Effect of different nitrogen supply on the temporal and spatial distribution and remobilization of canopy nitrogen in winter wheat under limited irrigation condition Preliminary study on limited irrigation for spring wheat field in semi-arid region of loess plateau Effects of nitrogen application on grain yield, nitrogen utilization and balance of winter wheat under limited irrigation condition Effects of Limited Irrigation on the Root Development of Spring Wheat in a Semi-arid Region The responses and their physio-ecological bases of spring wheat to limited irrigation in Loess Plateau Effect of limited irrigation on diurnal variation in flag-leaf photosynthesis and yield of dryland wheat