The Role of Sugarcane Residues in the Sorption and Leachingof Herbicides in Two Tropical Soils

Fabrício Garcia Giori & Valdemar Luiz Tornisielo &

Jussara Borges Regitano

Received: 11 November 2013 /Accepted: 19 March 2014 /Published online: 1 April 2014# Springer International Publishing Switzerland 2014

Abstract Sugarcane is a major crop in Brazil that gen-erates huge amounts of organic residues that are usuallyleft deposited in, or applied to the soil, and thereby affectthe behavior of herbicides. This study assessed the ef-fects of sugarcane residues (straw, ash, and compost)and residence time (“aging”) on the sorption of alachlorand diuron in two contrasting soils (LVd and LVAd), aswell as the effects of these residues on the leaching ofalachlor. Adding straw and compost had no effect,whereas adding ash significantly increased sorption ofboth herbicides. Aging (28 days) increased apparentsorption distribution coefficients (Kd,app values) by 1.2to 2.3 times. Straw and ash amendments resulted in lessleaching of alachlor (<1.0 % of the applied amount) thancompost or control soil (~6 % of the applied amount).The straw retained ~80 % of the applied alachlor duringleaching. Although this may be overrated due to anartifact of the methodology adopted, alachlor retentionin the straw could not be predicted by the use of Kd,app.The transport potential of alachlor may be overestimatedif aging and sugarcane straw management are not fac-tored into the models.

Keywords Diuron . Alachlor . Straw. Ash . Compost .

Transport

1 Introduction

Sugarcane is one of the most important crops in Brazil,occupying more than 8.5 million ha, producing 40million Mg of sugar and 24 billion L of ethanol (harvestof 2011/2012). The sector moves more than US$ 50billion, which corresponds to nearly 2 % of Brazil’sgross income and generates 1.3 million jobs (UNICA2012). In recent years, sugarcane burning practices havebeen phased out giving rise to 8 to 20 Mg ha−1 of strawthat enhances soil organic fraction and leads to improve-ments in chemical, physical, and biological soil attri-butes (Ceddia et al. 1999; Pinheiro et al. 2010). Previ-ously, straw burning resulted in the accumulation of ashand released large amounts of greenhouse gases andashes into the atmosphere. Furthermore, other sugarcaneindustry wastes, such as filter cake, vinasse, and boilerash (which corresponds to the bagasse burnt in theboiler), as well as their composts are now applied tosoils in order to reduce the cost of mineral fertilizers. In2011, nearly 11 million Mg of filter cake, 4 million Mgof boiler ash, and 380 million m3 of vinasse wereyielded, which correspond to 630,000 Mg of urea,225,000 Mg of MAP, and 1,800,000 Mg of KCl (about2.6 million Mg of fertilizers) (Luz and Korndörfer2011). These practices may reduce pesticide contamina-tion of surface and ground waters due to either sorptionenhancement in the residues or transport hindrance since

Water Air Soil Pollut (2014) 225:1935DOI 10.1007/s11270-014-1935-8

F. G. Giori : J. B. Regitano (*)Department of Soil Science, College of Agriculture “Luiz deQueiroz”, University of São Paulo - ESALQ/USP,P.O. Box 9, 13418-900 Piracicaba, SP, Brazile-mail: regitano@usp.br

V. L. TornisieloEcotoxicology Laboratory, Center for Nuclear Energy inAgriculture, University of São Paulo - CENA/USP,P.O. Box 96, 13400-970 Piracicaba, SP, Brazil

there is no ash to co-transport sorbed pesticides to thebodies of water (Langenbach et al. 2008; Dal Boscoet al. 2012). Additionally, the remaining straw is capableof reducing erosion by up to 32 % (Rossetto 2010).

The availability of herbicides in the soil solution isthe primary factor that dictates transport and degradationof pesticides and effectiveness of weed control, and it isinversely related to its sorption potential. Soil sorptionof non-polar or low-polarity herbicides is usually relatedto hydrophobic partition and organic carbon content(Dorado et al. 2005; Liu et al. 2010). The use of reliablesorption distribution coefficients (Kd values) in modelsto predict either the transport or the environmental fateof pesticides is an important tool that provides usefulinformation at a lower cost than laboratory or fieldstudies. However, in order to generate reliable predic-tions, the parameters must be calibrated to reflect eachindividual set of soil management conditions andphysical-chemical attributes of the soil and moleculesunder study. Furthermore, the residence time of a herbi-cide in soil also affects its sorption potential, which isknown as the aging effect. Increased Kd values withaging have been reported for various classes of herbi-cides (Regitano et al. 2006; Regitano and Koskinen2008; Martin et al. 2012), but it was not significant inthe case of dicamba (Menasseri et al. 2003).

The environmental fate of pesticides already beenevaluated under many scenarios, but with little regardto the effects of using sugarcane residues. However,such use would represent a suitable solution for thedisposal of wastes generated by the sugarcane industryin Brazil. Interception of herbicides by sugarcane strawor other residues has been examined only recently fo-cusing mostly on weed control effects (Correia et al.2013). The literature shows that crop residues and otherorganic wastes may enhance sorption, reduce leachingand surface runoff (Selim et al. 2003; Yang et al. 2006;Langenbach et al. 2008), but the magnitude of theseeffects will depend on environmental factors (e.g., oc-currence, intensity, and duration of rainfall) and on theherbicides properties (e.g., their solubility in water).

A l a c h l o r ( 2 - c h l o r o - 2 ' , 6 ' - d i e t h y l -N -methoxymethylacetanilide) and diuron (3-(3,4-dichlorophenyl)-1,1-dimethylurea) are herbicides usedon a large scale in Brazil. They are registered for pre-emergence application (diuron can be used as a post-emergent as well) to various commercially importantcrops, including sugarcane (Rodrigues and Almeida2011). Despite their importance for agriculture, these

molecules have been detected in both surface andground waters (Vryzas et al. 2012a) and may therebyimpact human health and the equilibrium of aquaticecosystems. Understanding how these herbicides be-have and where they ultimately end up in the environ-ment under the new no-burn sugarcane cropping regimein Brazil is critical to both the controlling of weeds andthe minimizing of negative environmental impacts.Thus, the aim of this study was to assess how sugarcaneresidues and soil residence time (“aging”) affect sorp-tion of alachlor and diuron in soils as well as the effectsof these organic residues on the leaching of alachlor dueto its high mobility.

2 Materials and Methods

2.1 Herbicides and Soils

Analytical (Fluka Analytical, Seelze, Germany) andradiolabeled (14C-uniform-ring-labeled, Ciba Geigy,Delhi, India) standards of the herbicides alachlor (spe-cific activity=3.70 MBq mg−1 and purity >98 %) anddiuron (specific activity=2.43 MBq mg−1 and purity>98 %) were used.

Soils (LVAd and LVd) were classified as typichapludoxes (Soil Survey Staff 1999) and collected fromthe surface layer (0–10 cm) of sugarcane-growing areas(located in the small towns of Novo Horizonte andPradópolis in the state of São Paulo, Brazil). Sugarcanehas been grown in these towns for approximately50 years, and in the last 5–6 years, they have adopteda no-burn harvest policy. These soils were selectedbecause they are representative of sugarcane areas, butdiffer in texture and organic carbon contents (Table 1).Soil samples were air-dried, sieved through 2-mmmesh,and stored at ambient temperature. Texture was quanti-fied via densimetry. Acidity (pH) was determined in0.01 mol L−1 CaCl2. Calcium, potassium, and magne-sium were extracted using the ion-exchange resin meth-od and Ca+2 and Mg+2 determined by atomic absorptionspectrophotometry (Perkin Elmer, AAnalyst 400) andK+ with flame photometry (Digimed, DM-62). Potentialacidity (H+Al) was determined via pH-SMP, and theconcentration of total soil organic carbon via dry com-bustion in an elemental autoanalyzer (Leco, TruSpecCN). Cation-exchange capacity (CEC) was calculatedas the ∑Ca+2, Mg+2, K+, and H+Al. Poorly crystallized(“amorphous”) iron, aluminum, and manganese oxides

1935, Page 2 of 9 Water Air Soil Pollut (2014) 225:1935

were determined using an acid solution of ammoniumoxalate and “free” or crystalline iron, aluminum, andmanganese oxides using a dithionite-citrate-bicarbonate(DCB) solution (Camargo et al. 2009) (Table 1).

2.2 Residues

The straw (SP91-1285 variety) was collected aftermechanized harvesting, oven-dried (65 °C for 3 days),and either sieved through 8-mm mesh for the sorptionexperiment or cut into ~2.5-cm fragments for theleaching experiment. Ash was obtained by burningstraw in a partially closed container for 8 min(~280 °C). The particle size distributions of the ash were43, 36, 9, and 12 % for mesh sizes of <0.30, 0.30–0.84,0.84–1.19, and 1.19–2.50 mm, respectively. Compostwas obtained by composting filter cakes and boiler ashin a 2:1 proportion (v/v) for 80 days, and then sievedthrough 2-mm mesh. The chemical and physical attri-butes of the organic residues were determined accordingto Alcarde (2009) and are presented in Table 2.

2.3 Soil Amendments and Aging on the Sorptionof Alachlor and Diuron

Aliquots of 5 g of air-dried soils were placed intocentrifuge tubes (Teflon, 50mL) and then amended with5.3 and 14Mg ha−1 of ash and straw, respectively, whichcorresponds to the mean values remaining in the fieldafter the sugarcane had been harvested with and withoutburning, respectively, and with 10 Mg ha−1 of compostwhich corresponds to the mean value applied to thefield. It was estimated assuming soil density equals to1.2 g cm−3 and soil depth equals to 10 cm. The amend-ments were not mixed, but layered on the surface of thesoils. Then, 50 μL of the herbicide solutions (280 and267 μg mL−1 for alachlor and diuron, respectively,having radioactive concentrations of ~35 kBq mL−1)were applied to reach the field rates (= 3.36 and

3.20 kg a.i. ha−1 for alachlor and diuron, respectively).Afterwards, soil moisture contents were adjusted andmaintained at 75 % of field capacity for 0 (t0), 7 (t7), and28 days (t28), in a semi-dark room at 25±2 °C (the tubeswere kept partially open to avoid anaerobiosis). Aftereach incubation period, replicate soil-residue sampleswere extracted with 10 mL of 0.005 mol L−1 CaCl2solution by shaking in a horizontal shaker at 160 rpmfor 24 h. The tubes were centrifuged at 3,000 rpm(830g) for 15 min and 1-mL aliquots of the supernatantsanalyzed for 14C by liquid scintillation counting (LSC)(Packard, Tri-carb 1500). The supernatants werediscarded, and the remaining slurries were dried in aventilation oven (40 °C, 48 h) and macerated, andtriplicates of 0.20 g subsamples were combusted usinga biological oxidizer (900 °C, for 3 min) (Harvey In-struments, OX500) to determine the sorbed concentra-t ions . The resul t ing 14CO2 was trapped inmonoethanolamine-basis scintillation solution and the14C quantified by LSC. Recovery of the applied radio-activity ranged from 94 to 110 % (data not shown).

To determine the identity of the 14C, the supernatantswere concentrated in a ventilation oven (40 °C, 48 h)and identified via thin layer chromatography (TLC)using a radio scanner (Berthold GmbH & Co.) . Thesolvent systems were isopropyl alcohol, dichlorometh-ane, and formic acid (4:5:1v/v/v) for alachlor and hexaneand acetone (3:2 v/v) for diuron. For all treatments, 14Ccorresponded exclusively to the parent molecules (datanot shown).

To calculate apparent sorption distribution coeffi-cients (Kd,app, L kg−1) after different aging periods, itwas assumed that the CaCl2-extractable fraction repre-sented the solution phase concentration (Ce’), theoxidated fraction represented the sorbed phase concen-tration (S’), and thatKd,app=S’/Ce’ (Regitano et al. 2006).We use the word apparent because the coefficients werenot estimated according to traditional sorption experi-ments, but the literature considers this approach

Table 1 Chemical and physical attributes of soils

Soils pH CEC C FeDCB FeOx AlDCB AlOx MnDCB MnOx Sand Silt Clay

mmolc dm−3 g kg−1

LVAd 6.4 58.9 6.8 11.9 0.7 3.8 0.5 0.4 0.05 768 30 202

LVd 5.1 84.5 20.0 117.5 4.8 20.5 5.6 1.4 0.6 98 218 684

Fe, Al, and MnDCB crystalline oxides, Fe, Al, and MnOx poorly crystallized oxides

Water Air Soil Pollut (2014) 225:1935 Page 3 of 9, 1935

reasonable since Kd,app attained at time zero usuallygenerates similar values to the traditional Kd values(Regitano et al. 2006; Regitano and Koskinen 2008).

2.4 Soil Amendments on the Leaching of Alachlor

Alachlor and the LVAd soil were selected because theyrepresented the worst scenario for leaching due to thelowest sorption of alachlor in this soil. The study wascarried out in accordance with OECD protocol (OECD2004), with minor adaptations.

Glass columns (length=30 cm, diameter=5 cm, anda conical end) were used to pack the soils. Fiberglassand sterilized sand (with HCl) were added to the conicalportion to serve as a support. Soil packing was donemanually up to a height of 20 cm, with a density of~1.48 g cm−3. The residues (15.0 g of straw, 8.0 g ofcompost, and 3.5 g of ash, which corresponded to thesame application rates of the previous assay consideringsoil weight) were added to the top of the soils, and a finelayer of glass wool was used to ensure the homogeneousdispersion of the water and to avoid surface disturbance.Soil columns were then saturated by capillarity with a0.005 mol L−1 CaCl2 solution and excess water drainedby gravity. Immediately afterwards, 200 μL of the 14C-alachlor solution at 8,125 μg a.i. mL−1 (radioactiveconcentration of~429 kBq mL−1) were added to thecolumns to represent field rate (3.36 kg a.i. ha−1). Thecolumns were stored in a semi-dark room at a tempera-ture of 25±2 °C. The water (170 mm of 0.005 mol L−1

CaCl2 solution) was applied using a peristaltic pumpwith continuous flow for 48 h.

The leachate was collected at 12-h intervals and1-mL aliquots analyzed via LSS. After 48 h, soil sam-ples were removed from the inside of the columns withpressurized air in 5-cm sections, placed in aluminumcontainers, air-dried, macerated, and homogenized forposterior oxidation of subsamples (0.2 g), as describedin the sorption experiment. The straw was removed

separately from the 0–5 cm layer, air-dried, macerated,and oxidized to determine herbicide concentration. Ashand compost could not be separated from the top layer.Recovery of the applied radioactivity varied from 94.9to 108.2 %, with a mean value of 104.5±6.8 % (data notshown). The percentages of the herbicide leached orretained in each soil layer were subjected to varianceanalysis and to Tukey’s test (p<0.05).

3 Results and Discussion

3.1 Soil Amendments and Aging on the Sorptionof Alachlor and Diuron

The retention of the studied herbicides varied stronglyaccording to soil type, residence time (aging), and or-ganic residue amendments (Table 3). Initially (at t0),alachlor showed a low to moderate sorption potentialfor the soils and their respective treatments (Kd,app<1.6 L kg−1 in the LVAd soil and <4.0 L kg−1 in theLVd soil), except for the ash (Kd,app=5.4–7.6 L kg−1).This is in line with the results of previous studies usingbatch sorptionKd values (Laabs and Amelung 2005; DalBosco et al. 2012). By contrast, the sorption potential ofdiuron was consistently high at t0 (Kd,app=5.5–94.6 L kg−1) (Table 3). These values are also similar tothose reported in the literature for batch experiments(Inoue et al. 2006; Liu et al. 2010). Therefore, the useofKd,app seems reasonable since the values attained hereat t0 (Kd,app for alachlor=1.2 and 3.8 and for diuron=5.5and 50.4 L kg−1 in the LVAd and LVd, respectively)were close to the batch Kd values obtained in our previ-ous work (Kd for alachlor=1.0 and 3.2 and for diuron=5.9 and 52.1 L kg−1 in the LVAd and LVd, respectively)(Giori et al. 2014, in press), as well as those in theliterature. Moreover, their use is advantageous oncevalues are attained at proper soil moisture and allow-ances are made for aging effects. In general, weakly

Table 2 Chemical and physical attributes of the straw, ash, and compost

Wastes pH K2O P2O5 Mg Ca S N C C:N CEC Density

CaCl2 g kg−1 mmolc kg−1 g cm−3

Straw 5.6 2.1 1.9 1.1 18.2 1.7 6.4 446.0 69:1 250 0.23

Ash 8.0 9.5 5.7 2.9 32.3 3.6 10.1 316.0 31:1 340 0.23

Compost 7.9 3.7 10.4 3.6 21.7 1.5 7.2 83.5 12:1 150 0.66

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sorbed or easily desorbed pesticides are readily availablefor leaching and transformation in soils (Alexander2000; Regitano et al. 2006).

It is well known that diuron has greater sorptionpotential than alachlor, in part due to its lower solubilityin water (40 versus 200 mg L−1) that favors hydrophobicpartitioning. In addition, the retention of both herbicidesin the LVdwas higher than in the LVAd (Table 3), a resultthat had been expected, based on the greater organiccarbon and clay contents and CEC of the former soil(Table 1). Both herbicides are sorbed to soils primarily byhydrophobic partitioning, which implies that sorption ismostly related to the organic fraction of the soil (Liu et al.2010). Clay content may play an important role in theirsorption, but only when organic carbon content in the soilis very low (<1 %). Tropical soils showed Koc values of74–150 and 741–1,080 L kg−1 for alachlor and diuron,respectively (Inoue et al. 2006; Oliveira et al. 2001).

The Kd,app values increased considerably with resi-dence time (aging) of the molecule in the soils (Table 3).In certain cases, alachlor even showed high sorptionpotential (Kd,app>5 L kg−1). Increases in Kd,app valueswere more abrupt in the first 7 days of incubation,except for diuron in the LVd due to its high initialsorption (>94.8 % of applied amount) (Fig. 1). It is wellknown that pesticide sorption–desorption takes place intwo distinct phases: a rapid initial phase followed by aslower secondary phase (Hatzinger and Alexander1995). In general, the initial phase is due to rapid sorp-tion at easily available (external) sites, while the slower

phase is associated with diffusion/immobilization to-wards the interior of the soil matrix (Alexander 2000),reducing pesticide desorption and availability to soilmicroorganisms. Within our incubation period(28 days), Kd,app values increased 1.6–2.2 times foralachlor and 1.3–2.3 times for diuron, and were morestriking in the LVAd soil due to its lower bufferingcapacity (CEC). The mechanisms by which moleculesand especially hydrophobic molecules become moreretained with aging remain poorly understood. The solidphase of the organic matter (Brusseau et al. 1991), itsnanopores (Chung and Alexander 1998), and the slowdiffusion to the interior of soil aggregates (Brusseauet al. 1991) play important roles in this process, whichmay result in a fraction that is resistant to desorption andlead to the formation of non-extractable (bound) resi-dues (Mamy and Barriuso 2007). It is likely that thesemechanisms act jointly to some degree, enhancing pes-ticide sorption. Thus, it is important that aging effectsare examined so that transport models can be adequatelyparameterized.

Straw and compost had little effect on the sorption ofalachlor and diuron (Table 3). Conversely, ash markedlyincreased their sorption ratifying its trapping efficiencyfor organic molecules. In the LVAd, ash increased sorp-tion of alachlor by ~4 times and diuron by ~10 times. Inthe LVd, for both herbicides, ash increased sorption by~2 times. Adding wheat ash to soils (1 %) enhancedsorption of diuron by up to 80 times (Yang et al. 2006).As a matter of fact, the sorption potential of the ash mayexceed that of the soil’s humic substances (Amonetteand Joseph 2009), suggesting that it should affect pesti-cide bioavailability and, subsequently, its environmentalfate and agronomic efficacy. The high sorption potentialof various classes of herbicides to ash may be explainedby its high organic carbon content and by the heteroge-neity and reactivity of its surface, which may includehydrophilic, hydrophobic, acidic, and basic groups(Amonette and Joseph 2009). The reactive nature of itssurface is also reflected by its high CEC (Table 2).

The Kd,app values at t0 were positively correlated withthe organic carbon content of the soils before and afterresidue amendments (r=0.86 and 0.90 for the alachlorand diuron, respectively, p<0.01), except for the straw(Fig. 2). The organic carbon content of the amendedsoils was calculated by adding the total amounts in thesoil and in the residue and then dividing by the totalmass. The same trend was observed for the aged Kd,app

(r>0.75 and p<0.01 for both t7 and t28, excluding the

Table 3 Effects of organic waste amendments (straw, compost,and ash) and aging (0, 7, and 28 days) on the apparent distributioncoefficients (Kd,app, L kg−1) of alachlor and diuron in two soils(LVAd and LVd soils)

Kd,app values (L kg−1)

Treatments Alachlor Diuron

0 day 7 days 28 days 0 day 7 days 28 days

LVAd (control) 1.2 2.4 2.6 5.5 8.4 13.2

LVAd+straw 1.6 2.6 3.3 5.6 8.0 10.4

LVAd+compost 1.5 2.7 2.7 7.5 11.0 14.7

LVAd+ash 5.4 8.9 10.3 61.6 86.6 86.3

LVd (control) 3.8 6.0 6.5 50.4 73.5 84.7

LVd+straw 4.0 5.9 7.0 41.0 45.1 53.0

LVd+compost 3.9 6.0 6.2 49.4 75.8 87.4

LVd+ash 7.6 9.8 11.8 94.6 137.4 147.5

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straw), reinforcing that hydrophobic partition may in-crease with time due to either intra-particle diffusioninto organic matter (Brusseau et al. 1991) or inter-particle diffusion within organomineral aggregates inthe soils (Nan and Alexander 1998). These results sug-gest that deriving organic matter content for amendedsoils may be meaningful even when they are not mixed,but layered on the surface, except by organic residueshaving a low degree of humification (highlighted byhigh C:N ratio) and low reactive surface, such as thestraw that has epidermis covered with cuticle and hairs.

3.2 Soil Amendments on Leaching of Alachlor

The addition of sugarcane residues affected the leachingpotential of alachlor. Straw and ash reduced its leaching(<1.0 % of the applied alachlor was leached) whereasthe used compost did not (~6 % of the applied alachlorwas leached, similar to the control soil) (Fig. 3). Theconcentration in the leachate corresponded to 82.2 μgi.a. L−1 for the non-amended and to 9.9, 6.0, and 83.0μgi.a. L−1 for the straw, ash, and compost amended soil,respectively. Although previous studies have shownlimited movement in the soil profile (Clay et al. 1991),alachlor has been reported in surface and ground waters

(Vryzas et al. 2012a) and in deeper soil layers (up to160 cm deep at concentrations of 211 or >0.1 μg L−1 at18 h or 40 months after application, respectively)(Vryzas et al. 2012b), which raises concerns about theacceptable limits adopted for water resources in Brazil.Brazil has adopted 20 μg L−1 as standard for drinkingwater and the maximum limit for groundwater(BRASIL 2004, 2008), while the European Community(Directiva 98/83/CE 1998) and the USA (US-EPA2012) have adopted values of 0.1 and 0.2 μg L−1, re-spectively. The US-EPA has classified alachlor as hav-ing a “high” leaching potential due to its volume of use,low sorption, and high persistence (US-EPA 1998).

Alachlor residues remained mostly in the surfacelayer of the soil (0–5 cm+residues), with the ash show-ing greater retention (105 % of the amount applied) thanthe straw (87 %), which in turn was greater than thecompost (68 %) and the control (45 %) (Fig. 4). Overall,>74% of the applied alachlor was retained in the top 10-cm layer. The literature showed that >60 % of theapplied alachlor was in the soil surface layer (0–5 cm)for both non-till and conventional till areas (Clay et al.1991). Furthermore, soil profile redistribution of ala-chlor was greater in the non-amended soil, but stillrelevant when compost was amended (Fig. 4) (Dorado

LVAd

30

45

60

75

90

14C

-ala

chlo

r S

orpt

ion

(%)

LVAd

70

80

90

100

0 8 16 24 32

14C

-diu

ron

Sor

ptio

n (%

)

Incubation (days)

LVd

LVd

0 8 16 24 32

Incubation (days)

Ash

Compost

Straw

Soil (control)

Fig. 1 Sorbed percentages of alachlor and diuron as affected by residue amendments (straw, compost, and ash) and aging (0, 7, and 28 days)

1935, Page 6 of 9 Water Air Soil Pollut (2014) 225:1935

et al. 2005). Composting materials with C:N ratiossimilar to or lower than ours (12:1, Table 2) usuallyenhance herbicides sorption due to their advanced stageof humification (Huang et al. 2006), but this enhance-ment was not abrupt in our case. Besides organic carboncontent and C:N ratio, the quality of the added residuealso dictates sorption strength and amount. For example,animal manure, another residue product rich in organicmatter, also reduced atrazine (Langenbach et al. 2008)and metribuzin (Majumdar and Singh 2007) leaching.

The high retention of alachlor on the soil surfaceamended with ash (Fig. 4) appears to be directlyrelated to sorption, since ash markedly enhanced ala-chlor sorption (Kd,app=1.2 versus 5.4 L kg−1 at t0)(Table 3). Ashes were also highly efficient inretaining other organic compounds (Hiller et al.2008; Singh 2009). However, the same reasoningcould not be used for the straw since it had littleeffect on sorption (Kd,app=1.2 versus 1.6 L kg−1 at t0)(Table 3). The straw appears to work as a physicalbarrier to the transport, holding about 80 % of theapplied alachlor even after heavy rainfall was simu-lated (170 mm in 48 h, starting soon after herbicideapplication). It is important to clear that this percent-age (80 %) may be overestimated since herbicideapplication was not even (it was performed in small

AlachlorK

d,ap

p va

lues

(L

kg-1

)

0

2

4

6

8

StrawOther treatments

Diuron

Organic carbon (g kg-1)

0 10 20 30 40 50 60

Kd,

app

valu

es (

L kg

-1)

0

20

40

60

80

100

Fig. 2 Apparent sorption distribution of alachlor and diuron(Kd,app) as affected by total organic carbon contents

a

bb

a

bb

a

a

a

a

0

2

4

6

8

12 24 36 48

Cum

ulat

ive

% a

lach

lor

leac

hed

Time (hours)

Soil (control) StrawAsh Compost

Fig. 3 Leaching of alachlor as affected by straw, compost, and ashamendments. Bars represent the standard deviations. Differentletters mean that treatments differ statistically within the sametime period (Tukey’s test, p<0.05)

a

c

c

a

b

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a

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b

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a

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a

0 15 30 45 60 75 90 105

0-5

5-10

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Redistribution of Alachlor (% of applied)

Soi

l dep

th (

cm)

Ash

Straw

Compost

Soil (control)

Fig. 4 Soil profile redistribution of alachlor as affected by straw,compost, and ash amendments. Bars represent the standard devi-ations. Different letters mean that treatments differ statisticallywithin the same time period (Tukey’s test, p<0.05)

Water Air Soil Pollut (2014) 225:1935 Page 7 of 9, 1935

drops) and rainfall was simulated at just one point (asproposed in the guideline for soils), but differentlyfrom soils, the straw has huge amounts of macroporesthat may have favored preferential flow of water only,masking part of the results. However, the presence ofgrass straw also reduced leaching of atrazine in soilcolumns (Langenbach et al. 2008), whereas sugarcanestraw reduced surface runoff of atrazine andpendimethalin by at least 50 % (Selim et al. 2003).For sugarcane, the amount of sorbed herbicide isusually proportional to the amount of straw left onthe soil and more soluble molecules usually runthrough the straw easily (and earlier) (Rossi et al.2013). However, it will depend to a large degree onthe period between pesticide application and the firstrain, besides its quantity, intensity, and distribution(Rodrigues 1993). Therefore, straw management, her-bicide properties, and rainfall patterns are importantparameters dictating sorption and leaching of pesti-cides (Correia et al. 2013; Rossi et al. 2013).

Based on screening models criteria (Kd<3–5 L kg−1

and t1/2>14–21 d), our Kd,app suggests that alachlorshould always leach from the studied soils, except whenamended with ash. Therefore, this parameter may notprovide adequate description of leaching in soilsamended with non-humified organic residues, such asthe straw.

4 Conclusions

Sugarcane straw and compost had little effect whereasash significantly increased alachlor and diuron sorption.Leaching corresponded to ~6.0 % in the control soil, butash and straw amendments reduced it to less than 1 %.The compost had little effect on the leaching of alachlor.Unexpectedly, the straw was capable of holding 80% ofthe applied alachlor in the leaching experiment. Despitethis value may be overestimated, alachlor retention inthe straw could not be predicted by the use of Kd,app

values. Therefore, the transport potential of these herbi-cides may be overestimated if aging and sugarcanestraw management practices are not taken into accountby the models.

Acknowledgments The authors thank FAPESP for providingfinancial support for the research (Grant 2012/15843-0) and CNPqfor granting a scholarship to the first author. We are grateful to theUsina Estiva and the agronomy engineers Marcelo Rocha andJúlio Araújo for making the soils available and to our colleagues

Carlos Alberto Dorelli and Rodrigo Pimpinato for their technicalassistance in carrying out the experiments.

References

Alcarde, J. C. (2009). Métodos-padrão, detalhes analíticos ecálculos. In E. M. Neves (Ed.), Manual de análise defertilizantes (pp. 41–170). Piracicaba: FEALQ.

Alexander, M. (2000). Aging, bioavailability, and overestimationof risk from environmental pollutants. EnvironmentalScience and Technology, 34(20), 4259–4265.

Amonette, J. E., & Joseph, S. (2009). Characteristics of biochar:microchemical properties. In J. Lehmann & S. Joseph (Eds.),Biochar for environmental management: Science and tech-nology (pp. 33–52). London: Earthscan.

BRASIL. (2004). Ministério da Saúde. http://dtr2001.saude.gov.br/sas/PORTARIAS/Port2004/GM/GM-518.htm Accessed15 Jan 2013.

BRASIL. (2008). Ministério do Meio Ambiente. http://www.mma.gov.br/port/conama/legiabre.cfm?codlegi=562Accessed 15 Jan 2013.

Brusseau, M. L., Larsen, T., & Christensen, T. H. (1991). Rate-limited sorption and non-equilibrium transport of organicchemicals in low organic carbon aquifer materials. WaterResources Research, 27(6), 1137–1145.

Camargo, O. A., Moniz, A. C., Jorge, J. A., & Valadares, J. M. A.S. (2009). Métodos de Análise Química, Mineralógica eFísica de Solos. Campinas: Instituto Agronômico deCampinas.

Ceddia, M. B., Ravelli Neto, A., Lima, E., Anjos, L. H. C., &Silva, L. A. (1999). Sistemas de colheita da cana-de-açúcar ealterações nas propriedades físicas de um solo Podzólicoamarelo no Estado do Espírito Santo. PesquisaAgropecuária Brasileira, 34(8), 1467–1473.

Chung, N., & Alexander, M. (1998). Differences in sequestrationand bioavailability of organic compounds aged in dissimilarsoils. Environmental Science and Technology, 32(7), 855–860.

Clay, S. A., Koskinen, W. C., & Carlson, P. (1991). Alachlormovement through intact soil columns taken from two tillagesystems. Weed Technology, 5(3), 485–489.

Correia, N. M., Camilo, E. H., & Santos, E. A. (2013).Sulfentrazone efficiency on Ipomoea hederifolia andIpomoea quamoclit as influenced by rain and sugarcanestraw. Planta Daninha, 31(1), 165–174.

Dal Bosco, T. C., Sampaio, S. C., Coelho, S. R. M., Cosmann, N.J., & Smanhotto, A. (2012). Effects of the organic matterfrom swine residuewater on the adsorption and desorption ofalachlor in soil. Journal of Environmental Science andHealth Part B: Pesticides, Food Contaminants andAgricultural Residues, 47(6), 485–494.

Directiva 98/83/CE. (1998). Quality of water intended forhuman consumption. http://eurlex.europa.eu/LexUriServ/LexUriServ.do?uri=CONSLEG:1998L0083:20090807:EN:PDF. Accessed 12 Apr 2013.

Dorado, J., Lopez-Fando, C., Zancada, M. C., & Almendros, G.(2005). Sorption–desorption of alachlor and linuron in a

1935, Page 8 of 9 Water Air Soil Pollut (2014) 225:1935

semiarid soil as influenced by organic matter properties after16 years of periodic inputs. Journal of Agricultural and FoodChemistry, 53(13), 5359–5365.

Giori, F. G., Tornisielo, V. L., Cerri, C. E. P., & Regitano, J. B.(2014, in press). Sugarcane straw management and soil attri-butes on alachlor and diuron sorption in highly weatheredtropical soils. Journal of Environmental Science and Health,Part B, 49, 1–9.

Hatzinger, P. B., & Alexander, M. (1995). Effect of aging ofchemicals in soil on their biodegradability and extractability.Environmental Science and Technology, 29(2), 537–545.

Hiller, E., Fargasová, A., & Bartal, M. (2008). Influence of wheatash on the MCPA immobilization in agricultural soils.Bulletin of Environmental Contamination and Toxicology,81(3), 285–288.

Huang, G. F., Wu, Q. T., Wong, J. W. C., & Nagar, B. B. (2006).Transformation of organic matter during co-composting ofpig manure with sawdust. Bioresource Technology, 97(15),1834–1842.

Inoue, M. H., Oliveira, R. S., Jr., Regitano, J. B., Tormena, C. A.,Constantin, J., & Tornisielo, V. L. (2006). Sorption–desorp-tion of atrazine and diuron in soils from Southern Brazil.Journal of Environmental Science and Health Part B:Pesticides, Food Contaminants and Agricultural Residues,41(5), 605–621.

Laabs, V., & Amelung, W. (2005). Sorption and aging ofcorn and soybean pesticides in tropical soils of Brazil.Journal of Agricultural and Food Chemistry, 53(18),7184–7192.

Langenbach, T., Correia, F. V., Macrae, A., Vargas, E. A., Jr., &Campos, T.M. (2008). Atrazine leaching through surface andsubsurface of a tropical Oxisol. Journal of EnvironmentalScience and Health Part B: Pesticides, Food Contaminantsand Agricultural Residues, 43(3), 214–218.

Liu, Y., Xu, Z., Wu, X., Gui, W., & Zhu, G. (2010). Adsorptionand desorption behavior of herbicide diuron on variousChinese cultivated soils. Journal of Hazardous Materials,178(1–3), 462–468.

Luz, P. H. C., & Korndörfer, G. H. (2011). Reciclagem desubprodutos na agricultura. In H. P. Vasconcelos, P. Ferrari,L. E. V. Salgado, L. I. Prochnow, & A. S. Lopes (Eds.),Contribuições para produção de alimentos: Idéias parauma agricultura eficaz (pp. 123–142). São Paulo: NovaBandeira.

Majumdar, K., & Singh, N. (2007). Effect of soil amendments onsorption and mobility of metribuzin in soils. Chemosphere,66(4), 630–637.

Mamy, L., & Barriuso, E. (2007). Desorption and time-dependentsorption of herbicides in soils. European Journal of SoilScience, 58(1), 174–187.

Martin, S. M., Kookana, R. S., Zwieten, L. V., & Krull, E. (2012).Marked changes in herbicide sorption–desorption upon age-ing of biochars in soil. Journal of HazardousMaterials, 231–232(11), 70–78.

Menasseri, S., Koskinen, W. C., & Yen, P. Y. (2003). Sorption ofaged dicamba residues in soil. Pest Management Science,60(3), 297–304.

Nan, K., & Alexander, M. (1998). Role of nanoporosity andhydrophobicity in sequestration and bioavailability: testswith model solids. Environmental Science & Technology,32(1), 71–74.

OECD. (2004). Organization for economic co-operation and de-velopment. Test No 312: Leaching in Soil Columns. http://www.oecd-ilibrary.org/ Accessed 20 June 2012.

Oliveira, R. S., Jr., Koskinen, W. C., & Ferreira, F. A. (2001).Sorption and leaching potential of herbicides on Braziliansoils. Weed Research, 41(2), 97–110.

Pinheiro, E. F. M., Lima, E., Ceddia, M. B., Urquiaga, S., Alves,B. J. R., & Boddley, R. M. (2010). Impact of pre-harvestburning versus trash conservation on soil carbon and nitrogenstocks on a sugarcane plantation in the Brazilian Atlanticforest region. Plant and Soil, 333(1–2), 71–80.

Regitano, J. B., & Koskinen, W. C. (2008). Characterization ofnicosulfuron availability in aged soils. Journal ofAgricultural and Food Chemistry, 56(14), 5801–5805.

Regitano, J. B., Koskinen, W. C., & Sadowsky, M. J. (2006).Influence of soil aging on sorption and bioavailability ofsimazine. Journal of Agricultural and Food Chemistry,54(4), 1373–1379.

Rodrigues, B. N. (1993). Influência da cobertura morta nocomportamento dos herbicidas imazaquin e clomazone.Planta Daninha, 11(1–2), 21–28.

Rodrigues, M. N., & Almeida, F. S. (2011). Guia de herbicidas.Londrina: IAPAR.

Rossetto, R. (2010). A cana-de-açúcar e a questão ambiental. In L.L. Dinardo-Miranda, A. C. M. Vasconcelos, & M. G. A.Landell (Eds.), Cana-de-açúcar (pp. 885–869). Campinas:Instituto Agronômico.

Rossi, C. V. S., Velini, E. D., Luchini, L. C., Negrisoli, E., Correa,M. R., Pivetta, J. P., et al. (2013). Dinâmica do herbicidametribuzin aplicado sobre palha de cana-de-açúcar(Saccarum officinarum). Planta Daninha, 31(1), 223–230.

Selim, H. M., Zhou, L., & Zhu, H. (2003). Herbicide retention insoil as affected by sugarcane mulch residue. Journal ofEnvironmental Quality, 32(4), 1445–1454.

Singh, N. (2009). Adsorption of herbicides on coal fly ash fromaqueous solutions. Journal of Hazardous Materials, 168(1),233–237.

Soil Survey Staff. (1999). Soil taxonomy. Washington, DC:USDA-NRCS.

UNICA. (2012). União da Indústria de cana-de-açúcar. http://www.unica.com.br/documentos/publicacoes/sid/6537316/.Accessed 19 Apr 2013.

US-EPA. (1998). United States Environmental Protection Agency.Reregistration eligibility decision (RED), alachlor. http://www.epa.gov/oppsrrd1/REDs/0063.pdf. Accessed 10 Jan2013.

US-EPA. (2012). United States Environmental Protection Agency.http://water.epa.gov/drink/contaminants/basicinformation/alachlor.cfm 2012 Accessed 12 Jan 2013.

Vryzas, Z., Papadakis, E. N., Vassiliou, G., & Papadopoulou-Mourkidou, E. (2012a). Occurrence of pesticides intransboundary aquifers of North-eastern Greece. Science ofthe Total Environment, 441(6), 41–48.

Vryzas, Z., Papadakis, E. N., & Papadopoulou-Mourkidou, E.(2012b). Leaching of Br−, metolachlor, alachlor, atrazine,deethylatrazine and deisopropylatrazine in clayey vadozezone: a field scale experiment in north-east Greece. WaterResearch, 46(6), 979–989.

Yang, Y., Sheng, G., & Huang, M. (2006). Bioavailability ofdiuron in soil containing wheat straw-derived char. Scienceof the Total Environment, 354(2–3), 170–178.

Water Air Soil Pollut (2014) 225:1935 Page 9 of 9, 1935