Effects of regulated deficit drip irrigation under film on the growth indices and tuber characteristics of potato.
Irrigation with different levels of regulated deficit in different growth stages significantly affected the biological characteristics of potato (Table 2). Compared with that in CK, plant height in the treatments decreased, although the decrease in mild regulated deficit treatments (WD1, WD2, WD3, and WD4) was not significant (P > 0.05). In the moderate deficit treatments WD6 and WD7, plant height decreased significantly (P < 0.05). Stem diameter decreased in all treatments to various degrees but the smallest decrease was in WD1 and WD5 with the water deficit in the seedling stage. Compared with that in CK, the diameter decreased by 3.37% in WD1 and by 5.62% in WD5. However, when the deficit occurred in the tuber initiation and tuber bulking stages, the diameter decreased by 3.93–8.99% and by 6.74–10.64%, respectively, indicating that a water deficit in those two stages reduced potato stem growth.
Compared with CK, all treatments caused the leaf area index to decrease to varying degrees, ranging from 4.14–22.07%. The greatest decreases in leaf area index were in WD6 and WD8, with significant decreases of 11.72% and 22.07%, respectively. The leaf area index was least affected in WD5, with a decrease of only 4.14%. This result showed that mild water deficit at the seedling stage did not significantly affect leaf growth. By contrast, water deficit in the other stages hindered leaf growth. Both the longitudinal and transverse lengths of the potato tubers decreased, to different degrees. The greatest effect was in WD8, with significant decreases ranging from 11.51–14.28%. In WD1, WD2, WD5, and WD6, the decreases in both diameters were slight and not significant.
Table 2
Indices of potato growth in conventional irrigation (CK) and regulated deficit drip irrigation treatments in three years and averaged across years. Diameters are those of tubers.
Year
|
Treatment
|
Plant height
|
Stem diameter
|
Leaf area index
|
Longitudinal diameter
|
Cross diameter
|
(cm)
|
(cm)
|
(mm)
|
(mm)
|
2017
|
CK
|
141.62a
|
1.74a
|
1.25a
|
83.89a
|
65.62ab
|
WD1
|
139.55ab
|
1.69ab
|
1.19ab
|
82.55ab
|
65.74a
|
WD2
|
137.54ab
|
1.62b
|
1.12bc
|
81.77ab
|
63.88ab
|
WD3
|
139.39ab
|
1.58bc
|
1.07c
|
80.96ab
|
63.57ab
|
WD4
|
140.85ab
|
1.48 cd
|
0.98d
|
80.06ab
|
61.34bc
|
WD5
|
136.01ab
|
1.61bc
|
1.13b
|
82.03ab
|
64.12ab
|
WD6
|
130.15b
|
1.53c
|
1.09bc
|
81.01ab
|
62.69ab
|
WD7
|
135.36ab
|
1.36d
|
1.02 cd
|
78.58b
|
61.66b
|
WD8
|
137.52ab
|
1.28e
|
0.72e
|
78.05bc
|
57.62c
|
2018
|
CK
|
144.3a
|
1.93a
|
1.76ab
|
83.31a
|
65.54a
|
WD1
|
140.5ab
|
1.84ab
|
1.66bc
|
80.54ab
|
63.81ab
|
WD2
|
136.3ab
|
1.86ab
|
1.51c
|
79.86ab
|
61.95ab
|
WD3
|
134.6ab
|
1.88ab
|
1.61bc
|
78.55ab
|
59.47bc
|
WD4
|
134b
|
1.85ab
|
1.84ab
|
75.14bc
|
57.18bc
|
WD5
|
133bc
|
1.78b
|
1.85a
|
81.22ab
|
61.88ab
|
WD6
|
126bc
|
1.74bc
|
1.76ab
|
80.07ab
|
60.35b
|
WD7
|
136ab
|
1.81ab
|
1.69b
|
76.43b
|
58.74bc
|
WD8
|
139.5ab
|
1.86ab
|
1.67bc
|
72.69bc
|
54.38c
|
2019
|
CK
|
146.40a
|
1.67a
|
1.34a
|
88.53a
|
68.87a
|
WD1
|
145.10ab
|
1.63ab
|
1.29ab
|
87.17ab
|
68.09ab
|
WD2
|
143.80ab
|
1.64ab
|
1.251b
|
86.59ab
|
67.91ab
|
WD3
|
145.67ab
|
1.53b
|
1.24bc
|
87.41ab
|
64.38b
|
WD4
|
145.70ab
|
1.60ab
|
1.18c
|
84.26ab
|
62.93bc
|
WD5
|
140.37ab
|
1.64ab
|
1.19bc
|
87.04ab
|
67.44ab
|
WD6
|
133.07bc
|
1.59ab
|
0.99de
|
85.59ab
|
66.39ab
|
WD7
|
135.73b
|
1.60ab
|
1.23bc
|
82.76b
|
65.52ab
|
WD8
|
139.30ab
|
1.45c
|
1.01d
|
75.54c
|
59.48c
|
Average
|
CK
|
144.11a
|
1.78a
|
1.45a
|
85.24a
|
66.68a
|
WD1
|
141.72ab
|
1.72ab
|
1.38ab
|
83.42ab
|
65.88ab
|
WD2
|
139.21ab
|
1.71ab
|
1.29b
|
82.74ab
|
64.58ab
|
WD3
|
139.89ab
|
1.66b
|
1.31bc
|
82.31ab
|
62.47ab
|
WD4
|
140.25ab
|
1.64bc
|
1.33 cd
|
79.82ab
|
60.48bc
|
WD5
|
136.46ab
|
1.68ab
|
1.39bc
|
83.43ab
|
64.48ab
|
WD6
|
129.74bc
|
1.62b
|
1.28d
|
82.22ab
|
63.14ab
|
WD7
|
135.7b
|
1.59c
|
1.31c
|
79.26b
|
61.97b
|
WD8
|
138.77ab
|
1.53d
|
1.13e
|
75.43bc
|
57.16c
|
Note: Different lowercase letters within a column for a year or the average indicate significant differences among treatments (P < 0.05). The irrigation treatments were conventional irrigation (CK) and mild or moderate water deficit during each of four stages of potato growth. Mild deficit was in treatments WD1 (seedling), WD2 (tuber initiation), WD3 (tuber bulking), and WD4 (starch accumulation); moderate deficit was in treatments WD5 (seedling), WD6 (tuber initiation), WD7 (tuber bulking), and WD8 (starch accumulation). |
Potato Leaf Photosynthetic Characteristics
Net photosynthetic rate.
The net photosynthetic rate (Pn) of potato leaf from seedling to starch accumulation stage increased first and then decreased, showing a single-peak in CK and all treatments (Fig. 3). Mild regulated deficit treatments did not significantly affect the rate in the seedling stage. In the moderate deficit treatment WD5, the Pn decreased by 13.14% compared that with in CK, although the decrease was not significant. In the tuber initiation stage, the rate decreased significantly to 0.410 µmol·m− 2·s− 1 in WD2 (mild deficit) and to 0.337 µmol·m− 2·s− 1 in WD6 (moderate deficit), decreases of 19.28% (WD2) and 33.70% (WD6) compared with that in CK. The Pn was not significantly affected in the other treatments in this stage.
In the tuber bulking stage, the Pn decreased by 8.31% in WD3 (mild deficit) and by 29.37% in WD7 (moderate deficit), compared with that in CK. The compensation effect in WD2 after rehydration was greater than that in WD6, but neither rate was significantly different from that in CK. The Pn did not decrease from the tuber initiation stage to the tuber expansion stage, and the mean value in the bulking stage was between 0.323 and 0.463 µmol·m− 2·s− 1. In the starch accumulation stage, the absolute value of the Pn was lower than that at tuber initiation and expansion stages, with a mean value between 0.227 and 0.348 µmol·m− 2·s− 1. However, the Pn was significantly higher than that in the seedling stage. The Pn decreased by 15.12% in WD4 (mild deficit) and by 33.46% in WD8 (moderate deficit), compared with that in CK, indicating that a regulated deficit at the starch accumulation stage negatively affected the net photosynthetic rate.
Stomatal conductance.
Throughout the growth period, the stomatal conductance (Gs) increased successively from the seedling stage to the tuber initiation stage and then tuber bulking stage; however, the Gs decreased at the starch accumulation stage. There were differences in the range of decrease among the treatments (Fig. 4). The lowest Gs was in the seedling stage, ranging from 5.96 to 6.71 mol.m− 2.s− 1. In WD1 (mild deficit) and WD5 (moderate deficit), Gs decreased significantly by 7.29% and 11.09%, respectively, compared with that in CK. The Gs in the seedling stage was not affected in the other treatments. The Gs increased in the tuber initiation stage in all treatments except WD2 and WD6, with values increasing to between 12.68 and 14.70 mol m− 2.s− 1. The Gs in WD2 decreased by 13.70% and that in WD6 decreased by 14.83%. In the tuber bulking stage, Gs increased to the highest levels of the entire growth period, ranging from 14.73 to 17.00 mmol m − 2 s − 1, although it was lower in regulated deficit treatments than in CK. Compared with that in CK, the Gs decreased significantly in WD3 by 8.96% and in WD7 by 13.34%, which showed that regulated deficit in the tuber initiation and expansion stages did not favor stomatal opening. The Gs decreased significantly from the tuber bulking stage to the starch accumulation stage. With sufficient irrigation in this period, Gs was not significantly different from that in CK, whereas in WD4 (mild deficit) and WD8 (moderate deficit), it decreased significantly by 17.22% and 25.05%, respectively. This result demonstrated that regulated deficit during starch accumulation affected stomatal conductance.
Transpiration Rate.
In all treatments, the transpiration rate (Tr) first increased as growth progressed and then decreased, with a peak at the tuber expansion stage (Fig. 5). In the seedling stage, the Tr decreased by 13.01% in WD1 (mild deficit) and by 22.29% in WD5 (moderate deficit), compared with that in CK. In the tuber initiation stage, the Tr was 5.45 µmol mol− 1 s− 1 in WD2 (mild deficit) and 4.84 µmol mol− 1 s− 1 in WD6 (moderate deficit), decreasing by 10.68% in WD2 and by 20.63% in WD6 compared with that in CK.
In the tuber bulking stage, the Tr in WD1, WD2, WD5, and WD6 was not significantly different from that in CK after rehydration, showing evidence of a compensation effect. Compared with the tuber initiation stage, the Tr showed a large increase in all treatments. The Tr in WD7 (moderate deficit) decreased significantly by 10.28% compared with that in CK, whereas in WD3 (mild deficit), the Tr decreased by 5.25%, but it was not significantly different from that in CK. In the tuber initiation and tuber bulking stages, the Tr was higher than that in the seedling stage. In the starch accumulation stage, the Tr was 4.59 µmol mol− 1 s− 1 in WD4 (mild deficit) and 4.53 µmol mol− 1 s− 1 in WD8 (moderate deficit), decreasing by 15.58% in WD4 and by 16.64% in WD8 compared with that in CK, although the decreases were not significant. After rehydration, the Tr in WD3 and WD7 decreased, but it was not significantly different from that in CK.
Effect of regulated deficit drip irrigation under film on potato quality.
Regulated deficit treatment had different effects on the characteristics of potato quality (Table 3). Compared with that in CK, deficient irrigation in the seedling stage did not significantly affect total sugar content in potato. However, in the other growth stages, regulated deficit reduced sugar content by 6.55–44.64%, and the greatest reduction was in WD8 with the deficit at starch accumulation. With the deficit in the seedling stage, the protein content in WD5 (moderate deficit) was 2.18 mg·g− 1, an increase of 0.77% compared with that in CK. The protein contents decreased by 4.46–32.46% in the other treatments. The greatest reductions compared with the protein content in CK were in WD3 (18.31%), WD7 (21.85%), and WD8 (32.46%). With the deficit in the seedling stage, the starch content reached 36.06% in WD1 (mild deficit), a 3.34% increase compared with that in CK. In the other mild deficit treatments, although the starch content decreased, it was not significantly different from that in CK. In the moderate deficit treatments, the starch content decreased significantly by 10.66% in WD6, by 20.41% in WD7, and by 27.55% in WD8. With the deficit in the seedling stage, vitamin C and calcium contents decreased significantly by 9.21% in WD1 (mild deficit), compared with the contents in CK. However, the vitamin C content increased in the other mild and moderate deficit treatments, with the values increasing by 11.55–55.35% compared with that in CK. In addition, the vitamin C content tended to increase with the delay in deficit treatment, and the greatest increase was in WD8, with the content increasing significantly by 55.35% compared with that in CK.
Table 3
Indices of potato quality at harvest in conventional irrigation (CK) and regulated deficit drip irrigation treatments in three years and averaged across years.
Year
|
Treatment
|
Total sugar
|
Protein
|
Starch
|
Vitamin C
|
(%)
|
(mg·g− 1)
|
(%)
|
(mg·100 g− 1)
|
2017
|
CK
|
0.62a
|
2.31b
|
41.42ab
|
15.77de
|
WD1
|
0.59ab
|
2.29bc
|
43.01a
|
14.26e
|
WD2
|
0.54bc
|
2.14bc
|
40.95ab
|
17.02d
|
WD3
|
0.43de
|
1.88c
|
38.36bc
|
18.53 cd
|
WD4
|
0.48 cd
|
2.17bc
|
37.79bc
|
20.15bc
|
WD5
|
0.57b
|
2.54a
|
38.54b
|
19.07c
|
WD6
|
0.51c
|
2.27bc
|
36.05bc
|
21.53b
|
WD7
|
0.44d
|
1.72d
|
30.26c
|
21.97ab
|
WD8
|
0.36e
|
1.54e
|
27.93 cd
|
23.49a
|
2018
|
CK
|
0.32b
|
1.93ab
|
19.33ab
|
12.14e
|
WD1
|
0.37a
|
1.99a
|
19.4a
|
11.57ef
|
WD2
|
0.22d
|
1.9ab
|
18.92ab
|
13.35d
|
WD3
|
0.31bc
|
1.68bc
|
18.18bc
|
14.05 cd
|
WD4
|
0.3c
|
1.91ab
|
19.02ab
|
14.92c
|
WD5
|
0.29 cd
|
1.59c
|
18.37b
|
13.31de
|
WD6
|
0.21de
|
1.46d
|
18.15bc
|
16.97b
|
WD7
|
0.3c
|
1.71b
|
19.3ab
|
15.63bc
|
WD8
|
0.17e
|
1.38e
|
17.5bc
|
19.38a
|
2019
|
CK
|
0.68a
|
2.29ab
|
42.68ab
|
15.01e
|
WD1
|
0.68a
|
2.26b
|
44.39a
|
13.35f
|
WD2
|
0.59b
|
2.16bc
|
41.87ab
|
16.84d
|
WD3
|
0.48c
|
1.82c
|
39.79bc
|
18.41 cd
|
WD4
|
0.47 cd
|
2.1bc
|
38.91bc
|
19.79bc
|
WD5
|
0.64ab
|
2.48a
|
39.87b
|
18.97c
|
WD6
|
0.56bc
|
2.2bc
|
37.69bc
|
21.06b
|
WD7
|
0.48c
|
1.69 cd
|
32.01c
|
21.72ab
|
WD8
|
0.38d
|
1.51d
|
29.17d
|
23.05a
|
Average
|
CK
|
0.56ab
|
2.17ab
|
34.89ab
|
14.05d
|
WD1
|
0.58a
|
2.17ab
|
36.06a
|
12.76e
|
WD2
|
0.47c
|
2.07ab
|
34.22ab
|
15.67 cd
|
WD3
|
0.42d
|
1.77c
|
32.59bc
|
16.95 cd
|
WD4
|
0.41de
|
2.03ab
|
32.28bc
|
18.17bc
|
WD5
|
0.52b
|
2.18a
|
32.7b
|
17.08c
|
WD6
|
0.44 cd
|
1.95b
|
31.17bc
|
19.69b
|
WD7
|
0.42de
|
1.69 cd
|
27.77c
|
19.69bc
|
WD8
|
0.31e
|
1.46d
|
25.28 cd
|
21.83a
|
Note: Different lowercase letters within a column for a year or the average indicate significant differences among treatments (P < 0.05). The irrigation treatments were conventional irrigation (CK) and mild or moderate water deficit during each of four stages of potato growth. Mild deficit was in treatments WD1 (seedling), WD2 (tuber initiation), WD3 (tuber bulking), and WD4 (starch accumulation); moderate deficit was in treatments WD5 (seedling), WD6 (tuber initiation), WD7 (tuber bulking), and WD8 (starch accumulation). |
Tuber yield and its components.
Regulated deficit in all growth stages significantly affected water consumption, yield, water use efficiency, and irrigation water use efficiency (Table 4). Water deficit in all growth stages significantly decreased water consumption by potato. Compared with 5,837.20 m3 ha− 1 in CK, water consumption decreased to 4,977.10 m3 ha− 1 in WD3, 4,952.03 m3 ha− 1 in WD5, 4,769.13 m3 ha− 1 in WD6, and 4,723.63 m3 ha− 1 in WD8, which were decreases of 14.73% (WD3), 15.16% (WD5), 18.30% (WD6), and 19.08% (WD8) compared with that in CK. In WD2 (mild deficit) and WD7 (moderate deficit), the decrease was slight. The regulated deficit treatments caused decreases in potato yield to different degrees. The water deficit in the seedling stage in WD1 caused the smallest decrease in yield to 43,961.91 kg ha− 1, a decrease of only 4.50% compared with that in CK. Water deficit in the tuber bulking stage in WD7 (moderate deficit) caused the greatest decrease in yield to 33,834.86 kg ha− 1, a decrease of 26.50% compared with that in CK. The decreases in yield under moderate regulated deficit treatment were greater than those under mild treatment, indicating that the larger decrease in irrigation had a greater negative effect on potato yield. Affected by yield, the output values showed similar trends by treatment. Output value per cubic water was the lowest in WD7 (moderate deficit), decreasing by 15.56% compared with that in CK. By contrast, the values increased in the other treatments by 0.07–50.93%, compared with that in CK.
Table 4
Potato yield, output value, and water use in conventional irrigation (CK) and regulated water deficit drip irrigation treatments in three years and averaged across years.
Years
|
Treatment
|
Rainfall
|
Irrigation volume
|
Water consumption
|
Yield
|
Output value
|
Unilateral aquatic product value
|
Water use efficiency
|
Irrigation water use efficiency
|
(m3·ha− 1)
|
(m3·ha− 1)
|
(m3·ha− 1)
|
(kg·ha− 1)
|
(yuan·ha− 1)
|
(yuan·m− 3)
|
(kg·m− 3)
|
(kg·m− 3)
|
2017
|
CK
|
3017.5
|
2574.50
|
6462.20
|
58160.00
|
75608.03
|
29.37
|
9.00
|
22.59
|
WD1
|
3017.5
|
1829.40
|
4883.70
|
50400.20
|
65520.25
|
35.81
|
10.32
|
27.55
|
WD2
|
3017.5
|
2074.50
|
5096.00
|
45099.90
|
58629.90
|
28.26
|
8.85
|
21.74
|
WD3
|
3017.5
|
1741.70
|
4761.50
|
40234.40
|
52304.71
|
30.03
|
8.45
|
23.10
|
WD4
|
3017.5
|
1895.70
|
4912.10
|
49858.30
|
64815.73
|
34.19
|
10.15
|
26.30
|
WD5
|
3017.5
|
1479.60
|
4495.20
|
48548.10
|
63112.49
|
42.65
|
10.80
|
32.81
|
WD6
|
3017.5
|
1884.90
|
4904.00
|
42223.50
|
54890.52
|
29.12
|
8.61
|
22.40
|
WD7
|
3017.5
|
2484.30
|
5502.70
|
35327.20
|
45925.33
|
18.49
|
6.42
|
14.22
|
WD8
|
3017.5
|
1371.30
|
3682.30
|
38590.70
|
50167.92
|
36.58
|
10.48
|
28.14
|
2018
|
CK
|
1974
|
2805.24
|
5520.10
|
35317.71
|
45913.02
|
16.37
|
6.39
|
12.59
|
WD1
|
1974
|
2540.72
|
4859.10
|
31913.54
|
41487.60
|
16.33
|
6.57
|
12.56
|
WD2
|
1974
|
2530.99
|
4465.80
|
34852.08
|
45307.70
|
17.90
|
7.80
|
13.77
|
WD3
|
1974
|
2753.43
|
4807.40
|
29747.92
|
38672.30
|
14.05
|
6.18
|
10.80
|
WD4
|
1974
|
2730.44
|
5252.72
|
33619.79
|
43705.73
|
16.01
|
6.40
|
12.31
|
WD5
|
1974
|
2321.73
|
5010.40
|
32508.33
|
42260.83
|
18.20
|
6.49
|
14.00
|
WD6
|
1974
|
2108.91
|
4110.80
|
32879.17
|
42742.92
|
20.27
|
7.99
|
15.59
|
WD7
|
1974
|
2072.00
|
4227.90
|
28633.33
|
37223.33
|
17.96
|
6.77
|
13.82
|
WD8
|
1974
|
2460.65
|
5224.00
|
34050.00
|
44265.00
|
17.99
|
6.52
|
13.84
|
2019
|
CK
|
3051.3
|
2337.70
|
5529.30
|
44621.97
|
58008.57
|
33.70
|
8.07
|
19.09
|
WD1
|
3051.3
|
2128.90
|
5438.40
|
49572.00
|
64443.60
|
30.27
|
9.12
|
23.29
|
WD2
|
3051.3
|
2042.90
|
5463.00
|
43098.02
|
56027.42
|
49.63
|
7.89
|
21.10
|
WD3
|
3051.3
|
1807.80
|
5362.40
|
39309.81
|
51102.75
|
35.42
|
7.33
|
21.74
|
WD4
|
3051.3
|
1972.10
|
5422.50
|
43308.67
|
56301.27
|
69.70
|
7.99
|
21.96
|
WD5
|
3051.3
|
1695.30
|
5350.50
|
40364.17
|
52473.42
|
38.24
|
7.54
|
23.81
|
WD6
|
3051.3
|
1793.80
|
5292.60
|
37281.21
|
48465.57
|
44.25
|
7.04
|
20.78
|
WD7
|
3051.3
|
1983.30
|
5188.30
|
37544.06
|
48807.28
|
30.62
|
7.24
|
18.93
|
WD8
|
3051.3
|
1521.50
|
5264.60
|
40158.12
|
52205.56
|
44.12
|
7.63
|
26.39
|
Average
|
CK
|
2680.93
|
2572.48
|
5837.20
|
46033.23
|
59843.21
|
26.48
|
7.82
|
18.09
|
WD1
|
2680.93
|
2166.34
|
5060.40
|
43961.91
|
57150.48
|
27.47
|
8.67
|
21.13
|
WD2
|
2680.93
|
2216.13
|
5008.27
|
41016.67
|
53321.67
|
31.93
|
8.18
|
18.87
|
WD3
|
2680.93
|
2100.98
|
4977.10
|
36430.71
|
47359.92
|
26.50
|
7.32
|
18.55
|
WD4
|
2680.93
|
2199.41
|
5195.77
|
42262.25
|
54940.91
|
39.97
|
8.18
|
20.19
|
WD5
|
2680.93
|
1832.21
|
4952.03
|
40473.53
|
52615.58
|
33.03
|
8.28
|
23.54
|
WD6
|
2680.93
|
1929.20
|
4769.13
|
37461.29
|
48699.67
|
31.21
|
7.88
|
19.59
|
WD7
|
2680.93
|
2179.87
|
4972.97
|
33834.86
|
43985.31
|
22.36
|
6.81
|
15.66
|
WD8
|
2680.93
|
1784.48
|
4723.63
|
37599.61
|
48879.49
|
32.90
|
8.21
|
22.79
|
Note: The irrigation treatments were conventional irrigation (CK) and mild or moderate water deficit during each of four stages of potato growth. Mild deficit was in treatments WD1 (seedling), WD2 (tuber initiation), WD3 (tuber bulking), and WD4 (starch accumulation); moderate deficit was in treatments WD5 (seedling), WD6 (tuber initiation), WD7 (tuber bulking), and WD8 (starch accumulation). |
Water use efficiency and irrigation water use efficiency.
With water deficit in the starch accumulation stage, it increased most significantly in WD4 by 13.49 yuan m− 3, an increase of 50.93% compared with that in CK. Water use efficiency was the highest in WD1 at 8.67 kg·m− 3, followed by WD5, WD4, and WD8, representing increases of 10.87% (WD1), 5.84% (WD5), 4.60% (WD4), and 4.99% (WD8) compared with that in CK. By contrast, WUE decreased by 6.39% in WD3 and by 12.92% in WD7 (6.81 kg·m− 3) compared with that in CK. The lowest IWUE was in WD7 at only 15.66 kg·m− 3, a decrease of 13.45% compared with that in CK. By contrast, IWUE increased in the other treatments by 2.52–30.13%. The highest IWUE was in WD5 at 23.54 kg·m− 3, followed by WD8 at 22.79 kg·m− 3, increases of 30.13% and 25.98%, respectively, compared with that in CK.
Comprehensive evaluation of different irrigation deficit methods.
We calculated the correlation matrix of 11 beneficial evaluation indices of the regulated deficit irrigation methods in the Hexi Oasis (Tables 5 and 6). Feature analysis of the matrix showed that the first five major components (comprehensive indices) had an accumulated contribution of 99.57% to the evaluation equation. Thus, we established the comprehensive formulas based on the first five indices, namely, yield, WUE, IWUE, output value per cubic water, and output value:
Y1 = 0.3465X1′+0.238X2′+0.0638X3′+0.0621X4′+0.3465X5′+0.3202X6′+0.3131X7′+0.3501X8′−0.341X9′+0.3611X10′−0.3542X11′=0.00007X1 + 0.27026X2 + 0.01084X3 + 0.00813X4 + 0.00005X5 + 3.04111X6 + 0.99172X7 + 0.07054X8 − 0.10740X9 + 0.00246X10 − 0.02884X11 + 22.38355
Y2 = 0.0717X1′+0.362X2′+0.6094X3′+0.61X4′+0.0717X5′−0.2455X6′+0.0025X7′−0.1024X8′+0.2X9′−0.0627X10′+0.0229X11′=0.00001X1 + 0.41107X2 + 0.10355X3 + 0.07989X4 + 0.00001X5 − 2.33164X6 + 0.00792X7 − 0.02063X8 + 0.06299X9 − 0.00043X10 + 0.00186X11 + 7.765402
Y3 = − 0.2953X1′−0.4626X2′+0.2021X3′+0.2009X4′−0.2953X5′+0.2318X6′+0.6051X7′+0.2362X8′+0.2301X9′+0.0246X10′−0.0354X11′=−0.00006X1 − 0.52530X2 + 0.03434X3 + 0.02631X4 − 0.00004X5 + 2.20152X6 + 1.91661X7 + 0.04759X8 + 0.07247X9 + 0.00017X10 − 0.00288X11 + 1.32316
Y4 = 0.2945X1′+0.1369X2′−0.0846X3′−0.0831X4′+0.2945X5′+0.4041X6′+0.3817X7′−0.3322X8′+0.2156X9′−0.3331X10′+0.4657X11′=0.000006X1 + 0.15546X2 − 0.01437X3 − 0.01088X4 + 0.00004X5 + 3.83795X6 + 1.20901X7 − 0.06693X8 + 0.06790X9 − 0.00227X10 + 0.03792X11 + 1.515379
Y5 = 0.3889X1′−0.6895X2′+0.144X3′+0.1437X4′+0.3889X5′−0.2128X6′−0.1677X7′+0.1894X8′−0.1358X9′−0.1427X10′+0.1806X11′=0.00008X1 − 0.78296X2 + 0.02447X3 + 0.01882X4 + 0.00006X5 − 2.02107X6 − 0.53118X7 + 0.03816X8 − 0.04277X9 − 0.00097X10 + 0.01471X11 − 3.484436
According to the principal component analysis, the principal component values of deficit irrigation at different growth stages were ranked as WD1 > CK > WD5 > WD4 > WD2 > WD3 > WD6 > WD8 > WD7. In conclusion, WD1 was optimal in the valuation.
Table 5
Indices used to evaluate potato in conventional irrigation (CK) and regulated deficit drip irrigation treatments.
Treatment
|
Yield
|
Water use efficiency
|
Irrigation water use efficiency
|
Output value
|
Unilateral aquatic product value
|
Total sugar
|
Protein
|
Starch
|
Vitamin C
|
Potassium
|
Calcium
|
(kg·ha− 1)
|
(kg·m− 3)
|
(kg·m− 3)
|
(yuan·ha− 1)
|
(yuan·m− 3)
|
(%)
|
(mg·g− 1)
|
(%)
|
(mg·100 g− 1)
|
(mg·kg− 1)
|
(mg·kg− 1)
|
X1
|
X2
|
X3
|
X4
|
X5
|
X6
|
X7
|
X8
|
X9
|
X10
|
X11
|
CK
|
46033.23
|
7.82
|
18.09
|
59843.21
|
26.48
|
0.58
|
2.17
|
36.06
|
12.76
|
5065.17
|
93.12
|
WD1
|
43961.91
|
8.67
|
21.13
|
57150.48
|
27.47
|
0.47
|
2.07
|
34.22
|
15.67
|
5106.18
|
87.26
|
WD2
|
41016.67
|
8.18
|
18.87
|
53321.67
|
31.93
|
0.42
|
1.77
|
32.59
|
16.95
|
5021.78
|
94.92
|
WD3
|
36430.71
|
7.32
|
18.55
|
47359.92
|
26.50
|
0.41
|
2.03
|
32.28
|
18.17
|
4968.96
|
96.24
|
WD4
|
42262.25
|
8.18
|
20.19
|
54940.91
|
39.97
|
0.52
|
2.18
|
32.7
|
17.08
|
4900.08
|
102.9
|
WD5
|
40473.53
|
8.28
|
23.54
|
52615.58
|
33.03
|
0.44
|
1.95
|
31.17
|
19.69
|
5016.32
|
95.12
|
WD6
|
37461.29
|
7.88
|
19.59
|
48699.67
|
31.21
|
0.42
|
1.69
|
27.77
|
19.69
|
4833.46
|
109.7
|
WD7
|
33834.86
|
6.81
|
15.66
|
43985.31
|
22.36
|
0.31
|
1.46
|
25.28
|
21.83
|
4695.38
|
123.29
|
WD8
|
37599.61
|
8.21
|
22.79
|
48879.49
|
32.90
|
0.58
|
2.17
|
36.06
|
12.76
|
4728.83
|
118.35
|
Note: The irrigation treatments were conventional irrigation (CK) and mild or moderate water deficit during each of four stages of potato growth. Mild deficit was in treatments WD1 (seedling), WD2 (tuber initiation), WD3 (tuber bulking), and WD4 (starch accumulation); moderate deficit was in treatments WD5 (seedling), WD6 (tuber initiation), WD7 (tuber bulking), and WD8 (starch accumulation). |
Table 6
Comprehensive index values and evaluation coefficients of potato in conventional irrigation (CK) and regulated deficit drip irrigation treatments.
Treatment
|
Y1
|
Y2
|
Y3
|
Y4
|
Y5
|
Overall rating
|
CK
|
2.90995
|
−1.28064
|
−0.48612
|
0.60484
|
0.62713
|
1.60239
|
WD1
|
3.60267
|
−0.76356
|
−0.93734
|
0.01499
|
−0.42728
|
2.09771
|
WD2
|
1.18469
|
−0.01058
|
0.46858
|
−0.57993
|
0.14227
|
0.77424
|
WD3
|
−0.78786
|
−0.89969
|
0.00027
|
−1.43324
|
−0.04555
|
−0.77183
|
WD4
|
0.44446
|
3.01387
|
0.15027
|
−0.02647
|
0.73174
|
1.00346
|
WD5
|
1.55440
|
0.63227
|
0.86751
|
0.42978
|
−0.80347
|
1.20040
|
WD6
|
−1.27528
|
−0.17980
|
1.17898
|
0.37273
|
−0.07906
|
−0.78804
|
WD7
|
−4.14625
|
−2.19086
|
0.00953
|
0.43179
|
0.26601
|
−3.16771
|
WD8
|
−3.48678
|
1.67900
|
−1.25170
|
0.18551
|
−0.41179
|
−1.95061
|
Note: The positive and negative values in the table indicate their position only relative to the average. The irrigation treatments were conventional irrigation (CK) and mild or moderate water deficit during each of four stages of potato growth. Mild deficit was in treatments WD1 (seedling), WD2 (tuber initiation), WD3 (tuber bulking), and WD4 (starch accumulation); moderate deficit was in treatments WD5 (seedling), WD6 (tuber initiation), WD7 (tuber bulking), and WD8 (starch accumulation). |