TENSIOMETER AUTOMATION DEVICE FOR GREENHOUSE IRRIGATION SCHEDULING
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Date
2018
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Division of Agricultural Engineering ICAR–Indian Agricultural Research Institute New Delhi
Abstract
The rapid increase of human population is putting an incredible strain on our
environment. Water demand already exceeds supply in many parts of the world and
more areas are expected to experience this imbalance in near future. Agriculture is by
far the largest consumer of the Earth’s available freshwater. Due to shrinking fresh
water resources, micro irrigation plays an important role in sustainable use of water in
agriculture. Automation of irrigation further helps in conserving the water by timely
even distribution of water and thus prevents wastage of water. Hence, the present
research entitled “Tensiometer Automation Device for Greenhouse irrigation
Scheduling” was carried out in Rabi season of 2017-18 at farm Green-house, Centre for
protected cultivation technology, Indian Agricultural Research Institute, New Delhi.
The main objective of the Study was to design, develop and evaluate the performance
of Piezo resistive based soil moisture sensor in green house irrigation scheduling under
Chrysanthemum and Tomato crops. The experimental soil was found as sandy loamy
soil. An experimental area of 300 m2 was selected to grow tomato and chrysanthemum
crops irrigated by drip irrigation system. The area was divided in to two plots of size
10 × 15 m (150 m2) each. The piezo-resistive based soil moisture sensor was designed
and was incorporated in automation of greenhouse irrigation scheduling. To evaluate
the performance of sensors, both developed piezo resistive based soil moisture sensors
and tensiometers were installed at 15 cm and 30 cm depth. The sensor readings and
corresponding soil samples were taken on daily basis to measure the volumetric soil
moisture content. The volumetric soil moisture content were calculated from the
corresponding voltage readings recorded by the piezo resistive based soil moisture
sensor and tensiometer using Soil characteristic curve and then they were compared
with soil moisture content obtained by gravimetric method. The results revealed that
the coefficient of determination (R2) was found to be 0.83 and 0.82 between volumetric
soil moisture content calculated by piezo-resistive based soil moisture sensor (based on
its voltage readings) and soil moisture content measured by the gravimetric method in
Chrysanthemum at 15 cm and 30 cm depths, respectively, while, for Tomato it was 0.84
and 0.82, respectively for same methods. The coefficient of Determination (R2
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between volumetric soil moisture content measured by tensiometer and volumetric soil
moisture content measured by standard gravimetric method for chrysanthemum at 15
and 30 cm depth were found to be 0.72 and 0.71, respectively, while for Tomato it was
recoded as 0.71 and 0.71. The results also revealed that the voltage readings were in
inverse relation with the soil moisture status. The RRMSE of soil moisture content for
tensiometer and piezo resistive based soil moisture sensor varied from 9.47 to 19.38
and 7.44 to 18.28, respectively. Lower RRMSE values and higher coefficient of
determination (R2
) were recorded by the piezo resistive based soil moisture sensor as
compared to tensiometer indicating higher degree of accuracy. The paired t-test
indicated that both piezo resistive based soil moisture sensor and tensiometer were
significantly different at 5% significance level. The results showed that piezo resistive
based soil moisture sensor measured soil moisture tension efficiently than the normal
tensiometer for both greenhouse Chrysanthemum and Tomato crops
Description
t-9898
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