Yield response and N-fertiliser recovery of tomato grownunder deficit irrigation
S. Topcu a,∗, C. Kirda a, Y. Dasgan a, H. Kaman a, M. Cetin a, A. Yazici a, M.A. Bacon b
a Cukurova University, Faculty of Agriculture, 01330 Adana, Turkeyb The Lancaster Environment Centre, Lancaster University, Lancaster LA1 4YQ, UK
Received 11 April 2005; received in revised form 19 July 2006; accepted 30 August 2006
bstract
In search of new innovations for saving irrigation water, fruit yield response and N-fertiliser recovery of greenhouse grown spring-plantedomato (Lycopersicon esculentum Mill., cv. F1 Fantastic) were assessed as influenced by deficit irrigation, imposed using either conventionaleficit irrigation (DI) or partial root drying (PRD). Three irrigation treatments were tested: (1) FULL, control treatment where the full amount ofrrigation water, which was measured using Class-A pan evaporation data, was applied uniformly on the two halves of plant-root zone; (2) PRD,0% deficit irrigation in which wetted and partially dry halves of the root-zone were interchanged every irrigation; (3) DI, conventional deficitrrigation maintained at 50% deficit, compared to FULL irrigation, with water applied on the both halves of the root-zone. During a growth periodf 153 days, the highest fruit yield of 145.4 t ha−1 was measured under FULL irrigation treatment, which was followed by PRD and DI treatmentsith statistically lower (P ≤ 0.01) yields of 114.6 and 103.4 t ha−1, respectively. Irrigation water use efficiencies (IWUE) of both deficit treatmentsere significantly (P ≤ 0.01) higher (52.7% for PRD and 38.3% for DI) compared to FULL irrigation. Nitrogen-fertiliser recovery was over 70%,ith no significant difference among the irrigation treatments. Both deficit treatments (DI and PRD) showed lower values of leaf water potential,
hotosynthetic rate and stomatal conductance compared to FULL irrigation. Before irrigation, xylem-sap abscisic acid (ABA) concentrationsere 28% and 38% higher under water-stressed deficit treatments DI0 and PRD, respectively, compared to FULL irrigation, and the high ABA
oncentrations was maintained only under PRD effect, following irrigation. The results of this work suggest that PRD practices can be viable anddvantageous compared to conventional techniques to minimise crop-yield reductions during deficit irrigation.
2006 Elsevier B.V. All rights reserved.
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eywords: Abscisic acid; Fertiliser recovery; Lycopersicon esculentum L.; Wa
. Introduction
Shortage of water in arid and semi-arid regions is an impor-ant limiting factor for irrigated crop production. In areas ofater scarcity, irrigation strategies need to be devised to save irri-ation water with marginal yield reductions. One widely usedpproach is conventional deficit irrigation (DI) but it requiresrop specific information for its effective use (Kirda et al., 1999).omato plants grown under conventional DI exhibited watertress and had significant reduction in gas exchange rate, whiched to significant reductions in tomato yield (Pulupol et al., 1996;
ay and Gonzalerz, 1999). Partial root drying (PRD) practice,nother approach for saving irrigation water, is based on split-oot studies, which have shown that plants wetted at the one half
f their roots and allowed to dry out at the other half develop nor-ally with reduced stomatal opening and no visible leaf water
eficit (e.g., Davies and Zhang, 1991; Davies et al., 1994). Thencreased concentration of abscisic acid (ABA) in the xylemows (Zhang and Davies, 1990, 1991), chemical or other sig-als (e.g., Davies and Zhang, 1991; Tardieu and Davies, 1993)rom roots to leaves, resulting from exposure of plant roots torying cycles, triggers stomatal closure, which conditions plantsor effective and sparing use of available water.
Recent results on maize (Kang et al., 2000; Kirda et al., 2005),ot-grown pepper (Kang et al., 2001), tomato (Davies et al.,000; Kirda et al., 2004; Zegbe-Dominguez et al., 2003; Zegbe etl., 2004 and pear (Kang et al., 2002) confirmed that use of PRDractice increased IWUE with only marginal yield reduction,
ompared to non-deficit full irrigation.
A work by Kirda et al. (2005) showed that the PRD practicemproved N-fertiliser recovery of maize, compared to conven-ional deficit and full irrigation, with minimal mineral N-residue
eft in the soil after harvest. Similarly irrigation methods andanagement in tomato production affected fertiliser uptake
Kirda et al., 2003). Although studies on yield response andrrigation water use efficiency (IWUE) of tomato crop, irrigatedith PRD practice, are numerous in confined rooting environ-ents such as pots and wooden boxes (e.g., Davies et al., 2000;ingo et al., 2003; Zegbe-Dominguez et al., 2003; Zegbe et
l., 2004, 2006), a thorough assessment of how PRD affects-fertiliser uptake and IWUE in natural soil environment haveet to be addressed. The objective of this work was therefore tossess yield and physiological responses of greenhouse-grownomato, in addition to measuring N-fertiliser recovery, underULL, DI and PRD irrigation practices.
. Materials and methods
The experiment was carried out in plastic greenhouses of theesearch Farm at the Faculty of Agriculture, Cukurova Uni-ersity; Adana, Turkey, for spring-planted fresh-market tomatoultivar (Lycopersicon esculentum L., cv. F1 Fantastic, Israelrigin) in 2002. A randomised complete block experimentalesign with four replicates, consisting of three-irrigation treat-ents was used. Two plastic houses, each had two replicates (i.e.,
locks), were allocated for the experiment. Mean temperaturesrom February to April and from May to July, inside the green-ouses, were 16 and 25 ◦C, respectively. The relative humidityecorded during the growing season changed within the rangerom 40 to 80%. The plastic houses, oriented in North-Southirection, were 15 m × 24 m in size and the cover material wasV + IR + Antifog added polyethylene. The seeds were germi-ated in plastic bags filled with peat and transplanting was donehen the seedlings had reached a plant height of 15 cm on 11ebruary 2002. The distances between rows and between plants
n the rows were 80 and 50 cm, respectively. Each row consistedf 21 tomato plants. The plants were hung on wires running at75 cm height over the rows. Plant stems were laid along theows when the height of the plants went beyond 175 cm dur-ng the progress of growth season. Sub-plots of each irrigationreatment had six rows of plant, of which three rows did noteceive N-fertiliser to measure N-fertiliser recovery using dif-erence method (e.g., Moll et al., 1982; Ma et al., 1999; Kirdat al., 2005). Fruit yields of 19 plants of central row in theertilised-three rows, excluding the two plants at extreme ends,ere recorded during harvest. Nitrogen yield (kg N ha−1), nitro-en derived from soil (Ndfs, %) and N-fertiliser recovery (NFR,) were calculated following the procedure described in detail
y Kirda et al. (2005). Fertilisers were applied continuouslyith irrigation water. Concentrations of 100, 30 and 200 mg l−1
f N, P and K, respectively were maintained in irrigation wateror FULL treatment, following recommendations in a previousork, carried out in the same greenhouses (Kirda et al., 2003).he nutrient concentrations were adjusted for other treatments
n proportion to percentage reduction of applied irrigation water
o ensure that all irrigation treatments received the same amountf fertiliser. Forms of the fertilisers used were urea, phospho-ic acid and potassium sulfate for nitrogen, phosphorous andotassium, respectively.
scFw
nomy 26 (2007) 64–70 65
Experimental soil in the greenhouse was classified asalexerollic Chromoxerert with heavy textured clay soilverlaying medium textured sandy clay sub-soil. Soil hadedium permeability with high water retention capacity
12–14 cm (100 cm)−1], with field capacity (−0.033 MPa) of.33 cm3 cm−3 and wilting point (−1.5 MPa) of 0.20 cm3 cm−3.he average soil bulk density was 1.15 g cm−3.
A drip irrigation system with two laterals laid down alonghe rows was used for irrigation. The two laterals with drippersf 4 l h−1 flow rate and spaced at 100 cm were arranged in suchway that there was always one dripper centred between the
wo plants, but installed alternately on the two separate laterals.he irrigation water applied was measured with a flow meter,
nstalled in the water delivery unit of the irrigation system, whichas designed for independent control of water delivery to each
rrigation treatment. The water delivery unit had both mesh andand filters for preventing dripper clogging. Depending on thereatment, we had the option of applying irrigation water throughither single lateral, or the two laterals. If the two laterals weresed, all sides of the roots were wetted, as practiced under FULLnd DI treatments. Applying water through only a single lateralesulted in wetting of alternate spacing between the plants, asequired under the PRD-treatments. The wetted side of the rootone was changed by turning on the laterals, wetting alternat-ngly only one half of the roots during irrigation.
We used a fixed irrigation interval (7 days) until mid season91 days after transplanting), then two irrigations were appliedeekly, at 3- and 4-day intervals. Irrigation water applied was
imited to a maximum quantity of 6 l per plant per irrigation,hich prevented deep percolation. Maximum depth of wettinguring each irrigation event was 60–70 cm, which was measurednd controlled with neutron gauge (CPN Hydroprobe 503) mea-urements, carried out before and after each irrigation over aepth of 110 cm. The neutron access tubes were installed, mid-ay between the drippers and the plants.A Class-A evaporation pan located in the centre of each
reenhouse was used to estimate irrigation water requirementI, mm) for FULL irrigation using the equation
= KEp
here K is a coefficient comprising plant coverage, wettedrea (diameter of 45–50 cm) and pan coefficient; Ep is cumu-ative evaporation (mm) measured during the allowed irrigationnterval. Soil–water-content profiles measured before and afterrrigation with the neutron gauge were used to adjust irrigationater requirement under the FULL treatment. Ideally the soilater storage under FULL irrigation was supposed to reach toeld capacity fallowing irrigation. If not, the coefficient K wasrbitrarily increased to apply increased amount of water in theollowing irrigation. The coefficient K was therefore allowed tohange within the range of 0.30–1.25, depending on root-zoneoil water status of the FULL treatment, during the progress of
eason. However, soil water storage after 80 DAT could, in noase, reach to soil field capacity, following irrigation under theULL treatment (Fig. 1). The crop water consumption (i.e., ET)as estimated using water balance equation.
Leaf area index (LAI) was measured monthly on cut-lant samples. Additionally, plant physiological measurementsncluding diurnal photosynthetic rate and stomatal conductanceboth) using an ADC, LCA4 portable photosynthesis unit (LCA-, ADC, Hert, UK), and leaf water potential using a pressurehamber (PMS, Corvallis, USA), were taken on fully expandedoungest four leaves of third branch from the top in each repli-ate. Together with leaf water potential measurements, xylem-ap samples were collected in Eppendorf vials, frozen in liquiditrogen and stored at −80 ◦C. The samples were later analysedor abscisic acid (ABA) using a radioimmuno-assay techniqueescribed by Quarrie et al. (1988).
Crop yields and total seasonal irrigation water applied underhe described irrigation treatments were recorded. Irrigation-ater-use efficiency (IWUE), which was used to assess compar-
tive benefits of the irrigation treatments, was calculated usinghe equation
WUE = Y
I
here Y is crop yield (kg ha−1) and I is seasonal-irrigation watermm) applied in different irrigation treatments.
. Results
The soil water storage under FULL treatment was propor-ionally higher than the treatments conventional DI and PRDaverage of wet and dry sides of root-zone), throughout the grow-ng season (Fig. 1) as envisaged. Plant growth under both deficitrrigation treatments was hindered and slowed down in compar-son to well watered plants under FULL treatment. However,o statistical significance was observed in biomass production,lthough the end-season leaf area index under the deficit treat-ents (DI and PRD) was significantly lower than those of FULL
reatment (Fig. 2).The highest tomato fruit yield was obtained under the FULL
rrigation (Table 1). The percentage of marketable fruit qualityI. Quality) was also highest under FULL (86%) irrigation with
Fig. 1. Seasonal changes of soil water storage.
Fdma
Fea
ig. 2. Seasonal changes of LAI and total biomass during the progress of growtheason under three irrigation treatments. Data points are means (n = 4) ± S.D.SDs (P = 0.05) are presented as vertical line-bars.
RD yielding 70% of I. Quality fruit. However, the conventionalI practice gave the lowest marketable yield (60.9%). As regards
o IWUE, the PRD treatment gave the highest value, and theowest IWUE was recorded under FULL treatment (Table 1).ruits under the PRD treatment were matured comparativelyarlier, which therefore would give 7–10 days of market advan-age over other treatments (Fig. 3). Additionally, the fruits underRD practice, quality wise, were not statistically different thanULL treatment (Table 2). Although there were no significant
ifferences in fruit weight, total acidity (%), water soluble dryatter (%) and fruit juice pH among the tested treatments, the
verage fruit volume was reduced the most under conventional
ig. 3. Cumulative fruit yield (a) and comparison of irrigation treatments forarly harvest (b). Data are means (n = 4) ± S.D. LSDs (P = 0.05) are presenteds vertical line-bars in each graph.
S. Topcu et al. / Europ. J. Agronomy 26 (2007) 64–70 67
Table 1Tomato yield and water use efficiency
Treatments Yield (t ha−1) I (mm) ET (mm) IWUE (kg(ha mm)−1)
I. Qualitya II. Qualitya Total
FULL 126.3 a 19.1 b 145.4 a 314 330 463.7 bPRD 80.0 b 34.6 a 114.6 b 162 200 708.0 aDI 63.0 b 40.4 a 103.4 b 162 213 641.5 aTukey’s CV 21.0 5.5 28.0 – – 164.9P 0.0002 0.0001 0.001 0.001
Data in columns followed with different letters (a and b) are significantly different based on Tukey’s mean range test for indicated critical value for comparison (CV)at α = 0.01 rejection level.
a If average fruit weights were greater than 60 g, they were classified as first quality, otherwise, rated as second quality.
Table 2Tomato fruit quality parameters
Treatments Average fruit weight (g) Average fruit volumea (cm3) WSDMb (%) Total acidity (%) Dry matter (%) pH
FULL 137.5 135.7 a 4.7 0.58 5.69 3.66PRD 122.5 118.5 ab 4.7 0.53 6.08 3.79DI 114.8 109.9 b 4.6 0.48 5.72 3.73Tukey’s CV NS 21.8 NS NS NS NSSignificance (P) 0.078 0.02 0.90 0.24 0.29 0.14
Data in columns followed with different letters (a and b) are significantly different based on Tukey’s mean range test for indicated critical values for comparison(
DP
iTtcfgptltt
lastoa
TNc
T
FPDS
tLwLa(tcdeficit irrigation treatments, PRD and DI (Fig. 6). However, thePRD plants had the lowest LWP in the afternoon, and the stom-atal conductance measurements were significantly (P ≤ 0.05)
Table 4Total N yield and partition of N in different parts of tomato as influenced byirrigation treatments
N yield (g N plant−1) Tukey’s CV
FULL PRD DI
CV) at α = 0.05 rejection level.a Fruit volume is measured based on displaced volume of water.b WSDM, water soluble dry matter.
I (Table 2). It was further noted that fruit dry matter under theRD treatment was the highest.
The highest N yield (kg N ha−1) was noted under the FULLrrigation; whereas, it was the least under DI treatment (Table 3).he N yield under PRD was 8% lower compared to FULL irriga-
ion, however the difference was not statistically significant. Theonventional deficit treatment (DI) gave the lowest N yield. Asor N-fertiliser recovery, it was over 70% irrespective of the irri-ation treatments tested (Table 3). The fruits took up the largestortion of N compared to other plant parts, irrespective of theested irrigation treatments (Table 4). While N translocation toeaves, stem and shoots were proportionally greater under FULLreatment, the translocation was selectively towards fruits underhe PRD treatment (Table 4).
Diurnal xylem-sap abscisic acid (ABA) concentration wasowest, although statistically significant (P ≤ 0.05) only in thefternoon, under non-stressed plants of FULL treatment, and theimilar behavior was maintained irrespective of the sampling
ime, before or after irrigation (Fig. 5). The ABA concentrationf plants under the FULL and DI treatments decreased soonfter irrigation while the plants under PRD treatment main-
able 3itrogen yield, soil-N uptake (Ndfs) and N-fertiliser recovery (NFR) of tomato
ained higher ABA concentration (Fig. 5). Up until noon, theWP in all treatments, measured before irrigation, fluctuatedithin the range of −0.3 to −0.6 MPa, however, the highestWP was observed under FULL irrigation throughout the day,nd most obviously in the afternoon (Fig. 6). The ranking,FULL > PRD50 > DI50), of stomatal conductance among thereatments, was maintained throughout the day and it was signifi-antly (P ≤ 0.05) higher under FULL treatment, compared to the
tems 1.78 1.30 1.42 NSeaves 3.28 a 2.27 b 2.39 b 0.71runed shoots 0.26 a 0.06 b 0.19 a 0.079ruits 10.74 10.97 9.63 NS
otal 15.81 14.54 13.43 NS
atio of shoots N yield (%)NShoots/NBiomass × 100 1.64 1.02 1.43 NS
atio of fruits N yield (%)NFruits/NBiomass × 100 68.1 b 75.4 a 71.9 ab 7.21
ata in rows followed with different letters (a and b) are significantly differentased on Tukey’s mean range test for indicated critical values for comparisonCV) at α = 0.05 rejection level. Significance of treatment effects is shown inarenthesis.
6 . Agronomy 26 (2007) 64–70
htt(ab
4
th(LDlliktctcbPFettatwft(
dssd(
F(
F1(
iacsg(ghbiprt
8 S. Topcu et al. / Europ. J
igher than those of DI. It appeared further that the photosyn-hetic rate measured under PRD was nearly the same as the FULLreatment; whereas, the conventional DI exhibited the lowest rateFig. 6). Seasonal measurements of LWP, stomatal conductancend the photosynthetic rate, not given here, showed the similarehaviour as the diurnal measurements.
. Discussion
Although a 20% yield reduction, compared to FULL irriga-ion, was observed under PRD, irrigation water saved was asigh as 50% (Table 1). Consistent with findings by Gautier et al.2001), inhibition of plant growth, demonstrated by decrease ofAI and biomass production, which become apparent about 60AT (Fig. 2), suggest that photosynthetic assimilates were most
ikely partitioned to fruit growth so that the yield reduction wasimited to a mere 20% corresponding as high as 50% reduction ofrrigation water applied under PRD treatment (Table 1). The mar-etable and total yields under DI were the lowest, which showedhat the PRD treatment had higher yield benefit compared toonventional DI practice. Early harvest of greenhouse-grownomato crop provides a significant market advantage with highash earnings to growers (Table 1). Consistent with earlier worky Ramalan and Nwokeocha (2000), our results suggest that theRD practice facilitates 7–10 days early harvest compared toULL and DI (Fig. 3). Irrigation deficit as high as 50% had noffect on fruit quality with exception of fruit size, which washe least influenced when the deficit was implemented throughhe PRD practice (Table 2). Results of Davies et al. (2000)nd Mingo et al. (2003) were similar to our findings in thatomato fruit quality was influenced the least if the water deficitas imposed through the PRD practice. Marginal reduction of
ruit size showed no apparent association with soluble dry mat-er (WSDM), which has profound influence on tomato flavourBertin et al., 2000).
The rate of N uptake exhibited a sudden increase around 90ays after transplanting (DAT), during the initial fruit setting
tage (Fig. 4). Although the N-fertiliser recoveries (NFR) mea-ured were rather high, above 70%, statistically no significantifferences were existed among the tested irrigation practicesTable 3). The high recovery must be attributed to character-
ig. 4. Nitrogen yield, soil- and fertiliser-N uptake of tomato. Data are meansn = 4) ± S.D.
hguytdegaecFlcepr
p
ig. 5. Diurnal xylem-sap ABA concentration before and after irrigation on16 and 118 days after transplanting, respectively. Data points are meansn = 4) ± S.D. LSDs (P = 0.05) are presented as vertical line-bars.
stics of fertigation through drip irrigation, which facilitatespplication of fertilisers directly in plant-root zone at requiredoncentrations when needed (Kirda et al., 2003), and thereforeignificant savings in fertiliser use can be achieved with ferti-ation. The FULL irrigation treatment had the highest N yieldkg N ha−1), which resulted from higher uptake of soil nitro-en compared to the deficit irrigation treatments (Table 3). Theigher uptake of soil nitrogen, under the FULL irrigation, shoulde attributed to proportionally larger volume of soil wetted dur-ng irrigation, since double amount of water was applied tolant-root zone. Consistent with our findings, Guidi et al. (1997)eported a decrease of N yield under water stress conditions foromato plants. It should be noted however that proportionallyigher portion of N taken up went to shoots under FULL irri-ation; whereas, it was the fruits, where N was largely used upnder PRD effect (Table 4). Higher N went to fruits, compared tooung shoots and leaves under PRD practice (Table 4) supportshe hypothesis of preferential translocation of N to fruits. Ourata therefore confirms the earlier findings (e.g., Singandhupet al., 2003) that the water deficit like in PRD practice promotesenerative growth and fruiting, and it increases harvest index,nd thereby it recovers higher portion of input costs (Loveyst al., 2000; Stoll et al., 2000; Zegbe-Dominguez et al., 2003),ompared to FULL or conventional DI irrigation. The results inig. 4 show further that tomato N requirement is the highest fol-
owing early fruiting stage (i.e., 90 DAT) when N deficiency mayause drastic yield reductions (Kirda et al., 2003; Singandhupet al., 2003). It is essential therefore that an effective fertiliser
ractice, in particular for field grown tomato, must consider Nequirement which changes depending on plant growth stage.
Re-watering decreased ABA concentration of FULL and DIlants while the ABA of PRD plants remained high (Fig. 5).
arlier work by Zhang et al. (1987) has led us to suggest that halff the root zone maintained proportionally dry under the PRDractice was sufficient to keep relatively higher concentrationsf ABA compared to FULL and conventional DI. Consistentith LWP data, the higher stomatal conductance of plants underULL irrigation confirmed the earlier reports (e.g., Gollan et al.,992; Vanrensburg et al., 1996; Wilkinson and Davies, 1997) thatBA may indeed be an important means of chemical signalling,
egulating stomatal control. Increased concentration of ABA inhe xylem flow to plant shoots triggers closure of stomata (Zhangnd Davies, 1990; Gollan et al., 1992; Liang and Zhang, 1999;smail et al., 2002), as the case noted under the water deficitreatments (Fig. 5), and thereby enables the plant to use sparinglyupplied water efficiently.
Stomatal conductance was most significantly reduced underonventional DI suggesting that this method of irrigationmposes the greatest restriction on stomatal aperture. This treat-
ent also resulted in the measurement of the lowest midday (butnly the measurements at 8:00, 13:00 and 19:00 CET were sta-istically different from the PRD treatment) photosynthetic rate
mong all treatments. It can not be determined whether stomatallosure limited photosynthetic rate, but this seems likely whenaken together with the strict relationship between seasonal tran-piration and yield. This would explain the significant reduction
ig. 6. Diurnal changes of LWP, stomatal conductance (gs) and photosyntheticate (A) before irrigation on 116 days after transplanting. Data points are meansn = 4) ± S.D. LSDs (P = 0.05) are presented as vertical line-bars.
Atatmwp
A
mMrGmt
R
B
C
D
D
D
G
nomy 26 (2007) 64–70 69
n yield of the crop under deficit irrigation (DI). Diurnal stom-tal conductance measurements under PRD fall between FULLnd DI treatments, whereas, photosynthetic rate follows closelyo that of FULL treatment (Fig. 6). One can therefore deducehat while the leaf water relations are maintained, photosynthe-is is affected least under PRD irrigation. Plants irrigated underRD can use water in the most efficient way, without wilting of
eaves (Jones, 1980; Cowan, 1982); whereas plants under con-entional deficit irrigation (DI), not having hormonal stomataontrol mechanisms, may lose leaf turgidity, which adverselyffects photosynthesis between the irrigations.
. Conclusions
The results of this work suggest that PRD practices can beiable and advantageous compared to conventional techniqueso minimise crop-yield reductions during deficit irrigation. Goodrop yields with no adverse effects on fruit quality can beustained under scenarios of water shortage with PRD whererst-quality-fruit yield was nearly same as FULL irrigation.dditionally, the PRD practice promotes early harvest and can
hereby provide to growers a market advantage when the pricesre high. The PRD practice had no adverse effect on recoveringhe applied N-fertiliser (which might be expected given the pro-
otion of tomato root growth with PRD—Mingo et al., 2003),hich is largely translocated to fruits, with least N spent forlant stems, leaves and pruned shoots.
cknowledgments
Authors gratefully acknowledge that this work was imple-ented with funds provided by European Union, through INCO-ED RTD project (ICA3-CT-1999-00008) and partial support
eceived from Cukurova University, Adana through Researchrant ZF-2002 BAP 23. Thanks are due to the Staff of Depart-ent of Biological Sciences, University of Lancaster, UK for
heir help in ABA analysis.
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