| In order to study the changes in soil water-salt-heat during freezing and thawing period and evaluate the effect of autumn irrigation in Hetao Irrigation District. The water-salt transportation under the changing temperature and soil water-salt-heat condition before maize seeding were analyzed based on field experiment. The results show that temperature of the soil layer during freezing and thawing period changed similarly for each period, affecting the moving of water and salt. In the freezing period, the non-frozen area water moved to the frozen area according to the temperature gradient, as increased by 4.02% to 18.18% by soil moisture. In the melting period, the 0～10 cm layer soil moisture content increased 11.54%～111.15% higher than freezing period. With the increase of temperature in spring season, the salt first moved with water to the surface soil under the water potential gradient. In the freezing period, the salt below the root layer is taken to the upper layer of soil, and the average increase rate in salt content is 11.19%～50.19%. Because of the infiltration of melt water and downward transport of the salt, the subsoil showed a trendency to desalination after soil melting, the salt content decreased on average by 15.71%～44.95% in the 20～100 cm layer. Autumn irrigation quota of 1 500 m3·hm-2, is suitable for planting pattern of maize mulching and furrow irrigation. The results of this study could be used to formulate autumn irrigation scheduling in Hetao irrigation district. |