Soil 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. Previously reported accelerated technique of soil EC mapping was optimized on the research farm of RiceTec, Inc in Lajas, PR in August of 2014. More then 450 EC data points were collected in less than two field days with two LandMappers to cover two depths (30 and 60 cm) simultaneously. Twenty eight soil samples were collected from the locations of extreme EC and send out for analysis of TDS (total dissolved solids) and differential chemical analysis. The results of chemical analysis from the samples were used to correlate with field-measured EC and to invert EC data into soil salinity map of the farm. The recommendations of salinity management of the seed test plots were provided.

1. Larisa Golovko, PhD
Landviser LLC and RiceTec Inc,
Houston, TX
Presented at
Agricultural Geophysics and Material Properties. Symposium on
the Application of Geophysics to Engineering and Environmental
Problems 2015: pp. 1-11.
https://doi.org/10.4133/SAGEEP.28-001

3. 3

4. 4
10 Ohm m =1 dS/m = 1 mS/cm =
1 mmho/cm = 640 ppm =
640 mg/L= 0.64 g/L=0.064%.

5. Veris
USDA Salinity Lab

6. AEMP-14, from KB Electrometry (Russia)
Quick EM method of EC mapping
down to 10 m, 14 frequencies.
Other EM Equipment by Dualem,
Geonics, GF Instruments, etc.

7. 7

8.  Fits in shirt pocket
 Runs all season from standard
9V battery
 Measures EC/ER in irrigation
water, saturated soil paste
as well as in the field soils
from 2 cm to ~20 m depth
8

9.  No calibration – EC output
calibrated once for each probe
size.
 No GPS integration – no wait for
satellite fix
 Push one button – get EC value
in 4 seconds!
 Stores 1000 EC values – can be
merged with concurrently taken
GPS data to produce quick
maps.
9

14. .

15.  Planted hybrids along with
varietal checks at the farm.
 Variable readings 300 – 1700
ppm in test area

16. 0
1000
2000
3000
4000
5000
6000
7000
8000
9000
EP1122
EP1122
CLXL8
CLXL8
CL161
CL161
CL131
CL131
XP730
XP730
XP729
XP729
Rice yield, lb/acre Soil salinity at planting, ppm Soil salinity at harvest, ppm

17. No salt 294 ppm
0.5 gm/kg 378 ppm
1.0 gm/kg 302 ppm
1.5 gm/kg 581 ppm
2.0 gm/kg 721 ppm
2.3 gm/kg 1043 ppm
LA soil (check) 1570 ppm

19. 25
35
45
55
65
75
85
95
%ofhealthyplants

24.  Storm surge brings in salt
water
 Drought leaves it in place
 High pumping cost
reduces options for
flushing soil

26.  Spatial variability
 Temporal
variability
 Many samples
are needed to
characterize a
single field.

27.  management practices
 water table depths
 soil properties
 evapotranspiration rates
 rainfalls
 salinity levels of
groundwater
 hydrogeological
conditions

28.  Speed of
turn-over
 Units
 Techniques –
results non-
comparable
between
different labs
1000 umho/cm = 1 dS/m = 10 Ohm m = 1/ 640 ppm = 0.64 g/L =
0.064% = 45.7 grains per gallon

30. y = 0.1225x + 2.7372
R² = 0.5156
0
1
2
3
4
5
6
7
8
0 5 10 15 20 25 30
FieldERin1',Ohmm
TAMU Soil Extract conductivity, Ohm m
Resistivity of soil solution vs in-situ values

31. • 910 acres research farm
• 426 points ER measured at
1’ and 2’ depth
• 2 days, 2 LandMappers, 3
people, AT vehicle (mule)

32.  More dense measurements
in problem fields
 Cross-scanning other fields
 Collecting samples from
areas of very low/high
resistivity

33. Top: bad, deep: non-salty
Top: bad, deep: salty

36.  Good soil EC in top 30 cm < 1.5 dS/m (ER > 6
Ohm m) measured in flooded or “mud” conditions
 EC of irrigation water <1 dS/m (ER > 10 Ohm m) –
no yield reduction
 EC of irrigation water 1-3 dS/m (ER=3-10 Ohm m)
– yield reduction up to 50%
 On marginally salty soils/water:
 delay permanent flood - use several flushing with fresh
water instead, reduce N fertilizer, apply some gypsum on
sodic soil pre-season, consider switching to other crops or
rice hybrids
36

38.  USA Farmers (James Gentz, Jim White, David Murrel, Mr. Saltzman, Mr.
Goulding).
 RiceTec Inc. (Derrol Grimes, Robert Miller, Mark Spilman, Jose Plaza, Jaime
Suarez) & Helena Chemicals (Ronnie Melancor)
 Russian Visiting Scientists (Alexey Rusakov, Anatoly Pozdnyakov)
 Indonesian STEM Oil and Gas University, Cepu, Central Java)
www.landviser.net