Evaluation of Wireless Soil Moisture
Measurement Systems with regards to water
quantity and quality
Sanjay Shukla
Chambal Pandey
Department of Agricultural and Biological Engineering
Introduction
 Florida ranks 2nd in vegetable production in US
 Seepage irrigation is common - upflux from the shallow
water table (~45 cm)
 Visual observation and/or hand-feel methods result in
under/over irrigation
 Conventional practice-high water table
•
•

Wastage of water, more runoff, and less rainfall storage
Nutrient leaching to groundwater
Solutions

Soil moisture based water table management
Objectives
 Collect background soil moisture data at
a vegetable farm in South Florida.
 Evaluate the effects of wireless soil
moisture based water table management
practice on water use, water quantity and
crop yield
Experimental Details
 Study area = 6.5 ha
 Eight fields (each: 274 m x 31
m)
 Subsurface irrigation and
drainage system (SID)
 Study periods:
• Sep, 02 - May 03
• Sep, 03 - Apr 04
 Soil: Myakka sand
 Eggplant and Pepper
Data Collection

Hydrologic
•
Soil moisture
•
•
•
•
•

Wireless Capacitance probe
Data transmission from field to grower’s office
Water table
Rainfall
Irrigation
Nutrients
•
•
Groundwater
Soil
Monitoring Design
Background and Test Period
Soil Moisture and Water Table
SM @ 10 cm (Conventional)
Water Table Depth (Improved)
Water Table Depth (Conventional)
Test period
0
70
0.2
60
0.4
50
0.6
40
0.8
Permanent wilting
point
30
1
Field capacity
Date
04/23/03
04/09/03
03/26/03
03/12/03
02/26/03
02/12/03
01/29/03
01/15/03
01/01/03
12/17/02
12/03/02
1.6
11/19/02
0
11/05/02
1.4
10/22/02
10
10/08/02
1.2
09/24/02
20
Water Table Depth (m)
Background period
Potential runoff
80
% Soil Moisture (VWC)
SM @ 10 cm (Improved)
Evaluation Period
Soil Moisture and Water Table
SM @ 10 cm (Improved)
SM @ 10 cm (Conventional)
Water table depth (Improved)
Water table depth (Conventional)
70
0.2
60
0.4
50
0.6
40
0.8
Permanent wilting point
30
1
Field capacity
Date
04/22/04
04/10/04
03/28/04
03/16/04
03/03/04
02/20/04
02/07/04
01/26/04
01/13/04
01/01/04
12/19/03
12/07/03
11/24/03
1.6
11/12/03
0
10/30/03
1.4
10/18/03
10
10/05/03
1.2
09/23/03
20
Water Table Depth (m)
0
Potential runoff
09/10/03
% Soil Moisture (VWC)
80
Total water use
180
157
Total Water Use (Million L)
160
140
120
101
100
80
60
40
20
0
Improved
Conventional
 36%
saving
of total
water use
Groundwater P
Improved
Conventional
1.2
p-value = 0.28
p-value = 0.00
Total P Concentrations (mg/L)
1
0.8
p-value = 0.00
0.6
0.4
0.2
0
Field 2
Field 4
Field 7
Groundwater NO3
Improved
Conventional
80
Groundwater NOx-N concentrations (mg/L)
p-value = 0.38
70
60
50
40
30
20
p-value = 0.37
p-value = 0.21
10
0
Field 2
Field 4
Field 7
Fruit Weight
Improved
Conventional
1600
p-value = 0.18
Average fruit weight (g/plant)
1400
1200
1000
p-value = 0.18
800
p-value = 0.47
600
p-value = 0.06
p-value = 0.19
p-value = 0.65
400
p-value = 0.03
200
0
1
2
3
4
Field
5
6
8
Waterborne disease-Phytophthora
Summary

Soil moisture based water table management
saved 36% of water.
 50% less runoff
 reduced nitrate leaching to the groundwater
 better crop performance

 overall
better or equal yield
 100% more yield compared to the conventional side due
to crop disease
Conclusions
1. Considerable reduction in irrigation water use
by soil moisture based water table management
compared to the conventional irrigation
management.
2. Soil moisture based water table management
increased available soil water storage resulting
in less frequent drainage and runoff events
3. Soil moisture based water table management
reduced nutrient leaching