in five development stages. The root weight growth rates were 0.845, 0.386, 1.921, 2.500 and 0.427g/m²· day and root length growth rates were 0.062, 0.0329, 0.310, 0.221km/m²· day in seedling, overwintering, jointing, heading and seed filling stages, respectively. The total root length and total root weight with time could be described by logistic growth function, and the exponential model was suggested for describing root system distribution with soil depth. N and P fertilizer application could promote the growth of winter wheat root system. Water stress reduced the root dry weight and root length, but root length and weight was greater in 0.3-1.20m depth under water stress than that of irrigated wheat. Irrigation could significantly increase roots in the stages of vegetative development and extend the root lifespan in the stages of reproductive development.

Key words: Winter wheat, Root system, Nitrogen, Phosphorus, Water stress