Soil water potential sensors are the core equipment for accurately monitoring soil moisture dynamics, and their installation quality directly affects the accuracy and reliability of data collection. The following are the standardized installation process and key technical points:
1、 Preliminary planning and site selection
1. Principle of typicality
Select representative monitoring points based on research objectives: farmland should avoid ridges and ridges, forest land should be away from the base of tree trunks, and slopes should be selected in the middle of gentle slopes. It is recommended to set 3-5 repeated sampling points per hectare to eliminate spatial heterogeneity errors.
2. Layered deployment strategy
Determine the burial depth based on the distribution depth of the main root systems of crops (such as 40-60cm in corn fields and 80-120cm in orchards). When monitoring multiple layers, the spacing between each layer should be greater than 20cm to avoid mutual interference.
3. Environmental avoidance
It is prohibited to install in fertilizer accumulation areas, irrigation pipe outlets, or large root system intersections, and to maintain a distance of more than 30cm from stones/building foundations to reduce zero drift caused by physical compression.
2、 Standardized installation steps
1. Pre drilling operation
Use a stainless steel probe rod slightly smaller than the outer diameter of the sensor to vertically drill holes, and the hole wall should be kept smooth without collapse. Sandy soil can be directly screwed in, and for heavy clay soil, it is recommended to lubricate it with water before inserting.
2. Precise positioning and fixation
Place the ceramic cup of the sensor facing downwards at the bottom of the hole, and use a specialized film pressing tool to compact the surrounding soil layer by layer to ensure that the sensor is in close contact with the soil. A small amount of quartz sand can be mixed in the clay area to improve the contact interface.
3. Cable protection treatment
The lead out cable is bent and buried in a 'U' shape to prevent tension from being transmitted to the probe. The underground section is covered with PVC corrugated pipes, and the surface section is threaded with metal hoses. The joints are wrapped with three layers of waterproof tape.
4. Sealed to prevent evaporation
The pores are backfilled in layers with original soil that has removed stones, and the surface is covered with a 5cm thick mixture of peat to maintain gas exchange and suppress water evaporation. Rock landforms can be sealed with silicone injection.
3、 Special scenario adaptation plan
Application in freezing and thawing zone: wrap 20cm thick foam insulation material around the sensor before winter, and remove it in time after thawing in spring.
Saline alkali land improvement: Soak the sensor in deionized water for 48 hours first, and then inject dilute hydrochloric acid solution every week to rinse the ceramic surface after installation.
Mobile observation: In conjunction with a portable solar power supply system, it adopts a quick connect plug design to facilitate frequent relocation of monitoring points.
4、 Verification and maintenance cycle
Newly installed equipment needs to establish a calibration curve with the gravity moisture content measured by the drying method, and conduct on-site comparison and verification before and after the rainy season every year. Daily maintenance includes monthly inspection of cable insulation resistance (>100M Ω), quarterly calibration of pressure permeable plate aperture, and long-term storage in a drying oven when not in use.
By strictly implementing the above installation specifications, the spatiotemporal representativeness of soil water potential monitoring data can be effectively improved, providing reliable basis for irrigation decision-making and ecological research. It is recommended to combine IoT technology to achieve remote monitoring, but attention should be paid to the impact of electromagnetic interference on signal transmission.