The water shortage in China, particularly in Northwest China, is very serious. There is, therefore, great potential for improving the water use efficiency (WUE) in agriculture, particularly in areas where the need for water is greatest. A two-season (2012 and 2013) study evaluated the effects of irrigation and fertilizer rate on tomato (
Technologies such as drip irrigation and fertigation can improve WUE and decrease salinization while maintaining or increasing yields [
Tomato is one of the most popular and widely grown vegetables in the world. The first reason for this is that tomatoes are beneficial to our heath and are good sources of provitamins,
Tomato responds well to fertilizer application and is reported to be a heavy feeder of nitrogen (N), phosphorus (P), and potassium (K) fertilizer [
Therefore, the development of efficient agricultural water use is not only necessary but also feasible, being critical to improve the fruit yield and WUE. To obtain high yields and maximum profits in commercial tomato production, the optimal management of both fertilizer and water is required. Previous studies have focused on the influence of irrigation amount and fertilizer rate on tomato growth, fruit yield, and quality. Meanwhile, it is necessary to select an optimal combination of irrigation and fertilization to improve agricultural water and fertilizer management practices. Therefore, the aim of this study is to explore the effect of irrigation and fertilization on the growth, yield, and quality of tomato with fertigation by drip irrigation and to make recommendations regarding the strategies for growing greenhouse tomatoes.
The tomatoes plant (
In this experiment, nine treatments were designed with three different irrigation levels (W1: 100%
The layout of experiment included water sources, water meter, check valve, fertigation equipment, and ball valve and drip irrigation pipe positions of different treatments in greenhouse.
The tomato seedlings were transplanted on 21 Mar 2012 and 31 Mar 2013. The furrow-film mulch was cultivated by the local traditional planting patterns and calendars using tomato ridging in a tube with a two-line spaced layout; the tubes were placed 50 cm apart, with a 45 cm planting distance and 78 plants in each experimental plot. Drip fertigation was performed using a fertilizer of urea (46% N), diammonium phosphate (44% P2O5), and potassium chloride (60% K2O). This fertilizer was applied five times at the recovering stage, the blossoming and bearing fruits stage, the first fruit enlargement period, the second fruit enlargement period, and the third fruit enlargement period, and the fertilization ratio was 1 : 1 : 2 : 2 : 2 for those applications.
The plant height in each treatment was measured every 15 to 20 days after transplanting. The height of 3 randomly selected plants from each experimental unit was measured three times per month from the soil level to the growing point.
Changes in stem diameter were continuously recorded during the treatment period using a shrinkage-type microdisplacement detector (Portable Battery Internal Resistance Tester, JZ-1A, Peking, 2010). All of the measurements were recorded three times and the pattern of response was similar in all.
The number of leaves longer than 20 mm was determined once every 2 weeks, and the maximal leaf width was measured for every leaf. The leaf area was estimated by multiplying the product of leaf length and leaf width by a conversion factor estimated from the destructive sampling.
Plants were harvested in three replicates and separated into roots, leaves, fruits, and stem. The plant parts were dried in an open-air draught oven at 75°C for 72 h to estimate the dry weight.
Ripe tomatoes were harvested and fresh total yield and total number of tomatoes from all of the plants in each plot were determined. The fruit yield was measured throughout the crop. Fruits were harvested twice a week for a period of 9 weeks and were separated into marketable and total yields.
Irrigation treatments were initiated using the surface drip irrigation system during transplanting, and the irrigation amount was 40 mm. Irrigation was applied using a subsurface drip system based on the daily crop evapotranspiration (
The FAO 56 Penman-Monteith method is recommended as the standard method for
Daily variation of the reference evapotranspiration (
The
In tomato growing season, the distribution of daily average temperature, irrigation interval, and numbers were recorded in the study years.
The water use efficiency (WUE) was determined using the following equation [
Analysis of variance was conducted on the plant height, stem diameter, dry biomass accumulation, and distribution in different organs using a two-way analysis of variance (SAS GLM procedure version 9.2, SAS Institute Ltd., North Carolina, USA). Duncan’s multiple range tests were considered significant when
The effects of irrigation amount and fertilizer rate on plant height at the whole growth stages are shown in Table
The effects of irrigation amount and fertilizer rate on plant height of tomato (cm).
Treatments | 2012 | 2013 | ||||||
---|---|---|---|---|---|---|---|---|
23 D | 37 D | 53 D | 70 D | 20 D | 40 D | 60 D | 80 D | |
W1F1 | 35 |
71.2 |
102 |
125.8 |
23.9 |
70.9 |
93.9 |
112.5 |
W1F2 | 35.7 |
72.5 |
109 |
134.1 |
24.1 |
68.6 |
101.5 |
117.4 |
W1F3 | 34.3 |
70.3 |
105 |
130 |
23.2 |
67.8 |
88 |
112 |
W2F1 | 40.8 |
76.5 |
110.5 |
140.3 |
29.7 |
68.4 |
94.1 |
111.5 |
W2F2 | 37.2 |
72.5 |
103.5 |
131.5 |
30 |
74.1 |
87.2 |
110.4 |
W2F3 | 34.3 |
68.3 |
100.5 |
127.7 |
26.1 |
62 |
86.2 |
110.2 |
W3F1 | 38 |
73 |
113.5 |
135.1 |
23.1 |
63.8 |
97.5 |
113.3 |
W3F2 | 35.5 |
78 |
115 |
136.9 |
24.6 |
64.3 |
95.2 |
113 |
W3F3 | 34.1 |
73.8 |
111 |
132.1 |
22.8 |
59.7 |
92.1 |
107 |
|
||||||||
Irrigation |
|
NS |
|
NS |
|
|
|
NS |
Fertilizer |
|
|
NS | NS |
|
|
|
NS |
Irrigation × fertilizer |
|
NS |
|
NS | NS | NS | NS | NS |
D is the days after transplanting and columns with the same letter represent values that are significant at the 5% probability level. “
The plant stem plays a very important role in plant anchorage and in the movement and transport of water, solutes, and nutrients. Importantly, the stem functions in photosynthesis and nutrient storage. The effects of irrigation and fertilizer on tomato stem diameter at the whole growth stages are shown in Table
The effects of irrigation and fertilizer on stem diameter tomato (mm).
Treatment | 2012 | 2013 | ||||||
---|---|---|---|---|---|---|---|---|
23 D | 37 D | 53 D | 70 D | 20 D | 40 D | 60 D | 80 D | |
W1F1 | 8.46 |
10.66 |
10.98 |
12.28 |
7.85 |
8.74 |
10.95 |
12.18 |
W1F2 | 7.66 |
9.58 |
10.1 |
11.3 |
7.28 |
9.14 |
11.68 |
12.88 |
W1F3 | 7.45 |
8.57 |
9.6 |
11.01 |
6.84 |
7.8 |
10.55 |
11.26 |
W2F1 | 8.9 |
10.15 |
10.74 |
12.47 |
7.29 |
8.89 |
9.91 |
11.33 |
W2F2 | 8.13 |
9.16 |
10.11 |
11.6 |
7.09 |
9.59 |
11.37 |
11.43 |
W2F3 | 6.49 |
8.44 |
9.26 |
10.39 |
6.8 |
7.37 |
9.01 |
10.45 |
W3F1 | 8.39 |
9.33 |
9.98 |
11.86 |
6.62 |
7.87 |
9.07 |
11.78 |
W3F2 | 8.03 |
8.93 |
9.53 |
10.84 |
6.24 |
8.44 |
9.43 |
10.54 |
W3F3 | 5.94 |
8.21 |
8.91 |
10.29 |
5.96 |
6.65 |
7.93 |
9.25 |
| ||||||||
Irrigation | NS |
|
NS | NS |
|
|
|
|
Fertilizer |
|
|
|
|
|
|
|
|
Irrigation × fertilizer |
|
NS | NS | NS | NS | NS | NS | NS |
D is the days after transplanting and columns with the same letter represent values that are significant at the 5% probability level. “
The major function of leaves is to take in carbon dioxide for photosynthesis, the process of converting light energy into chemical energy. The effects of irrigation and fertilization on the leaf growth rate at the whole growth stages are shown in Figure
The effects of irrigation and fertilizer on tomato leaf growth rate.
2012
2013
The effects of irrigation and fertilizer on tomato dry biomass accumulation and the distribution in different organs are shown in Table
Effects of irrigation and fertilizer on tomato dry biomass accumulation and distribution in different organs.
Year | Treatment | Dry biomass accumulation (kg⋅hm−2) | Distribution in different organs (%) | |||||||
---|---|---|---|---|---|---|---|---|---|---|
Fruit | Stem | Leaf | Root | Total | Fruit | Stem | Leaf | Root | ||
2012 | W1F1 | 6219 |
2922 |
2635 |
247 |
12023 |
51.7 |
24.3 |
21.9 |
2.1 |
W1F2 | 5828 |
2785 |
2552 |
223 |
11389 |
51.2 |
24.4 |
22.4 |
2 | |
W1F3 | 5100 |
2660 |
2172 |
195 |
10127 |
50.4 |
26.3 |
21.4 |
1.9 | |
W2F1 | 5615 |
2504 |
2573 |
230 |
10922 |
51.4 |
22.9 |
23.6 |
2.1 | |
W2F2 | 5475 |
2221 |
2309 |
215 |
10221 |
53.6 |
21.7 |
22.6 |
2.1 | |
W2F3 | 5030d |
1993 |
1720 |
174 |
8917 |
56.4 |
22.3 |
19.3 |
2 | |
W3F1 | 5119 |
2231 |
2247 |
197 |
9794 |
52.3 |
22.8 |
23 |
2 | |
W3F2 | 4984 |
2221 |
1849 |
194 |
9247 |
53.9 |
24 |
20 |
2.1 | |
W3F3 | 4722 |
1876 |
1460 |
140 |
8198 |
57.6 |
22.9 |
17.8 |
1.7 | |
|
||||||||||
Irrigation |
|
|
|
|
|
|
|
|
|
|
Fertilizer |
|
NS |
|
|
|
|
NS |
|
| |
Irrigation × fertilizer |
|
NS |
|
NS | NS |
|
NS |
|
NS | |
|
||||||||||
2013 | W1F1 | 5100 |
1818 |
1973 |
254 |
9145 |
55.8 |
19.9 |
21.6 |
2.8 |
W1F2 | 4781 |
2106 |
2031 |
330 |
9248 |
51.7 |
22.8 |
22 |
3.6 | |
W1F3 | 4090 |
1663 |
1965 |
209 |
7927 |
51.5 |
21 |
24.8 |
2.6 | |
W2F1 | 4461 |
1477 |
1757 |
217 |
7913 |
56.3 |
18.7 |
22.2 |
2.7 | |
W2F2 | 4300 |
1960 |
1809 |
306 |
8375 |
51.3 |
23.4 |
21.6 |
3.7 | |
W2F3 | 3707 |
1772 |
1394 |
193 |
7066 |
52.4 |
25.1 |
19.7 |
2.7 | |
W3F1 | 4087 |
1692 |
1498 |
197 |
7473 |
54.6 |
22.7 |
20.1 |
2.6 | |
W3F2 | 3945 |
1502 |
1607 |
151 |
7206 |
54.7 |
20.9 |
22.3 |
2.1 | |
W3F3 | 3740 |
1168 |
1243 |
139 |
6290 |
59.4 |
18.6 |
19.8 |
2.2 | |
|
||||||||||
Irrigation |
|
|
|
|
|
|
|
|
|
|
Fertilizer |
|
NS |
|
|
|
|
NS |
|
| |
Irrigation × fertilizer |
|
NS |
|
NS | NS |
|
NS |
|
NS |
Columns with the same letter represent values that are significant at the 5% probability level. “
The interactions between irrigation and fertilizer treatments were important for tomato yield, and the single factors of irrigation or fertilizer very significantly (
The effects of irrigation and fertilizer on tomato fruit yield in 2012 and 2013.
2012
2013
The effects of irrigation and fertilizer on the WUE are shown in Figure
The effects of irrigation and fertilizer on water use efficiency in 2012 and 2013; the same letter represents values that are significant at the 5% probability level.
The regression model was used to predict the effect of an unknown dependent variable on the fruit yield and WUE, given the values of the independent variables of irrigation amount and fertilizer level. The fertilizer and irrigation supply affected the fruit yield and WUE, with a very significant interaction between them in both years. In the two successive growing seasons, the extreme calculation results showed that the fruit yield peaked at the maximal irrigation amount, while the WUE peaked at the minimal irrigation amount. Therefore, the tomato yield and WUE cannot simultaneously reach their maxima.
When the WUE was maximal, irrigation was minimal, and the fertilizer amount was close to maximal. Therefore, it is necessary to perform further studies on the input of irrigation and fertilizer, which affect fruit yield and WUE.
In our study, a multiple regression analysis was used to develop a hypothesis in which fruit yield and WUE were equally important (
The optimal value of the target function was calculated by MATLAB. The irrigation amount and fertilizer amount were 151 mm and 453.6 kg·ha−1 (nitrogen, phosphorus, and potassium fertilizers were 213.5, 106.7, and 133.4 kg·ha−1, resp.) in 2012, respectively. The irrigation amount and fertilizer amount were 207.8 mm and 461.08 kg·ha−1 (nitrogen, phosphorus, and potassic fertilizers were 217, 108, and 135.6 kg·ha−1, resp.) in 2013, respectively.
The relationships between the growth indexes and the irrigation amount and fertilizer level were statistically analyzed, and the positive correlation was significant. In two consecutive years, the plant height and leaf growth rate were higher in W2F1 than in the other treatments at 23 days after transplanting, which may be due to water consumption. The results were the same as those of Zhu et al. [
The results showed that irrigation and fertilization had significant effects on tomato yield, and the effects of the interaction between irrigation and fertilizer were very significant. The same results were obtained in greenhouse that there was a significant difference in the tomato yield in the irrigation and fertilization treatments, due to irrigation, fertilizer, and the interaction between the two factors [
The results showed that different irrigation and fertilization supplies significantly affected the WUE and that the effect of irrigation treatment on the WUE was significant. The influence of the interaction between irrigation and fertilization on the WUE was not significant; however, the effect of irrigation treatment on the WUE was greater than the effect of fertilization. Javanmardi and Kubota [
Generally, it is difficult to obtain the maximal WUE and the maximum yield simultaneously. Reducing the amount of irrigation water will result in higher WUE; based on this characteristic, the highest WUE and fruit yield cannot occur at the same time. According to this characteristic, tomatoes require fertilizer and water at the same time. The tomato yield and WUE are equally important and the tomato yield and WUE coefficients are each 0.5. An irrigation amount of 151.1 to 207.8 mm and a fertilizer amount of 453.6 to 461.1 kg·ha−1 for greenhouse tomato surface drip fertigation are recommended (nitrogen fertilizer, 213.5–217 kg·ha−1; phosphate fertilizer, 106.7−108 kg·ha−1; and potassium fertilizer, 133.4–135.6 kg·ha−1).
The authors declare that there is no conflict of interests regarding the publication of this paper.
This research was supported by Specialized Research Fund for the Doctoral Program of Yan’an University (205040119, 205040123), Shaanxi Province High-Level University Construction Special Fund Projects of Ecology (2012SXTC03), and Special Scientific Research Project in Shaanxi Province Department of Education (16JK1853).