This document discusses using multiple coil electromagnetic (EM) technology to rapidly assess and map soil salinity. Surveys were conducted at two sites in India using DUALEM instruments, which can measure conductivity to depths of 3-10 meters. Over 3,000 data points were collected at one site along with soil samples. Inversion modeling was used to generate 2D and 3D maps of apparent electrical conductivity (ECa) and estimated soil salinity (ECe) with good accuracy compared to soil samples. The results demonstrate that DUALEM technology allows efficient generation of digital soil salinity maps in 2D and 3D, which can help with effective salinity management strategies such as drainage, leaching, and irrigation practices.

1. (National Workshop on Challenges In Irrigation Management
For Food Security, Roorkee, 26 Nov 2016)
D.S. Bundela*, D.K. Sharma, J. Triantafilis, Bhaskar Narjary and Aslam Pathan
ICAR-Central Soil Salinity Research Institute, Karnaly
& UNSW, Sydney, Australia
E-mail: ds.bundela@icar.gov.in

2. Background
• Canal irrigation development paradigm resulted in several-
folds increase in crop productivity during green revolutionfolds increase in crop productivity during green revolution
• It was forgotten that mega quantities of water also
introduce mega quantities of salts into an irrigated areaintroduce mega quantities of salts into an irrigated area
and change its hydrology and salt balance
• Consequently, irrigated lands has started losing yield gain
and over a period of time, these lands develop into twin
problems- soil salinity & waterlogging.
• Soil salinity and sodicity are widespread in irrigated areas
under arid & semi-arid regions of India as well in the World.
• In India, irrigation water mobilizes salts and aggravates the
secondary salinization problem in ~20% of irrigated areas

3. Background…
• Remote sensing provides spatial distribution of soil surface
salinity that too moderate and severe classes but not slightsalinity that too moderate and severe classes, but not slight
class of surface salinity and NOT at all sub surface salinity
P i l i b d h i l th d id• Proximal sensing based geophysical methods provide
spatial & vertical distribution of salts in soil profiles/regolith
f• Therefore, there is need to apply multiple coil DUALEM
technology in salinity research to collect EM data quickly for
3D salinity assessment and mappingy pp g

4. • Expansion of secondary salinization in canal commands
• 50,000 ha under waterlogged saline soils in Haryana
• 2.95 m ha saline soils in the country
Huge Potential: Proximal sensing for rapid assessment of soil salinity
Single coil (EM38)  multiple coils (DUALEM)

5. Objectives
• To assess and map soil salinity at two Indian sites to
generate reliable 2D /3D EM conductivity/ soil salinity
images for salinity managementimages for salinity management
• To monitor the efficacy and impact of salinity
management strategies implemented by re measuringmanagement strategies implemented by re-measuring
and remapping salinity

6. Study Area: Western Yamuna CanalStudy Area: Western Yamuna Canal CommandCommand
WYC
GCA: 13,543 sq km
CCA 10 840 kCCA: 10,840 sq km
7 Water Circles
Districts: 5 Full
7 Part
Tehsils: 14 Full
22 Part
Nain Field
Mokha Kheri
Villages: 2206
Mokha Kheri

7. Technology shift from EM38 to DUALEM System
Conventional: Geonics EM-38
DUALEM‐21, 421 and 642 can investigate
vertical salt distribution and soil/ water salinityvertical salt distribution and soil/ water salinity
up to 3, 6 and 10 m depth
Modern EM tool: DUALEM-21

8. DUALEM 21DUALEM‐21
Theoretical depth of ECa measurement
S.
N
EM
S t
Depth
l d( )
Variety of DUALEM Systems
No System resolved(m)
1. DUALEM-2 3 (1)
2. DUALEM-21 3 (4)
3. DUALEM-421 6 (6)
Geonics EM38 0 0 5 m
( )
4. DUALEM-642 10 (6)
Operating
Frequency: 9.0 kHz
Geonics EM38 0‐0.5 m
0‐1.5 m
0‐1.0 m
0 3 0 m0‐3.0 m
DUALEM‐21
DUALEM-21 http://www.dualem.com/

9. Survey Transect & Soil samples at Nain Farm
Data point:3349Data point:3349
Soil sampled points: 32

10. Site Salinity Assessment
Nain Field

11. Survey Transects
32 Sample Locations at Nain Farm32 Sample Locations at Nain Farm
4 depth soil samples
(0-15 15-45 45-75 &
Total soil samples collected: 128 (32x4) (8-9 Jan 2016)
(0 15, 15 45, 45 75 &
75-105 cm)
(10 11 Jan 2016)
Mokhra Kheri Field
Total soil samples
collected: 96 (24x4)
(10-11 Jan 2016)

12. 55.5
60
0‐15 cm 15‐45 cm 45‐75 cm 75‐105 cm
Soil salinity sample and depth wise at Nain Farm
50
ECe
12 soil samples (37.5%) Ece < 4.0
20 samples (62.5%) with ECe range 4.12 to 55.5
32.8 32.1
33.2
30
40
14.62
16.54
12.51
19.55 19.8
20
10.311.07
4.76
3.153.652.88
1.6
3.02
4.343.563.232.65
6.06
5
8.96
2.22
4.984.123.94 3.8
1.82
5.74
3.98
8.17
0
10
0
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32
Sampling point ID

13. St ti ti f EC f 32 l t N i F )Statistics of ECe of 32 samples at Nain Farm)
Depth (cm) n Min Mean Median SD Max Skewness
0-15 32 1.60 10.8 4.87 12.2 55.5 2.2
15-45 32 0.81 7.6 5.29 6.8 30.8 1.7
45-75 32 0.93 9.9 7.36 8.6 38.0 1.4
75-105 32 1.00 10.1 6.79 8.3 28.0 0.7

14. EM Data of Nain Site

15. 2D EM Conductivity Images of Four Receivers
1m Hcon
(0-1.5m)
2m Hcon
(0-3 m)
1m Pcon 2m Pcon
(0-0.5m) (0-1.0m)

16. Quasi-2d and 3d inversion modellingQuas d a d 3d e s o ode g
WE CAN use a
single frequency and
multiple array technology
Inversion modelling parameters
Forward modelling: CF or FS (Maxwell) multiple array technology
DUALEM
g ( )
Inversion algorithm:
Occam’s regularization with S1 or S2
( )
+
2D/3D inversion software
DUALEM‐21Dampness factor (λ): 0.07-3.0
Best Inversion Results:
EM4Soil
/3Best Inversion Results:
Cumulative function(CF) forward
modeling,
l h d d
EM4Soil
Quasi‐2D/3D Module
S2 inversion algorithm, and damping
factor λ (0.07)
To generate 3D salinity Images

17. Salinity inversion modelling results (32 sets)Salinity inversion modelling results (32 sets)

18. Q3D Results

19. Coefficient of determination (R2) between soil ECe andCoefficient of determination (R ) between soil ECe and
apparent electrical conductivity (ECa) at Nain Farm
and between True ECe and ECe
Depth (cm) 1mPcon 1mHcon 2mPcon 2mHcon
0-15 0.90 0.82 0.85 0.69
15-45 0.78 0.79 0.81 0.76
45-75 0.70 0.75 0.77 0.83
75-105 0.60 0.64 0.67 0. 73
Best Parameters Regression model between True ECe and ECe
0 07 S2 CF R2 0 780.07, S2, CF R2=0.78

20. Inverted ECe Images (Nain Field)
(0-0 2m) (0 2 0 5m)(0-0.2m) (0.2-0.5m)
(0.5-0.8m) (0.5-1.1m)
Seven depths, Z= 0-0.2, 0.2-0.5, 0.5-0.8, 0.8-1.1, 1.1-1.5, 1.5-2.3 and 2.3-3.3 m

21. 3D Conductivity Images (Nain Field)
Layer 1: < 0.2 m
Layer 2: 0.2-0.5 m
Layer 3: 0.5-0.8 my
Layer 4: 0.8-1.1m
Layer 5: 1.1-1.5 m
Layer 6:1.5- 2.3 m
Layer 7:2 3 3 3 mLayer 7:2.3- 3.3 m

22. 3D Conductivity Images (X‐Cut)

23. 3D Conductivity Images (Y‐Cut)

24. Mapping salinity in 3D Mokhra Kheri sitepp g y

25. Salinity Management Strategies
• Pre-reclamation management components
• Reclamation components
P l i• Post-reclamation management components

26. Salinity Management Strategies
Group/sub‐group Technology/StrategiesGroup/sub group Technology/Strategies
Reclamation  Surface & Subsurface drainage
 On‐farm land development including surface drainage
 Leaching Leaching
Management
Crop management
 Selection of crops and cropping sequences
 Exploitation of varietal differencesCrop management  Exploitation of varietal differences
 Improved agronomic practices
Soil management  Land forming/seeding
 Application of additional nutrients
Irrigation water management Shallow depth‐high frequency irrigation
Pre/post‐sowing irrigationPre/post sowing irrigation
Switchover to improved irrigation techniques
Leaching for salt balance
Chemical management  A li ti f h i l d t ( )Chemical management  Application of chemical amendments (gypsum)
Rainwater management In‐situ rainwater conservation, Rainwater harvesting
and reuse, Fallowing

27. Conclusions •Conclusions
• Dual geometry multiple coil EM methodology tested has
shown its potential for rapid salinity assessment across
• .
shown its potential for rapid salinity assessment across
affected field and with depths.
• Salinity inversion (EM4Soil) software inverts ECa data with
best inversion parameters to generate 2D/3D salinity mapsbest inversion parameters to generate 2D/3D- salinity maps
of sites using 2D/ 3D quasi-inversion modeling.
• The modelled ECe values showed the close match with the
b d EC l f N i Fi ld (R2 0 78)observed ECe values for Nain Field (R2 = 0.78).
• DUALEM technology makes salinity mapping both spatially
and vertically a single step process and thereby a efficienty g p p y
way of generating 2D/3D digital soil salinity maps for
effective salinity management

28. /kU;okn/kU;~okn
Email:
ds.bundela@icar.gov.inThis is not the end…but the beginning!