覆膜不同开孔程度蒸发条件下土壤水热变化动态研究

覆膜灌溉播前铺膜通常无法覆盖全田面 ,而播种后需为作物破土预留出苗孔 ,覆膜灌溉时还需增设灌水孔 ,对上述各类孔的问题 ,可采用覆膜开孔率来统一表征。到目前为止 ,尚未见国内外关于覆膜开孔蒸发的水热耦合迁移方面的报道。在研制了室内蒸发水热动态观测实验系统的基础上 ,本文根据剖面初始含水率均匀的覆膜开孔蒸发土壤水分和温度的动态观测资料 ,分析了土壤温度变化规律及剖面水分的降低趋势 ,并建立了覆膜开孔蒸发的累积蒸发量、相对累积蒸发量及单位膜孔面积累积蒸发量随时间和不同覆膜开孔率变化的函数关系。分析结果表明 ,不同覆膜开孔率控制下的累积蒸发量与时间平方根之间均符合Gardner提出的裸土蒸发理论关系。该结果发展了传统的Gardner方程 ,拓展了该关系的应用途径 ,对今后进一步研究覆膜开孔蒸发的水热运动规律有重要意义。

DYNAMIC VARIATIONS OF SOIL WATER AND HEAT UNDER EVAPORATION CONDITIONS VARYING WITH APERTURE RATIO OF PLASTIC MULCH

The soil cannot be totally covered by plastic mulch in the field. And normally in the mulch holes should be preset for plants to emerge after sowing, and irrigation holes added for irrigation. The term of aperture ratio is often used to represent the above issue. So far very few national or international papers about evaporation from soil under perforated plastic mulch have been reported. In order to study characteristics of evaporation from the soil with initial homogeneous soil water content, a laboratory system of evaporation has been set up. Based on the dynamic observations of soil water and soil temperature, their variation regularities during evaporation and at the end of the evaporation were described, and calculations and analyses of soil temperature variation and soil water content distribution, functions of cumulative evaporation, relatively evaporation and cumulative evaporation per unit area of the film holes to aperture ratios performed. The results showed that under the influence of evaporation, the cumulative evaporation varied linearly with the square of the evaporation time, which corresponded to the bare soil evaporation theory presented by Gardner. These results have extended Gardner equation and expanded its application ranges, thus being very useful for further study on water and heat transport in plastic mulched field.