Download - Survey of herbicide residues in soil and wells in three citrus orchards in Valencia, Spain

Weed Research. 1991, Volume 31, 14J-151

Survey of herbicide residues in soil and wells in three citrusorchards in Valencia, Spain

D. G6MHZ DE BARREDA', E, LORENZO*,M, GAMdNt. E, MONTEAGUDOt,A, SAEZt, J.D, DE LA CUADRAt, A. DELBUSTO*. C. RAMOS* ANDE,A, CARBONELL* Departamento deEcologia, I.V.I.A. - C.A.P., GeneralitatValenciana, fLaboratorio Agrario. C.A.P.Generalitat Valenciana, Valencia, Spain

Received 6 July 1990Revised version accepted 29 October 1990

Summary: Resume: Zusammenfassung

Soil samples taken in summer 1989 and winter1990 at different depths from three citrusorchards of the Valencia region (Spain) with along history of residual herbicide treatmentswere analysed with bioassays and chromato-graphic procedures. The herbicides involvedwere atrazine, bromacil, diuron, simazine.terbuthylazine, terbumetone. terbutryn and tri-fluralin. Water samples from wells in theorchards were also analysed. The concentra-tions of the herbicides were very low, oftenbelow the limit of determination, and werealways highest in the upper layers of soil, After avery unusual period of heavy rain, small quanti-ties of some chemicals were found in the wellwater. The conclusion was that in these orchardsthe herbicides applied at currently used rates areunlikely to accumulate in any layers of the soil,

Enquete sur les risidus d'herbicides dans le sol etles puits, au sein de 3 vergers d'agrumes aValence, Espagne

Des echantillons de sol ont 6X6 pr616ves k diff6r-entes profondeurs dans 3 vergers d'agrumes de

la region de Valence (Espagne), lors de I'etd1989 et de l'hiver 1990, Ces sols avaient tous unlourd passe de traitements herbicidesresiduaires; ils furent analyses selon des proce-dures de chromatographie et d'essais biologi-ques, Les herbicides int6ress6s ont ete: atrazine,bromacile, diuron, simazine, terbuthylazine,terbumetone. terbutryne et trifluraline. On aaussi analyse des echantillons d'eau provenantde puits situ6s dans les vergers, Les concentra-tions des herbicides ont ete tres basses etsouvent inferieures k la limite de determinationde la methode d'analyse. Elles ont &tisystematiquement plus elevfees dans les couchessup6rieures du sol. Apr6s une periode de fortespluies exceptionnelles, des petites quantit^s decertains herbicides ont ti€ trouvees dans l'eaudes puits. En conclusion, les herbicidesappliques dans ces vergers aux dosescouramment utilisees ne sont vraisemblable-ment pas susceptibles de s'accumuler dansaucune des diff^rentes couches de sol.

Herbizidriickstdnde in Boden und Brunnen-wasser in drei Citrus-Plantagen bei Valencia,Spanien

Bei der Analyse von im Sommer 1989 undWinter 1990 verschieden tief entnommenenBoden- und Brunnenwasserproben aus 3 Citrus-Plantagen um Valencia, die seit langerer Zeit mitpersistenteren Herbiziden (Atrazin, Bromacil,Diuron, Simazin, Terbuthylazin, Terbumeton,Terbutryn und Trifluralin) behandelt wordenwaren, lag deren Konzentrationen sehr niedrig,oft unter der Nachweisgrenze (Biotests undGaschromatographie); in den oberen Boden-schichten waren sie immer am hochsten, Nacheiner Periode ungewohnlich heftiger Nieder-schlage wurden geringe Mengen einigerChemikalien im Brunnenwasser gefunden. In

144 Gomez de Barreda et al.

diesen Obstanlagen fuhrt der normale Aufwandvon Herbiziden offensichtlich zu keinenerhohten Ruckstanden im Boden.

Introduction

Understanding of the fate and behaviour ofherbicides following repeated applications isimportant to agriculture, particularly in peren-nial crops. Fryer & Kirkland (1979) andGrossbard (1971) concluded that repeatedtreatments at recommended rates of MCPA,linuron, simazine and triallate did not adverselyaffect soil fertility. However, these resultsconcerned only certain chemicals in a particularenvironment in a temperate climate (inEngland).

Marriage, Saidak & van Stryck (1975) foundthat after nine consecutive annual treatments ofatrazine at a relatively high rate (4-5 kg Al ha"')to an orchard soil, the residues in soil samplestaken 4-5 months after the last application wereat low levels (0-4 mg kg"'). Burnside, Fenster &Wicks (1971) observed that atrazine residues in-creased with successive applications during3 years on several loam soils.

Sheets & Harris (1965) emphasized that thepersistence of residual herbicides may varybetween sites and Horowitz (1971) stated that insubtropical regions the behaviour of herbicidesoften differs markedly from that in temperateclimates.

In many countries nowadays, the use ofresidual herbicides in citrus plantations hasbecome standard practice. In these situations,damage has been reported (G6mez de Barreda,1970):

(a) to crops other than citrus grown as anintercrop;(b) in fields where citrus has been replaced byother crops;(c) following overdosing;(d) in very sandy soils;(e) to young citrus trees.

Nevertheless, few cases of phytotoxicity dueto residues have been reported.

More than 80% of the residual herbicidesused in citrus are derivatives of urea, triazine.uracil or dinitroaniline. For example, the mainresidual herbicides used in Valencia areatrazine, bromacil, diuron, simazine, terbuthyl-azine, terbumeton, terbutryn and trifluralin

(G6mez de Barreda 1987). The last is normallyused in herbigation.

Hance (1987, 1989) reviewed generally thepersistence of herbicides in soil and their ingressinto groundwater. There are few papers report-ing herbicide residues in groundwater beneathcitrus orchards, but Wheeler & Mansell (1974)found terbacil and 2,4-D (10-110 jig T') in sub-surface drainage water collected from a citrusgrove.

This report deals with the situation withregard to the occurrence of herbicides in soilsand wells in citrus orchards in the Valenciaregion (Spain).

Materials and methods

A survey was made in order to locate citrusorchards in the Valencia area with herbicideproblems, but no cases of clear phytotoxicitywere found. Therefore three orchards wereselected with the following characteristics: (i) along history of residual herbicide applications;(ii) adequate herbicide application records; (iii)more than 5 years without cultivation; (iv) thepresence of a well for irrigation.

One orchard was situated in the Benifay6area (15 km south of Valencia) in whichtriazines, urea, uracil and dinitroaniline deriva-tives have been applied over the last 22 years. Inanother area, Jdtiva (45 km south of Valencia),triazine herbicides have been the only group ofresidual weed-killers applied for 23 years. Athird orchard, in the Ribarroja area (10 km westof Valencia), was selected because some type ofno-tillage system has been used for the past 24years, and for the last 5 years (1985-89) anannual treatment with a mixture of diuron plusbromacil (2-4 kg AI ha"' of each) has beenapplied. The Benifayo and Jativa orchards areeach approximately 1 ha; that at Ribarroja islarger, over 400 ha.

Soil samples were obtained at 10 representa-tive pioints in the orchard with a two-man-operated coring machine fitted with a home-made drill. Soil from the same depths from eachcore was mixed, taking care not to mix the soilfrom different depths. The soil samples are re-presentative of the orchards in Benifay6 andJativa and of the plots chosen in the orchard ofRibarroja.

Herbicide residues in citrus orchards 145

Tubte 1 Soil characteristics of the citrus orchards

Sand SiltO.M.

Clay (%)Calcium

carbonate (%) PHWater holdingcapacity (%)

C.E.C.(tneqlOOg-')

Jativa0-30

30-60

Benifay60-30

3()-60

RibarrojaplotA-fB

0-3030-50

plotC0-20

40-60

62-250-0

70-369-2

54-853-8

55-645-4

30-528-6

17-413-3

23-024-0

25-229-4

7-321-4

12-317-5

22-222-2

19-225-2

0-790-37

0-450-28

0-790-54

0-840-42

21-622-8

3-34-0

25-924-4

37-438-7

7-68-0

7-67-8

7-57-5

7-47-7

4947

4036

3939

3432

1712

1511

1617

1212

Table 2 Herbicide treatments in the Benitay6 orchard over 22 years

Amount of herbicide applied (kg Al ha" ' )

Years1968-711972-781979-801981-8719881989

Total herbicide applied 1968-1989

Sim.

8-0—2-50

18-50——

29-00

Ter,CI

11-25

4-35—1-20

16-80

Ter.O

11-25

4-35—

1-2016-80

Ter.S

_

4-20

—4-20

Atra.

,

2-80

1-604-40

Diu.

3-205-757-252-40

18-60

Brom.

2-401-60

4-002-40

10-40

Tri.

4-006-50

10-50

Sim. = simazine; Ter.Cl = terbuthylazine; Ter.O = terbumeton; Ter.S = terbutryn; Atra. = atrazine; Diu. = diuron; Brom, =bromacil; Tri. = trifluralin.

Two spot treatments were applied as a mixture of 0-5 paraquat+0-5,2.4-D kg Al ha" ' in 1968-1969,1970,1973 and one, in 1978and 1980.

Diuron was mixed with amitrole during 1979, 1980 and 1983,

Tabk 3 Herbicide treatments in the Jativa orchard over 23 years

Amount of herbicide applied (kg Al ha~')

Years1967-«91970-741975-871988-89

Total herbicide applied 1967-1989

Sim.

18-0

9-00

27(K)

Ter.Cl

24-0033-12

2-8860-00

Ter.O

24-0033-122-88

6()-(X)

Ter.S

19-201-92

2112

Atra.

18-00

24-%1-92

44-88

Non-residual herbicides were used as spot treatment during several years.Sim. = simazine; Ter.Cl = terbuthylazine; Ter.O = terbumeton; Ter.S = terbutryn; Atra. = atrazine.

The analyses of soils in the three orchards areshown in Table 1, The treatment programmes inthe first two orchards are given in Tables 2 and 3,

Soil and well water samples were taken insummer 1989 and winter 1990 in the Benifaydand Jativa orchards. Rainfall data are shown inTable 4.

The Ribarroja orchard was sampled on 4April 1990 in three plots. For plot A this was1 day after and for plots B and C 1 daybefore the 1990 diuron plus bromacil applica-tion. Plot C has a longer history of non-tillagemanagement (since 1966), but no adequateearly herbicide records were available and


1

p p p CO p

p p p p ao pCT- S ^ *o * m

»fi p p p^ C oc ^

p p p p r- p

o o .^ o 00 9

^2 =a = fi

7̂ o -a o N o

.Q 9 o o ae 9c --• 00 r j ^ r*l

9 9 9 9 9 9

g § §li, g, S.

§ § S


jjso, in some years, a shallow cultivation hadbeen given.

Herbicide residue contents in soil weremeasured by GLC, HPLC and by bioassays.Only the parent compounds were measuredwith the chromatographie methods.

Herbicides were analysed as follows: Diuronby HPLC (Cotterill, 1980); bromacil by GLC(Pease, 1966); trifluralin by GLC (Tepe &Scroggs, 1967); triazines by GLC (Byast,Cotterill & Hance, 1977; Ramsteiner, Hormann& Eberle, 1974), The detection limits for soilwere 0-04 mg kg"' for diuron, 0-01 mg kg"' forthe rest of the herbicides, and 0-1 |ig T ' for allcompounds in water. The recovery percentagesin soil samples were higher than 90%, except forbromacil, which was 80%,

A study of the variability of the analyticalprocedures using 10 replicates prepared withtap water, at the 1-10 \x.g T ' level gave CVs inthe range 3-8%, except for trifluralin, whichwas 12%.

The bioassays were conducted in a growthchamber (100 ( s"' PAR, at 25°C, 16/8 hlight/dark) with Avena sativa cv Prodes 101 asthe test plant. Seven oat seeds were sown in 90 gof soil in plastic cups and cultivated as describedby Harris (1966), Plants were thinned to five perpot and growth was measured by shoot freshweight 14 days after sowing. The five plants ineach pot were weighed together.

Results and discussion

Instrumental analyses

Benifayo orchard. The results of the analyses ofsamples taken in July 1989 are shown in Table 5,

Only low quantities of the herbicides werefound, always in the upper soil layers. Thetrifluralin residues are probably aconsequence ofboth the high persistence of the product and theuse of herbigation during 1988/89, However, themost important finding in this orchard was thealmost complete absence of all herbicides in thesamples taken in 1990, Only trifluralin was de-tected in very low concentration (data notshown).

This orchard has an irrigation well,surrounded by untilled plots. The water level is15 m below ground. No herbicides weredetected in the samples taken in summer 1989,but in the following winter some were found(Table 6). No replicate measurements could betaken because the conditions changed with time.Hence, no statistical statements can be made.However, the figures show that the concentra-tions of chemicals were very low, but usuallyabove the limits set in the EC Directive fordrinking water (EC, 1980), Terbumetonconcentration was higher than terbuthylazine,indicating that it perhaps has more pollutionpotential since the two chemicals occur in thesame proportion in the commercial productused.

Jativa orchard. Herbicide concentrations in soilare shown in Table 7, In all cases herbicide con-centration decreased with depth. The relativelyhigh value for atrazine at 0-10 cm is presumablyderived from the last application made in spring1989. Again, as at Benifay6, in the second set ofsamples atrazine and terbutryn were below thelimits of determination, and the other triazineswere at low levels.

The water level in the orchard well was 50 mdeep. In the first water samples no herbicide was

Table 5 Herbicide concentration (mg kg ') in soil samples taken at the Benifay6 orchard

Depth (cm)

^-3030-60

Atra. = atrazineBrom = bromacil;

TabIt 6 Herbicide

Atra.

1-2

Atra. Sim.

0-02 0-04O-OI 0-02

; Sim. = simazine;Tri. = trifluralin.

concentration (|ig 1"')

Sim. Ter

<0-l 1

Ter.Cl Ter.O

0-08 0-110-01 0-01

Ter.S

0-06<0-01

Diu.

0-08<0-04

Ter.Cl = terbuthylazine; Ter.O —terbumeton; Ter.S

in well water from the Benifay6 orchard

Cl.

-8

Ter.O Ter.S

6-3 <0-l

Diu.

<0-4

Brom.

0-01<0-01

= lerbutryn;

Brom.

4-4

Tri.

0-06<0-01

Diu. = diuron;

Tri.

4 1

Atra -atrazine; Sim. = simazine; Ter .a = terbuthylazine; Ter.O = terbumeton; Ter.S. = terbutryn; Diu. = diuron;Brom. = bromacil; Tri. = trifluralin.


Table 7 Herbicide concentration (mg kg' ') in the soil samples taken at the JAtiva orchard

Depth in cm

(a) Samples taken in July 19890-10

10-2020-3030-40

(b) Samples taken in February 10-10

10-2020-3030-4040-5050-7070-90

Atra.

0-300-040-03001

1990<0-01<0-01<0-01<0-01< 0 01<0-01<0-01

Atra. = atrazine; Sim. = simazine; Ter.Cl.

Table 8 Herbicide ajncentration (mg kg~') i

Depth (cm)

Plot A0-10

10-2020-3030-4040-50

PlotB0-10

10-2020-3030-4040-50

PlotC0-20

20-4040-60

Atra.

<0-01<0-01<0-01<0-01<0-01

<0-01<0-01<0-01<0-01<0-01

<0-01<0-01<0 01

Sim.

<0-01<0-01<0-01<0-01<0-01

<0-01<0-01<0-01<0-01<0-01

<0-01<0-01<0-01

Sim.

0-050-01

<0-01<0-01

0-02<0-01<0-0I<0-01<0-01<0-01<0-01

= terbutylazine; Ter.

Ter.Cl.

0-080-030-020-01

0-030-020-020-010-01

<0-01<0-01

= terbumeton; Ter

Ter.O.

0-060-020-01

<0-01

0-040-030-030-020-010-0!0-01

S. = terbutryn.

in the soil samples taken at the Ribarroja orchard

Ter.O

traces001

tracestracestraces

traces<0-01<0-01<0-01<0-01

traces0-01

traces

Ter.a

traces0-01

traces1-01

traces

<0-010-01

tracestracestraces

traces0-01

traces

Ter.S

<0-010-03

<0-01traces

<0-01

<0-01<0-01<0-01<0-0I<0-01

<0-01<0-01<0-01

Brom.

010<0-01<0-01<0-01<0-01

<0-01<0-01<0-01<0-01<0-01

<0-01<0-01<0-01

Ter.S.

001<0-01<0-01<0-01

0-01<0-01<0-01<0-01<0-01<0-01<0-01

Diu.

0-600-07

<0-01<0-01<0-01

<0-01<0-01<0-01<0-01<0-01

<0-01<0-OI<0-01

Atra. = atrazine; Sim = simazine; Ter.O = terbumeton; Ter.Cl = terbuthylazine; Ter.S = terbutryn;Brom. = bromacil. Tri. = trifluralin.

Diu.-diuron;

found, but in the second only terbumeton wasdetected, at 0-02 ( igT ' .

Ribarroja orchard. The results from this orchardare shown in Table 8. The difference foundbetween plots A and B reflects the presence ofresidues of diuron and bromacil resulting fromthe last herbicide application, the day beforesampling for plot A. Since the commercialherbicide is a mixture of 40% diuron and 40%bromacil, the data suggest that the dissipationrates were lower. Again on examination of theresults for the three plots, it can be concludedthat there is no build-up of herbicide residues inthis location.

Bioa.ssay results

{a) Benifayd orchard. The results are given in

Table 9 for soils sampled in 1989. The data showthat the phytotoxic residues were far greater inthe 0-30 cm layer than in the 30-60 cm layer.

Results of a bioassay with the tilled soil atrates of 0,0-25,0-50,1,2 and 4 ppm of simazineare shown in Table 10. Using this growth res-ponse data, it can be estimated that the residuesin the non-tilled soil (Table 9) are the phytotoxicequivalents of simazine concentrations of 170and 0-35 mg kg"', respectively, for the two soillayers.

{b) Jativa orchard. In this case, soil from the0-10 cm layer taken in July 1989 in the tilled soiland at two dates (VII/89 and 11/90) in the non-tilled soil was bioassayed. The growth values(plant weights; x(4)±S.D.) from the threesamples were 1-22 ±0-08, 0-31 ±0-06. 0-77 ±0-08. The amount of residues decreased with


TOk ' Bioassay with Avena saliva L. in the Benifayd orchard

Depth (cm)

0-3030-60

Orchard management

Non-tillage

0-26+ 0040-75 ±011

Tillage

l-50±0161-59 ±0 25

Percentage of growthtillage/non-tillage

J747

Level of significancet

• »•*

Values are fresh weight (in g) of the five plants per pot, mean ± standard deviation of 4 replicates.tBetween orchards, and depths in the non-tillage orchard; ("P<OOi%).

Table 10 Growth response of Avena saliva L. to simazineusing Ihe Benifay6 tilled soil

Simazine (mg kg ')

00-250-501-002-004-00

x(n = 4)±S.D.

106±0100-62 ±0 070 30 ±0 030 22 + 0020 1 6 ± 0 04012 ±0 04

Peroentage treated/check

5828211611

Values are fresh weight (in g) of the five plants per pot,mean ± standard deviation of 4 replicates.

Tibk 11 Bioassay with Avena saliva L. in Ribarroja soil*

Depth (cm) Plot A PlotB

0-1010-2020-30

0 09 ±0 010-18 ±0-010-86 ±0 09

0 98 ±0 07105 ±0 08103 ±0 09

The values are fresh weight (in g) of the five plants per pot,mean ± standard deviation of 4 replicates.

Plot A: sampling day after the 1990 treatment.Plot B: sampling before the 1990 treatment.•Soil sampling date: 4/4/90.

Table 12 Bioassay with Avena saliva L. in plot C of theRibarroja orchard

Depth (cm) !t±S.D.

0-2020-40

015 ±0 020 21 ±0-080-67 ± 0-04

The values are fresh weight (in g) of the five plants per pot,mean ± standard deviation of 4 replicates.

time, but 7 months after the first samplingthere were still measurable residues in the soil.

(c) Ribarroja orchard. Plots with tilled soil(without residual herbicides) were not availablein this orchard. Table 11 shows the results of thebioassay of plots A and B. The two plots A andB had the same treatment history. The markeddifference in results must be due to theherbicide application that plot A received 1day before sampling. The difference in valuesbetween plot A and B decreased with depth.

indicating that the diuron-t-bromacil herbicideremains in the upper layers.

It is well known that the results from instru-mental methods are not completely comparableto bioassays, because they analyse specificcompounds, whereas bioassays estimate thelevel of phytotoxicity. Nevertheless there areseveral papers that show a high correlationbetween the two methods (Menges & Hubbard1970; Sheets et al., 1968; Sikka & Davis, 1966).Sheets et al. (1968) suggested that the bestestimate of dichlobenil concentration in soilwould be the average of the bioassay and GLCvalues.

In the present work the conclusions derivedfrom the two methods in the three orchards arerather similar. The fact that some degradationproducts, not analysed here, are phytotoxicmakes the bioassay technique useful in this typeof study.

The widespread use of chemical weed controlin Valencia citrus orchards has led to concernabout the behaviour of residual herbicidesfollowing repeated applications. Several authors(Dawson, Bums & Clore, 1968; Clay & Stott,1973; Burnside, 1974; Majka & Lavy, 1977;Miller et al., 1978) reported that the residuesfrom long-term applications of the herbicidesstudied here remain in the upper layers of soil.The results of the present study are consistentwith these observations.

The comparison between plots A and B inRibarroja orchard indicates that bromacil anddiuron disappear rapidly, and this also applies tothe other herbicides in plot C, as well as in theBenifay6 and Jativa orchards. Certainly thevery high total quantities of herbicides appliedin the period of 22-24 years left very smallresidues. Tucker & Phillips (1969) reportedsimilar data for bromacil and diuron in Floridacitrus soils.

Therefore it can be concluded that theherbicides studied here, applied at normal rates.

150 Gdmezde Barreda ex al.

are unlikely to accumulate in soil, even aftermore than 20 years of repeated applica-tions.

In the second sampling of the Benifay6 well,atrazine. bromacil, terbuthylazine, terbumetonand trifluralin were apparently present atabove the (EC, 1980) maximum allowableconcentration of the EC drinking waterdirective. This is important because the wellis 15 m deep and the chemicals found belongto different mobility classes (atrazine,bromacil > terbumeton, terbuthylazine >terbutryn>trifluralin; unpublished data).

As shown in Table 4, the rainfall betweenSeptember and February was approximatelytwice the average, so leaching would havebeen greater than in a normal year.

Although these results provide no statisticalproof that pesticides reached the well water,they clearly suggest that the upper layers ofthe orchard soils, under continuous no-tillagesystems in our regions, contain small amountsof residual herbicides which can subsequentlybe leached by heavy rains to deep soil layersand, from the comparison of results from theBenifayc!) well before and after heavy rains,presumably into shallow groundwaters.

Acknowledgements

We wish to thank the following for help in thepreparation of this study: the Extension Serviceofficials; Ciba-Geigy Chemical Company andDupont Chemical Company; Demetrio Machi;Francisco Parra, and REV A team; AmparoCaballer and Mike Harrison.

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