Effects of Intermittent Combined Irrigation on the Characteristics of Soil Water and Salt Movement in Farm Land of Salt-affected Soil

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Supported by the National Major Science and Technology Program for Water Pollution Control and Treatment (No.2015ZX07203-007), the National Natural Science Foundation of China (No.41402208) and the Natural Science Foundation of Shandong Province (No.ZR2016EEM34)

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    【Objective】Researchers in the Salt Soil Laboratory of the USA (United States Department of Agriculture,1954) and ASCE (American Society of Civil Engineers,1990) have brought forth a series of advice aiming at ameliorating salt-affected soils. Amelioration of salt-affected soils requires for the first priority removal of excessive soluble salt. However, in actual productive application, the only method available for reducing soluble salt content in the root zone of the crop is to wash the salt off the soil with fresh water. Owing to shortage of fresh water resources, the use of brackish water as replacement has aroused extensive attention. Reasonable exploitation of brackish water can not only improve crop production, but also ameliorate salt-affected soils. To explore characteristics of soil and water movement in the fields under intermittent combined irrigation (ICI), a lab experiment was conducted in an attempt to provide certain theoretical basis and technical support for reasonable use of brackish water in moderately salt-affected soil. 【Method】The experimental system consisted of soil columns and Mariotte bottles. The latter was used to supply water with a constant water head of 1.5~2 cm. The one-dimension vertical water infiltration experiment was designed to have four treatments in terms of interval in intermittent irrigation, i.e. 0 min,30 min,60 min and 120 min and five treatments in terms of combination of the irrigation water, i.e. simple fresh water (F), simple brackish water (B), 2:1 (brackish and fresh water), 1:1 (brackish and fresh water) and 1:2 (brackish and fresh water). During the experiment, wetting front movement and cumulative infiltration was monitored. At the end of the experiment, soil samples were extracted at the soil extraction port as quickly as possible to avoid the effect of water redistribution inside the cylinder, and soil water content was measured with the oven-drying method and electrical conductivity of the soil solution with a conductivity meter. 【Result】Cumulative infiltration was relatively high during the initial stage of infiltration, and dropped drastically with the experiment going on. Measurements done at the same time show that the treatments of ICI were all higher than Treatments F, but differed slightly from Treatment B in cumulative infiltration, and among the treatments of ICI, the same in quantity of water supply, cumulative infiltration increased with the ratio of brackish water. And the infiltration lasted longer when the ratio of fresh water was higher. Cumulative infiltration was in good linear relationship with wetting front movement (R 2>0.99). Determination of soil water content at the same soil depth shows that the treatments of ICI exhibited an order of ICI 2:1 (Brackish water : Fresh water) > ICI 1:1 > ICI 1:2, indicating that soil water content was positively related proportional to ratio of brackish water. Treatments ICI were all higher than Treatment F in irrigation uniformity, which was negatively related to ratio of fresh water. In the 5~45 cm crop root zone, soil desalinization rate was significantly higher in Treatments ICI than in Treatment B, and varied sharply between the treatments. The higher the proportion of fresh water, the higher the soil desalinization rate, the more favorable the salt-water environment for the crop to grow in. Significance tests of the effects of Treatments ICI on soil desalinization rate show that all the treatments reached significant levels, regardless of combination ratio and length of interval, indicating that the parameters of ICI have important on soil salt movement. 【Conclusion】Intermittent combined irrigation is more conducive than other irrigation modes to the formation of a good soil water-salt environment for crops to grow. In actual productive application, a proper combination (fresh water and brackish water ratio and interval) should be designed and used in the light of crop salt tolerance and depth of the main root system active zone, so as to minimize damage of salt stress to crops.

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LIU Xiaoyuan, GAO Peiling, YANG Daming, ZHANG Qingwen, ZHANG Yuhang. Effects of Intermittent Combined Irrigation on the Characteristics of Soil Water and Salt Movement in Farm Land of Salt-affected Soil[J]. Acta Pedologica Sinica,2017,54(6):1404-1413.

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  • Received:May 09,2017
  • Revised:July 23,2017
  • Adopted:August 16,2017
  • Online: September 04,2017
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