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Water and salt behavior in the soil under micro irrigation

微灌下土壤水盐行为

基本信息

批准号：
08660294
负责人：
YANO Tomohisa
金额：
$ 1.47万
依托单位：
Tottori University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
1996
资助国家：
日本
起止时间：
1996 至 1997
项目状态：
已结题

项目摘要

In weighing lysimeters with 1.5m of diameter and 1.6m of soil depth filled with coastal sand in a green house, orange trees were drip irrigated with synthesized saline water for about one month from mid-September in 1996 and one and half month from mid-August in 1997. Two chemicals, NaCl and CaCl_2 were used to make up the irrigation water to a total concentration of 2,000mg/l (EC=4.0dS/m). Water was supplied every day with an amount equal to 1.2 times of evapotranspiration (ET) on the previous day. The maximum daily ET with tap water irrigation was 4.2kg/day. In the case of tap water irrigation, there was a strong correlation between daily ET and pan evaporation with a correlation coefficient of 0.955. The effect of salt on the ET occurred immediately after saline irrigation started. Compared with the case of tap water irrigation, ET decreased by 20-25% under saline water irrigation condition in two weeks. At the end of experiment, high salt accumulation in the soil with ECe=3.5dS/m was found mostly at the root of orange tree and the relatively lower values with 1.4-1.6dS/m was observed at the depth of 10-60cm at 10cm apart from the tree. Orange production decrease is said to be nil at soil ECe less than 1.7dS/m and is 25% with ECe=3.3dS/m. More serious and adverse effect on ET than the production was suggested from this study. A computer program was used to simulate water and solute behavior in the soil by using the finite element method. Although the code was found to be reliable, the accuracy in both water and salt content was not quantitatively satisfactory when compared with the measured values.

在温室内直径1.5米、土层1.6米、填满滨海沙土的称量蒸渗仪上，从1996年9月中旬开始用合成盐水滴灌1个月左右，从1997年8月中旬开始滴灌一个半月。用氯化钠和氯化钙两种化学物质配制灌溉用水，总浓度为2000 mg/L(EC=4.0dS/m)。每天供水的水量相当于前一天蒸散量的1.2倍。自来水灌溉的最大日蒸散量为4.2 kg/d。在自来水灌溉条件下，日蒸散量与蒸发皿蒸发量之间存在很强的相关性，相关系数为0.955。盐分对ET的影响在盐水灌溉开始后即刻发生。与自来水灌溉相比，在盐水灌溉条件下，两周内ET下降了20-25%。试验结束时，土壤Ece=3.5dS/m的土壤盐分积累量较大，主要集中在橘树根部，在距树10 cm的10~60 cm土层，盐分积累量相对较低，为1.4~1.6dS/m。当土壤Ece低于1.7dS/m时，柑橘减产为零，当Ece=3.3dS/m时，减产为25%，对ET的影响比产量更严重和不利。采用有限元方法，用计算机程序模拟了土壤中的水和溶质行为。尽管代码被发现是可靠的，但与实测值相比，水和盐含量的准确性在数量上都不令人满意。