and flood) and localized (drip and subsurface) irrigation methods on the ... and phenological stage of the crop, ease of use, automation, effects on crops, water ...
Analysis of water consumptive use: a comparison between different irrigation methods on the behavior of vegetative growts and production of fruit in orange trees on the Plain of GioiaTauro, Southern Italy
Abstract In a representative environment in the plain of Gioia Tauro ( Southern Italy) the effects induced by traditional (sprinkler and flood) and localized (drip and subsurface) irrigation methods on the vegetative and productive behavior of the W. Navel orange variety were investigated over a ten year period. Drip and subsurface-irrigation methods use approximately two thirds less water than sprinkler and flood methods. For the calculation of the effective evapotranspriration (ETE) the application of the Tournon’s K oasis proved to be very interesting, highlights a different “water use/evaporation” ratio according to the irrigation method used. Using traditional methods the ratio increases through the irrigation season, with a yearly average from 0.4 in April to 0.8 in October. Employing localized methods the ratio remains almost constant until July at about 0.35, reaching a value of about 0.7 in August-September. The four irrigation methods tested induced significant differences neither in the vegetative growth of the orange trees nor in the quality of fruit production over the period tested.
Introduction Water is the key factor for the growth of crops, especially in arid and semiarid climates, due to limited and uneven distribution of precipitation. Data on the water consumptive use of crops grown in these climates are essential for optimum irrigation management strategies and water conservation. For this reason irrigation represents a determining factor for agricultural production, increasing and stabilizing yields, as well as allowing greater uniformity of product quality. This is particularly true for spring-summer crops, given their sensitivity to water stress. This is even more pronounced for citrus fruit in consideration of its area of cultivation and sensitivity to water deficit. The use of irrigation, however, involves a number of choices of great interest. The most important concerns are the daily length of irrigation, the volume of water and the method of distribution. Parameters that contribute to improved water use efficiency (WUE), have long been used to quantify beneficial use of irrigation water (ASCE, 1978).
Irrigation performance parameters Performance parameters for irrigation are tools that can help to optimize the use of water. Water use efficiency includes any measure that reduces the amount of water used per unit of any given activity, consistent with the maintenance or enhancement of water quality. The daily length of irrigation, the volume of water, the method of distribution are the parameters that contribute to this goal according to the irrigation system used. Choice of the time of irrigation The most appropriate time to perform irrigation operations may be chosen according to the daily water conditions of the soil, the climate, and the conditions of the plant. There are no lack of methodologies that reference these factors taken together, but, in general, the most common methodologies consider these factors individually. With regard to the water conditions of the soil (Hillel 1971, Gardner 1960, Cavazza 1981), one can refer to both the water content and the soil water potential, In the first case soil moisture us measured, in the second case a tensiometer is used. As regards the conditions of the plant, water potential in the plant, resistance and stomatal conductance were measured. Visible indicator of water stress were not considered due to their subjective. However, when water resources are limited, phonological criteria can indicate when the crop is must sensitive to water stress, maximizing water efficiency and, thus, avoiding a reduction in yield.
IRRIGATION VOLUME The water volume per unit is closely related to, the method of irrigation, as well as the criteria for irrigation (such as leaching of salts, temperature control and maintaining soil moisture).
Additional factor are the duration of the crop and the irrigation season. In general, those criteria that aim to maintain a costant level of soil moisture use a fixed volume of water, but with variable application times, whereas those which are based on ETE use a variable volume of water but with fixed application times. In some cases, however, both the volume and application times are fixed, and in other cases both are variable. Irrigation methods The different methods irrigation are classified according to the criteria used. One of the main criteria what is the energy that moves the water (Cavazza, 1981). On this basis, there are two groups: gravity flow, distribution methods and pressure. Distribution methods gravity flow methods include furrows, soil border and flooding while pressure methods include sprinklers and micro flow systems including the drip method and subsurface irrigation. The choice of irrigation method is based installation costs, operating costs, soil type, slope, and land development, type and phenological stage of the crop, ease of use, automation, effects on crops, water consumptive use, flow of water available and water quality. In the Plain of Gioia Tauro (Southern Italy), in the period under consideration, most irrigation systems were pressure distributed. Of these, subsurface irrigation offers free access to people and machines as well as a lower water consumptive use.
Materials and methods The trial was carried out in the Plain of Gioia Tauro (Southern Italy) in the years 1975-1985. The orange groves, with the Washington Navel Orange 3033 grafted on sour orange, was planted in 1972 with a spacing of 5 m between trees. The soil type was sandy loam; its main physical-chemical features are shown in table 1; while the tensiometer curves are shown in figure 1. Four methods of water distribution were compared: sprinkler, drip, subsurface irrigation and flooding. Plots were in a randomized plot design with 3 replications. Each individual plot had 75 trees covering an area of 1,800 square meters. Table 1: Physico-chemical characteristics of the soil
Depth (cm)
pH
Coarse sand
Fine sand
Silt (%)
Clay (%)
O.M. (%)
Ntotal (‰)
0-60 60-120 120-210
5.5 5.6 6.0
21.2 21.7 34.4
32.0 35.4 37.8
42.2 31.2 20.4
4.6 11.7 7.4
2.15 1.55 1.50
3.22 1.54 1.16
60
50
Mousture (%) on the dry weight (105°C)
40
0-75 cm 30 75-135 cm
20
10
0 0
0,5
1
1,5
2
Mpa
Fig 1 Relations between soil water potential and soil moisture For the drip method the daily distribution of the water was supplied through realized the type "Labirint drippers " with a flow rate of 4 l/h, by placing the pipe along the row, with two dispensers per plant at a distance of 0.50 m from the trunk. Subsurface irrigation was performed with the "Tournon method" (Tournon, 1968, 1972, 1979). The pipes (internal diameter 16 mm), consisting of an elastomeric substance particularly resistant to aging, were placed at a depth of 0.50 m below ground and at a distance of 0.70 m from the plant; the pipes are provided with longitudinal slots of 7 mm in length, at a distance of 0.50 to 0.70 m from the axis of the plant (fig. 2). The minimum effluent flow rate was 1.8 l/h with a pressure of 0.65 bar. Flooding was carried out by dividing the land into sections of 5 x 5 m with low earth dykes.
Ap= Area proiezione chioma (Crown projection area) As= Area competenza pianta nel sesto (Area competence plant in the sixth )
Fig 2: Network diagram of pipes for subsurface irrigation method (from Tournon, 1979)
Fig 3: Curve for the determination of K oasis
The start of the irrigation, in all the years observed (1975-1985), occurred when soil moisture, in the top 0.50 m, had dropped below 50% of the available water for traditional methods (such as sprinkling and flooding) and below 75% for localized methods (drip and subsurface irrigation). The policy intervention was to replenishing daily ETE for localized methods and to reach of 50% of the possible water in the top 0.50 m layer for sprinkler and flooding. The irrigation volume for localized methods was determined by a class A Pan evaporimeter using the formula: ETE= Ao x Kc x Ko x Kr, where ETE is actual evapotranspiration, Ao is height of evaporation from class A evaporimeter, Kc is the crop coefficient, Ko is oasis coefficient proposed by Tournon and Kr is coefficient of reduction associated with percentage crop cover (to be determined based on the results of the hydrologic balance) that was between 0.6 and 0.8. For the flood and sprinkler methods, the water volume was determined based on the hydrological characteristics of the soil, with reference to the total field capacity determined before the first irrigation. After start of the irrigation season, the following parameters were measured: hydrological soil balance to a depth of 0.90 m, crop water consumptive use, plant growth (trunk diameter and canopy projection), fruit production (maturity index, the average weight of the fruits, the juice yield, acidity, the content of total soluble solids and the content of vitamin C). The water budget for the drip and subsurface irrigation method was performed by determining the soil moisture gravimetrically each 15 days from April to late October in six point for each plot. Three points were chosen in row at a distance of 0.85, 1.60 and 2.50 m from the tree, and three point were chosen in the inter-row space at the same distances. For the sprinkler and the flood methods the soil moisture was detected in same points before and after each irrigation interval, also using the above method. Water use was calculated as the sum of the water supplied, rain and changes in soil water reserve. The yield for each plot was recorded on all 75 trees; plant growth (as an increase in trunk diameter) was measured on 26 trees annually in spring. Fruit growth was followed on 25 fruits per tree, distributed evenly in the canopy, and for three trees per replication, measuring their diameter weekly. The qualitative characteristics of the fruits were determined on 1 kg of fruit per replication. These characteristic were fruit maturity, the average weight of the fruit, the juice yield, acidity, total soluble solids and vitamin C content. The data were subject to variance analysis. Tables 2, 3 and 4 show the average temperature, rainfall and E pan evaporation for April to October.
Table 2: Monthly average temperatures
Month Year April May June July August September October 1975 11.7 15.9 17.5 20.8 21.0 20.2 15.8 1976 11.8 16.6 20.0 22.6 21.6 19.5 17.7 1977 12.8 17.5 20.2 23.3 23.4 20.3 16.9 1978 13.3 16.2 20.1 21.8 22.5 19.4 16.3 1979 13.1 15.2 20.6 20.6 22.6 19.4 17.1 1980 11.7 16.0 18.0 20.3 22.9 19.7 16.6 1981 12.6 15.3 20.8 21.5 22.0 20.4 17.5 1982 12.4 16.5 21.0 22.9 22.7 21.3 18.1 1983 13.6 15.1 18.6 22.5 22.4 19.1 15.4 1984 12.2 15.5 18.8 21.1 21.5 19.1 16.9 1985 13.5 16.7 19.5 22.2 21.9 20.0 16.1
Table 3: Monthly average rainfall
Year April May 1975 23 80 1976 87 51 1977 140 12 1978 122 69 1979 117 43 1980 87 84 1981 19 58 1982 81 3 1983 22 61 1984 192 0 1985 56 39
June 11 68 34 2 18 27 4 73 -
Month July August September 13 47 11 74 27 19 4 31 1 60 18 28 33 36 15 19 30 57 38 41 3 45 93 20 81 42 26 3 92
October 198 187 39 117 57 47 33 172 148 40 34
Table 4: Daily class A pan evaporation, monthly average
Month Year April May June July August September October 1975 4.4 5.4 6.0 5.3 4.2 2.8 4.4 1976 3.9 4.7 5.5 5.0 4.0 2.5 3.9 1977 4.3 4.8 5.9 5.9 4.0 2.4 4.3 1978 4.0 5.4 6.0 5.6 3.7 1.7 4.0 1979 4.1 5.2 5.7 5.3 3.5 2.1 4.1 1980 3.6 5.3 5.7 5.3 3.8 1.9 3.6 1981 4.4 5.1 6.0 5.7 4.0 2.8 4.4 1982 4.6 6.4 7.4 6.2 4.2 2.2 4.6 1983 4.4 5.0 5.8 5.7 4.5 2.8 4.4 1984 5.5 6.7 7.4 5.4 4.5 2.5 5.5 1985 4.6 7.0 7.2 6.6 4.7 2.7 4.6 During the research period, temperature, rainfall and evaporation varied widely 1977 and 1982 were the hottest years, while in 1975, 1980 and 1984 lower temperatures were recorded. The highest rainfall was recorded in 1976, followed
by 1983; the lowest in 1977, followed by 1981 and 1985. Likewise the highest figures for evaporation were in 1982, 1984 and 1985, while the lowest were in 1976, 1979 and 1980. Statistical analysis The experiments were based on complete randomized block design with three replications. The data were analyzed using test procedures. Results and discussion Water consumptive use
1000
1000
800
800
Seasonal water consumptive use (mm)
Seasonal water consumptive use (mm)
Seasonal cumulative water use from April to end of October, are reported in figures 4a and 4b. The results differ greatly according to the irrigation method adopted: water consumptive use was higher for traditional methods (sprinkler and flood; fig 4a) and lower for localized methods (drip and subsurface irrigation; fig. 4b). There was little difference in water consumptive use between flood and sprinkler methods, and likewise, little difference between drip and subsurface methods. Thus, two averages are reported and referred to: one for traditional methods and one for localized methods. The ratio between these two average decreased from 2.30 in 1975 to 1.30 1985, with a weighted average of 1.50. The reason for this decrease is a corresponding increase in canopy equal the “oasis coefficient” (fig. 3). Over time, the seasonal water use increased until 1982 (the tenth year from transplanting), but remained fairly stable over the last 4 years, For the seasonal water use the three parameters of the budget (irrigation, rain and soil water reserve) were involved in different ways, given the climate variability of the different seasons. On average, however, for the localized methods (drip and subsurface irrigation) the relative involvement expressed as a percentage of the total, was 45%, 47% and 8%, for irrigation, rain and soil reserves and for traditional methods 62%, 37% and 7% respectively. Monthly of water consumptive use also varied according to the irrigation used. (fig. 5).
600
400
600
400
200
200
0
0 1975 1976 1977 1978 1979 1980 1981 1982 1983 1984 1985
1975 1976 1977 1978 1979 1980 1981 1982 1983 1984 1985 Year
Year
Fig, 4a: Seasonal water consumptive use in the years 1975-1985 as the average of sprinkler and flood methods subsurface
Fig, 4b: Seasonal water consumptive use in the years 1975-1985 as the average of drip and irrigation methods
5
Water consumptive use (mmd-1)
4
3
2
1
Drip and subsurface irrigation Flood and sprinkler 0 A
M
J
J
A
S
O
Month
Fig 5: Average of monthly water consumptive use for the four methods
With traditional methods, maximum water consumptive use was in July (with a significant increase between MayJune), while for the localized methods the maximum was reached in August. In April and October, however, the differences of daily water consumptive use were small. This type of trend, most likely, was influenced by surface evaporation, which is very most influential in the months of June and July. Similar results have been found in other papers (Ruggiero, 1986, Ruggiero and Andiloro 1972) The ratio between water and A Pan evaporation increased over the years, with a roughly parallel trend, reaching a maximum in 1982 (the tenth year from transplanting), and remaining (fig. 6a) on this level in the following years. Water consumptive use using traditional methods was approximately 35% higher than water consumptive use using localized methods. During the season the ratio between A Pan evaporation and water consumptive use (fig. 6b) differed according the irrigation method. With traditional methods, this ratio increased over the entire growing season, from a monthly of 0.4 in April to 0.8 in October. With localized methods, however, values remained roughly constant around 0.35 until July, increasing in August, September and to a greater extent in October, reaching a value of 0.7. This may be due, to increased precipitation with a greater availability of water for the whole root system, and the gradual adaptation of the roots to the irrigation method.
0,9
0,8
0,7
Water consumptive use/evaporation
0,6
0,5
0,4
0,3
0,2 Drip and subsurface irrigation Flood and sprinkler 0,1
0 1974
1976
1978
1980
1982
1984
Year
Fig 6a: Average annual water consumptive use/evaporation ratio
0,9
Water consumptive use/evaporation
0,8
0,7
0,6
0,5
0,4
0,3
0,2 Drip and subsurface irrigation Flood and sprinkler 0,1
0 A
M
J
J
A
S
O
Month
Fig, 6b: Average montly water consumptive use/evaporation ratio (1975-1985)
Vegetative growth Trunk diameter increased continuously in the period 1975 – 1983 (fig. 7), although it slowed in the last year (1983). Growth in trunk diameter varied little according to the irrigation method used (fig. 8). Canopy growth was measured only for localized irrigation methods, and similar trend were shown for both subsurface and drip irrigation at the beginning and end of the experimental period (fig. 9).
300
300
Flood
250 Sprinkler 250 Drip
200 Subsurface irrigation
Trunk growth (%)
Fruit growth
200
150
150
100
Flood
Sprinkler
Drip
Subsurface irrigation
50 100 1975
1976
1977
1978
1979
1980
1981
1982
1983
Year
0 1975
1976
1977
1978
1979
Year
Fig 7: Trunk growth
Fig 8: Fruit growth
1980
1981
1982
1983
300
250
Canopy growth %
200
Drip
Subsurface irrigation
150
100 1975 1976 1977 1978 1979 1980 1981 1982 1983 1984 1985 Year
Fig 9: Canopy growth in the years 1975-1985 for subsurface and drip irrigation methods Yield The fruit yield, on average, increased until 1983 (fig. 10a). Among the irrigation methods, on average, there were no statistically significant differences (fig. 10b). Neither were statistically significant differences found for the qualitative characteristics of the according to irrigation used (table 5).
35
40
30
30
20 Sprinkler Flood Subsurface irrigation Drip
15
Fruit production (t/ha-1)
Fruit production (t/ha-1)
25
20
Sprinkler Flood Subsurface irrigation Drip
10 10
5
0 0
Sprinkler
Flood
1976 1977 1978 1979 1980 1981 1982 1983 1984
Subsurface irrigation
Drip
Irrigation method
Year
Fig 10b: Average production in relation to the four irrigation methods
Fig 10a: Fruits production per year according to irrigation methods
Table 5: Fruit quality
Irrigation method
Sprinkler Flood Drip Subsurface irrigation
Production (t/h-1)
Fruit weight (g)
Fruit diameter (cm)
Juice yield (%)
27.6 27.7 29.7
28.7 29.8 29.0
13.2 13.4 13.5
26.4 25.4 26.0
30.0
29.5
13.2
25.2
Total soluble solids (Brix degrees) 9.42 9.42 9.25 9.32
Acidity (mg-l)
Maturity index
Vitamin C (mg-l)
1.07 1.15 1.16
8.43 8.51 8.31
64.1 68.4 68.0
1.18
8.16
67.5
*The average values are not significantly different at P= 0.05
Conclusion From the data reported in this research it is possible to draw the following conclusions. Water consumptive use using drip and subsurface irrigation methods are two thirds lower on average than those obtained by sprinkler and flood. The four irrigation methods tested reduced significant differences neither in the growth of the orange trees, nor in the quality of fruit production over the period tested. Taking this into account, all other conditions being equal, the drip and subsurface irrigation methods are therefore preferable to those for flood and sprinkler. The application of Tournon’s Koasi proved to be very interesting. The performance ratio of water consumptive use/evaporation were significantly different for the different irrigation methods tested: for the sprinkler and flood methods this ratio, increased over the entire growing season, from a montly average of 0.4 in April to 0.8 in October. For drip and subsurface irrigation
methods the ratio remained almost constant at around 0.35, until of July, increasing August-September and to a greater extent in October, reaching a value close at 0.7. The information obtained over this ten year period seem: to provide useful data for the cultivation of oranges and to determine actual evapotranspiration of the orange trees on the Plain of Gioia Tauro (Southern Italy).
References ASCE (1978) Describing Irrigatrion Efficiency and Uniformity, Journal of the I&D Division, ASCE , Vol 104, No, IR 1 Cavazza L, (1981) Fisica del terreno Agrario, UTET Gadner WR, (1960) Soil, water relations in arid and semi-arid conditions, Plant water relationships in arid and semiarid conditions, UNESCO 15 Hillel D, (1971) Soil and water, Phisical principles and processes, Accademic Press New York, San Francisco, London Ruggiero C, (1986) Consumo idrico dell’albicocco irrigato a goccia, per aspersione e non irrigato durante I primi 5 anni dall’impianto, Riv, Ortoflorofrutticoltura, It, 1, Ruggiero C, Andiloro F (1972) Consumo idrico dell’arancio irrigato a goccia e non irrigato, Atti Conv, AIGR, Padova Tournon G, (1968) Irrigazione sotteranee con tubi di plastica, Congresso Internazionale delle materie plastiche ed elastomeriche, 1 -10 Tounon G, (1972) Irrigazione di superficie ed irrigazione sotterranea, Problemi tecnici ed economici di impianto e di esercizio, Atti delle giornate di studio nella prima Sezione della Commissione Internazionale du Genie Rural, Firenze, I, 13- 52 Tounon G, (1979) La subirrigazione capillare, Agricoltura Ricerca, 7, 26-33
