Water balance in a young almond orchard under drip irrigation with water of low quality

24 Pages·1999·0.47 MB·English

AgriculturalWaterManagement43(2000)75–98
Water balance in a young almond orchard under
drip irrigation with water of low quality
J.A. Francoa, J.M. Abrisquetab,*, A. Hernansa´ezb, F. Morenoc
aDepartamentodeIngenier´ıaAplicada,UniversidaddeMurcia,AlfonsoXIII4230204Cartagena,Spain
bDepartamentodeRiegoySalinidad,CentrodeEdafolog´ıayBiolog´ıaAplicadadelSegura(CSIC),
P.O.Box4195,30080Murcia,Spain
cDepartamentodeSostenibilidaddelSistemaSuelo-Planta-Atmo´sfera,InstitutodeRecursosNaturalesy
Agrobiolog´ıadeSevilla(CSIC).P.O.Box1052,41080Sevilla,Spain
Accepted9March1999
Abstract
The water balance of young almond trees (Amygdalus communis L. cv. Atocha grafted onto
‘Pestan˜eta’ almond rootstock), drip-irrigated with low quality water, was determined during two
and a half years. Four irrigation treatments based on the reduction coefficients of Class A pan
evaporationwereusedtodeterminethewateruptakeofthisspecies,althoughthewaterbalancewas
onlydeterminedinthehighestandlowestirrigationtreatments.Thewaterbalanceparametersfor
these treatments are shown and discussed in detail. The ET calculated for the two treatments
c
differedmarkedlyduringsummer,reachingvaluesof4.3and3.3mmperday(forthehighestand
the lowest irrigation treatments, respectively), during the last year of the experiment, coinciding
withthemonthsofhighestevaporation.Whenvariousvegetativeandproductiveparameterswere
studied in relation with the irrigation treatments, no clear conclusions were reached. This was
mainlyduetotheexcessivesalinityoftheirrigation water used(4.26dSm(cid:255)1),whichlimited the
trees’vegetativegrowth and production rate, which in our casewas 1583kgha(cid:255)1 compared with
the 2955kgha(cid:255)1 obtained when less saline irrigation water (0.8dSm(cid:255)1) and similar irrigation
watervolumes(408and368mm,respectively)wereusedforthesamecultivar(Atocha).#2000
Elsevier Science B.V.Allrights reserved.
Keywords: Waterbalance;Almondtree;Dripirrigation;Salinewater
*Correspondingauthor.Tel.:[phone];fax:[phone].
E-mailaddress:[email protected]
0378-3774/00/$–seefrontmatter#2000ElsevierScienceB.V.Allrightsreserved.
PII:S0378-3774(99)00049-9
76 J.A.Francoetal./AgriculturalWaterManagement43(2000)75–98
1. Introduction
Spain, Italy, and USA have traditionally been world leaders in almond production.
However, Italian almond production has decreased since the seventies (Barbera and
Monastra, 1989), whereas the Spanish and particularly the North-American crops have
increased.
InSpainalmondismainlycultivatedintheMediterraneanareainbothdry(92%)and
irrigatedplantations (8%).This highpercentageofdrycultivation isduebasicallytothe
gooddrought-resistanceofthespecies,whichcanstillbeproductiveinhighwaterdeficit
situations. Indeed its irrigation has been considered not only useless but counter-
productive, as was confirmed by the use in clay soils of almond scion cultivar, which is
very sensitive to root asphyxia and so little tolerant of soil flooding (Barbera and
Monastra, 1989).
Nevertheless, almond is a species that responds well to irrigation and behaves well
underdifferentwaterregimes(Fereres,1978).Wateringhasbeenshowntobeoneofthe
most important production factors of this species, as confirmed by numerous studies
reporting thepositiveeffectofirrigationonbothproductionandvegetativedevelopment
(Micke et al., 1972; Veihmeyer, 1975; Fereres et al., 1981a, b, 1982; Shirra et al., 1988;
Fereres and Goldhamer, 1990). Some of these studies have been carried out with
autochthonousMurcianspecies(Leo´netal.,1985;Ruiz-Sa´nchezetal.,1988;Torrecillas
et al., 1989), and many authors have attempted to define parameters of irrigation
efficiency,whichisparticularlyimportantwhenusingacommoditywhichisbothlimited
in supply and expensive.
GiventheproblemsoriginatedbywaterdeficitinSESpainandthelowqualityofthis
resource,itisessential tostudyhowbesttousewhatisavailable, sothatthedosage can
be adjusted to a minimum, with no drop in the quality or quantity of the yield.
Theobjectofthisworkwastostudythewaterbalanceofdrip-irrigatedyoungalmond
treesprovidedwithdifferentlevelsofirrigationwatertoachievetheaboveaims.Wealso
present a model for estimating water balance parameters, taking into account both the
areas which are affected and those not affected by the irrigation water. This model
includes a weighted method to express changes in water storage and drainage in the
mentioned areas.
2. Materials and methods
2.1. Experimental site
Theexperimentwascarriedoutatafarmlocated22kmSEofthecityofMurciaonthe
Mediterranean coast of Spain (378470N; 08370W; altitude 130m). The soil is a Xeric
torriorthent with silt loam texture, showing no variation at any of the depths studied
(1.5m). The main characteristics of the soil are shown in Table 1.
Texture characterisation was carried out from 40 profiles of soil forming a regular
network.Soilsamplesweretakenwithanaugerat0.25mintervalsandwithamaximum
depth of 1.5m. The granulometric composition was determined for each sample
J.A.Francoetal./AgriculturalWaterManagement43(2000)75–98 77
Table1
Maincharacteristicsofthesoil
FractionD(<0.002mm)(%) 16.3
Fractionc(0.05–0.002mm)(%) 59.1
FractionB(0.2–0.05mm)(%) 20.0
FractionA(2–0.2mm)(%) 4.5
Texture Silt-loam
EC(1:5)(dSm(cid:255)1) 1.2
CEC(cmolkg(cid:255)1) 7.93
Organicmatter(%) 0.92
Totalcalciumcarbonate(%) 44.83
Activecalciumcarbonate(%) 15.0
(fractions: A, 2–0.2mm; B, 0.2–0.05mm; C, 0.05–0.002mm and D<0.002mm), as
were the d parameter, the mean granulometrics and the mean d for each profile, and
50 50
the mean values for each depth.
Noverticalvariabilityinthetexturecouldbeobserved.Thehorizontalvariabilitywas
expressed by taking into account the parameter d (which correctly characterises the
50
granulometricfractions).Thisparameterdidnotpresentanyanisotropy,butitdidshowa
structure with spatial variation that fitted an exponential variogram model, with a sill of
1.09 (with no nugget effect) and a range of 12m. On the map of d isovalues that was
50
obtainedbykriging,itwaspossibletodetailthezonewherethemeasuringpointsshould
be located (Franco, 1993).
A hydrodynamic characterisation of the soil was made to define the function K((cid:18))
of the bottom of the profile (and to enable an estimation of drainage) according to
Hillel et al. (1972). The K((cid:18)) relationship is given by
K (cid:136)2(cid:2)10(cid:255)8e0:501(cid:18) (cid:133)R2 (cid:136)0:916(cid:3)(cid:3)(cid:3)(cid:134) (1)
where K is the hydraulic conductivity (mmh(cid:255)1) and (cid:18) the volumetric water content
(cm3cm(cid:255)3).
TheclimateoftheareaistypicallyMediterranean,withmildwintersandlowrainfall,
and hot dry summers.
2.2. Crop management, irrigation treatments and experimental design.
Theplantmaterialstudiedwasthealmondtree(AmygdaluscommunisL.cvs.Atocha,
RamilleteandCartageneragraftedonto"Pestan˜etaalmondrootstock).Thesecultivarsare
autochthonoustoSESpainandarehighlyconsideredbecauseoftheirgoodadaptationto
differentcultivationconditionsandtheirexcellentproduction.Theyflowerearlyandtheir
aptitude forcombiningwithothercultivarsensuresgoodcrosspollination (Godinietal.,
1991).
The trees were planted in December 1987, spaced 6m(cid:2)4m apart. The plots were
dripirrigatedbylinesofemittersusingthreeautocompensatingemitterspertreeset1m
fromeachother.Eachhada41h(cid:255)1flowrate(Fig. 1).Duetothelowqualitywaterused
78 J.A.Francoetal./AgriculturalWaterManagement43(2000)75–98
Fig.1. Distributionofneutronprobeaccesstubesintheplant-spacing.
forirrigation,problemsoccasionallyarosewithclogging.Thiswassolvedbyperiodically
cleaning emitters or replacing them.
Yearly,inMarchorApril,acultivator(tillagedepth:10cm)wasrunbetweentreerows
to remove weeds and break the soil surface to increase its infiltrability.
Allthetreesinthisexperimentreceivedthesamefertiliserdosage,takingintoaccount
datafromtheliteratureonalmondtreecultivationunderlocalisedirrigationintheRegion
deMurcia(Torrecillasetal.,1989).Thedatawereadjustedwhennecessaryinaccordance
with the results of the periodical leaf analyses carried out. The fertilising doses were
147kgha(cid:255)1 N, 34kgha(cid:255)1 P (P O ), and 44.6kgha(cid:255)1 K (K O)
2 5 2
From May 1989, the trees were subjected to four drip irrigation treatments (T-3, T-2,
T-1 and T-0) with three replications per treatment distributed in randon blocks within
the same variety. The irrigation treatments were programmed using four reduction
percentagesoftheU.S. Weather BureauClass Apanevaporation.Thereduction applied
were 0, 20, 30 and 40% for T-3, T-2, T-1 and T-0 treatments, respectively.
ThewaterappliedinT-3wasconsideredsufficienttosatisfyfullytheneedsofthecrop
(100%ET ),andtoallowgoodrootingandtreegrowth,bearinginmindthesusceptibility
c
of almond trees to excess moisture, particularly at the plant neck (Hoare et al., 1974;
Leo´n et al., 1985).
The total amount of irrigation water (TIW) applied in treatment T-3 was calculated
from:
K K K
TIW(cid:136) p c 1E (2)
E E pan
a u
whereK isthepancoefficient(0.65;DoorenbosandPruitt,1977).K thecropcoefficient
p c
(0.75;DoorenbosandPruitt,1977).K theshadecoefficient(0.176;FreemanandGarzoli
1
(cited by Vermeiren and Jobling, 1986), taking into account that the estimated mean
shaded surface provided by the tree canopies in 1989 was 17.4% of the total surface of
J.A.Francoetal./AgriculturalWaterManagement43(2000)75–98 79
theorchard),E theefficiencyoftheirrigationmethod(0.95;accordingtoGuidelinesfor
a
Pressure Irrigation, 1983), E the coefficient of uniformity of emitters (0.9).
u
Applying the reduction percentages mentioned above to Eq. (2) gives the following
total amounts of irrigation water in each treatment:
TIW(cid:133)T-3(cid:134) (cid:136)0:1Epan (cid:133)for treatment T-3(cid:134) (3)
TIW(cid:133)T-2(cid:134) (cid:136)0:08Epan (cid:133)for treatment T-2(cid:134) (4)
TIW (cid:136)0:07E (cid:133)for treatment T-1(cid:134) (5)
(cid:133)T(cid:255)1(cid:134) pan
TIW(cid:133)T-0(cid:134) (cid:136)0:06Epan (cid:133)for treatment T-0(cid:134) (6)
The coefficient K in Eqs. (3)–(6) was increased annually in accordance with the
l
increase in shaded area provided by the tree canopy.
The amount of irrigation water to be applied during a particular week was calculated
fromthedailyevaporationvaluesmeasuredintheClassApanduringtheprecedingweek
(Ferereset al.,1982; Leo´n etal., 1985; Torrecillas etal., 1989). The coefficientsused in
the irrigation treatment schedule and the annual amount of water applied are shown in
Table 2, while the characteristics of the irrigation water are shown in Table 3. Its high
electricalconductivity(anaverageof4.18dSm(cid:255)1duringtheexperimentalperiod)andits
high chloride, sulphate and sodium content should be noted. It is clear that using such
watermaygiverisetosalinityproblemsintheplantandsalinizationofthesoilbecauseof
the high sulphate content, and specific toxicity problems of medium intensityas a result
of the high sodium and chloride concentrations. On the farm in which the experiment
tookplace, irrigationwascarriedoutwiththislowqualitywaterbecauseitwastheonly
water available, this being the case in many others farms in the Province of Murcia.
Rainfall must have helped in leaching the salt from the root zone but this point was not
evaluated in detail within the framework of this study.
For determination of the water balance, six trees of cv. Atocha were chosen: three
under treatment T-0 (T0A, T0B andT0C) andthree under treatmentT-3(T3A,T3B and
T3C).
Two criteria were taken into account for this choice:
1. The homogeneity and representativity of the trees.
Table2
CoefficientsusingClassApanevaporationandirrigation(mm,inbrackets),ofthefourirrigationtreatments.
Thedifferentialirrigationexperimentstartedon20May1989
Year Irrigationtreatment
T-0 T-1 T-2 T-3
1989a 0.06(44) 0.07(89) 0.08(105) 0.1(120)
1990 0.06(44) 0.07(103) 0.08(106) 0.1(110)
1991b 0.078(111) 0.128(212) 0.178(273) 0.228(329)
1992 0.101(147) 0.171(267) 0.242(368) 0.314(412)
1993c 0.131(93) 0.245(185) 0.370(244) 0.487(413)
aIrrigationfromMay20.
bWaterbalancestarts.
cIrrigationtoJuly31.
80 J.A.Francoetal./AgriculturalWaterManagement43(2000)75–98
Table3
Maincharacteristicsoftheirrigationwater
Year
1989 1990 1991 1992 1993 Mean
pH 7.70 7.81 7.71 7.90 7.86 7.79
EC 258C(dSm(cid:255)1) 4.63 3.91 3.96 3.90 4.54 4.20
w
Totaldissolvedsolids(gl(cid:255)1) 4.19 4.40 3.45 4.36 4.08 4.09
Chloride(gl(cid:255)1) 0.47 0.44 0.42 0.47 0.46 0.45
Sulphate(gl(cid:255)1) 2.20 2.15 2.00 2.38 2.20 2.18
Bicarbonate(gl(cid:255)1) 0.27 0.21 0.10 0.28 0.27 0.22
Calcium(gl(cid:255)1) 0.56 0.47 0.35 0.54 0.48 0.48
Magnesium(gl(cid:255)1) 0.30 0.28 0.26 0.30 0.30 0.28
Sodium(gl(cid:255)1) 0.37 0.35 0.31 0.36 0.35 0.34
Potassium(gl(cid:255)1) 0.02 0.03 0.02 0.03 0.02 0.02
SAR(adjusted) 5.41 5.22 4.51 5.33 5.19 5.14
2. The representativity of the soil texture characteristics with the trees located in zones
where the d approached its mean value (6.45(cid:6)1.06mm).
50
Thirty-twoneutronprobeaccesstubeswereinstalled:fiveoneachchosentree,andtwo
more (CS and CS ) in the centre of the zone not affected by irrigation (see Fig. 1).
1 2
Each tube was identified according to an alphanumeric sequence that indicated: the
treatment (T0 or T3), the replications (A, B or C) and the position with respect to the
trunk (1 to 5).
To determine the hydraulic head of the soil, trees A of each treatment were equipped
withmercurytensiometers,located40cmfromtubes1and2ofeachtree,andatadepth
of 20, 52, 85, 117 and 150cm.
2.3. Measurements
The soil water content was measured every 10 days using a neutron probe (Troxler
mod. 4300), from 10 January, 1991 to 30 March, 1993. The moisture content was
monitored at 10cm intervals down to 1.5m starting at 20cm depth. The soil moisture
content of the top 10cm of the profile was determined gravimetrically. The program
‘AideauTraitementdeMesuresHydriquesduSol’(AIDHYS),specificallydevelopedby
LatyandVachaud(1987),wasusedtotreatthehighnumberofdataobtained(morethan
35000).
The measurements of the hydraulic head of the soil were carried out every two days
with mercury tensiometers from 12 April 1991 to 30 March 1993.
Both air temperature and air moisture were continuously recorded. Daily measure-
ments of the evaporation from the Class A pan and rainfall were also made in a field
meteorological station located on the farm.
Fleming (1964) showed that the ET calculated by Penman’s equation can be
o
reasonably well estimated from evaporation data obtained in a Class A pan.
J.A.Francoetal./AgriculturalWaterManagement43(2000)75–98 81
In this way, several studies carried out in the Province of Murcia (Sa´nchez-Toribio,
1992; Castell et al., 1987) clearly showed that the ET estimated from measurements of
o
evaporation in a Class A pan is satisfactory for the climatic condictions of this region.
The relationship between the evaporation (E ) calculated using Penman’s equation and
o
the evaporation measured in the pan (E ) for the region is given by
pan
E (cid:136)0:86E (cid:255)0:53 (7)
o pan
with a correlation coefficient r(cid:136)0.9769***
The ET was then calculated multiplying the E obtained from Eq. (7) by an empiric
o o
coefficient (0.8 in summer, 0.7 in spring and autumn, and 0.6 in winter) according with
Sa´nchez-Toribio (1992).
The irrigation water supplied in each treatment was measured by volumetric counters
installed in the water supply.
Yearly,between1988and1992andcoincidingwiththeendoftheisvegetativecycle,
the following measurements were taken before pruning for the three cultivars studied
(Atocha, Ramillete and Cartagenera): total height of the tree, shaded area, and trunk
diameter 30 centimetres above soil surface.
Although the trees were planted in December 1987, they did not have their first
significant crop until 1990, from which data production data for the three cultivars
studied were recorded up to and including 1993.
Rather than replicate the measurement sites in different subplots of the T-0 and T-3
treatments, detailed measurements were taken in the trees equipped with instruments
within one plot, to determine the water balance components accurately.
The spatial representativity of the measurement sites was considered in terms of a
geostatistical analysis of soil texture and of space-time series of soil water content
measurements (Franco, 1993).
The time fluctuation of the mean deviation in the soil water content (the relative
deviation between the means) was determined following the method developed by
Vachaud et al. (1985a), and, the correlation between the total soil water content in one
tube and the mean content of the other two tubes located in the same relative position
and on the same date, was estimated for each treatment. In all cases, linear regressions
were obtained. As regards the time fluctuation of the soil water content measurements,
it was observed that the total water content in all the tubes of the T-3 irrigation treat-
menthardlydifferedfromthemeancontent,withamaximumvalueof9%intubeT2B5,
while the rest exhibited values lower than 5%. In treatment T-0, it is of note that all the
tubes showing soil water content values abovethe meanbelongedto the same repetition
(tree B).
2.4. Mass conservation law
The three-dimensional aspect of the water flux in the soil-plant-atmosphere system
meansthatitisessentialtodeterminetheareasandvolumesofsoiloverwhichwaterruns
orisstored.Itiscustomarytorelatethewaterbalancetotheplantationspacing(Sharples
etal.,1985;Vachaudetal.,1985b;Morenoetal.,1988),downtoadepthslightlybelow
that reached by the roots (1.5m in our case).
82 J.A.Francoetal./AgriculturalWaterManagement43(2000)75–98
Fig. 2. Mean hydraulic head profiles (*, TO-5; *, TO-2; &, T3-5; &, T3-2; ^, gravitatory hydraulic
gradient).Thehorizontallineshavebeenomittedforgreaterclarity.
The water balance in the soil is estimated by means of the equation of mass
conservation:
ET (cid:136)P(cid:135)I(cid:255)(cid:1)S(cid:255)D(cid:255)R (8)
c
whereET istheevapotranspirationoftheculture;P,rain;I,irrigation;(cid:1)S,watercontent
c
variation between two dates; D, drainage, and R, the runoff. All terms are in mm.
2.4.1. Drainage estimation
Drainagebelowadepthof1.5m(chosenbecauseno,orhardlyanyrootswerefoundat
this depth, as shown by Abrisqueta et al. (1994), Franco et al. (1995) and Franco and
Abrisqueta, 1997)) was estimated using the K((cid:18)) relationship obtained in Section 2.1.
(Eq. (1))basedonthehypothesisofagravitatoryhydraulicgradientatthisdepth.Sucha
hypothesiswasverifiedbytensiometricmeasurementsinfouroftheaccesstubesforthe
neutron probe (Fig. 2).
2.4.2. Runoff estimation
Runoff,whichwasconsideredonlyinperiodsofintenserain,wasmeasuredindirectly
byassumingthatinsuchconditionscropevapotranspiration(ET )equalsPenman’sET ,
c o
asdescribedbyVachaudetal.(1985b)andMorenoetal.(1988).Thustherunoff(R)for
the periods in which heavy rain fell occurred, was estimated from:
R(cid:136)P(cid:135)I(cid:255)(cid:1)S(cid:255)D(cid:255)ET (9)
o
2.4.3. Soil water content calculation
The soil water content down to a depth of 1.5m was calculated by totalling thewater
content of individual layers of 100mm thickness. The water content of these layers is
expressed as the product of the thickness (in mm) and its volumetric water content
(cm3cm(cid:255)3). The variation in water content is represented by the difference in water
content between two consecutive measurement dates as measured by neutron probe.
J.A.Francoetal./AgriculturalWaterManagement43(2000)75–98 83
2.4.4. Irrigation water measurement
The difference between the readings of the volumetric counters on two consecutive
dates of neutron probe measurement constituted the volume of irrigation water supplied
to the trees in a given irrigation treatment.
3. Results and discussion
3.1. Effect of irrigation on soil water content
Changes in the soil water content during the experimental period are shown in Fig. 3,
whichillustratestheaveragevariationofthewatercontentdowntois1.5mdepthinthe
tubesinposition2and5oftreatmentsT-0andT-3.Ascanbeseen,thesoilwatercontent
of the profile in the zone affected by irrigation changed very little in both treatments
during theexperimental period. However,the soilofT-3,which receivedmostirrigation
water, always stored more water, 413.6(cid:6)26.3mm (average) than in the least-irrigated
treatment (T-0), 346.7(cid:6)27.7mm (average). Although these values were statistically
different, the difference between them (66.9mm) suggests that the amount of water
supplied in T-0 was too high.
Fig.3. Meanwatercontentchangesdownto1.5mdepthinTO-2,T3-2,TO-5andT3-5tubes.Verticallines
indicatethestandarddeviation.
84 J.A.Francoetal./AgriculturalWaterManagement43(2000)75–98
Fig. 3 also shows that the water content observed in tubes 2 of both irrigation
treatmentsshowedmuchlowervariationsthentubes5.Whereasthesoilwatercontentas
shownbyT0-2andT3-2wasalmostconstant,aclearseasonalpatterncouldbeobserved
in T0-5 and T3-5, with maximum values coinciding with the most-rainy periods, and
minimum values occurring during June. From the end of July, these values increased
progressively due to the effect of the area wetted by irrigation, an increase which was
more evident in treatment T-3. The expressions T0-2, T0-5, T3-2, and T3-5 represented
theaveragewatercontentoftherepetitionsA,BandC,fortheT-0andT-3treatmentsin
the tubes of position 2 and 5, respectively.
Thedistributionindepthofthemoistureduring1992wasingeneralscarcelyaffected
byseasonalchanges(Fig. 4).Inthisfigure,itcanbeseenthatthewaterprofilesoftubes
2(especiallyintheT-3treatment)variedlessthanthoseoftubes5,inwhichthemoisture
differencesbetweensummerandwinterweregreater.Thesedifferenceswereparticularly
evident near the surface. A similar situation occurred in 1991.
Theeffectofthedifferentirrigationtreatmentsonwaterdistributioninthesoilprofile
during summer and winter months was evident from thewater profiles corresponding to
Fig. 4. Mean water profiles of the TO-2, TO-5, T3-2 and T3-5 tubes, on six representatives dates of the
experimentalperiod (*,7 February1992; !, 28April 1992; ~,8 June 1992;*, 20 August1992;r, 29
October1992;(cid:1),21December1992).Thehorizontallineshavebeenomittedforclarity.