Regional Soil Moisture Automatic Monitoring System

1: System functions

Soil is a complex heterogeneous system. Although traditional soil moisture monitoring methods such as drying, neutron method, and dielectric constant method can accurately reflect the soil moisture content at measurement points, the soil moisture content in a large area can often only be inferred from limited measurement point data; Although remote sensing can quickly determine the surface soil moisture content in a region, remote sensing products usually require time scale extension and validation using ground observation data. Therefore, at small and medium-sized scales such as farmland and small watersheds, the above methods often cannot meet the growing demand for large, fast, and accurate soil moisture dynamic information in soil science research and modern precision agriculture.

American scientists have designed a regional soil moisture measurement method based on the relationship between near ground environment cosmic ray fast neutron concentration and soil moisture content, which is harmless, non-contact, does not damage soil structure, is not affected by soil texture, salt or soil moisture physical state, has a large measurement range, and suitable measurement depth/The snow depth monitoring system can continuously and automatically measure the soil moisture content or equivalent snow depth over a large area in the field, and is an effective verification method for remote sensing inversion of soil moisture content.

2: Basic principles

Cosmic ray particles in the environment collide with atomic nuclei to generate high-energy neutrons. These high-energy neutrons undergo elastic collisions with atomic nuclei, especially hydrogen atoms, in the medium as they pass through air and soil, changing direction and losing some energy, gradually slowing down. The fast and slow neutrons returning to the surface after collision will reach equilibrium at an extremely fast speed on the surface, and their concentration is significantly affected by the surface soil moisture. By using a neutron detector to detect the intensity of fast or slow neutrons in a specific energy range near the surface, the average soil moisture content over a large area can be calculated by modifying the relationship. Fast neutron intensity is used to calculate soil moisture content, while slow neutron intensity is used to calculate surface snow depth.

3: Application Fields

Mainly used in soil moisture measurement, drought monitoring, snow depth measurement, agricultural irrigation guidance, slope stability analysis, flash flood forecasting, water supply management, numerical forecasting, climate modeling, etc. In addition, it can be installed on mobile platforms to draw large-scale soil moisture maps.

4: System features

Easy to install, sturdy and durable, easy to operate, no need for professional personnel, suitable for long-term continuous automatic measurement in the field;

Measurement range * up to700 meters (40 hectares), with a measurement depth of up to 70 centimeters;

Non hazardous, non-contact, and non-destructive to soil structure;

Almost unaffected by physical and chemical properties such as soil texture, density, and salinity;

Can be used to measure snow depth;

Remote sensing inversion of soil moisture provides ground validation at a matching pixel scale;

Comes with data processing software for easy data processing.

system parameter

System power supply:6～26VDC；

System power consumption:95mA@12V ；

Collection interval:1 minute to 1 year is optional;

Data Storage: InternalSD card, external replaceable SD card;

Data interface:USB、RS232；

Measurement range: * Large measurement range700 meters, with a maximum measurement depth of 70 centimeters;

measure Cheng:0~saturation;

Uncertainty:0～4%；

Software features: Visual graphical display interface, easy for users to operate;

Software functions: data quality control, coefficient comparison selection, soil moisture calculation;

Software input data format:Txt or excel;

Software output data format:txt；

If there is a one hour counting interval, the software can process no less than onceThree years of data;

The software can linearly display the calculation results of soil moisture.

5: System composition

Mainly composed of neutron detector, data collector, solar power supply system, installation bracket, chassisComposed of GSM transmission module, data processing software, and optional sensors for soil moisture and rainfall.

Specialized data processing software

The data processing software for the cosmic ray neutron soil moisture observation system is designed for measuring soil moisture using the cosmic ray neutron method. Software utilizes cosmic ray neutron sensorsThe neutron count measured by the cosmic ray sensing sensor is combined with relevant meteorological data, and the corresponding calculation formula is used to calculate and output the soil moisture value of the region.

The data processing result interface of the software is shown in the following figure:

6: References

M. Zreda, W. J. Shuttleworth, X. Zeng, C. Zweck, D. Desilets, T. Franz, et al.(2012): COSMOS: The COsmic-ray Soil Moisture Observing System, Hydrol. Earth Syst. Sci. Discuss., 9, 4505–4551.

Rivera Villarreyes, C. A., Baroni, G., and Oswald, S. E. (2011): Integral quantification of seasonal soil.

moisture changes in farmland by cosmic-ray neutrons, Hydrol. Earth Syst. Sci., 15, 3843–3859,

Desilets, D., Zreda, M., and Ferre, T. (2010): Nature’s neutron probe: land-surface hydrology at an elusive scale with cosmic rays, Water Resour. Res., 46, W11505.

Zreda, M., Desilets, D., Ferré, T. P. A., and Scott, R. L. (2008): Measuring soil moisture content non-invasively at intermediate spatial scale using cosmic-ray neutrons, Geophys. Res. Lett., 23(9), 949-952.

Jiao Qishun, Zhu Zhongli, Liu Shaomin, et al. Research and Application of Cosmic Ray Fast Neutron Method in Soil Moisture Measurement in FarmlandJ. Advances in Earth Sciences, 2013, 28 (10): 1136-1143.

Jia Xiaojun, Shi Shengjin, Huang Binxiang, et al., Principles and Applications of Measuring Soil Moisture by Cosmic Ray Neutron Method, China Agricultural Bulletin,2014,21:113-117.