Abstract: The available soil water at planting (ASWP) for winter wheat in Huanghuai Plain was mainly come from the precipitation in the period from July to the first ten-day of October. Based on the analysis of soil type and of precipitation pattern in summer time, and with 100 cm as the depth for calculating ASWP for winter wheat, the distribution pattern of ASWP in Huanghuai Plain was approached. The results showed that the ASWP had a linear relationship with the precipitation during the period from July to the first ten-day of October. The effective soil water content in normal years, plentiful precipitation years, and short precipitation years was 184-290 mm, 201-329 mm, and 148-265 mm, while the non-stressed soil water content at planting was 124-224 mm,135-266 mm, and 100-201 mm, respectively. The spatial distribution pattern of the ASWP for winter wheat in Huanghuai Plain had the characteristics of low in northwestern part and high in southwestern and eastern parts. In northwestern part, the sum of the ASWP in normal years plus the precipitation in growth period could not meet the water requirement of winter wheat, and 1-2 times irrigation would be necessary; while in southwestern and eastern parts, this sum could generally meet the growth and development of winter wheat, and no irrigation was needed.

Key words: Water stress, Photosynthesis rate, Water use efficiency, Diurnal change, Fraxinus mandshurica