无论在隔绝蒸发还是在自然蒸发条件下，短期内土壤水吸力有随土层深度的增加呈先下降后升高的趋势，而同一深度土层水吸力则随时间的推移而升高；
Regardless of preventing evaporation or not, soil water suction decreased firstly and then increased with the increase of soil depth, and soil water suction at the same depth increased with time.
保雨灌溉技术的核心是向天空要水，与蒸发夺水，充分利用自然降水和土壤水分，满足作物需要。
The kernels of the rain conservation irrigation technology are increasing effective rain - fall, decreasing evaporation and sufficiently using soil water to satisfy the crops demands.
研究结果表明：高聚物不仅能提高土壤的持水力和增加土壤水对植物的有效性，而且还能抑制土壤水的蒸发。
The result shows that the high polymers VAM and PHM can not only enhance the water retention ability and the available water content, but also prevent the evaporation from the surface soil.
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