APPLICATION OF SOIL MOISTURE

SENSOR: A REVIEW

A N C H I T G A R G , P R I YA M I T R A M U N O T H , R O H I T G O YA LM A L A V I YA N A T I O N A L I N S T I T U T E O F T E C H N O L O G Y, J A I P U R

E M A I L : 2 0 1 5 P C D 5 3 5 5 @ M N I T. A C . I N

2 1 s t I n t e r n a t i o n a l C o n f e r e n c e o n H y d r a u l i c s , W a t e r R e s o u r c e s a n d C o a s t a l

E n g i n e e r i n gC W P R S , P u n e

INTRODUCTION• The world, at present is facing shortage of water which is hampering the

development of agriculture and hence the food production. Agriculture is by far the largest consumer of the Earth’s available freshwater: 70% of water withdrawals from watercourses and groundwater are for agricultural usage, three times more than 50 years ago. By 2050, the global water demand of agriculture is estimated to increase by a further 19% due to irrigational needs. Approximately 40% of the world’s food is currently cultivated in artificially irrigated areas. In addition, in the coming years, climate change will bring about enormous and partly unpredictable changes in the availability of water. (http://www.globalagriculture.org)Total water withdrawal in 2010 =

761km3

(Source: FAO, 2010)

Water use in different sectors of India

Fig 1: Water use in different sectors of India

• Under-irrigation and over-irrigation are common phenomena in agriculture and landscapes. Over-irrigation of plants leads to deficiency of oxygen in the root zone as excess water in the pores decrease oxygen in the pores of the soil. Also, in this water-deficient world, saving water is becoming necessary.

• The soil moisture parameter in such situations play a lead role in helping the growers know the exact amount of watering to be done. The soil moisture can be measured in two following methods:-

a) Direct methods – least expensive methods. Eg: Feel & inspection method, Hand push probe and Gravimetric method

b) Meters and Sensors – All those which are based on tensiometric or dielectric sensors. Eg: tensiometer, gypsum blocks, TDR, FDR etc.

Soil-Water Relationship:-Water availability is illustrated in the figure by different water levels. Excess or gravitational water drains quickly from the soil after a heavy rain because of gravitational forces (saturation point to field capacity). Plants may use small amounts of this water before it moves out of the root zone. Available water is retained in the soil after the excess has drained (field capacity to wilting point). This water is the most important for crop or forage production. Plants can use approximately 50 percent of it without exhibiting stress, but if less than 50 percent is available, drought stress can result. Unavailable water is soil moisture that is held so tightly by the soil that it cannot be extracted by the plant. Water remains in the soil even below plants' wilting point. (Jeff Ball, 2001) (Yonts et al., undated)

Fig 2: Soil-Water Relationship

DIFFERENT TYPES OF SOIL MOISTURE SENSORS

Soil water tension based sensors:-

1. Tensiometer

2. Granular matrix sensor

TENSIOMETER

Fig 3: Tensiometer

Rapid, easy,

inexpensive

Can be used in freezing

and thawing

conditions

Ideal for sandy

loam and light

textured soils

Periodic maintenance

Malfunctions when soil water

tension > 80 cb

Measures tension only in

vicinity

Enciso-Medina et al., 2007Schmugge et al., 1979Alam et al., 1997

Hensley et al., 1999 Werner, 2002 Goodwin, 2009

Different response to different soil

types

GRANULAR MATRIX SENSOR

Fig 4: Granular Matrix Sensor

Less maintenanc

e in comparison

to tensiometer

Cheaper than

tensiometer

Less changes to

varying temperatur

es

Not responsive to rains < 0.5

in.

Less accurate in sandy soils

Shock et al., 1998Irmak et al., 1990

Enciso-Medina et al., 2007Berrada et al., 2014 Zazueta et al., 1994

DIFFERENT TYPES OF SOIL MOISTURE SENSORS

Soil water content based sensors:-

1. Time Domain Reflectrometry

2. Frequency Domain Reflectrometry

Need to be calibrated carefully

TIME DOMAIN REFLECTROMETRY (TDR)

Fig 5: TDR unit

Responds quickly to

varying soil moisture

Readings at multiple

depths with single

probe

Very little disturbance at test

site

Costly & Cannot be used in

highly saline soils

Reads soil moisture only in

its vicinity

Marenghi, 2013Pitts, 2016Skierucha et al., 2012

Paige et al., 2008Blonquist et al., 2005 Wolpert et al., 2013

Requires soil specific

calibration

FREQUENCY DOMAIN REFLECTROMETRY (FDR)

Fig 6: FDR unit

Very accurate

Can be used in highly

saline soils

Measures SM at

several depths in

same location

Formation of sir gaps , if sensor

& soil don’t make good

contact

Reads soil moisture only in

its vicinity

Abouatallaha et al., 2011 Muñoz-Carpena et al., 2004

Linmao et al., 2012Muñoz-Carpena et al., 2004 Wolpert et al., 2013

VH400 SOIL MOISTURE SENSOR

• Capacitance-based, small and rugged (Salih et al., 2013)

• Low cost monitoring of soil moisture, waterproof

• Rapid response time, more sensitive at higher water content

• Low power consumption (< 7mA) (www.vegetronix.com)

• Insensitive to salinity of water, does not corrode over time (Zaier et al., 2013)

•  Can be operated in wide range of temperature (-40 oC to 85 oC) (www.vegetronix.com)

• Data logger is means of communication between the sensor to the user.

• Data logger can store and relay readings through SMS, SD Cards and Bluetooth

• Increasing demand of water and food is creating stress on the water resources. The use of soil moisture sensors helps growers with irrigation scheduling by providing information about when to water the crops.

• The irrigation water applied to the soils can be controlled and automated using soil moisture sensors which help in determining the available water of the soil. This leads to judicious use of water.

• Since, there are variety of sensors available in the market, the growers must consider various factors while selecting the appropriate sensor for their use.

• The advantages and disadvantages of sensors must be considered as criteria for selection because the working principle behind each type of sensor varies with its application and type of soil.

• The VH400 sms is rapid and small capacitance-based sensor and its output can be relayed on data logger through SMS, bluetooth and SD cards

• The wireless sensors in agriculture increases efficiency, productivity, profitability of farming operations and maximises crop yield with minimum use of irrigation water.

CONCLUSION

REFERENCES1. Ball J (2001) “Soil and Water Relationships”, article published on The Samuel Roberts

Noble Foundation, http://www.noble.org/ag/soils/soilwaterrelationships/2. Global Agriculture Report, http://www.globalagriculture.org/report-topics/water.html3. Yonts D, Benham B (undated) Irrigation Chapter-3: Soil water. Plant & Soil Sciences e-

library,. http://passel.unl.edu/pages/printinformatonmodule.php?idinformationmodule=113044713 9&idcollectionmodule=1130274164

4. www.globalagriculture.org5. Food and Agriculture Organisation, 20106. Zaier R, Zekri S, Jayasuriya H, et al. (2015) Design and implementation of smart

irrigation system for groundwater use at farm scale. International Conference on Modelling, Identification and Control (ICMIC 2015)

7. Zazueta SF, Xin J (1994) Soil moisture sensors. Bulletin 292, Florida Cooperative Extension Service, Institute of Food and Agricultural Sciences, University of Florida

www.experimental-hydrology.net/wiki/index.php?title=Soil_moisture_- FDR_(profile_probe)

8. Enciso MJ, Porter D, Périès X (2007) Irrigation monitoring with soil water sensors. Cooperative Extension, B-6194, The Texas A&M University System.

9. Schmugge TJ, Jackson TJ, McKim HL (1979) Survey of methods for soil moisture determination. NASA Technical memorandum

10. Werner H (2002) Measuring soil moisture for irrigation water management. Cooperative Extension Services, College of Agriculture and Biological Sciences, South Dakota State University. http://agbiopubs.sdstate.edu/articles/FS876.pdf

11. Hensley D, Deputy J (1999) Using tensiometers for measuring soil water and scheduling irrigation. Coopertive Extensive Service. Department of horticulture, College of tropical agriculture & human resources, University of Hawaii at Manoa. Landscape L-10.

12. Goodwin I (2009) How to use tensiometers?. Department of environment and primary industries, Agriculture Victoria: ISSN 1329-8062

13. Irmak S, Payero OJ, Eisenhauer ED, Kranz LW, Martin LD, et al., (2006) Watermark Granular Matrix Sensor to Measure Soil Matric Potential for Irrigation Management. Extension EC783, Institute of Agriculture and Natural Resources, University of Nebraska-Lincoln

14. Berrada A, Hooten MT, Cardon EG, Broner I (2001) Assessment of irrigation water management and demonstration of irrigation scheduling tools in the full service area of the Dolores project: 1996-2000. Technical Report, TR01-7, Colorado State University

15. Marenghi P (2013) Soil moisture sensor: Types and technology. http://www.auroras.eu/soil- moisture-sensor-types-and-technology/

16. Pitts Larry (2016) Monitoring soil moisture for optimal crop growth. https://observant.zendesk.com/hc/en-us

17. Skierucha W, Wilczek A, Szypłowska A, Sławiński C, Lamorski K (2012) A TDR-based soil moisture monitoring system with simultaneous measurement of soil temperature and electrical conductivity. Sensors 10: 13545-13566. DOI: 10.3390/s121013545

18. Paige BG, Keefer OT (2008) Comparison of field performance of multiple soil moisture sensors in a semi-arid rangeland. Journal of the American Water Resources Association (JAWRA) 44(1):121-135. DOI: 10.1111/j.1752-1688.2007.00142.x

19. Blonquist JM, Jones SB, Robinson DA (2005) A time domain transmission sensor with TDR characteristics. Journal of Hydrology, 314:235-245.

20. Wolpert J (2013) Soil moisture sensors. University of California, Extension, articles.extension.org/pages/31515/soil-moisture-sensors

21. Salih Md. EJ, Adom HA, Shakaff Md. YA, Shuib AM (2013) Real time wireless agricultural ecosystem monitoring for cucumus melon Cultivation in natural ventilated greenhouse. International Journal of Scientific and Research Publications, 3 (11)

E-mail:- 2015PCD5355@MNIT.AC.INANCHIT141991@GMAIL.CO

M