matrix-based fertilizers reduce pesticide leaching in soil

Matrix-Based Fertilizers Reduce Pesticide Leaching in Soil

James A. Entry & Robert E. Sojka

Received: 14 July 2011 /Accepted: 22 August 2011 /Published online: 15 September 2011# Springer Science+Business Media B.V. (outside the USA) 2011

Abstract The presence of pesticides in groundwaterhas been documented in several large-scale studiesand numerous small-scale investigations. Pesticideleaching through soil has been identified as a majorcause for the occurrence of these chemicals in surfaceand groundwater. We developed matrix-based fertil-izers (MBFs) that have been shown to reduce N and Pleaching. We tested the efficacy of the ionic bonds inthe MBFs to reduce 2,4-dichlorophenoxyacetic acid(2,4-D), metolachlor, thiophanate methyl, carbaryl,diazinon, and malathion leaching in soil columns.After 7 days 2,4-D, thiophanate methyl, carbaryl, andmalathion did not leach in sufficient quantities todetermine if the MBF fertilizers reduced leachingcompared with the control and the slow-releasefertilizer Polyon®. The MBF fertilizers leached fromfive to 30 times less metolachlor than the control and

Polyon® treatment. Treatments with MBF fertilizersleached from two to 72 times less diazinon than thecontrol treatment. The MBF fertilizer treatmentleached from eight to 268 less diazinon than columnsreceiving Polyon®. The MBF formulations allowcompounds with both anionic and cationic chargesto bind with the Al(SO4)3 3H2O and/or Fe2(SO4)33H2O-lignin-cellulose matrix. When pesticides areadded to the soil amended with matrix-based fertil-izers, the ion exchange matrix will likely bind themetolachlor and diazinon to the Al(SO4)3 3H2O and/or Fe2(SO4)3 3H2O-starch-cellulose-lignin matrixthereby substantially reducing leaching. The MBFscould be used to limit both nutrients and pesticideleaching from agricultural fields.

Keywords Matrix-based fertilizers . 2,4-D .

Metolachlor . Thiophanate methyl . Carbaryl .

Diazinon .Malathion . Leaching

1 Introduction

The widespread presence of pesticides and theirdegradation products in groundwater of the USA hasbeen documented in several large-scale studies andnumerous small-scale investigations (Hallberg 1989;Barbash et al. 1999; Gilliom et al. 2006). Leachingthrough soil has been identified as a major cause forthe occurrence of agrochemicals in groundwater(Flury 1996). We developed matrix-based fertilizers

Water Air Soil Pollut (2012) 223:1295–1302DOI 10.1007/s11270-011-0945-z

J. A. Entry :R. E. SojkaUSDA Agricultural Research Service,Northwest Irrigation and Soils Research Laboratory,3793 North 3600 East,Kimberly, ID 83443, USA

R. E. Sojkae-mail: [email protected]

Present Address:J. A. Entry (*) : R. E. SojkaNurtigrown LCC.,9250 Bendix Road, North, Suite 545,Columbia, Maryland 21045, USAe-mail: [email protected]

(MBFs) that contain a high concentration of ionicexchange sites that may reduce pesticide leaching.The MBFs formulations contain common inorganicnutrient compounds combined with Al(SO4)3 3H2Oand/or Fe2(SO4)3, plus starch, cellulose, and lignin(Entry et al. 2010; Entry and Sojka 2010; 2009; 2008;2007). Starch, cellulose, and lignin were chosenbecause of their high concentration of anionic andcationic exchange sites and their decompositioncharacteristics. The Al(SO4)3 3H2O and/or Fe2(SO4)3were added to the MBFs to bind directly with somepesticides and to also bind with the starch-celluloseand lignin matrix increasing binding sites. Ions boundto the Al(SO4)3 3H2O and/or Fe2(SO4)3 starch-cellulose-lignin matrix become increasingly availableto plants as the matrix components degrade. Theorganic components in the matrix should degradestarch>cellulose>lignin in the order of more to lessrapid (Donnelly et al. 1990; Entry et al. 1991).

In previous experiments, the MBFs reduced N, P,Escherichia coli, and Enterococcus in column experi-ment leachate. When Osmocote® 14-14-14, a slow-release fertilizer (SRF), combined with Al2(SO4)33H2Oand Fe(SO4)33H2O was applied to soils, 78–84% moreNH4, 58–78% more total phosphorus (TP), 20–30%more total reactive phosphorus, and 61–77% moredissolved reactive phosphorus (DRP) were leachedthrough columns than when the MBFs were applied tothe same soils (Entry and Sojka 2007, 2008, 2009,2010; Entry et al. 2010). Plant weight did not differamong fertilizer treatments. Entry and Sojka (2008)found that in three soil textures, the SRF leachatecontained a higher amount of NH4, NO3, and TP thanleachate from MBF formulations. MBFs reduced E.coli and Enterococcus spp., DRP, TP, NH4, and NO3

leaching after 15 Mg ha−1 fresh dairy manure wasapplied to soil (Entry et al. 2010). Since the ionicbinding sites comprising the MBFs are able to bind N,P, E. coli, and Enterococcus spp., these binding sitesmay be able to bind some pesticides preventing themfrom leaching into surface and groundwater.

We chose to test the efficacy of MBFs to reduce 2,4-dichlorophenoxyacetic acid (2,4-D), metolachlor, thio-phanate methyl, carbaryl, diazinon, and malathionleaching in soil columns. 2,4-D is a widely usedsynthetic auxin which is absorbed through plant leavesand then translocated to the meristems where it causesuncontrolled growth and plant death (Grossmann 2007).Metolachlor (2-Chloro-N-(2-ethyl-6-methyl-phenyl)-N-

(1-methoxypropan-2-yl) acetamide) is used for grassand broadleaf weed control in corn, soybean, peanuts,sorghum, and cotton. Metolachlor has been detected inground and surface waters in concentrations rangingfrom 0.08 to 4.5 μg L−1 throughout the USA(Pothuluri et al. 1997; Shaner and Henry 2007).Carbaryl (1-naphthyl methylcarbamate) is an insecti-cide used on a wide variety of fruit trees, vegetables,turfgrass, and ornamental plants (Venkateswarlu, et al.1980). In aqueous solutions, carbaryl hydrolyzes to 1-naphthol, methylamine, and CO2 (Vontor et al. 1972).Carbaryl has low solubility in water and sorption tosoil particles depends on the organic matter content ofthe soil (Venkateswarlu, et al. 1980). Carbaryl ismoderately mobile in soils and can be found in thegroundwater and surface water due to its widespreaduse and persistence under acidic conditions (Bacci etal. 2008). Diazinon (O,O-diethyl-O-(2-isopropyl-6-methyl-pyrimidine-4-yl) phosphorothioate) kills a widevariety of insects by inhibiting acetylcholinesterase(Zhang and Pehkonen 1999). Diazinon released intothe environment is moderately persistent and moder-ately mobile and was the most frequently detectedinsecticide in surface waters prior to the phase-out ofurban uses in 2004. Since that time, diazinon concen-trations have declined in 90% of sampled streams inthe Midwestern and northeastern USA, many showingdeclines of 50% or more during the summer months(Phillips et al. 2007). Thiophanate methyl (dimethyl4,4′-(o-phenylene)) bis(3-thioallophanate) is a sys-temic fungicide effective against a wide range offungal pathogens. Thiophanate methyl persists insoil for 3–4 weeks and is not readily leached (Haithand Rossi 2003). Malathion (O,O-dimethyl S-(1,2-dicarbethoxyethyl) phosphorodithioate) is an organ-ophosphate insecticide widely used in agriculture,residential landscaping, public recreation areas, andfor mosquito control. Malathion degrades rapidly insoils (Okamoto and Shibamoto 2004) and is noteasily leached (Tao et al. 2009). The pesticideleaching potential indices of the pesticides used inthis study are 2,4-D=41, thiphanate methyl=31,carbaryl=39, malathion=11, metolachlor=55, anddiazinon=41 (McLaughlin et al. 1997). The highernumbers indicate that a pesticide is more likely tomove through a soil and potentially contaminatesurface or groundwater. Our objective was todetermine if MBFs would reduce 2,4-D, metolachlor,thiophanate methyl, carbaryl, diazinon, and malathi-

1296 Water Air Soil Pollut (2012) 223:1295–1302

on leaching compared with the SRF Polyon®through soil columns.

2 Materials and Methods

2.1 Experimental Design

The experiment was arranged in a completelyrandomized design (Kirk 1995) with eight fertilizertreatments (described above)×three replications for atotal of 24 columns planted with Kentucky bluegrass(Poa pratensis L.). We collected and analyzedleachate at 1, 3, and 7 days after pesticide applicationfor a total of 72 leachate measurements. Pesticidecollection was limited to 7 days to eliminate the majorchanges in the concentration of chemical in leachatedue to degradation of these chemicals in this soil.

2.2 Column Description and Soil Description

A screen with 2.00 mm polyvinyl spacing was cutinto squares (125×125-mm) and secured at thebottom of each 10-cm diameter×30-cm long polyvi-nyl chloride cylinder. A 10-cm diameter polyvinylscreen with a 0.10-mm mesh was then placed at thebottom of each cylinder. A 14-cm diameter plasticfunnel was placed below each column in the rack andsecured. Three kilograms of soil were placed in eachcolumn (columns were filled to 25 cm) leaving a 5-cm space at the top of each column. Soil in columnswas loosely packed and then repeatedly washed withreverse osmosis water to flush nutrients that could beloosely held to soil particles. Columns were allowedto drain for 1 h prior to the start of leachate collectionas described below. The soil was a coarse-loamy sandand classified as a mixed non-acid, mesic XericTorriorthent. Soil physical, chemical, and microbio-logical properties are presented in previous reports(Entry et al. 2004; Sojka et al. 2005).

2.3 Fertilizer Treatments, Pesticide Application,and Growing Conditions

The MBF formulations are comprised of inorganicchemicals combined with starch, cellulose and lignin(Sigma, St. Louis, MO). The amounts of fertilizer asmg N and mg P per column and as kg N ha−1 and kgP ha−1 are presented in Table 1. The MBF formula- T

able

1Chemical

compo

unds

used

tocomprisetheslow

-release

fertilizer,andthematrix-basedfertilizers

with

andwith

outadditio

nalAvail®

Treatment

12

34

56

78

Fertilizer

CONT

(mgcompound

percolumn)

Polyon®

(mgcompound

percolumn)

MBF6a

MBF6a

MBF6a

MBF7a

MBF7a

MBF7a

Rate

Low

(mgcompound

percolumn)

High(m

gcompound

percolumn)

Avail®

(mgcompound

percolumn)

Low

(mgcompound

percolumn)

High(m

gcompound

percolumn)

Avail®

(mgcompound

percolumn)

Al(SO4) 33H

2O

000.0

000.0

000.0

000.0

000.0

366.0

732.0

366.0

Fe 2(SO4) 3

000.0

000.0

400.0

800.0

400.0

800.0

1,600.0

800.0

Al(OH4) 33H

2O

000.0

000.0

1,000.0

1,000.0

1,000.0

1,000.0

1,000.0

1,000.0

Starch

000.0

000.0

1,000.0

1,000.0

1,000.0

1,000.0

1,000.0

1,000.0

Cellulose

000.0

000.0

1,000.0

1,000.0

1,000.0

1,000.0

1,000.0

1,000.0

Lignin

000.0

000.0

1,000.0

1,000.0

1,000.0

1,000.0

1,000.0

1,000.0

Total

mgN

column

000.0

338.7

200.0

400.0

107.0

107.0

214.0

142.0

Total

mgPcolumn

000.0

000.0

149.0

298.0

435.0

435.0

870.0

583.0

Total

Nas

kgN

ha−1

000

191

255

510

136

136

272

180

Total

Pas

kgPha

−1000

000

189

378

554

554

1,108

740

aThe

amou

ntandform

ofchem

icalsin

MBF6andMBF7form

ulations

arestated

inEntry

andSojka

(201

0)

Water Air Soil Pollut (2012) 223:1295–1302 1297

tions were added as a powder, and SRF (Polyon®,ESN® and Avail®) were added as granular pellets andbroadcast into the top 5 cm of soil (Table 1).Pesticides were applied to a column which is8.098×10−7 ha2. Pesticide rate per hectare=numberof hectares (8.098×10−7 ha2/column)×% active in-gredient (ai=% ai/100)×dilution factor of pesticideconcentrate in the container×dilution factor in water.Pesticides were applied to columns at rates commonlyapplied to crops grown in the USA (Table 2). Theappropriate amount of each of the six pesticides wasadded to a single 100-ml volume of reverse osmosiswater and then slowly poured to the inner 5-cmdiameter (19.62 cm) of each column to minimize flowalong column walls. Columns were given 50-mL ofwater daily to maintain field capacity. Leachate didnot flow through columns when 50-mL water wasapplied. We collected leachate at 1, 3, and 7 days afterpesticide application by giving plants 200-mL reverseosmosis water on the above-stated days in lieu of the50-mL daily reverse osmosis water. On each samplingday, approximately 100-mL leachate was collectedfrom each column. Subsamples were analyzed for 2,4-D, metolachlor, thiophanate methyl, carbaryl, diazinon,and malathion as described below. The total amount ofeach pesticide leached was calculated from pesticideconcentration multiplied by the amount of water leachedfrom that column on that sampling date.

2.4 Pesticide Analysis

Pesticide concentrations were determined using anAgilent 1100 Liquid Chromatograph equipped with aG1946D Mass Selective Detector. An Agilent C18 at2.1×150 mm column was used for analysis. A gradientof 10-mM ammonium acetate, methanol, and acetoni-trile was used for analysis. The gradient was as followedas described in Table 3. Retention times and acquired

ions for each compound (the first ion listed for eachcompound was used to report the quantization of thatcompound) for each pesticide are shown in Table 4.The detection limit was 5 μg L−1 for each pesticide.

2.5 Statistical Analysis

All data sets were tested for normal distribution withStatistical Analysis Systems and then analyzed usinggeneral linear models procedures for a completelyrandom design. In all analyses, residuals were equallydistributed with constant variances. Differencesreported throughout are significant at a p≤0.05, asdetermined by the least squares means test.

3 Results

After 7 days, 2,4-D, thiophanate methyl, carbaryl, andmalathion did not leach in sufficient quantities todetermine if the MBFs reduced leaching comparedwith the control and the Polyon® SRF (Table 5). The

Table 2 Pesticide rate applied to columns

Pesticide μg ai column−1 lbs ai acre−1 kg ai ha−1

2,4-D 8.5 4.250 4.760

Metolachlor 6.0 3.000 3.360

Thiophanate methyl 1.6 0.800 0.896

Carbaryl 1.0 0.500 0.560

Diazinon 6.0 3.000 3.360

Malathion 1.5 0.750 0.840

Table 3 Pesticide analysis using an Agilent C18 2.1×150 mmcolumn using 10 mM NH4 acetate, methanol, and acetonitril

Time 10 mM NH4 acetate Methanol Acetonitril

0.00 70 15 15

9.00 10 45 45

9.10 10 45 45

12.00 10 45 45

12.10 70 15 15

18.00 70 15 15

Table 4 Retention times and acquired ions for each pesticide

Compound Retentiontime

Ions

2,4-D 4.916 219, 161, 163, 221

Thiophanate methyl 9.041 343, 311, 344, 365

Carbaryl 9.723 202, 219, 145

Malathion 12.591 331, 285, 332, 353

Metolachlor 13.169 284, 254, 252, 285, 286, 306

Diazinon 13.899 305, 153, 169, 306

a The first ion listed for each compound was used to report thequantization of that compoundb The detection limit was 5 μg L−1 for each pesticide


metolachlor concentration was five to 30 times lowerin the MBF treatments than the control and Polyon®treatments. The total amount of diazinon leachedMBF treatments was two to 35 times less from thecontrol and Polyon® treatments. The total amount ofmetolachlor leached from MBF treatments was two to25 times less from the than the control and Polyon®treatments (Table 6). The diazinon concentration wastwo to 268 times lower in the MBF treatments thanthe control and Polyon® treatments.

4 Discussion

Metolachlor and diazinon started to leach out of thecontrol and Polyon® SRF treatments after soil at7 days. Carbaryl and 2,4-D had similar leachingpotential indices but the amount of pesticides leachedfrom the control and the Polyon® treatments were lowor nonexistent. Malathion and thiophanate methylhave lower leaching potential indices and are notexpected to leach through columns until later in thestudy. Only small amounts of pesticides were leachedthrough the MBF formulations while much greateramounts of metolachlor and diazinon were leachedthrough control and Polyon® treatments indicatingthat the MBF formulations reduced pesticide leach-ing. Further testing is necessary to determine if theseMBF formulations will reduce 2,4-D, carbaryl, thio-phanate methyl, and malathion leaching.

Pesticide additions to soils are presently controlledvia various commercial micro-encapsulation techni-ques using styrene cross-linked anhydride carboxylcompounds, ethylcellulose, organoclays, and modi-fied smectitic clays with organic cations. Micro-encapsulation is defined as the process of coatingan active substance (molecules, solid particles, orliquid globules consisting of various materials),resulting in particles of micrometric size (Arshady1999). Microencapsulated ethylcellulose formula-tions reduced alachlor loss by 54% compared withthe commercial formulations (Dowler et al. 1999;Fernández-Urrusuno et al. 2000; Sopeña et al. 2007).Commercial slow-release pesticide formulationshave been encapsulated with a hydrophobic barrieroften from various styrene compounds, combinedwith mono- or di-carboxylic acids anhydride car-boxyl groups. These carboxyl groups are cross-linked with aromatic amines, aliphatic amines, andaromatic isocyanates (Asrar et al. 2004; Cryer andWilson, 2009). Celis et al. (2005) tested the efficacyof organoclays to bind hexazinone to reduce offsitemovement of pesticides in soil. The authors foundthat hexazinone formulations displayed slow-releaseproperties in water, retarded herbicide leachingthrough soil columns, and maintained an herbicidalefficacy similar to that of the currently availablecommercial powder formulations. Carrizosa et al.(2004) found that modified smectitic clays withorganic cations via cation-exchange reactions pro-

Table 5 Pesticide concentration in leachate after flowing through columns with control (no fertilizer applied), Polyon® (43-0-0) slow-release fertilizer (SRF), and matrix-based fertilizers (MBF) applied at different rates

Pesticide

Fertilizer 2,4-Da

(μg pesticide L−1

leachate)

Thiophanate methyla


leachate)

Carbaryla


leachate)

Malathiona


leachate)

Metolachlora


leachate)

Diazinona


leachate)

Control (no fertilizer applied) 2.56 a 0.00 a 0.00 c 0.00 b 216.56 a 39.77 b

Polyon® (43-0-0) 0.00 b 0.00 a 0.00 c 0.00 b 216.33 a 147.33 a

MBF6b—low rate 0.00 b 0.00 a 1.11 ab 0.00 b 10.44 d 4.65 d

MBF6b—high rate 0.00 b 0.00 a 3.33 a 0. 55 a 7.22 d 0.55 d

MBF6b low rate+avail 0.00 b 0.00 a 0.55 c 0.00 b 10.00 d 5.00 d

MBF7b—low rate 0.00 b 0.00 a 1.11 ab 0.00 b 31.89 bc 17.22 c

MBF7b—high rate 0.00 b 0.00 a 2.78 a 0.00 b 42.33 b 3.11 d

MBF7b—low rate+avail 0.00 b 0.00 a 0.55 c 0.00 b 21.33 bc 17.78 c

a In each column and soil, values followed by the same letter are not significantly different as determined by the least square meanstest (p≤0.05, n=9)b The amount and form of chemicals in MBF6 and MBF7 formulations are stated in Entry and Sojka (2010)


duces sorbents with an increased sorption capacityfor (bentazone [3-isopropyl-1H-2, 1, 3-benzothiadiazin-4 (3H) one 2, 2-dioxide] and dicamba [2-methoxy-3,6-dichlorobenzoic acid] in columns). Leaching losses insoil columns were reduced from 94% for freebentazone to 55–90% for bentazone-OCl complexes,and from 100% for technical dicamba to 50–100% fordicamba-OCl complexes. The MBFs should not havelong-term effects because in contrast to the abovemicro-encapsulation formulations the MBFs are com-posed of natural compounds and do not containcompounds that can possibly harm humans or wildlife.

The new MBF formulations may allow pesticideswith both anionic and cationic charges to bind withthe Al(SO4)3 3H2O and/or Fe2(SO4)3 3H2O-lignin-cellulose matrix. When pesticides are added to thesoil, new matrix-based fertilizers likely bind thepesticides to the Al(SO4)3 3H2O and/or Fe2(SO4)33H2O-starch-cellulose-lignin matrix thereby substan-tially reducing leaching. After the starch-cellulose-lignin matrix with Al(SO4)3 3H2O and/or Fe2(S-O4)33H2O is applied to soil the soil microorganismswill degrade the starch in the matrix comparativelyrapidly and will create some ionic exchange sites. Thecellulose will degrade less rapidly than starch butmore rapidly than lignin and is expected to retainmost of its ionic exchange sites for at least 1 year inmost soil environments. Pesticide leaching isexpected to be controlled to a large degree by varyingthe relative amounts of starch-cellulose-lignin matrixwith Al(SO4)3 3H2O and/or Fe2(SO4)33H2O in themixture. The efficacy of the MBFs to reduce pesticideleaching is expected to vary with the amount andstrength of ionic bonding, which will be controlled bythe amount and quality of organic matter and clays ina soil. Pesticide leaching in the coarse-loamy sandused in this study allows greater nutrient andpresumably pesticide leaching than in silt or claysoils (Entry and Sojka 2008).

MBFs are formulated as a solid matrix and whenapplied to soil, not only reduce the leaching of somepesticides, but also nutrients and pathogenic bacteria.The physico-chemical properties of pesticides, such ashydrophobicity, charge, and elasticity affect theiradherence to organic and inorganic particles in theMBFs, and therefore, the MBFs ability to controlleaching of each pesticide can be expected to vary.Improved technology cannot substitute fully foradhering to sound land management practices.T

able6

Totalam

ount

ofpesticideleachedfrom

control(no

fertilizerapplied),P

olyo

n®(43-0-0)

slow

-release

fertilizer(SRF),andmatrix-basedfertilizers(M

BF)appliedatdifferent

rates

Pesticide

Fertilizer

Leachate(m

l)2,4-Da

(μgpesticideL−1

leachate)

Thiophanate

methyla

(μgpesticideL−1

leachate)

Carbaryla

(μgpesticideL−1

leachate)

Malathion

a

(μgpesticideL−1

leachate)

Metolachlor

a

(μgpesticideL−1

leachate)

Diazinona

(μgpesticideL−1

leachate)

Control

(nofertilizerapplied)

128a

0.172a

0.000a

0.000c

0.000b

3.281a

1.115b

Polyon®

(43-0-0)

128a

0.000b

0.000a

0.000c

0.000b

3.289a

2.391a

MBF6b—

low

rate

124a

0.000b

0.000a

0.122b

0.000b

1.984b

0.320c

MBF6b—

high

rate

121a

0.000b

0.000a

0.528a

0.045a

1.129b

0.069c

MBF6b

low

rate+avail

126a

0.00

0b

0.000a

0.152b

0.000b

0.132c

0.455c

MBF7b—

low

rate

115a

0.00

0b

0.000a

0.091b

0.000b

1.601b

0.474c

MBF7b—

high

rate

115a

0.00

0b

0.000a

0.247b

0.000b

1.745b

0.205c

MBF7b—

low

rate+avail

125a

0.00

0b

0.000a

0.058b

0.000b

1.551b

0.594c

aIn

each

columnandsoil,

values

follo

wed

bythesameletterareno

tsign

ificantly

differentas

determ

ined

bytheleastsquare

means

test(p≤0

.05,

n=9)

bThe

amou

ntandform

ofchem

icalsin

MBF6andMBF7form

ulations

arestated

inEntry

andSojka

(201

0)


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