Soil Moisture Regime Evaluation And Time-space Change In Root Region At Growing Season In Heilongjiang

This paper analyzed the agricultural characteristics of soil including soil bulk density, field capacity, wilting moisture, soil relative capacity and available soil moisture in different agricultural soil horizons(0-2Ocm, 0-30cm, 0-50cm) in Heilongjiang Province. Soil bulk density varies with topography and soil tapes. The geographical distribution shows that the high values occurred in east and west regions, low values occurred in middle region, and the high value existed in south region and low values existed in north region; vertical distribution shows that soil bulk density increases with soil depth. The geographical distribution of wilting moisture show that these values decrease gradually from south to north region, and its vertical distribution is that its values decrease with soil depth. The geographical pattern of available moisture indicated that the high values appeared in mountain area and the low values appeared in plain. Soil relative moisture values were higher in east than that in west. Seasonal pattern was that high values were in spring and autumn, and low value was in summer. The time-space variable patterns of agricultural soil moisture in the past two decades in Heilongjiang Province are given by analyzing the two indexes of soil water storage capacity and its deficit-surplus status. The geographical distribution of the 0-20cm, 0- 30cm, 0-50cm soil water storage capacity shows the high value occurred in east and the low value occurred in west, and the growing seasonal distribution shows the low value appeared in summer and the high value appeared in autumn and spring, excluding the sandy soil in west region as the opposite case. The soil water storage capacities vary with soil depth depending on soil tapes. Based on the comprehensive analysis of the time-space distribution-pattern of the farm land soil moisture in Heilongjiang Province, nine indexes belonging to three categories are determined and six regimes are given including the 0-20cm soil moisture regimes in April, the 0-20cm and 0-50cm soil moisture regimes in May, the 30-50cm soil moisture regimes in July, and the 0-50cm and soil moisture regimes in summer, the 30- 50cm soil moisture in autumn, the 0-50cm soil moisture in the whole growing season(April-September). Finally the division results have been achieved. In each division there are seven sub-divisions: severe deficient, deficient, balanced, roughly balanced, obvious surplus and severe surplus moisture regimes.