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Soil Biology & Biochemistry 43 (2011) 1955e1960

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Soil Biology & Biochemistry

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Differential and successive effects of residue quality and soil mineral Non water-stable aggregation during crop residue decomposition

C. Le Guillou a,b,c, D.A. Angers d, P. Leterme a,b,c, S. Menasseri-Aubry a,b,c,*

aAgrocampus Ouest, UMR1069 Sol Agro et hydrosystème Spatialisation, F-35000 Rennes, Franceb INRA, UMR1069 Sol Agro et hydrosystème Spatialisation, F-35000 Rennes, FrancecUniversité européenne de Bretagne, FrancedAgriculture et Agroalimentaire Canada, Centre de Recherche sur les Sols et les Grandes Cultures, 2560 Boulevard Hochelaga, Sainte-Foy, Québec G1V 2J3, Canada

a r t i c l e i n f o

Article history:Received 18 November 2010Received in revised form6 June 2011Accepted 8 June 2011Available online 22 June 2011

Keywords:Residue qualityTemporal dynamicsNDecompositionAggregate stability

* Corresponding author. Agrocampus Ouest, UMRSpatialisation, 65 Route de Saint-Brieuc, CS 84215-3Tel.: þ33 2 23 48 54 73; fax: þ33 2 23 48 54 80.

E-mail address: Safya.Menasseri@agrocampus-oue

0038-0717/$ e see front matter � 2011 Elsevier Ltd.doi:10.1016/j.soilbio.2011.06.004

a b s t r a c t

Residue quality has been shown to influence soil water-stable aggregation (WSA) during crop residuedecomposition, but there is still little information about its interactive effect with soil mineral N avail-ability. The aim of this study was to determine the effect of soil mineral N on WSA during the decom-position of two high-C/N crop residues (wheat straw with C/N ¼ 125.6 and miscanthus straw withC/N ¼ 311.3). The two crop residues were combined with three mineral N addition rates (0, 60, and120 mg N kg�1 dry soil). Respiration, soil mineral N content, and WSA (expressed as mean-weightdiameter, MWD) were measured on several dates during a 56-d incubation. The effect of decomposingcrop residues on WSA followed two phases. (i) Between 0 and 7 d, the increase in WSA was related tointrinsic residue quality with higher decomposability of the wheat straw resulting in higher WSA.(ii) Thereafter, and until the end of the experiment, mineral N addition rates had a predominant butnegative influence on WSA. In this second phase, the average MWD of residue-treated soils was 0.92,0.55, and 0.44 mm for the 0, 60 and 120 mg N kg�1 dry soil addition rates, respectively. Mineral Naddition which did result in higher crop residue decomposition did not lead to higher WSA. WSA duringcrop residue decomposition is therefore not simply positively related to the induced microbial activity,and changes in microbial community composition with differential effects on WSA must be involved. Theimpact of high-C/N crop residues inputs on WSA, initially assumed to be low, could actually be strong andlong-lasting in situations with low soil mineral N content.

� 2011 Elsevier Ltd. All rights reserved.

1. Introduction

Organic matter is a major factor influencing soil water-stableaggregation (WSA) in most agricultural soils (Tisdall and Oades,1982), and as a feedback mechanism, aggregation is considered asa significant mechanism of organic matter protection in soils(Balesdent et al., 2000). The incorporation of fresh crop residues insoils initiates WSA by stimulating microbial activity (Angers andChenu, 1998). Crop residue effects on WSA generally depend onthe decomposability of the residues (Abiven et al., 2009) and havebeen related to themicrobial decomposition activity induced by theresidue input (De Gryze et al., 2005). Addition of easily decom-posable organic residues usually results in a rapid and strong but

Sol Agro et hydrosystème5042 Rennes Cedex, France.

st.fr (S. Menasseri-Aubry).

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transient increase of WSA whereas less decomposable residuesshow a more gradual but often moderate and longer-lasting effect(Martin et al., 1955; Monnier, 1965; Abiven et al., 2009).

Soil mineral N availability has been shown to influence thedecompositionof crop residues, especially those of high-C/N ratio forwhich decomposition is N-limited (Mary et al., 1996). As a conse-quence, some authors have suggested that a sufficient content of soilmineral N is usually needed tomaximize the effects of high-C/N ratiocrop residues addition onWSA (Avnimelech and Cohen,1989; Hadaset al., 1994). Therefore, recent studies evaluating the effects of high-C/N crop residue onWSAwere generally performed in nonN-limitedconditions to ensure optimal decomposition (Guggenberger et al.,1999; Cosentino et al., 2006; Abiven et al., 2007).

However, in contrast, other reports have shown that mineral Naddition may in fact decrease WSA following crop residue incor-poration (Schwartz et al., 1958; Acton et al., 1963; Bossuyt et al.,2001). Those laboratory incubation studies did not relate WSAdynamics to microbial decomposition activity (Schwartz et al.,1958; Acton et al., 1963; Avnimelech and Cohen, 1989; Hadas

C. Le Guillou et al. / Soil Biology & Biochemistry 43 (2011) 1955e19601956

et al., 1994) or drew their conclusions from a single sampling date(Bossuyt et al., 2001). Some recent field studies have also illustratedthese variable interactive effects of crop residue quality with Nfertilizer on WSA (Gentile et al., 2010; Fonte et al., 2009; Chivengeet al., 2011). It is interesting to note that when the positive effects ofthe residue was reduced by N fertilization, an associated decreasein soil organic carbon (Chivenge et al., 2011) and aggregate carboncontent (Fonte et al., 2009) was also observed, which suggestsa concomitant decrease in organic binding agents.

From these studies it appears that the interactive effect ofmineral N availability and residue quality on WSA dynamics duringcrop residue decomposition is not yet fully understood. The aim ofthis study was to determine the effect of soil mineral N availabilityon WSA during high-C/N crop residue decomposition.

2. Materials and methods

We carried out an experiment over 56 days under controlledconditions in the laboratory where we combined two biochemi-cally different high-C/N ratio crop residues with three mineral Naddition rates to quantify changes over time in WSA in relation tomineral N content and microbial respiration.

2.1. Soil and crop residues

The soil used in the experiment was sampled at the Champ Noëlexperimental site of INRA (Institut National de la RechercheAgronomique), near Rennes, France (48�070N,1�430W). The soil wasa Luvisol (FAO/ISRIC/ISSS,1998) with 15.1% clay, 71.1% silt, and 13.8%sand, a total C content of 9.7 g kg�1, a C/N ratio of 8.8, and a pH inwater of 6.2. The sampled plot had been under maize/wheat rota-tion with mineral fertilization since 1995. In March 2009, the soilwas sampled in the 0- to 15-cm layer using a shovel. The soil wasgently sieved at 5 mm, air-dried, and stored at 4 �C. Coarse visibleparticles (roots and plant debris) were removed by hand.

The two crop residues were wheat straw (Triticum aestivum L.)and miscanthus straw (Miscanthus � giganteus). These residueswere chosen for their high-C/N ratio and differences in biochemicalcharacteristics (Table 1). The residues were dried at 60 �C andground to less than 1 mm.

2.2. Incubation and experimental treatments

The soil water content was adjusted to 200 g kg�1 dry soilthrough the spraying of ultrafiltered water and allowed to equili-brate for 3 d. The remoistened soil was then preincubated at 25 �Cfor 10 d to minimize variations in microbial activity due to changesin temperature and water content conditions. Soil water contentwas readjusted to 217 g kg�1 dry soil (water content at �50 kPa)through the addition of ultrafiltered water for the treatmentswithout mineral N input and through the addition of KNO3 solu-tions for the treatments with mineral N input. Initial soil mineral Ncontent was 24.2 mg N kg�1 dry soil. Three mineral N input rateswere studied: 0 (N0), 60 (N1), and 120 (N2) mg N kg�1 dry soil.Therefore, the initial average total soil mineral N content corre-sponded to: N0 ¼ 24.2 mg N kg�1 dry soil, N1¼84.4 mg N kg�1 drysoil, N2 ¼ 143.2 mg N kg�1 dry soil.

Table 1Initial biochemical characteristics of the crop residues.

Crop residue C/N Lignin/N Van

Solu

Wheat straw 125.60 21.20 13.1Miscanthus straw 311.30 88.10 6.2

Crop residues were mixed with the preincubated andN-adjusted soil at a rate of 4 g C kg�1 dry soil. A control soiltreatment without crop residue input and two crop residue treat-ments were thus combined with three N treatments in a factorialdesign with three replicates. The incubation was performed inhermetically closed 1-L jars. The contents of each jar were mixedhomogenously before incubation. The treatments were incubatedat constant temperature (25 �C) for 56 d, and the soil water contentwas maintained at 217 g kg�1 dry soil with regular weighing of thejars and addition of water when necessary.

2.3. Measurements

The effects of the treatments on soil respiration were deter-mined bymeasuring CO2eC evolution continuously over the courseof the incubation. The evolved CO2 was trapped in 20 ml 0.1 MNaOH and back-titrated with 1 M HCl after the addition of 5 mlBaCl2 solution (30%) to precipitate the Na2CO3. The traps werereplaced periodically, after 2, 3, 5, 7, 10, 14, 21, 28, 35, 42, 49, and56 d. Air was renewed through replacement of the traps in each jaron each sampling date, thus maintaining aerobic conditions.

Changes in the mineral N content and WSA of soils over timewere measured by destructive sampling at 0, 2, 7, 14, 21, 35, and56 d. Three jars for each treatment were removed for analysis ateach sampling date. The content of each jar was homogenized anddivided into 2 subsamples for mineral N and WSA analyses. Theentire 0e5mm soil fractionwas used for both analyses. ThemineralN subsample was stored at �20 �C until analysis while the WSAsubsample was oven-dried at 40 �C for 24 h.

Soil inorganic N was extracted by 1 M KCl (soil to KClratio ¼ 1:2). The NH4

þeN and NO3�eN content of the KCl extrac-

tion were determined by continuous flow colorimetry (Alpken).Measurement of WSA was adapted from Angers et al. (2008). A

5-g subsample (0e5 mm) of the oven-dried soil was capillary-rewetted for 1 h and transferred to the top of a nest of sieves (2,1, and 0.5mm in diameter). The columnwas immersed in deionizedwater and shaken vertically 20 times, with the column kept in thewater. The fraction remaining on each sievewas oven-dried at 40 �Cfor 24 h and weighed. The mean-weight diameter (MWD) wascalculated as follows:

MWD ¼X

wi*xi

Where i corresponds to each fraction collected,wi is the dry weightof the fraction collected relative to the total soil used, xi is the meandiameter of the fraction collected.

2.4. Data and statistical analysis

An analysis of variance (ANOVA) using the whole data set wasfirst performed at each sampling date to test the effects of cropresidue addition andmineral N levels, and their interactions, on themeasured variables. As mineral N levels did not have any effect onthe WSA of control soils, data were expressed as the differencebetween the residue-treated and control soils within each Ntreatment. This calculation for both C and N mineralizationassumes that mineralization of soil organic C and N is not

Soest (% dry mass)

ble Hemicellulose Cellulose Lignin

6 34.04 45.58 7.228 28.08 52.43 13.21

Fig. 2. Cumulative respiration during the incubation (residue-treated minus controlwithin each N treatment). Treatments are Wheat (Wh) and Miscanthus (Mc) residuescombined with 0 (N0), 60 (N1), 120 (N2) mg N kg�1 dry soil addition rates. Error barsrepresent the standard error of the means. Means at day 56 that significantly differ arefollowed by different letters (LSD test, P ¼ 0.01).

C. Le Guillou et al. / Soil Biology & Biochemistry 43 (2011) 1955e1960 1957

significantly modified by the addition of residue (no priming effect)or that the priming effect is of the same order of magnitude for eachof the different residues, and does not bias interpretation regardingthe decomposability of the crop residues. An ANOVA was per-formed on the measured variables to test the specific effect of cropresidue type and the interaction with N treatment (crop residue-treated minus the non-amended control within each N treat-ment). Prior to analysis, data were tested for homogeneity of vari-ance using the Levene’s test and log-transformed when required.When effects were significant (P � 0.05), means were comparedwith the LSD test. Regression analysis was performed on respirationrates and MWD data (crop residue-treated minus the non-amended control within each N treatment) to investigate theoverall effect of N addition.

3. Results

3.1. Carbon mineralization

Respiration rates of wheat- and miscanthus-treated soils dis-played a peak after 3 days, and then followed an exponential decaythrough to the end of the experiment (Fig.1). Respiration ratesweresignificantly (P < 0.01) higher in wheat straw treatments than inmiscanthus at day 2 and 3. Thereafter and until day 42, respirationrates in the N1 and N2 wheat straw treatments were higher than inall miscanthus treatments. Between day 3 and 14, wheat strawdecomposition in the N1 and N2 treatments was significantly(P< 0.01) higher than in thewheat strawN0 treatment. Cumulativerespiration differed significantly (P < 0.01) between treatments(Fig. 2). It decreased in the order: Wheat þ N2 z Wheat þ N1 >

Wheat þ N0 z Miscanthus þ N1 > Miscanthus þN2 z Miscanthus þ N0. Nitrogen addition had a greater effect onwheat straw decomposition than on miscanthus.

3.2. Soil mineral N dynamics

Net N immobilization (residue-treated minus control withineach N treatment) following crop residue incorporation occurredrapidly and lasted until the end of the 56-day experiment (Fig. 3).Net N immobilization in Wheat þ N0 and Miscanthus þ N0 treat-ments was similar during the entire incubation. From day 7 to theend of the experiment, net N immobilization in both N1 and N2treatments was significantly (P < 0.01) higher in wheat strawtreatments than miscanthus treatments (except at day 56 for theN1 treatment). Within each crop residue treatment, net N

Fig. 1. Respiration rates during the incubation (residue-treated minus control withineach N treatment). Treatments are Wheat (Wh) and Miscanthus (Mc) residuescombined with 0 (N0), 60 (N1), 120 (N2) mg N kg�1 dry soil addition rates. Error barsrepresent the standard error of the means.

immobilization following N1 and N2 addition rates were notsignificantly (P > 0.05) different (except at day 7 for the wheatstraw treatment).

3.3. Water-stable aggregation

The ANOVA (Table 2) clearly showed the differential andsuccessive effects of crop residue quality and mineral N rate onWSA. Crop residue type was the main factor influencing WSA atdays 2 and 7 whereas mineral N rate was the main factor thereafterand until the end of the incubation. Between 0 and 7 d, WSAincreased for all crop residue-amended soils (Fig. 4), but theincrease was greater for wheat straw thanmiscanthus. At day 2 and7, WSA of wheat straw treatments was significantly higher thanmiscanthus (Table 2). Mineral N rates did not have any significanteffect at this stage. Between day 7 and day 14, when consideringonly N0 treatment, WSA of the wheat straw treatment remainedhigh and relatively stable whereas it increased in the miscanthustreatment (Fig. 4). This could explain the significant interactionbetween residue type and mineral N rate at day 14 (Table 2).Between day 14 and 56, the average MWD of the WSA was 0.92,0.55, and 0.44 mm for the 0, 60 and 120mg N kg�1 dry soil addition

Fig. 3. The effects of crop residue additions on soil mineral N content (residue-treatedminus control within each N treatment) during the 56-day incubation. Treatments areWheat (Wh) and Miscanthus (Mc) residues combined with 0 (N0), 60 (N1), 120(N2) mg N kg�1 dry soil addition rates. Error bars represent the standard error of themeans.

Table 2Effects of residue type and mineral N addition rate onWSA (MWD) at each sampling date (residue-treated minus control within each N treatment). Values represent the meanof three replicates. For each sampling date and parameter, means that significantly differ are followed by different letters (LSD test). When differences are significant, P valuesfrom the analysis of variance (ANOVA) are indicated. ns ¼ non-significant.

Treatment Day

2 7 14 21 35 56

Residue type (RT)Wheat 0.18 b 0.77 b 0.66 b 0.42 0.79 0.65Miscanthus 0.03 a 0.43 a 0.51 a 0.50 0.89 0.70

N addition rate (N)N0 0.14 0.67 0.78 b 0.75 b 1.19 b 0.98 bN1 0.08 0.59 0.49 a 0.38 a 0.79 a 0.53 aN2 0.10 0.53 0.49 a 0.24 a 0.54 a 0.50 a

ANOVA (P value)RT <0.001 <0.01 <0.05 ns ns nsN ns ns <0.001 <0.001 <0.01 <0.01RT � N ns ns <0.01 ns ns ns

C. Le Guillou et al. / Soil Biology & Biochemistry 43 (2011) 1955e19601958

rates, respectively. WSA of the N0 treatment remained significantlyhigher than the N1 and N2 treatments over all this second phase ofthe experiment (Table 2).

The overall effect of mineral N addition on soil respiration andWSA was investigated by regression analysis (Fig. 5). Relationshipswere performed between mean values of treatments under the N2treatment compared to N0 treatment. Values falling on the Y ¼ xline indicated a similar response for N2 fertilized vs. N0 unfertilizedtreatments, whereas points above or below this line indicateda stimulation or inhibition, respectively. From this analysis it can beseen that overall N addition stimulated respiration rates butinhibited WSA.

a

4. Discussion

4.1. Successive effects of residue quality and mineral N

The effects of crop residue on soil WSA have long been shownto be related to their decomposability (e.g. Browning and Milam,1944; Martin et al., 1955; Martens, 2000; Abiven et al., 2007;Helfrich et al., 2008). In line with these findings, the higherdecomposability of the wheat straw (Fig. 1) resulted in higherWSA (Fig. 4) than with miscanthus early in the decompositionprocess. The higher initial decomposition of wheat straw waslikely related to both its higher soluble fraction and lower C/N

-0,2

0

0,2

0,4

0,6

0,8

1

1,2

1,4

1,6

0 10 20 30 40 50 60Time (day)

MW

D (m

m)

(resi

due-

treat

ed m

inus

con

trol w

ithin

eac

h N

trea

tmen

t )

Wh N0 Wh N1 Wh N2 Mc N0 Mc N1 Mc N2

Fig. 4. WSA expressed as the MWD during the incubation (residue-treated minuscontrol within each N treatment). Treatments are Wheat (Wh) and Miscanthus (Mc)residues combined with 0 (N0), 60 (N1), 120 (N2) mg N kg�1 dry soil addition rates.Error bars represent the standard error of the means.

ratio. The initial decomposition rate is strongly related to thesoluble fraction of crop residues (Trinsoutrot et al., 2000).Microorganisms rapidly process the easily available C fractionduring the initial phase of decomposition (Ladd et al., 1996). Thebiomass and activity of the microorganisms increase andproduce binding agents that increase WSA (Golchin et al., 1998).However, in our case, crop residue decomposability influencedWSA only in the first 7 d of decomposition. Thereafter, and untilthe end of the experiment, initial N input rate became the mainfactor.

After 7 d, WSA was higher with lower mineral N addition rates.These results are consistent with some earlier studies showing that

b

Fig. 5. Effect of mineral N addition on (a) respiration rates (residue-treated minuscontrol within each N treatment) and (b) WSA (MWD) (residue-treated minus controlwithin each N treatment). Each point represents the mean of three replicates.Regression analysis (dashed lines) were significant at P ¼ 0.05.

C. Le Guillou et al. / Soil Biology & Biochemistry 43 (2011) 1955e1960 1959

WSA following wheat straw addition was higher when noconcomitant N fertilizer was added (Schwartz et al., 1958; Actonet al., 1963) but contrary to Avnimelech and Cohen (1989) whofound the opposite. In a three-year field experiment, Fonte et al.(2009) observed that fertilizer N along with crop residue resultedin lower WSA in comparison to residue inputs alone. At the end ofour experiment, WSA with no mineral N addition remained muchhigher than the other treatments with N addition (Table 2). Theseresults suggest that high-C/N crop residue effects onWSA persist intime when the soil mineral N content is low.

4.2. Differential effect of mineral N depending on residue quality

Aggregate dynamics following organic matter input generallyinvolve three phases: formation, stabilization, and breakdown(Tisdall and Oades, 1982) and the succession of these phases canvary and be influenced by mineral N content. For instance,Vandevivere et al. (1990) observed that in a soil amended withwheat straw, maximum WSA was reached earlier with increasingmineral N content. Our results also show that mineral N additionmodified the extent of these phases but in ways that depend oncrop residue quality.

Wheat straw decomposition appeared to be N-limited (Figs. 1and 2). Our results confirmed that when mineral N content meetsmicrobial N demands, extra N does not further stimulate wheatstraw decomposition (Recous et al., 1995). However, as seenpreviously, the early higher wheat straw decomposition observedwith N addition did not lead to higher WSA (Fig. 4); it is rather theintrinsic quality of the crop residues that determined the earlyeffects on WSA. After the first phase, WSA generally decreased inwheat treatments which had received mineral N. Similar observa-tion by Harris et al. (1963) were attributed to the metabolism ofaggregating agents bymicroorganisms and subsequent breakdown.The additional decomposition in wheat treatments with mineral Naddition could actually be partly related to this metabolism ofaggregating agents. The very large difference in WSA at the end ofthe incubation suggests that, if initially assumed to be intermediate(Abiven et al., 2009), the effect of wheat straw on soil aggregationcould actually be strong and relatively long-lasting in situationswith low soil mineral N content.

Mineral N addition also modified WSA dynamics following mis-canthus residue incorporation but in away that differed fromwheatstraw (Fig. 4). The extent of respiration (Figs. 1 and 2) andmineral Nimmobilization (Fig. 3) following N addition were lower inmiscanthus-treated soils, with the highest decomposition observedwith the intermediate level of N addition, which suggests that Navailability is not the most limiting factor in miscanthus decompo-sition. However, aswe did notmeasure gaseous emission ofNduringthe incubation, it is possible that we have overestimated N immo-bilization owing to N2 or N2O emission or NH3 volatilization.Nevertheless, we believe this is likely to be a very small effect(<1 mg kg�1 dry soil) compared to immobilization fluxes, asdemonstrated in previous studies (Gentile et al., 2008). Despite itshigh-C/N ratio, miscanthus decomposition was little affected bymineral N additionwhich illustrates the non-linearity of the effect ofN addition on litter decomposition (Sall et al., 2003; Knorr et al.,2005). Miscanthus residues have a twice higher lignin content thanwheat straw. We hypothesize that high mineral N addition couldhave repressed oxidative enzymes synthesis (Fog,1988; Sinsabaugh,2010) or increased formation of recalcitrant compounds (Fog, 1988)or decreased growth rate of microbial decomposers (Ågren et al.,2001). Mineral N addition did not directly modify WSA by alteringmiscanthus residue decomposition rate. It appears that mineral Naddition simply prevented the large increase inWSA observed in theabsence ofmineral N addition. One hypothesis could be that mineral

N addition decreased the involvement of binding agents such asfungi in forming/stabilizing soil aggregates.

Overall, our results showed that mineral N addition, which didresult in higher crop residue decomposition, did not lead to higherWSA (Fig. 5). Therefore it appears that WSA dynamics during cropresidue decomposition is not simply positively related to themicrobial decomposition activity induced as generally assumed (forreview, Abiven et al., 2009). Changes in microbial communitycomposition are known to occur during crop residue decomposition(Bastian et al., 2009)with possible differential effect onWSA (Harriset al., 1966). Fungi have awell known role in forming and stabilizingsoil aggregates in the presence of high-C/N crop residues (Bossuytet al., 2001; Denef et al., 2001). We hypothesize that the composi-tion of the developing microbial communities may have a func-tional role that is of greater importance than gross decompositionactivity which involves both the production and the degradation ofbinding agents by microorganisms. Further microbial analyses willmake it possible to gain insight into this hypothesis. Overall, weconclude that the impact of high-C/N crop residues inputs on WSA,initially assumed to be low, could actually be strong and long-lasting in situations with low soil mineral N content.

Acknowledgements

We are grateful to Armelle Racapé, Laurence Carteaux, SylvainBusnot and Yannick Fauvel for their technical assistance during theexperiment. We are grateful to Virginie Parnaudeau and NicolasBottinelli for their advice on the manuscript. We are grateful to the“College Doctoral International de l’Université Européenne deBretagne” for their financial support during the project.

References

Abiven, S., Menasseri, S., Angers, D.A., Leterme, P., 2007. Dynamics of aggregatestability and biological binding agents during decomposition of organic mate-rials. European Journal of Soil Science 58, 239e247.

Abiven, S., Menasseri, S., Chenu, C., 2009. The effects of organic inputs over time onsoil aggregate stability e a literature analysis. Soil Biology and Biochemistry 41,1e12.

Acton, C.J., Rennie, D.A., Paul, E.A., 1963. The relationship of polysaccharides to soilaggregation. Canadian Journal of Soil Science 43, 201e209.

Ågren, G.I., Bosatta, E., Magill, A.H., 2001. Combining theory and experiment tounderstand effects of inorganic nitrogen on litter decomposition. Oecologia128, 94e98.

Angers, D.A., Chenu, C., 1998. Dynamics of soil aggregation and C sequestration. In:Lal, R., Kimble, J.M., Follett, R.F., Stewart, B.A. (Eds.), Soil Processes and theCarbon Cycle. CRC Press, Boca Raton, FL, pp. 199e206.

Angers, D.A., Bullock, M.S., Mehuys, G.R., 2008. Aggregate stability to water. In:Carter, M.R., Gregorich, E.G. (Eds.), Soil Sampling and Methods of Analysis,second ed. CRC Press, Boca Raton, FL, pp. 811e820.

Avnimelech, Y., Cohen, A., 1989. Use of organic manures for amendment of com-pacted clay soils II. Effect of carbon to nitrogen ratio. Communications in SoilScience and Plant Analysis 20, 1635e1644.

Balesdent, J., Chenu, C., Balabane, M., 2000. Relationship of organic matter dynamicsto physical protection and tillage. Soil and Tillage Research 53, 215e230.

Bastian, F., Bouziri, L., Nicolardot, B., Ranjard, L., 2009. Impact of wheat strawdecomposition on successional patterns of soil microbial community structure.Soil Biology and Biochemistry 41, 262e275.

Bossuyt, H., Denef, K., Six, J., Frey, S.D., Merckx, R., Paustian, K., 2001. Influence ofmicrobial populations and residue quality on aggregate stability. Applied SoilEcology 16, 195e208.

Browning, G.M., Milam, F.M., 1944. The effect of different types of organic materialsand lime on soil aggregation. Soil Science 57, 91e106.

Chivenge, P., Vanlauwe, B., Gentile, R., Six, J., 2011. Organic resource quality influ-ences short-term aggregate dynamics and soil organic carbon and nitrogenaccumulation. Soil Biology and Biochemistry 43, 657e666.

Cosentino, D., Chenu, C., Bissonnais, Y.L., 2006. Aggregate stability and microbialcommunity dynamics under drying-wetting cycles in a silt loam soil. SoilBiology and Biochemistry 38, 2053e2062.

De Gryze, S., Six, J., Brits, C., Merckx, R., 2005. A quantification of short-termmacroaggregate dynamics: influences of wheat residue input and texture. SoilBiology and Biochemistry 37, 55e66.

Denef, K., Six, J., Bossuyt, H., Frey, S.D., Elliott, E.T., Merckx, R., Paustian, K., 2001.Influence of dry-wet cycles on the interrelationship between aggregate,

C. Le Guillou et al. / Soil Biology & Biochemistry 43 (2011) 1955e19601960

particulate organic matter, and microbial community dynamics. Soil Biologyand Biochemistry 33, 1599e1611.

FAO/ISRIC/ISSS, 1998. World Reference Base for Soil Resources. Food and AgricultureOrganization of the United Nations, Rome, Italy.

Fog, K., 1988. The effect of added nitrogen on the rate of decomposition organicmatter. Biological Reviews 63, 433e462.

Fonte, S.J., Yeboah, E., Ofori, P., Quansah, G.W., Vanlauwe, B., Six, J., 2009. Fertilizerand residue quality effects on organic matter stabilization in soil aggregates.Soil Science Society of America Journal 73, 961e966.

Gentile, R., Vanlauwe, B., Chivenge, P., Six, J., 2008. Interactive effects fromcombining fertilizer and organic residue inputs on nitrogen transformations.Soil Biology and Biochemistry 40, 2375e2384.

Gentile, R., Vanlauwe, B., Kavoo, A., Chivenge, P., Six, J., 2010. Residue quality and Nfertilizer do not influence aggregate stabilization of C and N in two tropical soilswith contrasting texture. Nutrient Cycling in Agroecosystems 88, 121e131.

Golchin, A., Baldock, J.A., Oades, J.M., 1998. A model linking organic matterdecomposition, chemistry, and aggregate dynamics. In: Lal, R., Kimble, J.M.,Follett, R.F., Stewart, B.A. (Eds.), Soil Processes and the Carbon Cycle. CRC Press,Boca Raton, FL, pp. 245e266.

Guggenberger, G., Elliott, E.T., Frey, S.D., Six, J., Paustian, K., 1999. Microbial contri-butions to the aggregation of a cultivated grassland soil amended with starch.Soil Biology and Biochemistry 31, 407e419.

Hadas, A., Rawitz, E., Etkin, H., Margolin, M., 1994. Short-term variations of soilphysical properties as a function of the amount and C/N ratio of decomposingcotton residues. I. Soil aggregation and aggregate tensile strength. Soil andTillage Research 32, 183e198.

Harris, R.F., Allen, O.N., Chesters, G., Attoe, O.J., 1963. Evaluation of microbial activityin soil aggregate stabilization and degradation by the use of artificial aggre-gates. Soil Science Society of America Journal 27, 542e545.

Harris, R.F., Chesters, G., Allen, O.N., 1966. Dynamics of soil aggregation. Advances inAgronomy 18, 107e160.

Helfrich, M., Ludwig, B., Potthoff, M., Flessa, H., 2008. Effect of litter quality and soilfungi on macroaggregate dynamics and associated partitioning of litter carbonand nitrogen. Soil Biology and Biochemistry 40, 1823e1835.

Knorr, M., Frey, S.D., Curtis, P.S., 2005. Nitrogen additions and litter decomposition:a meta-analysis. Ecology 86, 3252e3257.

Ladd, J.N., Foster, R.C., Nannipieri, P., Oades, J.M., 1996. Soil structure and biologicalactivity. In: Stotzky, G., Bollag, J.M. (Eds.), Soil Biochemistry, vol. 9. MarcelDekker, New York, pp. 23e78.

Martin, J.P., Martin, W.P., Page, J.B., Raney, W.A., de Ment, J.D., 1955. Soil aggregation.Advances in Agronomy 7, 1e37.

Martens, D.A., 2000. Plant residue biochemistry regulates soil carbon cycling andcarbon sequestration. Soil Biology and Biochemistry 32, 361e369.

Mary, B., Recous, S., Darwis, D., Robin, D., 1996. Interactions between decompositionof plant residues and nitrogen cycling in soil. Plant and Soil 181, 71e82.

Monnier, G., 1965. Action des matières organiques sur la stabilité structurale dessols. Thèse de la faculté des sciences de Paris, 140 pp.

Recous, S., Robin, D., Darwis, D., Mary, B., 1995. Soil inorganic N availability: effecton maize residue decomposition. Soil Biology and Biochemistry 27, 1529e1538.

Sall, S., Masse, D., Bernhard-Reversat, F., Guisse, A., Chotte, J.L., 2003. Microbialactivities during the early stage of laboratory decomposition of tropical leaflitters: the effect of interactions between litter quality and exogenous inorganicnitrogen. Biology and Fertility of Soils 39, 103e111.

Schwartz, S.M., Freeman, P.G., Russell, C.R., 1958. Soil-conditioning properties ofmodified agricultural residues and related materials: II. Persistence of soil-stabilizing activity as a function of type and extent of modification. SoilScience Society of America Journal 22, 409e414.

Sinsabaugh, R.L., 2010. Phenol oxidase, peroxidase and organic matter dynamics ofsoil. Soil Biology and Biochemistry 42, 391e404.

Tisdall, J.M., Oades, J.M., 1982. Organic matter and water-stable aggregates in soils.European Journal of Soil Science 33, 141e163.

Trinsoutrot, I., Recous, S., Bentz, B., Linères, M., Chèneby, D., Nicolardot, B., 2000.Biochemical quality of crop residues and carbon and nitrogen mineralizationkinetics under nonlimiting nitrogen conditions. Soil Science Society of AmericaJournal 64, 918e926.

Vandevivere, P., Moreau, B., Dufey, J.E., Chaing, C.N., 1990. Effet de l’azote minéralsur la stabilité structurale d’un sol limoneux amendé par des résidus organ-iques. Revue de l’Agriculture 43, 176e186.