Analysis of Water Characteristics of Black Soil over Long-term Experimental Researches in Northeast China

Long-term investigations of soil moisture at different precipitation patterns in the black soil in Hailun county, Northeast China were made. This area is an important base for marketable grains production due to a short cultivation history, high soil organic matter content, and high yield potential. In this region, precipitation is the principal water source during the cropping season, hence soil water storage is very important for agricultural production. Estimation of the soil water retention characteristics of the black soil is necessary to assess the risk of drought, soil water potential to meet crop water requirements, and irrigation scheduling. The soil water conditions are influenced by meteorology, soil physical properties, vegetation and other related factors. Ten years of field research were the basis for our definition of soil water characteristics of the black soils at Hailun Agri-ecology Experimental Station, Songnen plain, Northeast China. This paper identifies three different kinds of precipitation which affect soil water movement and soil water characteristics in different seasons. Investigations were performed during the normal rainfall year of 1995, the above normal rainfall year of 1997 and the drought year of 2001. The basic characteristics of soil water in farmland of the black soil region and also the vertical motion of soil water were discussed. Based on the results of soil water measurement and analysis, the movement of black soil water was divided into four periods a thawing stage in spring, a dry stage in summer, a wet stage in autumn and a frozen stage in winter. Four soil water zones were identified within the depth range 0-270 cm a highly varying zone (040 cm), a weakly