Effects of preharvest drip-irrigation scheduling on ... - CSIRO Publishing

CSIRO PUBLISHING

Australian Journal of Experimental Agriculture, 2003, 43, 105–111

www.publish.csiro.au/journals/ajea

Effects of preharvest drip-irrigation scheduling on strawberry yield, quality and growth H. KirnakA,D, C. KayaB, D. HiggsC, I. BolatB, M. SimsekA and A. IkinciB AUniversity of Harran, Agriculture Faculty, Irrigation Department, 63200 Sanliurfa-Turkey. BUniversity of Harran, Agriculture Faculty, Horticulture Department, 63200 Sanliurfa-Turkey. CUniversity

of Hertfordshire, Environmental Sciences, College Lane, Hatfield, Herts AL10 9AB, UK. DAuthor for correspondence; e-mail: [email protected]

Abstract. Strawberry (Fragaria × ananassa Duch) cultivars, Oso Grande and Camarosa were grown in the field from July 1999 to May 2000 in order to investigate the effectiveness of preharvest drip-irrigation management on fruit yield, quality (i.e. soluble dry matter, fruit size), leaf macro-nutrient composition and normal growth parameters. All plots were irrigated uniformly until 2 weeks before harvest. Differential treatments were then imposed ranging from a complete cut-off of irrigation to full irrigation through the harvest period. Preharvest drip-irrigation management treatments were (i) complete irrigation cut-off, dry (D), (ii) normal irrigation based on class A pan and percentage cover (C), (iii) 75% of normal irrigation, C (IR1), (iv) 50% of normal irrigation, C (IR2), and (v) 25% of normal irrigation, C (IR3). Normal irrigation (control, C) was created by irrigating plants once every 2 days at 100% A pan (Epan) evaporation. No irrigation (D) and IR3 treatments caused reductions in most parameters measured, except water-soluble dry matter concentrations (SDM) in fruit compared with other treatments. There were no significant differences between C, IR1, and IR2 treatments in normal growth parameters or leaf nutrient composition. Fruit size and SDM were both significantly affected by late-season irrigation management; individual fruit weight was significantly reduced and SDM increased even in the IR2 and IR3 treatments compared with control values. Fruit yield was not affected significantly by reduced water application except in the D treatment. These results clearly indicate that reduced preharvest irrigation was partially detrimental; a small reduction in irrigation (IR1) had little or no effect but 50% or less of normal irrigation, while not reducing overall fruit yield, resulted in smaller fruits. Additional keywords: Fragaria × ananassa Duch, plant growth, fruit yield, water deficit, nutrient concentrations, soil moisture.

Introduction Strawberry production in semiarid and arid regions requires irrigation to achieve acceptable yield and quality. Traditionally, furrow irrigation has been the technique of choice. However, use of drip irrigation has been more common in recent years. There is a widely accepted wrong perception among commercial producers and farmers that drip irrigation often produces strawberry fruit of inferior quality (low soluble solids and shorter storage life). Current strawberry production includes many different drip-irrigation management strategies among growers. The lower fruit quality mainly occurs as a result of inaccurate irrigation management strategies during the harvest and preharvest periods. Hence, preharvest irrigation management may be an important factor in obtaining high-quality fruits (Hartz 1997). When environmental factors are otherwise favourable for high crop yields, vegetable growth is often suppressed and © CSIRO 2003

yields reduced if supplemental water is inadequate or too infrequent during low-rainfall months. Vegetable crops have critical periods of growth when irrigation is a necessity for optimal yield and quality (Hardeman et al. 1999). Frequently, water shortages occur at times critical to vegetable growth. The optimal use of irrigation is characterised as the supply of sufficient water according to plant needs in the rooting area and, at the same time, avoiding the leaching of nutrients into deeper soil (Kruger et al. 1999). Drip-irrigation is well suited for use in black plastic mulched, raised-bed production cultures since water is applied directly to the soil, plant foliage remaining dry (Clark et al. 1996). Strawberry, which is a shallow-rooted crop very sensitive to water stress (Goulart and Funt 1986), has shown yield and quality improvements when using this technique. For example, McNiesh et al. (1985) and Clark et al. (1996) have shown positive links between the use of drip irrigation and growth and/or yield in strawberry. Wells

10.1071/EA02045

0816-1089/03/010105

Australian Journal of Experimental Agriculture

H. Kirnak et al.

and Nugent (1980) showed that maintaining high soil moisture during the fruit maturation period decreased soluble solids content of muskmelon fruit. The relationship between irrigation and fruit yield in strawberry has been widely recognised (e.g. Kruger et al. 1999) and in other fruit crops, e.g. muskmelon (Pew and Gardner 1983; Lester et al. 1994). However, effects of preharvest drip-irrigation regimes on physiology, nutrition, and yield in strawberry have not been studied. In this investigation, a field experiment with 2 commercial strawberry cultivars, Oso Grande and Camarosa, was carried out to determine the optimal strategy for irrigation management just before and during the harvest.

irrigation, C (IR1); 50% of normal irrigation, C (IR2); 25% of normal irrigation, C (IR3); and complete irrigation cut-off, dry treatment (D). Normal irrigation (control, C) was created by irrigating plants once every 2 days at 100% A pan (Epan) evaporation maintained soil moisture near field capacity. The plastic mulch covers were laid on plots 3 m long, formed on 0.75 m wide and 0.25 high beds spaced 0.80 m apart. A trickle irrigation system, with single laterals centred between rows of plants, was used. The drip-irrigation tubes (T-Systems, San Diego, CA) were placed over the soil surface under mulch. Drip-irrigation tubing emitters were spaced 30 cm apart and had a flow rate of 2.5 L/h. A wet band about 60 cm wide, covering the 2 rows of plants, was formed. Irrigation was monitored using tensiometers installed at 15 and 30 cm soil depths and centred between 2 plants in the rows. Soil moisture conditions within each plot were evaluated by daily readings. Each plot had a separate flow meter to monitor water input. Crop nutrients were provided by liquid injection of 202 and 166 kg/ha of nitrogen (N) and potassium (K), respectively. All plots received 17, 32 and 15 kg/ha of N, phosphorus (P) and K, respectively, as pre-plant dry fertiliser. Injection of liquid P was not used to avoid emitter plugging (Albregts et al. 1991). Nutrients were not applied during winter (from late-November to end of March). A regular spray program for disease and insect control was followed throughout the growing period. There was no precipitation during the fruit development or maturation stage. The first harvest was done in the third week of April 2000, and repeated at 2–3-day intervals (depending on fruit ripeness) for 1 month until the end of second week of May 2000.

Materials and methods Plant culture and treatments The experiment was carried out on a clay loam soil during the 1999–2000 production season at the University of Harran, Agriculture Research Station, Sanliurfa, Turkey. Sanlıurfa is semi-arid (annual rainfall 380 mm) with high summer temperatures and cool winters. Field capacity, permanent wilting point, dry bulk density, and pH of soil at the site for 30 cm soil depth were 31.75%, 22.40%, 1.32 g/cm3 and 7.3, respectively. Water quality at the site was good enough for irrigation (EC = 0.48 dS/m, and pH = 7.0). Cold-stored bare-rooted strawberry plants (cvv. Oso Grande and Camarosa), each with 1 well-developed crown of diameter 8–10 mm, were planted in the second week of July 1999. Twenty plants per replicate were planted at 30 cm between and within rows, with 3 replicates per treatment. Sprinkler irrigation was given at 4 mm/h from 0900 hours until 1800 hours for about 20 days to promote root system establishment without water stress. The normal irrigation was initiated in the second week of August 1999 and suspended in late November when the plants entered their dormant phase. Normal irrigation was re-started in March 2000 and preharvest irrigation management regimes initiated in the second week of April 2000 and continued until the end of the second week of May (Fig. 1). All plots were uniformly irrigated until 2 weeks before harvest when differential irrigation treatments were imposed. The amount of irrigation was calculated from the product of cumulative pan evaporation and Kc, where Kc was determined as the fraction of ground shaded by plant foliage. Preharvest drip-irrigation treatments were: normal irrigation based on class A pan and % cover (C); 75% of normal

Leaf analyses Plant leaf samples were collected in the third week of May (i.e. after last fruit harvest) and analysed for N, Ca (calcium), K, P and Mg (magnesium). Leaf area index (LAI) was determined using methods from Yang et al. (1990). The LAI was defined as the ratio of total leaf area of a plant to the projected horizontal ground area of the plant canopy. A total of 10 leaves per treatment were randomly selected to determine the relationship between the area of plant leaves and their length. By precisely measuring the area of each leaf with a portable leaf area meter (AM100, Eijkelkamp, The Netherlands), the relationship was determined as LAI = 17.14 × length – 38.28 (r2 = 0.974). Leaf relative water content (LRWC) was calculated based on the methods from Yamasaki and Dillenburg (1999). The LRWC was determined before the last harvest at the end of experiment. Leaves of

Applied water (mm)

300 250 Initiation of preharvest irrigation

200 Dormant stage

150 100 50

0 ay

20 0

00 0 M

.2 pr A

ar .2 00 0 M

Fe

b.

20 00

00 0 .2

19 99 D

ec .

99 9 .1 ov N

O

ct

.1 99 9

.1 99 9 Se pt

A

ug

.1

99 9

0 Ja n

106

Figure 1. Total applied water (mm) in strawberry plants under different preharvest irrigation scheduling conditions (closed bars, control; open bars, IR1; heavily shaded bars, IR2; lightly shaded bars, IR3) during growing period.

Effect of preharvest drip-irrigation on strawberry yield

2 randomly chosen plants per replicate were always collected from mid-section of plant in order to minimise age effects. Individual leaves were first removed from the stem and weighed to obtain fresh mass (FM). In order to determine the turgid mass (TM), which represents fully hydrated leaf weight, the leaves were floated in distilled water inside a closed petri dish. During the imbibition period, leaf samples were weighed periodically, after gently wiping the water from the leaf surface with tissue paper. At the end of the imbibition period, leaf samples were placed in a pre-heated oven at 80°C for 48 h, in order to obtain dry mass (DM). All mass measurements were made using an analytical balance, with precision of 0.0001 g. Values of FM, TM and DM were used to calculate LRWC using the equation below: LRWC (%) = [(FM – DM)/(TM – DM)] × 100. Chlorophyll concentration and electrolyte leakage Chlorophyll concentration in the plants was determined on 2 plants per replicate before the last harvest. Fresh leaf samples were taken from the fully expanded leaves, extracted with 90% acetone and read using a UV–visible spectrophotometer (Bausch & Lomb, Belgium) at 645–663 nm wavelengths. Chlorophyll concentration was calculated using the formulae from Strain and Svec (1966). Determination of electrolyte leakage was used to assess membrane permeability. This procedure was based on a method by Lutts et al. (1995). Electrolyte leakage was measured before the last harvest using an electrical conductivity meter. Two randomly chosen plants per treatment replicate (3 mature leaves per plant) were taken and cut into 1-cm segments. Leaf samples were then placed in individual stoppered vials containing 10 mL of distilled water after 3 washes with distilled water to remove surface contamination. Samples were incubated at room temperature (about 25°C) on a shaker (100 rpm) for 24 h. Electrical conductivity of the bathing solution (EC1) was read after incubation. The same samples were then placed in an autoclave at 120°C for 20 min and the second reading (EC2) was determined after cooling the solution to room temperature. The electrolyte leakage (EL) was calculated as EC1/EC2 and expressed as a percentage. Fruit yield and quality The values for the fruit yields are the means of the fruit yield of 20 plants per replicate and given in grams per plant. Average fruit size was calculated in grams on the basis of a randomly chosen 25 fruit per replicate at each harvest date. Soluble solids matter (SDM) was measured by a hand-held refractometer. Fruit was squeezed to obtain 2 drops of fruit juice and this was put on refractometer glass to read SDM values at room temperature. Dry weight determination and chemical analysis Plant dry weight was determined on 5 randomly chosen plants per treatment replicate at the end of experiment. Plants were separated into leaves, shoots and roots, weighed then dried at 70°C for 48 h to a constant weight. Leaves from the same plants were used for chemical analysis. Leaves were washed in detergent solution to remove any dust on leaf surfaces, soaked in 0.5 mol HCl/L for 20 s, followed by 3 or 4 rinses in distilled water and then dried at 70°C for 48 h to a constant weight. The dried leaves were ground to powder using a pestle and mortar, and stored in polyethylene bottles. Ground samples (about 0.5 g per replicate) were ashed at 550°C for 6 h. The white ash was mixed with 2 mol hot HCl/L, filtered into a 50-mL volumetric flask and made up to 50 mL with distilled water. Ca, K, P and Mg were determined in these sample solutions. Ca and Mg were determined with additional lanthanum and read by AAS (Perkin Elmer 403). Phosphorus was analysed by a vanadate–molybdate method using a UV–visible spectrophotometer and K was analysed using a flame photometer (Corning 400, UK). Total N was determined in samples of 0.1 g dry weight using a Kjeldahl method (Chapman and Pratt 1982).


107

Statistical analysis All the data from this randomised block design experiment (3 replications and 5 treatments) were analysed using a Statview computer program. Means were separated by Duncan’s multiple range test (P = 0.01).

Results Soil moisture levels in the root zone were determined using tensiometers and tensiometer readings in the control treatment never fell below –22 kPa at 30 cm and never below –38 kPa at 15 cm during the whole growing period. However, tension levels in the other treatments during the preharvest period reduced rapidly compared with C since applied water was diminished. The average tension values for IR1, IR2, IR3 and D treatments during late-season irrigation fell to –30, –40, –51, –59 kPa at 30 cm and to –42, –50, –61, and –76 kPa at 15 cm, respectively. Total water use for the treatments is shown in Figure 1. The amount of applied water for the whole growing season was 700 mm for C treatment. The amounts of applied water for C, IR1, IR2, IR3 and D during the preharvest drip-irrigation management period were 140, 105, 70, 35 mm and zero, respectively. Total chlorophyll content and dry matter production were used to assess the effects of preharvest drip-irrigation management on plant growth. Complete irrigation cut-off (D) and IR3 reduced both dry matter and chlorophyll content in strawberry cvv. Oso Grande and Camarosa (Table 1). The values obtained from IR1 and IR2 treatments were almost the same as those for the control treatment. Total chlorophyll content and dry matter production in D decreased 12 and 6%, respectively, compared with C treatment for both cultivars (Table 1). The D treatment resulted in significant (at P = 0.01) increases in electrolyte leakage (Table 2). Membrane permeability was restored to levels not significantly different from control (C) values by IR1, IR2 and IR3 treatments. Leaf relative water content (LRWC) was significantly lower than control values in both IR3 and D treatments; the lowest values were in treatment D. LRWC did not differ from control levels in IR1 and IR2 treatments (Table 2). Leaf area index (LAI) was reduced in D and IR3 treatments compared with the control (Fig. 2). The LAI reduction in IR3 was not significant. The LAI values of IR1 and IR2 were very close to the control (C) values (Table 3). Fruit yield was reduced by 13% in D treatment compared with unstressed (C) plants (Table 3). Fruit yield reductions in IR1, IR2 and IR3 treatments were not significant. Average fruit weights were unaffected by IR1 but progressively reduced by IR2, IR3 and D treatments compared with control values. Soluble dry matter (SDM) showed a similar pattern; no change in IR1 and a progressive increase in IR2, IR3 and D treatments. Numbers of fruit were increased by the higher water stress treatments; there were significant increases in the number of fruits in IR3 and D treatments compared with C (11 and 27%, respectively) for both strawberry cultivars.

108


Table 1.

H. Kirnak et al.

Dry weight (g/plant) and chlorophyll content (mg/kg fresh weight) in mature leaves of two drip-irrigated strawberry cultivars

For dry weight, means of 3 replicates, each including 5 plants; for chlorophyll, means of 3 replicates, each including 2 plants Within each column, treatment means followed by the same letter are not significantly different from each other by Duncan’s multiple range test at P = 0.01 Treatment

Shoot DW

Root DW

Whole plant DW

Chl. a content

Chl. b content

Chl. a+b content

C IR1 IR2 IR3 D

35.8a 35.5a 35.2ab 34.7b 34.0c

3.3a 3.3a 3.2a 3.2a 3.1a

Oso Grande 39.1a 38.8a 38.4ab 37.9b 37.1c

1015a 1000a 996a 935b 900c

750a 735a 724a 697b 655c

1765a 1735a 1720a 1632b 1555c

C IR1 IR2 IR3 D

35.6a 35.4ab 35.3ab 34.9b 34.1c

3.1a 3.1a 3.0ab 2.9ab 2.8b

Camarosa 38.7a 38.5ab 38.3ab 37.8b 36.9c

1012a 997a 981a 950b 899c

756a 739a 719ab 700b 661c

1768a 1736a 1700ab 1650b 1560c

Late-season irrigation management did not affect macro-element concentrations in the leaves significantly (at P = 0.01), except in the higher stress (IR3 and D) treatments (Table 4). In all cases, the lowest leaf nutrient values were in the D treatment compared with control values. Discussion It is well known that as soil water availability is limited, plant growth is usually decreased (Kirnak et al. 2001). Our results show that reduced levels of preharvest drip irrigation in strawberry produce insignificant reductions in both total dry biomass and in total chlorophyll except where reduced water application is large (IR3) or complete (D). This may be partially due to soil texture, since clay-based soils have a capability to hold precipitation for long periods (i.e. the residue of late winter–early spring rains). Also, mulch cover used in the experiment will minimise evaporation from the soil surface as well as regulating soil temperature in the root zone. These observations are in agreement with studies

Table 2. Effects of preharvest irrigation regimes on electrolyte leakage (EL, %), leaf area index (LAI) and leaf relative water content (LRWC, %) for two strawberry cultivars Means of 3 replicates are presented, each including 2 plants Within each column, treatment means followed by the same letter are not significantly different from each other by Duncan’s multiple range test at P = 0.01 Treatment LRWC C IR1 IR2 IR3 D

92.0a 91.5a 90.1a 88.9b 85.4c

Oso Grande EL LAI 8.6c 9.1bc 11.4bc 12.7bc 17.5a

4.85a 4.76a 4.50a 3.92a 2.50b

LRWC

Camarosa EL

LAI

91.2a 90.4a 89.2a 87.3b 84.2c

8.4c 9.7bc 11.5bc 13.1bc 18.7a

4.75a 4.68a 4.45a 3.84a 2.15b

conducted previously by Sharp (1996), and Jupp and Newman (1987). Another parameter partially affected by preharvest drip-irrigation management was electrolyte leakage. We suggest that the increase in electrolyte leakage that we have demonstrated under dry treatment (D) and IR3 is at least partly due to the combined effects of reduced water uptake and chlorophyll concentration. Dhindsa et al. (1981) and Chen et al. (1991) have linked increased electrolyte leakage to reductions in chlorophyll concentrations (due to leaf senescence) while Premachandra et al. (1992) and McDonald and Archbold (1998) have shown that reductions in water use affect electrolyte leakage. Our results support these views because the decreases in both applied water (Fig. 2) and chlorophyll concentrations (Table 1) during the preharvest period are shown to also increase electrolyte leakage (Table 2). The effects of water stress on leaf area index (LAI) during the preharvest period were not significant for IR1, IR2 and IR3. However, water stress during the preharvest period affected LAI for D treatment significantly compared with C. Use of plastic mulch covers probably mitigated the negative effects of water stress on LAI for IR1, IR2 and IR3 treatments. Gehrmann (1986) reported that higher water quantities led to an increased canopy and higher fruit production for strawberry. Although higher LAI values are generally indicative of excessive vegetative growth which may delay the onset of fruit production, maximum fruit yield occurred at LAI values of 3–5 (treatments C, IR1, IR2 and IR3) and yield was only significantly reduced in the dry (D) treatment. Higher LAI values increase light interception (Scholberg et al. 2000) and in our experiment this appears to be linked to fruit yield which only falls when LAI is significantly reduced.



109

6

Leaf area index

5 4 3 C IR2 D

2 1

IR1 IR3

A

20 M

ay

pr .

20

00 .2 ar M

00

00

0

0 00

0 00

Fe b. 2

n. 2 Ja

99

D

ec

.1

19 N

ov .

.1 O ct

9

99

9 99

99 pt .1

Se

A

ug .1 9

99

9

0

Figure 2. Mean leaf area index of both strawberry cultivars under different preharvest irrigation scheduling conditions during growing period. Bars are standard error of the mean of 3 replications.

It may seem surprising that reduced amounts of preharvest irrigation resulted in no fruit yield decreases (except in D treatment). The data presented here show both similarity and dissimilarity with previous work. The similarity in strawberry fruit yield among irrigation treatments (except D treatment) appears contrary to some previous reports. Penuelas et al. (1992) and McNiesh et al. (1985) reported that water stress decreased yield and vegetative growth of strawberry. On the other hand, Hartz (1997) reported that preharvest irrigation management did not affect the yield of muskmelon. The lack of significant irrigation treatment effects on strawberry yield in our experiment may have been related to the way in which the Table 3. Fruit yield, number of fruit, fruit size and water-soluble dry matter (SDM) of two strawberry cultivars grown under different preharvest irrigation regimes

treatments were imposed since all treatments received optimal irrigation through to fruit set. Also, the high soil water holding capacity (12% available, w/w), mulch cover and the early season management that would have been likely to encourage deeper rooting, would all have been likely to minimise the degree of stress imposed by the reduced preharvest irrigation treatments (IR1, IR2 and IR3). In our experiment, an average of –30 kPa in 30 cm soil depth was obtained for soil moisture tension in the unstressed (C) treatment. In the reduced water application treatments (IR1, IR2 and IR3), the soil moisture tensions were increased according to the decreases in water application. Under dry treatment, the soil moisture was reduced to an average of –59 kPa in 30 cm soil depth. Kruger et al. (1999) reported Table 4. Macro-element concentrations (g/kg DW) in mature leaves of two strawberry cultivars under different preharvest irrigation regimes

For fruit yield and number of fruit, means of 3 replicates are presented, each including 20 plants; for fruit size and SDM, means of 3 replicates are presented, each including 25 fruits Within each column, treatment means followed by the same letter are not significantly different from each other by Duncan’s multiple range test at P = 0.01

Means of 3 replicates are presented, each replicate including 5 plants Within each column, treatment means followed by the same letter are not significantly different from each other by Duncan’s multiple range test at P = 0.01

Treatment

Treatment

Fruit yield (g/plant)

Fruit weight No. of fruit (g/fruit) per plant

SDM (%)

N

P

Element K

Ca

Mg

C IR1 IR2 IR3 D

460a 455a 441a 438a 400b

Oso Grande 10.0a 9.7a 9.2b 8.6c 6.9d

46c 47c 48c 51b 58a

8.0d 8.1d 8.5c 8.8b 9.2a

C IR1 IR2 IR3 D

25.2a 24.8a 24.5a 23.0b 20.1c

Oso Grande 6.8a 32.2a 6.5a 31.7a 6.1a 31.4a 5.2b 30.0b 4.3c 27.5c

25.7a 25.5a 24.8a 23.4b 20.1c

5.5a 5.3a 5.0a 4.4b 3.7c

C IR1 IR2 IR3 D

455a 442a 436a 428a 395b

Camarosa 9.9a 9.6a 9.1b 8.4c 6.7d

46c 46c 48c 51b 59a

8.1d 8.2d 8.6c 8.9b 9.3a

C IR1 IR2 IR3 D

25.0a 24.7a 24.3a 23.1b 19.9c

Camarosa 6.7a 32.5a 6.5a 32.1a 6.2a 31.5a 5.4b 30.0b 4.2c 27.7c

25.5a 25.1a 24.7a 23.5b 20.0c

5.3a 5.1a 4.8a 4.2b 3.5c

110


that a value of between –10 and –30 kPa is generally considered to be optimal. Tensiometer measurements showed that hydraulic gradients were in an upward direction in all cases. Therefore, it seems unlikely that the leaching of minerals from the rooted area into deeper soil occurred (Kruger et al. 1999), indicating that nutrient concentrations in the root zone are unlikely to be reduced but availability may remain an issue depending on soil water content. The effects of irrigation treatments on fruit quality appear similar to previous studies where late season water management was shown to influence fruit quality. Kirnak et al. (2001) reported that water stress significantly reduced fruit size and increased SDM in strawberry. Preharvest irrigation scheduling did not significantly affect macro-element concentrations in leaves, except in dry (D) and severe water stress (IR3) treatments. These findings are in partial agreement with the findings of Albregts et al. (1991) for strawberry and Wien and Minotti (1987) for tomato. They stated that there was a good relationship between nutrient uptake and amount of irrigation water applied during the whole growing season. However, in our experiment, we scheduled irrigation just before preharvest not for the whole growing season. Besides, both papers described the effects of fertiliser rate on fruit yield and nutrient uptake without using any water stress treatment, which we used in our experiment. In conclusion, water stress during the preharvest period had little or no adverse effects on physiological, vegetative and nutritional development, or fruit yield of strawberry cultivars Oso Grande and Camarosa, except where irrigation was largely (IR3) or completely (D) stopped. However, fruit quality (individual fruit size and SDM) was significantly and adversely affected by water stress except where the reduction in applied water was small (IR1). This study demonstrated that with proper irrigation and agricultural management, high fruit quality in strawberry can be achieved with drip irrigation, without sacrificing fruit yield. Continuing drip irrigation into the harvest period is required for maximum yield and fruit size, but a reduced water application with drip irrigation and mulch cover can be suggested for saving water. Severe water stress as shown in D and IR3 during preharvest irrigation should be avoided for strawberry production. Acknowledgments The authors thank University of Harran (Turkey) and University of Hertfordshire (UK) for supporting this work. References Albregts EE, Clark GA, Stanley CD, Zazueta FS, Smajstrla AG (1991) Preplant fertilisation of fruiting microirrigated strawberry. HortScience 26, 1176–1177. Chapman HD, Pratt PF (1982) Method of plant analysis. In ‘Methods of analysis for soils, plants and water’. (Eds HD Chapman, PF Pratt) pp. 60–193. (Academic Press: Riverside, CA, USA)

H. Kirnak et al.

Chen CT, Li CC, Kao CH (1991) Senescence of rice leaves. Changes of chlorophyll, protein and polyamine contents and ethylene production during senescence of a chlorophyll-deficient mutant. Journal of Plant Growth Regulator 10, 201–205. Clark GA, Albregts EE, Stanly CD, Smajstrla AG, Zazueta FS (1996) Water requirements and crop coefficients of drip-irrigated strawberry plants. Transactions of the ASAE 39, 905–913. Dhindsa, RS, Plumb-Dhindsa P, Thorpe TA (1981) Leaf senescence correlated with increased levels of membrane permeability and lipid peroxidation, and decreased levels of superoxide dismutase and catalase. Journal of Experimental Botany 32, 93–101. Gehrmann H (1986) Wasserbedarf und Einfluss von Wassermangel bei Erdbeere (Fragaria × ananassa Duch.). Diss. Der Rheinischen Friedrich-Wilhelms-Universitat Bonn. Goulart BL, Funt RC (1986) Influence of raised beds and plant spacing on growth and yield of strawberry. Journal of the American Society for Horticultural Science 111, 176–181. Hardeman TL, Taber HG, Cox DF (1999) Trickle irrigation of vegetables: water conservation without yield reduction. Journal of Vegetable Crop Production 5, 23–33. Hartz TK (1997) Effects of drip irrigation scheduling on muskmelon yield and quality. Scientia Horticulturae 69, 117–122. Jupp AP, Newman EI (1987) Morphological and anatomical effects of severe drought on the roots of Lolium perenne L. New Phytologist 105, 393–402. Kirnak H, Kaya C, Higgs D, Gercek S (2001) A long-term experiment to study the role of mulches in physiology and macro-nutrition of strawberry grown under water stress. Australian Journal of Agricultural Research 52, 937–943. Kruger E, Schmidt G, Bruckner U (1999) Scheduling strawberry irrigation based upon tensiometer measurement and a climatic water balance model. Scientia Horticulturae 81, 409–424. Lester GE, Oebler NF, Coons J (1994) Preharvest furrow and drip irrigation schedule effects on postharvest muskmelon quality. Postharvest Biology and Technology 4, 57–63. Lutts S, Kinet JM, Bouharmont J (1995) Changes in plant response to NACI during development of rice varieties differing in salinity resistance. Journal of Experimental Botany 46,1843–1852. McDonald S, Archbold D (1998) Membrane competence among and within Fragaria species varies in response to dehydration stress. Journal of the American Society for Horticultural Science 123, 808–813. McNiesh CM, Welch NC, Nelson RD (1985) Trickle irrigation requirements for strawberries in coastal California. Journal of the American Society for Horticultural Science 110, 714. Penuelas J, Save R, Marfa O, Serrano L (1992) Remotely measured canopy temperature of greenhouse strawberries as indicator of water status and yield under mild and very mild water stress conditions. Agricultural and Forest Meteorology 58, 63–77. Pew WD, Gardner BR (1983) Effects of irrigation practices on vive growth, yield and quality of muskmelon. Journal of the American Society for Horticultural Science 108, 134–137. Premachandra GS, Saneoka H, Fufita K, Ogata S (1992) Leaf water relations, osmotic adjustment, cell membrane competence, epicuticular wax load and growth as affected by increasing water deficits in sorghum. Journal of Experimental Botany 43, 1569–1576. Scholberg J, McNeal BL, Jones JW, Boote KJ (2000) Growth and canopy characteristics of field-grown tomato. Agronomy Journal 92,152–159. Sharp RE (1996) Regulation of plant growth responses to low soil water potential. HortScience 31, 36–38.


Strain HH, Svec WA (1966) Extraction, speration, estimation and isolation of chlorophylls. In ‘The clorophylls’. (Eds LP Vernon, GR Seely) pp. 21–66. (Academic Press: New York) Wells JA, Nugent PE (1980) Effect of high soil moisture on quality of muskmelon. HortScience 15, 258–259. Wien HC, Minotti PL (1987) Growth, yield, and nutrient uptake of transplanted fresh-market tomatoes as affected by plastic mulch and initial nitrogen rate. Journal of the American Society for Horticultural Science 112, 759–763.


111

Yamasaki S, Dillenburg LR (1999) Measurements of leaf relative water content in araucaria angustifolia. Revista Brasilleira de Fisiologia Vegetal 11, 69–75. Yang X, Short TH, Fox RD, Bauerle WL (1990) Plant architectural parameters of a greenhouse cucumber crop. Agricultural and Forest Meteorology 51, 197–209.

Received 19 February 2002, accepted 3 May 2002

http://www.publish.csiro.au/journals/ajea