Abstract:Water and fertilizer are the most two active controlled factors that affect the yield of specific crops under specific ecologic conditions in an agricultural production system. In order to tackle the problem of the water resources shortage and low fertilizer use efficiency in dryland farming in north China, water and nutrient must be coordinated. For this purpose, the key and sensitive stage of water and nutrient coordination should be ascertained firstly, according to the law of their demand to water and nutrient. Many studies have been conducted to ascertain the key stage of winter wheat to (nitrogen,) but conclusions are not accordant. In this paper, pot experiments were carried out to study responses to nitrogen deficiency and compensation on the growth and yield of winter wheat at different stages under a normal irrigated condition, so that, the stress sensitive and compensative stage of winter wheat demanding nitrogen are fixed. Results indicated that the sensitive stages of winter wheat responding to nitrogen deficiency are over winter and jointing stage. The compensative stage is jointing stage. Nitrogen deficiency at over winter stage reduced the tillering number and dry weights of above-ground parts and root significantly. The effect on above-ground parts is greater than that of root and the R/S ratio reached maximum at this stage. Nitrogen deficiency at over winter and jointing stage reduced the yield of winter wheat markedly, but the effect on yield was neglected at late stage. The spikelet bearing number and 1000-grain weight reduced due to the nitrogen deficiency at over winter stage, while nitrogen deficiency at heading stage and maturity stage had (significant) effect on grain number per spike.