Does High Evapotranspiration Lead to Highest Yields in
Pistachios and Almonds?
55th Annual California Irrigation Institute
Meeting
Sacramento, CA
January 30-31, 2017
Daniel Howes, Ph.D. P.E.
Charles Burt, Ph.D. P.E.
Associate Professor and Senior Engineer
[email protected]
Chairman
[email protected]
Irrigation Training and Research Center (ITRC)
California Polytechnic State University
San Luis Obispo, California
www.itrc.org
(805) 756-2434
© Cal Poly ITRC 2017
Overview
•
•
•
•
Background
Methods
Results
Conclusions
© Cal Poly ITRC 2017
Background
• Concerns:
– Increased population growth and changes in
dietary habits
– Combined with groundwater overdraft and
competition for water supplies
• Traditional thoughts –
– To get more yield, you need more ET
© Cal Poly ITRC 2017
Background
• Traditional research focusing on single
variable, ETc finds a linear relationship
between yield and ET
© Cal Poly ITRC 2017
Adding more variables
• The linear relationship breaks down
– Nitrogen, ETc, and yield for example
– Research continues on yield vs. ET but farmers
have increased yields with numerous inputs other
than water.
Derived from data in Hanks
et alITRC
(1976)
© Cal Poly
2017
This Study
• Non-traditional research to look at the
question:
– Can we produce more crop per unit ET?
• Resulting in less hunger with sustainable water
consumption
• Hypothesis
– Looking at numerous almond and pistachio fields,
no good relationship can be found between ET
and yield for these crops
• There are more things to consider than ET
© Cal Poly ITRC 2017
Procedure
This study examines the relationship
between yield and ET with limited
evaluation of other factors
1. Actual ETc
2. Yield data and:
–
–
Tree age
Tree spacing
© Cal Poly ITRC 2017
Study includes fields in Kern and
Kings Counties of California
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Actual Evapotranspiration (ETc)
• Monthly actual plant
water use
• Developed from remote
sensing (ITRC-METRIC)
• Monthly spatial ET
• 30 meter resolution
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Actual Evapotranspiration (ETc)
• Field boundaries
overlaid in GIS
• Actual ET was extracted
from ET raster outputs
• Monthly outputs
• Summarized as AprilOctober Total Actual ETc
• For three years
© Cal Poly ITRC 2017
Yield Data
• Yield data from 236 fields
– Average field size = 117 acres
– Minimum = 17.8 acres
– Maximum = 242 acres
•
•
•
•
2011, 2013, and 2014
Different varieties were examined
But lumped into single lbs of meat per acre
Fields selected where greater than 5 yrs old
for almonds and 10 yrs old for pistachios
© Cal Poly ITRC 2017
Results
• ET vs. Yield
• Yield vs. age and tree spacing
© Cal Poly ITRC 2017
Individual Ranch
(multiple fields managed together)
2011 Ranch A Pistachio
Yield (lbs/acre)
5,000
y = 236.79x - 5594.3
R² = 0.8325
4,000
3,000
2,000
1,000
0
0
5
10
15
20
25
30
Apr-Oct ETc (inches)
35
40
45
© Cal Poly ITRC 2017
Almonds
2013 Almonds
5,500
5,000
4,500
4,000
3,500
3,000
2,500
2,000
1,500
1,000
500
0
0
5
10
Yield (lbs/acre)
y = 56.115x + 1121.5
R² = 0.0991
15 20 25 30 35
Apr-Oct ETc (inches)
40
45
5,500
5,000
4,500
4,000
3,500
3,000
2,500
2,000
1,500
1,000
500
0
50
y = 52.386x + 514.02
R² = 0.2194
0
5
10
15
20 25 30 35 40
Apr-Oct ETc (inches)
45
50
55
2014 Almonds
Yield (lbs/acre)
Yield (lbs/acre)
2011 Almonds
5,500
5,000
4,500
4,000
3,500
3,000
2,500
2,000
1,500
1,000
500
0
y = 62.998x - 501.38
R² = 0.2425
0
5
10
15
20 25 30 35 40
Apr-Oct ETc (inches)
45
50
55
© Cal Poly ITRC 2017
Almonds
Age and Tree Spacing
2011 Almonds
5,500
5,000
4,500
4,000
3,500
3,000
2,500
2,000
1,500
1,000
500
0
Yield (lbs/acre)
Yield (lbs/acre)
2011 Almonds
0
5
10
15
20
Age/Leaf (years)
25
5,500
5,000
4,500
4,000
3,500
3,000
2,500
2,000
1,500
1,000
500
0
30
0
25
5,500
5,000
4,500
4,000
3,500
3,000
2,500
2,000
1,500
1,000
500
0
0
5
10
15
20
Age/Leaf (years)
75
100 125
Trees/Acres
150
175
200
2014 Almonds
Yield (lbs/acre)
Yield (lbs/acre)
2014 Almonds
50
25
30
5,500
5,000
4,500
4,000
3,500
3,000
2,500
2,000
1,500
1,000
500
0
0
25
50
75
100 125 150 175 200
© Cal Poly ITRC 2017
Trees/Acres
2014 Almonds
1.0
0.9
0.8
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0.0
Relative Yield
Relative Yield
2011 Almonds
"West Side"
"East Side"
0.0
0.2
0.4
0.6
0.8
Apr-Oct Relative ETc)
1.0
0.9
0.8
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0.0
"West Side"
"East Side"
0.0
1.0
0.2
1.0
0.9
0.8
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0.0
"West Side"
"East Side"
0.0
0.2
0.4
0.6
Apr-Oct Relative ETc
0.8
1.0
2015 Almonds
Relative Yield
Relative Yield
2013 Almonds
0.4
0.6
Apr-Oct Relative ETc
0.8
1.0
1.0
0.9
0.8
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0.0
"West Side"
"East Side"
0.0
0.2
0.4
0.6
0.8
1.0
© Cal ETc
Poly ITRC 2017
Apr-Oct Relative
0
81
39
95
98
172
54
22
77
62
99
32
15
78
114
145
252
249
137
84
250
235
178
11
71
131
113
25
85
61
246
74
45
75
146
214
60
143
167
64
168
33
14
211
236
29
16
198
141
142
52
21
197
247
255
76
90
53
43
193
50
160
157
231
69
175
36
201
3
234
174
238
9
190
68
220
92
233
237
152
179
196
19
224
129
51
48
42
31
8
188
12
124
245
89
241
109
209
165
94
125
7
156
161
1
37
200
110
217
189
136
27
223
121
127
93
225
128
227
34
173
119
120
Rank of Yield/ET
0
154
80
39
82
162
54
104
138
140
84
142
64
108
137
14
77
130
25
252
60
168
250
13
62
16
253
21
52
133
71
34
19
107
63
184
106
247
152
10
24
51
29
201
243
36
91
9
242
75
233
135
245
66
228
226
50
27
42
115
31
177
197
211
169
89
191
125
5
118
221
155
192
195
7
48
216
119
213
196
190
219
158
6
224
189
4
Rank of Yield
Yield Ranking
300
250
200
150
100
50
Field ID
2011 Rank
2011 Y/ET Rank
2013 Rank
2013 Y/ET Rank
2014 Rank
2014 Y/ET Rank
2015 Rank
2015 Y/ET Rank
Avg Rank
300
Rank of Yield to ET Ratio
250
200
150
100
50
Field ID
Avg Rank
© Cal Poly ITRC 2017
Pistachios
8,000
7,000
6,000
5,000
4,000
3,000
2,000
1,000
0
2013 Pistachio
0
5
10
15
Yield (lbs/acre)
y = 79.096x + 1345.7
R² = 0.0944
20 25 30 35
Apr-Oct ETc (inches)
40
45
8,000
7,000
6,000
5,000
4,000
3,000
2,000
1,000
0
50
y = 61.785x + 566.45
R² = 0.0654
0
5
10
15
20 25 30 35
Apr-Oct ETc (inches)
40
45
50
2014 Pistachio
Yield (lbs/acre)
Yield (lbs/acre)
2011 Pistachio
8,000
7,000
6,000
5,000
4,000
3,000
2,000
1,000
0
y = 43.881x + 825.77
R² = 0.0364
0
5
10
15
20 25 30 35 40
Apr-Oct ETc (inches)
45
50
55
© Cal Poly ITRC 2017
Pistachio Age
2013 Pistachio
Yield (lbs/acre)
8,000
7,000
6,000
5,000
4,000
3,000
2,000
1,000
0
0
5
10
15
20 25 30 35
Age/Leaf (years)
40
45
50
8,000
7,000
6,000
5,000
4,000
3,000
2,000
1,000
0
0
5
10
15
20 25 30 35
Age/Leaf (years)
40
45
50
20 25 30 35
Age/Leaf (years)
40
45
50
2014 Pistachio
Yield (lbs/acre)
Yield (lbs/acre)
2011 Pistachio
8,000
7,000
6,000
5,000
4,000
3,000
2,000
1,000
0
0
5
10
15
© Cal Poly ITRC 2017
Conclusion
• No clear relationship between yield and ET for
almonds and pistachios
• If more variables are included in a study, the
relationship between yield and ET will be reduced
• Intensive research must begin on examining the
multiple factors that influence the yield besides
ET
• There is a tremendous opportunity to learn more
about what combination of variables are needed
to maximize yield
© Cal Poly ITRC 2017
Recommendations
• Future research is needed using a multivariate or systems approach to maximizing
yield per unit ET
• Investment is needed in the form of research
dollars in non-traditional research designs
• Coordination of numerous aspects of
agronomy and irrigation on a level that has
not yet been accomplished.
© Cal Poly ITRC 2017
Thank You
More Information visit
www.itrc.org
© Cal Poly ITRC 2017