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Seven-step approach for complete near-surface resistivity survey of farmland with LandMapper

Despite numerous EC-mapping case studies conducted in many countries, only a few studies have demonstrated a complex approach to electrical geophysical site survey. In most studies only one technique of EC-mapping, either EM, GPR or four-electrode method was employed. This is understandable since most commercially available EC/ER measuring equipment operate in limited range of resistivities and depths (1-2 manufacturer-set depths are typical).

Locations

Protvino, MOS
Russia
55° 44' 34.0548" N, 37° 36' 55.4436" E
United States
42° 52' 48.8676" N, 104° 45' 56.25" W

Table 2. Technical Specifications of LandMapper ERM-02

Table 2. Technical Specifications of LandMapper ERM-02

Range of measurements   ……………………………………….……..    ER= 0.1-1 106 Ohm m

LandMapper ERM-02 – three parameter geophysical instrument

The newest model, LandMapper ERM-02, can automatically output EC or ER, accepts four-electrode probes of any configuration, including dipole-dipole and rectangular probes, reaches down to 10 m depth in most soils and stores up to 999 resistivity values in non-volatile memory. Also, ERM-02 model can be used to measure natural electrical potentials in soils, plants and other media with two non-polarizing electrodes (Figs. 2&3).

Introducing LandMapper ERM-01

To address those applications Landviser, LLC has developed and commercialized first model of LandMapper ERM-01 in 2004, which was able to measure electrical resistivity with central-symmetric four-electrode probes of Shlumberger and Wenner configurations to the depth of five meters. Device became popular among agricultural researchers in USA and Europe, and was tested for fast mapping and monitoring of agricultural and horticultural lands (Pozdnyakova et al., 2004; Paillet et al., 2010; Duncan et al., 2008; Carrow and Duncan, 2004).

LandMapper ERM-02: handheld meter for near-surface electrical geophysical surveys

published in December, 2010 issue of FastTIMES, online peer-reviewed journal of EEGS. To cite this publication use:FastTIMES dec 2010 Agriculture: A budding field in Geophysics

Golovko, Larisa, Anatoly Pozdnyakov, and Antonina Pozdnyakova. “LandMapper ERM-02: Handheld Meter for Near-Surface Electrical Geophysical Surveys.” FastTIMES (EEGS) 15, no. 4 - Agriculture: A Budding Field in Geophysics (December 2010): 85–93. http://www.landviser.net/webfm_send/69

Abstract

On-the-go sensors, designed to measure soil electrical resistivity (ER) or electrical conductivity (EC) are vital for faster non-destructive soil mapping in precision agriculture, civil and environmental engineering, archaeology and other near-surface applications. Compared with electromagnetic methods and ground penetrating radar, methods of EC/ER measured with direct current and four-electrode probe have fewer limitations and were successfully applied on clayish and saline soils as well as on highly resistive sandy soils, such as Alfisols and Spodosols. However, commercially available contact devices, which utilize a four-electrode principle, are bulky, very expensive, and can be used only on fallow fields. Multi-electrode ER-imaging systems applied in deep geophysical explorations are heavy, cumbersome and their use is usually cost-prohibited in many near-surface applications, such as forestry, archaeology, environmental site assessment and cleanup, and in agricultural surveys on farms growing perennial horticultural crops, vegetables, or turf-grass. In such applications there is a need for accurate, portable, low-cost device to quickly check resistivity of the ground on-a-spot, especially on the sites non-accessible with heavy machinery.

LandMapper ERM-02 - versatile and affordable

Landmapper - field EC meter with lab accuracy

Don’t break your back collecting soil samples. Reduce amount of samples sent for laboratory analysis and save money. And still make detail soil map of your fields, which will be more accurate than conventional soil surveys. Impossible? Not at all with LandMapper ERM-02.
This device measures three important electrical properties of soil: electrical resistivity (ER), conductivity (EC), and potential (EP). Utilizing the most accurate four-electrode principle LandMapper measures ER or EC and helps delineate areas with contrasting soil properties within the fields quickly, non-destructively and cost-efficiently.

In a typical setting, a four-electrode probe is placed on the soil surface and an electrical resistivity or conductivity value is read from the digital display. Using the device prior to soil sampling you can significantly reduce the amount of samples required and precisely design a sampling plan based on the site spatial variability.
Bulk soil EC was correlated with salinity, texture, stone content, bulk density, total available nutrients, water holding capacity, and filtration rates. Guided by detailed soil EC map obtained with LandMapper, only minimal amount of soil samples is needed to invert EC map into correlated soil properties. Also, LandMapper can be used to measure EC in soil pastes, suspensions and solutions and quickly estimate total dissolved salts (TDS) in solid and liquid samples.

Locations

Beltsville 39° 2' 5.3952" N, 76° 54' 26.9064" W
34° 57' 16.8984" N, 91° 38' 52.6164" W
56° 17' 1.7628" N, 36° 59' 27.4812" E

Quick Estimation of Salinity in Field Soils and Irrigation Water with LandMapper ERM-02

ec mapping with Landmapper on dead rice field after hurracaine IkeSoil salinity is routinely evaluated in the labs from electrical conductivity of liquid soil saturation extract (ECe). The resulted total salinity is reported either directly in conductivity units (dS/m) or converted to TDS (total dissolved solids) concentration in ppm (parts per million) using formula: 1 dS/m = 1 mS/cm = 1 mmho/cm = 640 ppm = 640 mg/L= 0.64 g/L=0.064%

But now EC of soil and waters can be measured directly in the field using highly accurate method of four-electrode probe and Landmapper ERM-02 measuring device. Best of all, probes can be build to sense different soil layers down to 30 ft! Probes are simple and inexpensive to make from common materials available at any hardware store.

For irrigation water and soil solutions: To measure ECw just put 4-electrode probe of Landmapper used for mapping into a ditch, canal, or other water source. Make sure that all 4-electrodes are in contact with water. Take a reading in EC (conductivity) mode. Display will read (example):  
K0*C= 150m  - which indicates milli Siemens (mS/m)
To convert to dS/m, divide display number by 100, i.e. 150 mS/m=1.5 dS/m.

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1D Vertical Electrical Sounding (VES) with LandMapper Procedure

standard big manual VES cable set by LandviserThe technique and procedure described here can be performed with LandMapper ERM-01 or ERM-02 (set in resistivity mode). The electrode spacings provided in this example are identical to Landviser's supplied "big manual VES" cable set made to measure 16 layers of topsoil down to approximately 9 m. The worksheet for pre-set electrode spacings in such cable re-calculating measured resistivities to 1D VES profile can be downloaded as Manual 1D VES workbook (MS Excel format).

Other electrode spacings are possible for custom-made cable arrays to reach deeper profiles. For example, we developed and tested with LandMapper a 60m-long cable, measuring down to ~ 20 m for one custom hydrology project

This manual VES technique is most convenient to use with three people. Follow step-by-step instructions below. If you need further help, do not hesitate to contact Landviser, LLC @ +1-609-412-0555 or info@landviser.com. Register on our site and download 7 related publications and software!

Locations

San Antonio 29° 25' 26.8392" N, 98° 29' 37.0608" W
Dmitrov 56° 20' 39.0192" N, 37° 31' 2.5716" E
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