COTTON
WATER SUPPLY & DEMAND
SOUTHERN HIGH PLAINS
10
13-14 inches
during growing season
9
8
INCHES
7
PREC
PET
Record High 40.55
inches 1941
Record low 5.86 inches
2011
40-45 inches
during growing season
6
5
4
3
2
1
0
JAN
FEB
MAR
APR
MAY
JUNE
JULY
AUG
MONTH of YEAR
SEPT
OCT
NOV
DEC
Approximately 70% of
the Events are less than
0.5 Inches
IRRIGATION WATER SUPPLY
• ONE CUBIC FOOT OF WATER=
7.48 GALLONS
• ONE ACRE=43560 SQUARE FEET
• ONE ACRE FOOT OF WATER =
325,829 GALLONS
• ONE ACRE INCH= 27,152 GALLONS
• 1 GPMA= 1440GPAD/27152GPACIN
= 0.053 AC IN DAY-1
IRRIGATION WATER SUPPLY
27,225 gallons/acre inch
Gallons/Min/Acre
Acre Inches/Day
1.0
0.053
2.0
0.107
3.0
0.160
4.0
0.214
5.0
0.267
6.0
0.320
7.0
0.373
IRRIGATION APPLICATION RATES
125 acre pivot
VOLUME
GPMA
0.5in
1.0 in
1.5 in
Acre
Inches/hour
3
80 hrs
160 hrs
240 hrs
0.78
4
57 hrs
113 hrs
170 hrs
1.10
5
45 hrs
90 hrs
136 hrs
1.39
6
38 hrs
75 hrs
113 hrs
1.65
SOIL WATER DATA
TEXTURE
PULLMAN
CLAY LOAM
FIELD
CAPACITY
Inches/foot
PERMANENT
WILTING POINT
Inches/foot
PLANT
AVAILABLE
WATER
Inches/foot
INITIATION OF
STRESS
60% depletion
of PAW
INFILTRATION
RATE
Inches/hour
4.38
3.05
1.33
0.80
0.21
3.86
2.36
1.50
0.90
0.77
3.25
2.03
1.22
0.73
1.28
AMARILLO
FINE SANDY
LOAM
2.88
1.90
0.98
0.59
1.84
PATRICIA &
AMARILLOL
OAMY FINE
SAND
2.60
1.62
0.98
0.59
5.79
OLTON
LOAM
ACUFF
LOAM
POTENTIAL
EVAPOTRANSPIRATION
MODIFIED PENMAN EQUATION
ETo = c[W-Rn + (1-w) – f(u) – (ea-ed)]
= potential crop evapotranspiration (mm/day)
ETo
W
= temperature-related weighting factor
= net radiation in equivalent evaporation (mm/day)
Rn
f(u)
= wind related function
(ea-ed) = vapor pressure deficit of the air at mean air
temperature
c
= adjustment factor to compensate for the effect
of day and night weather conditions.
25-Sep
18-Sep
11-Sep
4-Sep
28-Aug
21-Aug
14-Aug
7-Aug
31-Jul
24-Jul
0.45
17-Jul
10-Jul
3-Jul
26-Jun
19-Jun
12-Jun
5-Jun
29-May
22-May
15-May
8-May
1-May
INCHES/DAY
2013 DAILY PET BY LOCATION
0.50
CANYON
TULIA
LUBBOCK
LAMESA
0.40
0.35
0.30
0.25
0.20
0.15
0.10
0.05
0.00
0
25-Sep
18-Sep
11-Sep
4-Sep
28-Aug
21-Aug
14-Aug
7-Aug
31-Jul
24-Jul
17-Jul
10-Jul
40
3-Jul
26-Jun
19-Jun
12-Jun
5-Jun
29-May
22-May
15-May
8-May
1-May
ACCUMULATED INCHES
2013 SEASONAL PET BY LOCATION
45
CANYON =37.4 Inches
TULIA = 40.0 Inches
LUBBOCK = 38.2 Inches
LAMESA = 38.7 Inches
35
30
25
20
15
10
5
CROP COEFFICIENTS-COTTON
1.20
30 Inch Rows
40 Inch Rows
CROP WATER USE/PET
1.00
0.80
0.60
PEAK FLOWER
FIRST MATURE BOLL
0.40
50%OPEN BOLLS
0.20
FIRST SQUARE
FIRST FLOWER
0.00
100
300
500
700
900
1100
1300
1500
1700
ACCUMULATED HEAT UNITS
1900
2100
2300
2500
25-Sep
18-Sep
11-Sep
4-Sep
28-Aug
21-Aug
14-Aug
7-Aug
31-Jul
24-Jul
17-Jul
10-Jul
3-Jul
26-Jun
19-Jun
12-Jun
5-Jun
29-May
22-May
3000
0.20
1500
0.15
1000
0.10
500
0.05
0
0.00
DAILY CROP WATER USE
15-May
ACCUMULATED HEAT UNITS
2013 COTTON WATER USE
0.35
ACC HEAT UNITS
DAILY CROP WATER USE
2500
0.30
0.25
2000
Regression Coefficients For Yield Components and
Water Supply at Various Developmental Stages
Stage of
Boll
Development Number/Acre
Lint/Boll
Lint
Yield/Acre
TWS
0.34
0.35
0.12
SI-FF
0.58
0.65
0.73
FF-PB
0.55
0.04
0.52
PB-M
-0.45
-0,56
-0.43
TWS= Total Water Supply; SI=Square Initiation; FF=First Flower;
PB= Peak Bloom; M=Maturity
COTTON WATER USE EFFICIENCY
TEXAS HIGH PLAINS
1800
1600
1400
LINT YIELD (Pounds/acre)
75-100 pounds/inch
1200
1000
800
40-50 pounds lint/inch
600
10-12 INCHES OF IRRIGATION WATER
HIGH EFFICIENCY APPLICATION
400
AVERAGE GROWING SEASON RAIN
200
0
0
2
4
6
8
10
12
14
16
WATER SUPPLY (Inches)
18
20
22
24
26
SUMMARY
• Lack of an adequate water supply throughout
the life of most crop plants is the primary cause
of yields being only a fraction of the genetic
yield potential
• When the water supply is adequate, the
availability of adequate essential nutrients is
responsible for less than optimum growth rates
and development of reproductive organs
• Understanding the needs and management of
rate limiting nutrient supplies will greatly
increase yield and quality of product within the
limits of the water supply