REGULAR ARTICLE

Plant-soil interactions in a fertigated ‘Manzanilla de Sevilla’olive orchard

A. Morales-Sillero & J. E. Fernández & J. Ordovás &

M. P. Suárez & J. A. Pérez & J. Liñán & E. P. López &

I. Girón & A. Troncoso

Received: 11 July 2008 /Accepted: 7 December 2008 / Published online: 4 January 2009# Springer Science + Business Media B.V. 2008

Abstract Main processes governing the plant-soilinteractions in adult olive (Olea europaea L.) treesunder fertigation were studied to better understand theresponse of the trees to this agricultural practicewidely used in new olive orchards. Our final objectivewas to obtain soundly based scientific evidences for arational choice of the fertilizer dose. Measurementswere made in a ‘Manzanilla de Sevilla’ olive orchardin which 200 g N, 400 g N and 600 g N per tree andirrigation period (T200, T400 and T600, respectively)of a 4N-1P-3K fertilizer were applied by fertigationfor 5 years (1999–2003); a control treatment (unfer-tilized) was also established. Four years after the startof the experiment mean values of soil P and K con-centrations were greater in the fertigation treatments

than in the control. For K, concentrations increasedwith fertilizer dose. The profile of NO3-N, P and Kconcentrations within the irrigation wetted zone wasstudied in 2003; in the top soil layer, the concen-trations of the three elements increased with fertilizerdose, generally showing linear responses to thedifferent doses; in deeper soil layers, concentrationsalso increased with fertigation, but to a lesser extent;the concentrations of NO3-N, P and K recorded at0.8–0.9 m depth in the soil of T600, together withobservations of root distribution, were enough tosuggest leaching losses and possible groundwatercontamination. As a consequence of the higher soilnutrient availability, leaf N, P and K increasedgenerally with dose. Leaf N deficiencies and low,but not deficient, leaf K levels were found in controltrees in 2002 and 2003, as well as in T200 trees in2003. Differences between treatments in shoot length,trunk circumference and canopy volume were notsignificant, for any studied year. Nevertheless, be-tween February 1999 and November 2003 there was asignificant increase in canopy volume with fertilizerdose. In 2003, fruit yield increased with fertilizerdose, as a consequence of an increase both in fruitnumber and weight. Cumulative yield for the exper-imental period also increased with fertilizer dose.These results are further evidence to confirm previousresearch made with the same experimental set-up:T400 for oil quality and T600 for table olive quality

Plant Soil (2009) 319:147–162DOI 10.1007/s11104-008-9857-0

Responsible Editor: Elizabeth (Liz) A. Stockdale.

A. Morales-Sillero (*) : J. Ordovás :M. P. Suárez :J. A. Pérez : E. P. LópezDepartamento de Ciencias Agroforestales,Universidad de Sevilla,Ctra. Utrera km 1,41013 Sevilla, Spaine-mail: amorales@us.es

J. E. Fernández : J. Liñán : I. Girón :A. TroncosoInstituto de Recursos Naturales y Agrobiología (IRNAS-CSIC),Apartado 1052,41080 Sevilla, Spain

seem to be the most appropriate treatments, althoughthere is a risk for leaching losses and the possibility ofgroundwater contamination with T600.

Keywords Olea europaea . Root distribution .

Nitrogen . Phosphorus . Potassium . Fruit yield

Introduction

The olive tree has been widely cropped in theMediterranean Basin for centuries and its productionis now extending to other areas, such as SouthAmerica, South Africa and Australia, which arebecoming significant producers. Many of the neworchards have localized irrigation systems whichallow for high-frequency fertigation (Connor 2005).The injection of fertilizers into the irrigation waterstarted at the beginning of the 1930s in California, butit was not until the 1960s that this practice was widelyadopted (Ginés 2004). It is assumed that benefits offertigation on crop performance are derived both fromadjusting the water and fertilizer supplies to the cropneeds and applying the fertilizers in the soil zoneswetted by irrigation, where most active roots arelocated. Fertilizers can be applied in each irrigationevent which improves nutrient uptake and decreasesleaching losses. In addition, high water contentswithin the wetted zones increase the growing periodof the roots and favour nutrient dissolution andassimilation (Fernández et al. 1991). Nevertheless,some disadvantages have been reported, such as soilnutrient depletion, especially within the root zone,and soil acidification (Peryea and Burrows 1999;Mmolawa and Or 2000; Neilsen et al. 2004).

Most of the existing information on traditionalfertilization is not directly extrapolable to fertigatedorchards, since it is known that fertigation allows for areduction of the fertilizer dose without affecting cropyield (Kipp 1992; Alva and Paramasivan 1998). Inaddition, fertigation may favour NO3-N leaching,which requires a careful calculation of the fertilizerdose to minimize the risk of groundwater contamina-tion. In non-irrigated traditionally managed oliveorchards, Ferreira et al. (1986) recommended N dosesbetween 0.6 kg and 1.0 kg per tree and year, dependingon the average yield per tree. For irrigated orchards,Hidalgo and Pastor (2005) recommended N dosesbetween 0.75 kg and 1 kg per tree and year, or greater

when deficiency occurs. According to Fernández-Escobar (2004), N doses between 0.5 kg and 1.0 kghave been enough to correct N deficiency in severalolive orchards. In a fertigated orchard planted with20 year-old ‘Manzanilla de Sevilla’ trees, Martín-Aranda and Troncoso (1986) observed no increase inyield for N doses greater than 580 g N per tree. Baenaet al. (2003) studied the dynamics of the NO3-Nconcentrations in the wetted soil zones of fertigated‘Picual’ olive trees, 8 year-old. They found positivecorrelations, at several soil depths, between the appliedN doses and the concentrations of NO3-N in the soilsolution. With the highest N dose of 496 g per tree theyfound a risk for leaching loses.

The previously cited research does not define afertilizer dose for achieving the best crop performancewith the minimum risk for soil water contamination.This lack of knowledge may be the reason that incommercial orchards the applied N doses are oftengreater than 1 kg N per tree and year (Fernández-Escobar et al. 1994). Our hypothesis is that thosesupplies are too high for olive tree requirements, andin many soils these rates may have an unacceptableimpact on groundwater contamination. This justified aset of experiments in which we started with thepurpose of studying the effects of increasing doses ofa 4N-1P-3K fertilizer applied by fertigation in a‘Manzanilla de Sevilla’ olive orchard. In a firstapproach, Morales-Sillero et al. (2007) found that oilyield increased significantly with the amount offertilizer; oil quality, however, was negatively affect-ed. The polyphenol content, K225 (bitterness) andoxidative stability were lower in the oil from treesreceiving higher fertilizer doses (T400 and T600).They also found decreased monounsaturated fattyacids contents, in particular oleic acid, and increasedpolyunsaturated fatty acids contents, in particularlinoleic acid, with increasing amounts of appliedfertilizers. Later, Morales-Sillero et al. (2008) reportedthat, although fruit weight, volume, and the pulp-topit ratio increased with fertilizer dose, both fruittexture and reducing sugars concentration decreasedin T400 and T600.

This work complements those two previous papersby focusing on the complementary aspects of soilnutrient dynamics, root distribution, plant nutrientstatus and long-term crop performance, to collectfurther evidence on the most advisable fertilizationdose for olive.

148 Plant Soil (2009) 319:147–162

Materials and methods

Orchard characteristics

A 5-year experiment (1999–2003) was established ina ‘Manzanilla de Sevilla’ (henceforth referred to as‘Manzanilla’) olive orchard located in Alcalá deGuadaíra, near Seville, southwest Spain (37° 18′ N,5° 54′ W). The trees were planted in 1989 at 7 m×7 m (204 trees ha−1) and have a spherical shape and asingle trunk with two main branches. Climate in thearea is typically Mediterranean, with mild rainywinters and hot, dry summers. The average annualrainfall and potential evapotranspiration are 569 mmand 1180 mm, respectively (period 1984–2003). Therainy season occurs from October to May.

The soil is a Calcic Rhodoxeralf of about 1 meffective depth, with a calcareous horizon at 0.65 m,approximately. The texture is sandy-clay-loam in thefirst 0.35 m and sandy-loam or loam below that depth.A fine and non continuous calcareous crust is generallyfound at about 0.4 m depth. Before the start of theexperiment the concentrations of soil P, extracted with0.1 N NaHCO3 at pH 8.5 (Murphy and Riley 1962),and soil K, extracted with 1 N CH3COONH4 (soil:water 1:10) at pH 7 (Bower et al. 1952), were verylow (4 mg kg−1 and 9 mg kg−1, respectively),according to Pastor et al. (1996). Other major soilchemical properties are indicated in Table 1. Labora-tory measurements indicated that the volumetric soilwater content (θ) at field capacity (−0.01 MPa) was0.24 m3 m−3 (±0.03) for the 0.10–0.14 m soil layerand 0.25 m3 m−3 (±0.03) for the 0.60–0.64 m soillayer. For those depths, θ values at −1.5 MPa, were0.09 m3 m−3 (±0.01) and 0.07 m3 m−3 (±0.03),respectively. The soil bulk density (ρb), measured inthe field, was 1.55 Mg m−3 (±0.03) for the 0.10–

0.14 m soil layer and 1.47 Mg m−3 (±0.04) for 0.60–0.64 m soil layer.

Each dry season, from 1999 to 2003, all the treeswere irrigated daily to replace the crop evapotranspi-ration (ETc, mm), with a lateral per tree row with four8 L h−1 compensating drippers per tree, 1 m apart,two on each side of the trunk. The crop coefficientwas used to calculate ETc (ETc = Kc Kr ETo). The Kc

values were those estimated by Fernández et al.(2006) in an orchard of similar characteristics (0.76in May, 0.70 in June, 0.63 in July and August, 0.72 inSeptember and 0.77 in October). The ground covercoefficient (Kr) was calculated according to Fereres etal. (1981). Potential evapotranspiration (ETo, mm)was determined using the FAO56 Penman-Monteithequation (Allen et al. 1998) and meteorological datafrom a weather station next to the orchard (CampbellScientific Ltd, Leicestershire, UK). Table 2 shows theETc values and irrigation amounts per treatment foreach irrigation period. A neutron probe (Troxler 3300,Research Triangle Park, NC, USA) measured θ every2 weeks during the irrigation seasons; three trees pertreatment were instrumented with one access tube at1.3 m from the trunk, in the direction of the irrigationpipe. The θ measurements were made every 0.1 m,from 0.2 m down to the maximum depth of therootzone (0.9–1.25 m). At the same sampling times, θvalues in the top 0.0–0.2 m soil layer were calculatedfrom gravimetric measurements and the average ρbvalues measured in the field. From the recorded soilwater profiles we calculated the relative extractablewater (REW, mm) as defined by Granier (1987).

Water for irrigation was sampled several timesduring the experimental period. Average values of pHand electrical conductivity were 7.17 (±0.12) and0.838 dS m−1 (±0.04). Average NO3-N concentrationwas 15.3 mg L−1 (±1.34), which resulted in an

Table 1 Selected chemical properties of soil profile at the experimental site

Depth (m) pHa CECb (cmolc kg−1) ECc (dS m−1) CaCO3

d (%) OMe (%) Nf (%) C/N

0–0.15 8.09 17.00 0.48 35.27 2.50 0.18 11.100.15–0.35 8.33 19.13 0.28 29.27 2.10 0.11 10.700.35–0.55 8.12 6.91 0.73 64.90 0.69 0.04 9.09>0.55 8.09 6.39 0.82 71.85 0.29 0.02 6.87

a, c Measured in 2:5 and 1:5 soil:water ratio, respectively, b Determined according to Sumner and Miller (1996), d Determined bymanometric method (Nelson 1982), e Calculated from Corg=0.58×OM; the organic carbon (Corg) was measured according to Walkleyand Black (1934), f Determined by the Kjeldahl method (Bremner and Mulvaney 1982)

Plant Soil (2009) 319:147–162 149

additional N supply of 60 g N per tree and irrigationperiod. Average Mg and K concentrations were4.25 mg L−1 (±0.55) and 0.44 mg L−1 (±0.25),respectively. No P was detected in the irrigationwater.

The trees were pruned in February 2000 andJanuary 2002. The orchard was clean cultivated bytilling and herbicides applied in the row of the trees.An early autumn application of copper oxychloridewas made each year to control leaf spot (Spilocaeaoleagina (Cast.) Hughes). In spring 2003, Benomylwas also applied because of a high incidence of thisdisease. Adult olive fly (Bactrocera oleae Gmel.) wasmonitored with traps containing diammonium phos-phate. An application of Dimethoate was necessary inJuly 2000 to control the fly.

Fertigation treatments

We had a control (unfertilized) and three fertigationtreatments. The increase in both the canopy volumeand yield of the trees caused us to increase thefertilization doses starting in 2002 (Table 3). Thefertigation treatments were labelled with the dosesapplied in the last two experimental years: T200,T400 and T600, in which 200 g N, 400 g N and 600 gN of a liquid 4N-1P-3K fertilizer was injected dailyinto the irrigation system, toward the end of eachirrigation event, allowing for 15 min rinse of the

laterals. N was derived from urea, NH4 and NO3

(2:1:1 mixture), P from H3PO4 and K from KCl. Weused a randomised complete block design with sixblocks per treatment and four trees each (24 trees pertreatment). Each plot was surrounded by 14 guardtrees.

The amounts of nutrients were based on a previousstudy (Martin-Aranda and Troncoso 1986), while thenutrient proportions (4N-1P-3K) correspond to thosecommonly used for ‘Manzanilla’ olive orchards in theregion. Other macro and microelements were notconsidered in the treatments because foliar analysesprior to the experiments showed good levels in theexperimental trees (data not shown).

Soil hydraulic conductivity

In June 2003 values of soil hydraulic conductivityclose to saturation (Ksat, mm s−1) were determined at0.15 m, 0.40 m and 0.65 m depth, at three locationswithin the orchard, according to the simple suctionmethod described by Ankeney et al. (1991), using a0.125 m radius disc infiltrometer.

Root distribution and wetted zone dimensions

We used the trench profile method (Van Noordwijk etal. 2000) to study root distribution in a soil sectionperpendicular to the drip line in three representative

Table 2 Irrigation period, crop evapotranspiration (ETc) and irrigation amounts applied for each year and treatment

Year Irrigation period ETc (mm) Irrigation amount (mm)

Control T200 T400 T600

1999 12/04–28/10 233 246 244 246 2412000 12/05–31/10 217 221 223 216 2232001 2/04–21/09 253 254 260 228 2542002 22/04–10/10 248 247 253 232 2552003 16/05–22/09 256 263 266 262 269

See Table 3 for details on the treatments

Treatment 1999–2001 2002–2003

N P K N P K

Control 0 0 0 0 0 0T200 100 25 75 200 50 150T400 200 50 150 400 100 300T600 400 100 300 600 150 450

Table 3 Amounts of N, Pand K (g tree−1) applied foreach year and treatment,1999–2003

150 Plant Soil (2009) 319:147–162

T400 treatment trees, in June 2003. The trenchopened from the trunk of each tree was 3 m longand 1.5 m wide. The depth was that of the rootzone,since we excavated to the lower limit of the effectivesoil depth (ca 1 m). Both the shape of the wettedzones and the root distribution were mapped via a0.1 m×0.1 m grid. Change in colour clearly indicatedthe limits of the wetted zones. We counted the numberof roots according to their diameter (∅):<1 mm, 1–5 mm, 5–10 mm and >10 mm.

Soil analysis

Annually from 1999 to 2003, soil samples wereobtained immediately before each irrigation period.Three soil layers (0–0.3 m, 0.3–0.6 m and 0.6–0.9 m)were sampled in a location at about 0.25 m from theemitter and 0.75 m from the trunk of one tree per plot, inthree plots per treatment. Samples were dried at 50°C,grounded and passed through a 2 mm sieve. Soil pHwasmeasured in water (soil:water 1:2.5) using a pH-metreCRISON micro pH 2002. Calcium carbonate contentwas determined by a manometric method (Nelson1982). Organic matter (OM, %) was measured accord-ing to Walkley and Black (1934) and calculated asCorg=0.58 OM. Nitrogen was determined by theKjeldahl method (Bremner and Mulvaney 1982). SoilP and K were determined as described previously. SoilCa and Mg were extracted with 1 N CH3COONH4

(soil:water 1:10) at pH 7, according to Bower et al.(1952).

In 2003 additional soil samples were collected notonly before (31 March), but also during (16 June, 28July and 8 September) and immediately after theirrigation period (14 October), after harvest (10 Sep-tember) and after the first rainfall event of thehydrological year (30 September). Three soil samples(one tree per plot, in three plots per treatment) wererandomly collected in the control, T200 and T600treatments at three soil depths (0.1–0.2 m, 0.4–0.5 mand 0.8–0.9 m), as mentioned above. A 10 g portion ofeach sample was analyzed for NO3-N concentration,measured by spectrophotometry in an AA-3 autoan-alyzer (Bran+Luebbe, Germany) within 24 h ofextraction with distilled water (soil:water ratio 1:2.5),after 30 min shaking, centrifuging at 5,000 rpm for10 min, and filtration through Whatman filter paper(Keeney and Nelson 1982). The remaining sampleswere used for pH, extractable P and exchangeable K

determinations, as previously described. Soil P and Klevels were evaluated according to Pastor et al. (1996).

Plant nutrient status and crop performance

Leaf samples were taken for nutrient analysis in July1998, 2002 and 2003. About 300 leaves per each plotof 24 (75 per tree) were sampled from the middleportion of current year’s shoots, around the trees andat 1.5–1.7 m above ground. Samples were washed indistilled water, dried at 65°C for 48 h and milled. Nconcentration was determined by Kjeldahl method.Concentrations of other leaf nutrients (P, K, Ca, Mg,Zn, B and Cu) were determined by ICP-OES(ThermoJarrell mod. IRIS ADVANTEGE, Waltham,MA, USA) after microwave digestion with concen-trated HNO3 (Walinga et al. 1995).

In February-March each year (before the irrigationperiod), as well as in November 2003 (at the end of theexperiment), canopy volume and trunk circumference at0.20 m above ground were determined per tree. Canopyvolume was estimated according to the equation:

V ¼ p=6� D1 � D2 � H ;

where D1 and D2 (m) are two perpendicular measure-ments of the maximum canopy diameter and H (m) isthe tree height.

Shoot growth was recorded each year, in two treesfor each plot, on ten flowering shoots per tree, allaround the canopy and at 1.5–1.7 m above ground.On the same trees, flower quantity was estimated atfull bloom in 2002 (3 May), 2003 (1 May) and 2004(25 April) in two trees per plot. We established fourcategories, from 1 (very low flower quantity) to 4(high flower quantity). Full bloom was defined as50% of the flowers open on at least 75% of theinflorescences, according to Rallo and Fernández-Escobar (1985). Each year, olive trees were picked byhand in September, at ripening index 1 (Uceda andFrias 1975), and fruit yield, fruit number and averagefruit weight were determined per each experimentaltree. Average fruit weight was determined on arandom sample of 0.5 kg fruit.

Statistical analysis

Analysis of variance (ANOVA) was used to determinestatistical differences between treatments of all stud-ied variables. To improve the precision of the

Plant Soil (2009) 319:147–162 151

experiment, analysis of covariance was used for fruityield data with the initial canopy (1999) as thecovariable. Polynomial contrasts were obtained whena significant F test was observed. Prior to the analysiswe tested the residuals for both homogeneity ofvariance and normality. Kendall’s tau test was usedfor the analysis of flower quantity estimation.

Results

Soil water

The soil was close to field capacity during theirrigation periods, for all treatments (data not shown).We can assume, therefore, that water availability wasnot a limiting factor. The mean values of Ksat werehigh (Fig. 1), but decreased markedly with thedecrease in soil matric potential (Ψm). At Ψm>−1.2 kPa, the highest Ksat values were found at0.40 m depth.

Root distribution and wetted zone dimensions

Highest root densities were found in the top 0.7 m soillayer (Fig. 2). Fine roots (∅<1 mm) comprised about75% of the total root number. Most of these (81%)were concentrated in the top 0.6 m, mainly around theemitters and close to the trunk. About 24% of theobserved roots were of ∅=1–5 mm. These roots, aswell as those of smallest diameter, were found down

to 1 m depth and as far as 1 m from the verticalprojection of the canopy. Just 0.7% of roots had ∅=5–10 mm, and they were mainly in the top soil layerand close to the trunk. Roots of ∅>10 mm were 0.3%of the total. These largest two classes of roots werefound in the top soil layers only, at a maximum depthof 0.4 m, and always within the limits of the canopy.In terms of root distribution in the soil, the roots of ∅<1 mm were the most affected by the dripperslocation. The wet areas of the trench profiles reachedthe lower limit of the soil depth. The mean diameterof the wetted ground areas around the drippers was0.45±0.03 m.

Soil nutrients

The fertigation treatments did not modify soil pH,CaCO3, OM, total N or exchangeable Ca 4 years afterthe start of the experiment (data not shown). Soil Kconcentration generally increased with the amount offertilizer applied at all depths, although valuesremained low in all treatments, even in the top soillayer where the highest values were recorded (Table 4).In the top soil layer P concentrations were very lowfor the control and T200 treatments, and reachednormal levels in T400 and T600. Differences betweentreatments were, however, not significant. Concen-trations of Mg were high in all treatments and showeda significant increase with the amount of fertilizer inthe top 0.6 m of soil.

The profiles of NO3-N, P and K within the wettedzones throughout 2003 indicated that, in the top soillayer, the concentrations of these elements increasedwith fertilizer dose, generally showing a linearresponse (Figs. 3, 4 and 5). In deeper soil layers, theconcentrations also increased with fertigation, but to alesser extent than in the top soil layer. Differencesbetween treatments were not always significant, likelybecause of the high soil variability and the lownumber of replicates.

Before the start of the fertigation period in 2003,NO3-N concentration was less than 6 mg kg−1 in thetop soil layer in all treatments, and decreased withdepth (Fig. 3). During the fertigation period, thehighest values of this element were recorded in T600in July, averaging 54 mg kg−1 at 0.1 m depth and17 mg kg−1 at 0.8 m depth. Values for this treatmentmeasured in September were, however, much lower.In October, after the cessation of fertigation and after

Water Potential (kPa)-1,2 -0,8 -0,3 -0,05

Hyd

raul

ic c

ondu

ctiv

ity (

mm

s-1

)

0,00

0,01

0,02

0,03

0,04

0,05

0.15 m 0.40 m 0.65 m

Fig. 1 Mean values (n=9) of soil hydraulic conductivity in therange near saturation, measured with a disc infiltrometer at0.15 m, 0.40 m and 0.65 m depth. Vertical bars indicate thestandard error

152 Plant Soil (2009) 319:147–162

the first rainfall events of the autumn, the recordedNO3-N concentrations were similar to March.

Values of extractable P recorded at 0.1–0.2 mdepth before the start of the fertigation period in 2003(Fig. 4) were low or very low, depending on thetreatment. Higher concentrations were later recordedin the fertigation treatments, reaching very high levelsin the top layer of the T600 soil, both in July andSeptember. In T200, however, P levels remained lowat the top 0.1–0.2 m. In October, at the end of theirrigation period, lower values of soil P concentrationwere recorded, although they were still high in the topsoil layer of the T600 treatment.

Before the fertigation period in 2003, soil ex-changeable K in the top 0.5 m was low or very low,

depending on the treatment (Fig. 5). At 0.8–0.9 mdepth, very low K values were measured for alltreatments. During the fertigation period K concen-tration increased for all the fertigation treatments anddecreased gradually with depth. In T600, soil K weregreatest, as high as 300 mg kg−1 in the surface layer, avalue considered to be high. In T200, however, Kconcentrations remained low, less than 130 mg kg−1.For T600, values recorded in October were similarthan those in September. For the control and T200treatments, values in October were generally lowerthan in September.

Soil pH increased with depth during the fertigationin 2003 (Table 5). Values recorded in T600 from Junewere significantly lower than in the control treatment,

N

0 - 10

11 - 20

21 - 30

31 - 40

0 - 5

6 - 10

11 - 15

N

0

1

01

N

No.roots< 1mm

0 - 10

11 - 20

21 - 30

31 - 40

No. roots1-5 mm

0 - 5

6 - 10

11 - 15

No. roots 5-10 mm

0

1

01

No. roots > 10 mm

Fig. 2 Root distribution foreach diameter range. Eachsquare represents the meanvalue (n=3) for 0.1 m2 ofthe soil section vertical tothe drip line of T400 trees.Circles indicate the posi-tions of the drippers. Arrowsindicate the limits of thetrunk (left) and canopy(right). See Table 3 fordetails on the treatments

Plant Soil (2009) 319:147–162 153

with a maximum difference of 0.4 units recordedclose to the emitters. Table 5 shows that pH valuesusually decreased with the amount of fertilizer,although differences were not always significant.

Leaf nutrients

In 1998, before the start of the experiment, theconcentrations of N and K in the leaves were notadequate, being lower than 1.4% and 0.8%, respec-tively, in all treatments (Table 6). According toFernández-Escobar (2004), N levels were deficientand K levels inadequate. In 2002 and 2003, thefertigation treatments increased leaf N, P and Kconcentrations, particularly in T400 and T600 treat-ments. In the control treatment the N level wasdeficient, and the K level inadequate, both in 2002and 2003. The same was found in 2003 in the T200treatment.

Significant differences among treatments with re-spect to other leaf nutrients concentrations weremeasured for B, Cu, Zn, Mg and Na. In 2002, leaf Bincreased from 20 mg kg−1 in control to 23 mg kg−1 inT600; in 2003 those amounts varied from 21 mg kg−1

in control to 24 mg kg−1, respectively. The Cuconcentration decreased from 7 mg kg−1 in control

to 6 mg kg−1 in T600, in 2002. In 2003, leaf Mg, Naand Zn concentrations decreased with fertilizer dose:the Mg concentration varied from 0.09% in control to0.07% in T600, the Na concentration varied from0.031% in control to 0.013% in T600, and the Znconcentration went from 14 mg kg−1 in control to11 mg kg−1 in T600. However, levels of all theseelements were adequate, except for Mg: according toFernández-Escobar (2004), the recorded Mg valueswere low in control, T200 and T400, and deficient inT600.

Crop performance

The fertigation treatments did not modify eithertrunk circumference or canopy volume (data notshown). In 2002 and 2003, the mean values of theseparameters were lower in the control than in thefertigation treatments, although differences were notsignificant. In November 2003, an increase of bothparameters with fertilizer dose was observed but,once again, differences were not significant. How-ever, we found that the increase in canopy volumebetween February 1999 and November 2003 fol-lowed a significant (P≤0.01) and linear increase withfertilizer dose.

Depth & treatment P (mg kg−1) K (mg kg−1) Mg (mg kg−1)

0.0–0.3 mControl 7 94 100T200 6 105 86T400 23 117 114T600 20 135 119Significance NS L** L*C.V.(%) 122.5 39.7 17.90.3–0.6 mControl 4 57 76T200 4 51 68T400 9 61 101T600 11 88 114Significance NS L* and Q* L**C.V.(%) 123.6 48.2 26.80.6–0.9 mControl 2 31 74T200 2 31 76T400 5 34 82T600 6 54 98Significance NS L* NSC.V. (%) 131.5 52.6 16.7

Table 4 Mean values forthe period 1999–2003 of theconcentration of extractableP, and exchangeable K andMg in the soil around treesof each treatment

Samples (one location perplot, three plots per treat-ment) were taken at about0.25 m from the emitter and0.75 m from the trunk atdifferent depths, before thestart of the irrigation peri-ods. See Table 3 for detailson the treatments

CV Coefficient of variation,NS non significant, L linear,Q Quadratic

*, ** significant at P≤0.05and 0.01, respectively

154 Plant Soil (2009) 319:147–162

Flower quantity was positively affected by fertiga-tion treatments in 2003, the last year of this fertigationexperiment. It increased with the amount of appliedfertilizer, an effect that persisted in 2004 (Table 7).With respect to fruit yield, no significant effect of thetreatments was found until 2003 (Table 8). Low yieldswere recorded in 2002 and 2003, in all treatments.Despite this, 2003 records showed a significant linearincrease in yield with fertilizer dose: in T200 andT600, yield was 188% and 251% greater than control,respectively. A similar trend was observed for boththe number of fruits per tree and the average fruitweight, but also for cumulative yield for the experi-mental period

Discussion

The observed root distribution pattern (Fig. 2) wastypical for the olive tree (Abd-El-Rahman et al. 1966;Fernández et al. 1991): greatest root densities were inthe top soil layers, close to the trunk and the emitters,where a good equilibrium between nutrients, waterand oxygen can be expected in this kind of soil. Inaddition, Fernández et al. (1991, 1992) found thatmost olive roots are of small diameter, which agreeswith our findings. Some roots were found far from thevertical projection of the canopy; these roots, whichlikely grew during wet months, suggest that the treescould have absorbed nutrients from soil volumes

September

October

0.8-0.9

0.4-0.5

0.1-0.2

June

Soil NO3- N (mg kg-1)0 20 40 60 80

T600T200Control

March

0 20 40 60 80

0.8-0.9

0.4-0.5

0.1-0.2

July

Dep

th (

m)

0.8-0.9

0.4-0.5

0.1-0.2

Fig. 3 Mean values (n=3;horizontal bars indicate thestandard error) of NO3-Nconcentration at differentdepths in the soil aroundcontrol, T200 and T600trees. Samples (one locationper plot, three plots pertreatment) were taken atabout 0.25 m from theemitter and 0.75 m from thetrunk at different depths, in2003, before (31 March),during (16 June, 28 July and8 September) and after (14October, after the first pre-cipitation event) the irriga-tion period. See Table 3 fordetails on the treatments

Plant Soil (2009) 319:147–162 155

outside of the wetted zones, at least during the periodsof the year when the soil water remained sufficient forroot function. The wet areas of the trench profilesindicated that water supplied by irrigation reached thelowest level of the rootzone.

During the irrigation period in 2003, NO3-N,extractable P and exchangeable K accumulated inthe soil of the fertigation treatments, generallyshowing a linear response to the fertilizer dose, withhighest concentrations for T600. This occurred par-ticularly in the top soil layer, around the drippers,where the greatest root densities were recorded(Fig. 2). Values of these nutrients decreased withdepth. Nitrate-N concentrations decreased rapidlyafter cessation of fertigation (Fig. 3). Both the high

NO3-N mobility when the soil is wet and its lowretention by soil particles could explain the lowconcentrations of this compound before the start andat the end of the fertigation period. In the controltreatment there was a small increase of NO3-N in thesoil during the fertigation period, probably due to theN contained in the irrigation water (sufficient toprovide about 60 g of N per tree). The OMmineralization, which could have been significantdue to the high OM content in the soil (Table 1),could have also contributed to that effect.

The high concentrations of NO3-N and K, and alsoP, found at the bottom of the rootzone in T600suggested possible nutrient leaching losses. The riskfor NO3-N groundwater contamination is enhanced

March

0 20 40 60 80

0.8-0.9

0.4-0.5

0.1-0.2

June

Soil P (mg kg-1)

0 20 40 60 80

T600T200Control

July

Dep

th (

m)

0.8-0.9

0.4-0.5

0.1-0.2

September

October

0.8-0.9

0.4-0.5

0.1-0.2

Fig. 4 Mean values (n=3;horizontal bars indicate thestandard error) of extract-able P concentration at dif-ferent depths in the soilaround control, T200 andT600 trees. Samples (onelocation per plot, three plotsper treatment) were taken atabout 0.25 m from theemitter and 0.75 m from thetrunk at different depths, in2003, before (31 March),during (16 June, 28 July and8 September) and after (14October, after the first pre-cipitation event) the irriga-tion period. See Table 3 fordetails on the treatments

156 Plant Soil (2009) 319:147–162

both because of the relatively high soil hydraulicconductivity of the soil (Fig. 1) and the low rootdensities found at the deepest explored soil layers(Fig. 2).

Positive responses of soil NO3-N, P and Kconcentrations to fertigation have also been found inother studies made in olive orchards (Troncoso et al.1997; Baena et al. 2003; Hidalgo et al. 2003; Pastor etal. 2005), as well as in orchards of other fruit treespecies (Uriu et al. 1980; Klein and Spieler 1987;Klein et al. 1989, 1999; Neilsen et al. 1998a). Inolive, Baena et al. (2003) found, at several soildepths, that the concentrations of NO3-N in the soilsolution increased with the applied N doses, and thatN losses occurred in the soil of trees fertilized with

496 g of N per tree. Pastor et al. (2005) found that soilNO3-N decreased with depth and that below thedrippers the NO3-N concentrations were lower than inthe surrounding dry soil. They also reported greaterNO3-N concentrations close to the wetted zonesperiphery than below the drippers. These authorsreported soil P movements as large as 0.5 m, bothvertically and horizontally, as well as an increase of Kavailability throughout the wetted zone. Our resultsshow movements to 0.8 m depth, both of P and K.The greater displacement we measured, relative tothat found by Pastor et al. (2005), was probably dueto the greater sand contents in our orchard soil.

Pastor et al. (2005) found, in several fertigatedolive orchards, than the pH of the soil solution

Soil K (mg kg-1)0 100 200 300 400

0.8-0.9

0.4-0.5

0.1-0.2

0 100 200 300 400

T600T200Control

Dep

th (

m)

0.8-0.9

0.4-0.5

0.1-0.2

September

October

0.8-0.9

0.4-0.5

0.1-0.2

July

March June

Fig. 5 Mean values (n=3;horizontal bars indicate thestandard error) of ex-changeable K concentrationat different depths in the soilaround control, T200 andT600 trees. Samples (onelocation per plot, three plotsper treatment) were taken atabout 0.25 m from theemitter and 0.75 m from thetrunk at different depths, in2003, before (31 March),during (16 June, 28 July and8 September) and after (14October, after the first pre-cipitation event) the irriga-tion period. See Table 3 fordetails on the treatments

Plant Soil (2009) 319:147–162 157

decreased more than 0.5 units. Some of the orchardswere on calcareous soils, which usually have a highbuffer capacity. They reported that the pH decreaseswere sufficient to increase the availability of P and Kin the soil, as well as other elements. In our case, we

think that the soil pH decrease (Table 5) could havebeen related to the acidity of the applied fertilizer,which included phosphoric acid. However, pHdecreases have also been observed in fruit treeorchards fertigated with N only (Klein and Spieler1987; Neilsen et al. 1994; He et al. 1999). Chung etal. (1994) suggested that this is a consequence of theapplication of fertilizer in a reduced soil volume.Peryea and Burrows (1999) reported that the acidifi-cation potential of a fertilizer can be related to theNH4

+ and urea concentrations. The mineralization ofboth organic-N and ammonium-N is a H+ producingprocess.

After 4 years of applying the fertigation treatments,soil K generally increased with the amount offertilizer, at all depths. However, soil Mg, an elementnot included in the supplied fertilizer, also increasedlinearly with the dose, until 0.6 m depth (Table 4). Wedon’t have a feasible explanation for these results,since there were no differences in Mg supply byirrigation water among treatments.

Leaf analyses in the control treatment in 2002 and2003, and also in T200 in 2003 (Table 6) showedlevels of N and K lower than 1.4% and 0.8% which,according to Fernández-Escobar (2004), are consid-ered as deficient and inadequate, respectively. Theyalso suggested that the increased soil NO3-N, P and Kconcentrations found in the fertigation treatments,with respect to the control, could have led to a higherleaf N, P and K concentrations, since increases wereconcentrated within the soil volumes with greatestdensities of active roots (Fig. 2). This positive relationbetween increased soil NO3-N, P and K availabilityand higher leaf nutrient concentrations, has also been

Table 6 Effect of fertigation treatments on leaf N, P, K concentrations (%) (n=6) in 1998, 2002 and 2003

Treatment N P K

1998 2002 2003 1998 2002 2003 1998 2002 2003

Control 1.27 1.38 1.26 0.11 0.103 0.104 0.60 0.600 0.638T200 1.16 1.54 1.22 0.10 0.113 0.105 0.60 0.799 0.757T400 1.27 1.54 1.56 0.11 0.110 0.120 0.66 0.815 0.962T600 1.27 1.53 1.57 0.10 0.103 0.119 0.67 0.860 1.091Significance NS L**, Q* L**, C** NS Q** L* NS L** L****C.V. (%) 9.5 4.6 6.2 6.9 5.6 9.3 13.4 12.9 15.3

Samples were taken in July from the middle portion of the shoots of the current year’s growth, around the trees and at 1.5–1.7 m aboveground. See Table 3 for details on the treatments

CV Coefficient of variation, NS non significant, L linear, Q Quadratic, C Cubic

*, **, **** significant at P≤0.05, 0.01 and 0.0001, respectively

Table 5 Mean values (n=3) of pH at different depths in thesoil around control, T200 and T600 tree

Depth & treatment March June July September October

0.10–0.20 mControl 8.20 8.46 8.22 8.40 8.57T200 8.16 8.65 8.16 7.99 8.34T600 8.30 8.13 7.80 8.32 8.51Significance NS Q* L** Q** NSC.V. (%) 5.6 3.1 2.6 2.6 1.80.40–0.50 mControl 8.20 8.63 8.26 8.63 8.54T200 8.23 8.66 8.20 8.31 8.69T600 8.30 8.27 8.06 8.33 8.44Significance NS L* NS L* NSC.V. (%) 2.6 2.5 2.7 2.2 3.00.80–0.90 mControl 8.30 8.87 8.56 8.99 8.73T200 8.35 8.71 8.48 8.64 8.66T600 8.40 8.34 8.16 8.38 8.60Significance NS NS NS NS NSC.V. (%) 2.2 2.4 2.8 4.1 1.8

Samples (one location per plot, three plots per treatment) weretaken at about 0.25 m from the emitter and 0.75 m from thetrunk at different depths, in 2003, before (31 March), during(16 June, 28 July and 8 September) and after (14 October, afterthe first precipitation event) the irrigation period. See Table 3for details on the treatments

CV Coefficient of variation, NS non significant, L linear, QQuadratic

*, ** significant at P≤0.05 and 0.01, respectively

158 Plant Soil (2009) 319:147–162

found in other fertigated fruit tree species (Uriu et al.1980; Klein et al. 1989; Neilsen et al. 1994, 1998b).

We don’t know why the fertigation treatments haddifferent concentrations of other leaf nutrients, apartfrom N, P and K, relative to the control. With respectto B, which increased with fertilizer dose both in 2002

and 2003, its availability in the soil likely increasedbecause pH decreased in the wetted zone of thefertigation treatments (Table 5). Concerning theconcentration of Mg in the leaves, which was low incontrol, T200 and T400, and deficient (<0.08%) inT600 in 2003, there are evidences of being relatedwith that of K. In apple orchards, Neilsen et al.(1998b, 2004) reported a compensatory uptake of Mgafter development of K deficiency conditions. Inparticular, Neilsen et al. (1998b) reported an increasein average annual leaf Mg concentration (which wasalways adequate) simultaneous to the decrease inaverage annual leaf K concentrations up to deficiencyconditions. In any case, this research suggests thatapplications of Mg should be considered in ourexperimental orchard to avoid the development ofplant deficiencies in the long term.

Despite differences among treatments found bothin soil and leaf nutrient concentrations, the fertigationtreatments did not significantly modify the annualmean values of trunk circumference and canopyvolume (data not shown). However, the increase in

Table 8 Effect of fertigation treatments on fruit yield, number of fruits per tree and average fruit weight (n=24) from 1999 to 2003

Treatment 1999 2000 2001 2002 2003 Total

Fruit yield (kg tree−1)Control 12.97 30.16 22.36 8.78 3.39 77.66T200 13.52 36.34 23.38 13.30 6.37 91.40T400 14.60 34.47 26.25 13.57 8.22 93.58T600 13.51 34.56 30.95 10.21 8.51 97.73Significance NS NS NS NS L* L**C.V. (%) 55.1 26.2 34.23 40.8 36.3 37.1

No. Fruit tree−1

Control 3,968 11,580 7,051 1,929 806 25,333T200 3,739 13,314 6,162 2,675 1,384 27,043T400 3,954 12,920 6,693 2,668 1,656 26,820T600 3,575 11,500 8,070 1,899 1,782 26,414Significance NS NS NS NS L* NSC.V. (%) 36.1 19.8 21.1 29.4 25.8 22.8Average fruit weight (g)Control 3.98 2.99 3.83 5.02 4.25 -T200 4.05 2.83 4.11 5.09 4.21 -T400 4.29 2.98 4.28 5.42 4.81 -T600 4.64 3.30 4.38 5.70 5.03 -Significance NS NS NS NS L*** -C.V. (%) 15.1 14.4 12.0 10.4 5.3 -

Trees were picked by hand in September, at maturity index 1. See Table 3 for details on the treatments

CV Coefficient of variation, NS non significant, L linear

*, **, *** significant at P≤0.05, 0.01 and 0.001, respectively

Table 7 Effect of fertigation treatments on flower quantityestimation (n=12) for the period 2002–2004

Treatment 2002 2003 2004

Control 1.9 1.3 2.0T200 1.8 1.7 2.1T400 2.0 2.3 2.9T600 1.5 2.3 3.1Significance NS ** **C.V. (%) 5.6 4.9 8.5

Data were taken at full bloom according to four categories,from 1 (very low) to 4 (high). See Table 3 for details on thetreatments

CV Coefficient of variation, NS non significant

**, significant at P≤0.01

Plant Soil (2009) 319:147–162 159

canopy volume between February 1999 and November2003 followed a significant and linear increased with theamount of fertilizer. Also, both the flower quantity andfruit yield were positively affected at the end of theexperimental period (Tables 7 and 8). The low yieldsrecorded in 2002 were likely due to the severe pruningmade in January, which probably caused an imbalancebetween vegetative and reproductive development. Inaddition, a severe attack of leaf spot (Spilocaeaoleagina (Cast.) Hughes) occurred this year, as wellas in 2003. Although the canopies of all treatmentswere sprayed with copper oxyclhoride both years inautumn, rainfall events occurred soon after the appli-cations, which may explain the low Cu concentrationsfound in the leaves (data not shown). In 2003 the leafspot attack was more severe than in 2002, causingmassive defoliation 4 weeks or 5 weeks after fullbloom. We randomly sampled about 200 leaves perplot (50 per tree), both in March and November 2003,and used the method described by Trapero and Blanco(2005) to detect latent infections and so evaluate thedifferences between treatments in the leaf spot inci-dence, which were not significant. It is known thatdefoliation affects olive tree growth and development.Proietti et al. (1994) found a fruits drop of about 29%in ‘Frantoio’ trees when shoots had been defoliated inJuly. Later, Proietti and Tombesi (1996) observed in‘Maurino’ trees that vegetative growth was affectednegatively by shoot defoliation in July, independent ofthe fruit load. In our case, fruit set decreased about72% in 2003 with respect to 2002. Trees, however,recovered noticeably, as indicated by mean values bothof shoot length (0.15 m±3.43) and canopy volume(48.78 m3±9.72) reached at the end of the vegetativeperiod in 2003.

Although production was low in 2003, fruit yieldincreased significantly with fertilizer dose (Table 8)and this was associated both with increased number offruits per tree and higher average fruit weight, acharacteristic of great importance for table olives.Increased fruit number was positively related toincreased canopy volume. Troncoso et al. (1997)found that fruit yield of 25 year-old fertigated‘Manzanilla’ trees increased when 2 kg of urea wereapplied per tree and year. They found that the greaterfruit yield of the fertigation treatment with respect tothe control, irrigated without fertilizer, resulted froman increase in fruit number but not in fruit weight.The increase in fruit weight recorded in this work

could have been due, at least in part, to increased fruitK concentration: results obtained by Morales-Silleroet al. (2007) from a research carried out in the sameorchard, suggested that the accumulation of Kinduced osmotic adjustment in the fruit cells, whichenhance water accumulation, leading to an increase infruit weight.

Finally, the fertigation treatments significantlyaffected the cumulative yield for the studied periodand, although we have no yield data for 2004, themean values of the flower quantity measured that year(Table 7) suggest that plant response to the fertigationtreatments still remained.

Conclusions

The increase on soil NO3-N, P and K concentrationswith the fertigation dose could have contributed to theobserved fruit yield increase with fertilizer dose. Infact, our data show a positive relation betweenincreased soil NO3-N, P and K availability and higherleaf N, P, K concentrations. This could have accountedfor the observed increase in canopy volume, flowerquantity, fruit number per tree and fruit weight with theamount of fertilizer. These conclusions are furtherevidence to confirm those reported in the two relatedpapers made with the same experimental design(Morales-Sillero et al. 2007, 2008). For these growingconditions and when the fruits are used for oilproduction, then T400 (460 g N per tree, the 400 gof the treatment plus the 60 g supplied by the irrigationwater) could be the most adequate treatment; if thefruits are for table olive production, the T600 treatment(660 g N per tree, the 600 g of the treatment plus the60 g supplied by the irrigation water) could be the mostappropriate for the producer, but there is a risk ofleaching losses and the possibility of groundwatercontamination. These conclusions reveal that thefertilizer doses often used in commercial oliveorchards, which amount to 1 kg N per tree and year,or more, are unnecessarily high and likely causeenvironmental problems.

Acknowledgement This work was supported by the Pro-grama de Mejora de la Calidad de la Producción del Aceitede Oliva (Olive Oil Quality Improvement)-CAO 98-004. Wethank Miguel Pastor, Ricardo Fernández-Escobar, MaríaLiñán, Javier Troncoso, Meritxell Justicia, Montserrat Baenaand Pilar Rallo.

160 Plant Soil (2009) 319:147–162

References

Abd-El-Rahman AA, Shalaby AF, Balegh MS (1966) Watereconomy of olive under desert conditions. Flora Abt B156:202–219

Allen R, Pereira LS, Raes D, Smith M (1998) Crop evapotrans-piration—guidelines for computing crop water require-ments—FAO irrigation and drainage paper 56. FAO, Romehttp://www.fao.org/docrep/X0490E/X0490E00.htm

Alva AK, Paramasivan S (1998) Nitrogen management for highyield and quality of Citrus in sandy soils. Soil Sci Soc AmJ 62:1335–1342

Ankeney MD, Ahmed M, Kaspar TC, Horton R (1991) Simplefield method determining unsaturated hydraulic conduc-tivity. Soil Sci Soc Am J 55:467–470

Baena G, Ordóñez R, Pastor M, González P (2003) Distrib-ución en el bulbo húmedo de los nutrientes aplicados enfertirriego en olivar. Estudios de la Zona no Saturada delSuelo VI:65–69

Bower CA, Reitemeier RF, Fireman M (1952) Exchangeablecation analysis of saline and alkali sails. Soil Sci 73:251–261 doi:10.1097/00010694-195204000-00001

Bremner JM, Mulvaney CS (1982) Nitrogen total. In: Page AL,Miller RH, Keeney DR (eds) Methods of soil analysis Part2, 2nd edition. Agronomy n°9. ASA, Madison, Wisconsin,pp 621–622

Chung JB, Zasoski RJ, Burau RG (1994) Aluminum-potassiumand aluminum-calcium exchange equilibria in bulk andrhizosphere. Soil Sci Soc Am J 58:1376–1382

Connor DJ (2005) Adaptation of olive (Olea europaea L.) towater-limited environments. Aust J Agric Res 56:1181–1189 doi:10.1071/AR05169

Fereres E, Pruitt WO, Beutel JA, Henderson DW, Holzapfel E,Shulbach H, Uriu K (1981) ET and drip irrigationscheduling. In: Fereres E (ed) Drip irrigation Management.University of California, Div. of Agric. Sci. No. 21259, pp8–13

Fernández JE, Moreno F, Cabrera F, Arrúe JL, Martín-Aranda J(1991) Drip irrigation, soil characteristics and the rootdistribution and root activity of olive trees. Plant Soil133:239–251 doi:10.1007/BF00009196

Fernández JE, Moreno F, Martín-Aranda J, Fereres E (1992)Olive-tree root dynamics under different soil waterregimes. Agricoltura Mediterranea 122:225–235

Fernández JE, Díaz-Espejo A, Infante JM, Durán P, PalomoMJ, Chamorro V, Girón IF, Villagarcía L (2006) Waterrelations and gas exchange in olive trees under regulateddéficit irrigation and partial rootzone drying. Plant Soil284:271–287 doi:10.1007/s11104-006-0045-9

Fernández-Escobar R (2004) Fertilización. In: Barranco D,Fernández-Escobar R, Rallo L (eds) El cultivo del olivo.Mundi-prensa, Madrid, pp 287–319

Fernández-Escobar R, García T, Benlloch M (1994) Estadonutritivo de las plantaciones de olivar en la provincia deGranada. ITEA 90:39–49

Ferreira J, García-Ortiz A, Frías L, Fernández A (1986) Losnutrientes N-P-K en la fertilización del olivar. Olea17:141–152

Ginés I (2004) Situación actual de la fertirrigación en España.Vida rural 185:33–36

Granier A (1987) Evaluation of transpiration in a Douglas-firstand by means of sap flow measurements. Tree Physiol3:309–320

He ZL, Alva AK, Calvert DV, Li YC, Banks DJ (1999) Effects ofnitrogen fertilization of grapefruit trees on soil acidificationand nutrient availability in a Riviera fine sand. Plant Soil206:11–19 doi:10.1023/A:1004364805789

Hidalgo JC, Pastor M (2005) Los nutrientes en el olivar. In:Pastor M (ed) Cultivo del olivo con riego localizado.Mundi-Prensa, Consejería de Agricultura y Pesca, Junta deAndalucía, Madrid, pp 477–504

Hidalgo JC, Pastor M, González P, Ordóñez R, Hidalgo J(2003) Resultados preliminares de la distribución depotasio extraíble en el bulbo húmedo en un olivar en elque se ha aplicado fertirrigación potásica. Estudios de lazona no saturada del Suelo VI:59–63

Keeney DR, Nelson DW (1982) Nitrogen-Inorganic forms. In:Page AL, Miller RH, Keeney DR (eds) Methods of soilanalysis Part 2, 2nd edition. Agronomy n°9. ASA,Madison, Wisconsin, pp 643–698

Kipp JA (1992) Thirty years fertilization and irrigation in Dutchapple orchards. Fert Res 32:149–156 doi:10.1007/BF01048777

Klein I, Spieler G (1987) Fertigation of apples with nitrate orammonium nitrogen under drip irrigation. II. Nutrientdistribution in the soil. Commun Soil Sci Plant Anal18:323–339 doi:10.1080/00103628709367822

Klein I, Levin I, Bar-Yosef B, Assaf R, Berkovitz A (1989)Drip nitrogen fertigation of ‘Starking Delicious’ appletrees. Plant Soil 119:305–314 doi:10.1007/BF02370423

Klein I, Meimon A, Skedi D (1999) Drip nitrogen, phosphorus,and potassium fertigation of ‘Spadona’ Pear. J Plant Nutr22:489–499 doi:10.1080/01904169909365646

Martín-Aranda J, Troncoso A (1986) Fertigation experiments intable-olive orchards of various plant spacings. XXIIInternational Horticulturae Congress. University of Cal-ifornia, Davis, USA

Mmolawa K, Or D (2000) Root zone solute dynamics under dripirrigation: a review. Plant Soil 222:163–190 doi:10.1023/A:1004756832038

Morales-Sillero A, Fernández JE, Beltrán G, Jiménez R,Troncoso A (2007) Influence of fertigation in ‘Manzanillade Sevilla’ olive oil quality. HortSci 42:1157–1162

Morales-Sillero A, Fernández JE, Rejano L, Jiménez R,Troncoso A (2008) Effect of fertigation on the ‘Manzanillade Sevilla’ table olive quality before and after ‘Spanish-style’ olive processing. HortSci 43:153–158

Murphy J, Riley JP (1962) A modified single method for thedetermination of phosphate in natural waters. Anal ChimActa 24:21–36

Neilsen GH, Parchomchuk P, Hogue EJ, Wolk WD, Lau OL(1994) Response of apple trees to fertigation-induced soilacidification. Can J Plant Sci 74:347–351

Neilsen D, Parchomchuk P, Neilsen GH, Hogue EJ (1998a)Using soil solution monitoring to determine the effects ofirrigation management and fertigation on nitrogen avail-ability in high-density apple orchards. J Am Soc HorticSci 123:706–713

Neilsen GH, Parchomchuk P, Meheriuk M, Neilsen D (1998b)Development and correction of K-deficiency in dripirrigated apple. HorstSci 33:258–261

Plant Soil (2009) 319:147–162 161

Neilsen GH, Neilsen D, Herbert LC, Hogue EJ (2004)Response of apple to fertigation of N and K underconditions susceptible to the development of K deficiency.J Am Soc Hortic Sci 129:26–31

Nelson RE (1982) Carbonate and gypsum. In: Page AL, MillerRH, Keeney DR (eds) Methods of soil analysis Part 2, 2ndedition. Agronomy n°9. ASA, Madison, Wisconsin, pp570–571

Pastor M, Castro J, García-Ortiz A, Martínez C, Mateos L,Navarro C, Orgaz F, Saavedra M, Vega V (1996)Manejo del olivar con riego por goteo. InformacionesTécnicas 41/96, Consejería de Agricultura y Pesca, Juntade Andalucía

Pastor M, Vega V, Hidalgo JC, Nieto J (2005) Fertilización enel olivar de riego. In: Pastor M (ed) Cultivo del olivo conriego localizado. Mundi-Prensa, Consejería de Agriculturay Pesca, Junta de Andalucía, Madrid, pp 506–546

Peryea FJ, Burrows RL (1999) Soil acidification caused by fourcommercial nitrogen fertilizer solutions and subsequentsoil pH rebound. Commun Soil Sci Plant Anal 30:525–533 doi:10.1080/00103629909370223

Proietti P, Tombesi A (1996) Translocation of assimilates andsource—sink influences on productive characteristics ofthe olive tree. Adv Hortic Sci 10:11–14

Proietti P, Tombesi A, Boco M (1994) Influence of leaf shadingand defoliation on oil synthesis and growth of olive fruits.Acta Hortic 356:272–277

Rallo L, Fernández-Escobar R (1985) Influence of cultivar andflower thinning within the inflorescence on competitionamong olive fruit. J Am Soc Hortic Sci 110:303–308

Sumner ME, Miller WP (1996) Cation exchange capacity andexchange coefficients. In: Sparks DL et al (ed) Methods ofsoil analysis Part 3, Chemical methods. Soil ScienceSociety America, Madison, Wisconsin, pp 1201–1229

Trapero A, Blanco MA (2005) Enfermedades. In: Barranco D,Fernández-Escobar R, Rallo L (eds) El cultivo del olivo.Mundi-prensa, Madrid, pp 557–614

Troncoso A, Liñán J, Cantos M, Zárate R, Lavee S (1997)Influencia de la fertirrigación con urea sobre la disponibi-lidad de N-NO3 y el desarrollo del olivo. Fruticulturaprofesional 88:83–87

Uceda M, Frias L (1975) Harvest dates. Evolution of the fruitoil content, oil composition and oil quality. Proceedings ofII Seminario Oleícola Internacional, Córdoba, Spain, pp125–130

Uriu K, Carlson RM, Henderson DW, Schulbach H, AldrichTM (1980) Potassium fertilization of prune trees underdrip irrigation. J Am Soc Hortic Sci 105:508–510

Van Noordwijk M, Brouwer G, Meijboom F, do Rosário M,Oliveira G (2000) Trench profile techniques and corebreak methods. In: Smit AL, Bengough AG, Engels C,Van Noordwijk M, Pellerin S, Van de Geijn SC (eds)Handbook. Springer-Verlag, pp 211–233

Walkley A, Black JA (1934) An examination of the Degtjareffmethod for determining soil organic matter and proposedmodification of the chromic acid titration method. Soil Sci37:29–38 doi:10.1097/00010694-193401000-00003

Walinga I, Van der Lee JJ, Houba VJG, Van Vark W,Novozamsky I (1995) Plant analysis manual. Chapter 5.Kluwer Academic, Dordrecht

162 Plant Soil (2009) 319:147–162