Effects of water deficit and supplemental irrigation at different growing stage on uptake and distribution of nitrogen, phosphorus and potassium in winter wheat

Pot experiment was conducted in green house to study the effect of water deficit and supplemental irrigation at different growing stage of winter wheat on the uptake and distribution of N, P and K by plants. The results showed that water deficit decreased wheat growth as well as its nutrient uptake. Tillering, jointing and filling stages were the critical stages of water deficit, and the dry weight of shoots was decreased by 36.1% to 72.3%, the total N uptake by 40.6% to 72.0%, the P by 40.5% to 72.4%, and the K by 25.9% to 69.5% when water stressed at these stages. However the winter stage was not so sensitive as those. When water deficit occurred, the plant growth and nutrient uptake decreased by only a relative lower percentage. Furthermore, supplemental irrigation at different stage could not all increase the plant growth and its nutrient uptake. When water was supplemented at jointing stage, the dry shoots were increased to the highest magnitude, being 18.2% higher than that of the control, and so did the total uptake of nitrogen, phosphorus and potassium, being increased by 14.5%, 15.6% and 38.2% respectively. Supplemental irrigation at winter and filling stage, although not so significant, also had the positive effects on winter wheat. Nevertheless, the plant dry biomass and the nutrient uptake were significantly reduced by supplemental irrigation at tillering stage. In addition, results also showed that, although supplemental irrigation conducted at winter, jointing or filling stage increased the growth and nutrient uptake of entire plant, yet the grain uptake of nutrients was not all increased correspondingly. When supplemental irrigation was conducted at winter and filling stage, grain N uptake was correspondingly increased by 5.5% and 20.9%, P 9.1% and 6.2%, while N was decreased by 19.6% and P by 13.5% when supplemental water was added at jointing stage. However, grain K uptake was decreased by 3.0% to 26.7%, when additionally irrigated at any of the 3 stages.