Soil & Tillage Research 120 (2012) 8–14

Soil organic matter characteristics, biochemical activity and antioxidant capacityin Mediterranean land use systems

R. Cardelli *, F. Marchini, A. Saviozzi

Department of Crop Biology, University of Pisa, Via del Borghetto, 80 56124 Pisa, Italy

A R T I C L E I N F O

Article history:

Received 26 September 2011

Received in revised form 29 December 2011

Accepted 8 January 2012

Available online 6 February 2012

Keywords:

Mediterranean environment

Land use

Soil quality indices

Soil antioxidant capacity

C mineralization

A B S T R A C T

The characteristics of soil quality were measured in adjacent agricultural (horticultural cropping

sequence, HC), native grassland (naturally grazed, NG) and forest (indigenous wood of holm-oak, F) soils.

The objective of the research was to assess the influence of different land uses on soil organic matter

characteristics, biochemical activity and antioxidant capacity in selected fields of the Mediterranean

environment in central Italy under a specific climatic regime.

Land use induced significant changes in the content and quality of soil organic matter, biochemical

activity and antioxidant capacity, with more pronounced differences between soils under HC and F than

soils under HC and NG. The HC soil showed the lowest amounts of total organic carbon (TOC), microbial

biomass C (MB-C), water-soluble organic C (WSOC), water- and alkali-soluble phenols. The organic

matter of HC was characterized by the lowest percentage of MB-C and of light fraction carbon (LF-C). The

dehydrogenase activity (DH-ase), metabolic potential (MP), hydrolyzing coefficient (HyC), potentially

mineralizable C (C0) and C mineralized (Cm) were clearly lower in HC. The specific respiration activity of

biomass (qCO2) was the highest in HC soil (1.3 mg CO2–C mg biomass C�1) and lowest in F soil

(0.5 mg CO2–C mg biomass C�1) and was inversely related with pH, TOC and MB-C contents. The

antioxidant capacity of soils (TEAC) was the highest in NG and related to the amount of alkali-soluble

phenols. The rate constant of organic matter mineralization (k) appeared to depend on TEAC rather than

the relative amounts of the labile C pools. These results seem to explain the role of phenols as controller

of the mineralization rate of organic matter.

� 2012 Elsevier B.V. All rights reserved.

Contents lists available at SciVerse ScienceDirect

Soil & Tillage Research

jou r nal h o mep age: w ww.els evier . co m/lo c ate /s t i l l

1. Introduction

Agronomic practices designed to optimize production inagriculture, including the interconversion of forest and agriculturalland, strongly affect soil quality. Long term researches (Haynes andTregurtha, 1999; Moscatelli et al., 2007; Saviozzi et al., 1994; Tanand Lal, 2005) have shown that cultivation of native soil, inaddition to climatic and pedogenic factors (Parton et al., 1987),decreases the soil organic matter content. Hajabbasi et al. (1997)reported that deforestation and subsequent tillage practicesresulted in almost a 50% decrease in organic matter. Maintainingthe organic matter content requires a balance between additionand decomposition rates. As changes in land use can markedlyaffect both the pool size and turnover rate of organic C, it isimportant to analyze their nature and impacts. Merino et al. (2004)showed that transformation of the cropland to pasture slightlyincreased the organic and microbial biomass C contents, whereasafforestation significantly increased these variables.

* Corresponding author. Tel.: +39 0502216614; fax: +39 0502216630.

E-mail address: cardelli@agr.unipi.it (R. Cardelli).

0167-1987/$ – see front matter � 2012 Elsevier B.V. All rights reserved.

doi:10.1016/j.still.2012.01.005

Changes in land use and soil management practices decreasingthe organic matter content are largely responsible for increases inatmospheric CO2 from terrestrial ecosystem (Canadell et al., 2000).Consequently, efficient utilization of soil as a C sink will requireidentification of soil systems with high potential for sequestrationand improved methods of monitoring soil C. Recently, landprotection from deforestation to minimize future emissions ofCO2 has gained wide international support (Gullison et al., 2007;Turner et al., 2009). The Copenhagen Accord (2009) features landprotection as a mechanism to provide diminished CO2 emissions,although some scientists question whether reduced deforestationcan appreciably decrease atmospheric CO2 (van der Werf et al.,2009).

Recently, it was hypothesized by Rimmer (2006) that theprotection of the organic matter from oxidation is linked to the soilantioxidant capacity (TEAC). The mechanism explaining this effectis probably the antioxidant activity of the phenol compounds insoil organic matter and in associated plant materials, able to slowthe rate of oxidation so controlling the rate of breakdown in morelabile and easily degradable fractions. As reported by Zibilske andBradford (2007), the accumulation of soil organic matter could bestimulated by using cover crops with higher phenol content, which

R. Cardelli et al. / Soil & Tillage Research 120 (2012) 8–14 9

could slow C mineralization. Rimmer and Smith (2009) and Rimmerand Abbott (2011) demonstrated that the amounts of antioxidantsvary from soil to soil, reflecting soil water-soluble organic (WSOC)and total (TOC) C contents. Since for a given soil within a givenclimate, land use and soil management determine the amount andquality of soil organic matter, the measure of the TEAC could be auseful tool to highlight any difference and especially providemechanisms for understanding these differences.

The relationship between land use and properties of soil organicmatter is not completely understood because a large proportion ofthe organic fraction is very stable with a turnover time that may beas long as several thousand years (Stevenson, 1982). Changes inorganic matter content occur slowly and do not always provideadequate information of changes in soil quality that may occur. Thelabile organic matter pools can be considered as fine indicators ofsoil quality because they are highly dynamic, readily available tosoil organisms and much more sensitive than total organic matterto changes in soil land use (Haynes, 2004). Within the labile pools,the light organic matter fraction consists of partially decomposedplant litter, and it acts as a substrate for soil microbial activity(Greenland and Ford, 1964). Water soluble organic matter consistsof organic compounds present in soil solution, and is a primarysource of mineralizable substrate for microbial biomass (Cook andAllan, 1992). Measurement of potentially mineralizable C has alsobeen suggested to be important because it represents a bioassay oflabile organic matter using the microorganisms to release labileorganic fractions of C (Gregorich et al., 1994; Riffaldi et al., 2003).

Soil biochemical parameters have also been seen to provide areliable tool with which to estimate early changes in the dynamicsand distribution of soil microbial processes in different land usesystems (Bending et al., 2004). Among them, soil enzymes can beconsidered as good markers of soil biological fertility because oftheir essential role in soil biology, ease of measurement, and rapidresponse to changes in soil management such as use of fertilizers,amendments, vegetation cover and pesticides (Gianfreda andBollag, 1996). Microbial biomass, respiration rate, specific respira-tion of biomass (qCO2, ratio of respired C to biomass C), ratio ofmicrobial biomass C to total organic C, are other valid biologicalmeasurements that have been suggested as indicators for assessinglong-term soil management effects on soil quality (Cardelli et al.,2004; Dilly et al., 2003; Levi-Minzi et al., 2002; Riffaldi et al., 2002;Saviozzi et al., 2007). In particular, such parameters are sensitive tochanges in soil C availability, caused by alterations in soilmanagement practice, and can change markedly before anychanges in organic matter content are detected (Haynes andBeare, 1996).

Saviozzi et al. (2001), studying several soil enzyme activities inadjacent differently managed soils, reported that generally all thebiological properties had maximal activity levels in nativegrassland soil, followed by forest and then by cultivated soil.Much of the literature agrees with these general trends but data forindividual sites show great variability because soils differconsiderably in their rates of organic matter loss (Riffaldi et al.,1996), as a result of their chemical and physical propertiesinfluencing the magnitude of biological processes and theimposition of different soil management systems. In the Mediter-ranean area, specifically in central Italy regions where many soilsare subjected to loss of organic matter and progressive degrada-tion, researches were carried out on the effect of land uses andmanagement practices on the soil characteristics (Marinari et al.,2007; Moscatelli et al., 2007; Saviozzi et al., 1994, 2001).

Since the management systems react differently in differentclimatic regimes with respect to soil quality, this research aims toassess the influence of different land uses on soil quality of selectedfields in Mediterranean environment of the central Italy under aspecific climatic regime.

2. Materials and methods

Three experimental plots were located at Lucignana, near Lucca(Italy), Lat 4480300000N Lon 1083201200E, on a hilly uniform areaabout 500 m from sea level. The location has a long-termprecipitation average of 1590 mm year�1 and a mean annualtemperature of 12.4 8C. The soil was sandy clay loam (USDA).

The three plots, located in adjacent sites, consisted of: (1)indigenous wood of holm-oak (Quercus Ilex L.) (F); (2) undisturbednative grassland (NG); (3) horticultural cropping sequence (HC).The F site was a natural age-old wood extended an area of about1 ha. NG site was a naturally grazed grassland (about 4000 m2). HCsite (about 2500 m2), consisting mainly and alternatively oflegumes and potatoes, was cultivated conventionally from aboutseventy years, according to local usage for what concerns annualtillage (depth ploughing 25 cm), fertilization, irrigation, and pestcontrol. In the last years, N, P, and K were applied in the form ofcompound fertilizer (12–12–12). Copper oxychloride was used asfungicide and imidacloprid as insecticide for pest control.

The soil samples, collected in May 2010 and consisting of 20 coresmeasuring 5 cm dia � 15 cm depth, were air-dried and passedthrough a 2 mm sieve. Any large root fragments found after sievingwere discarded, along with all soil particles larger than 2 mm. pH,cation exchange capacity (CEC), total N (TN), available P andexchangeable K were determined by standard methods (SISS, 1985).

Part of each sample was air dried and stored at 4 8C, before thefollowing analyses were carried out:

- total organic carbon (TOC) by dry combustion (induction furnace900 CS, Eltra), after removing carbonate C;

- water soluble organic carbon (WSOC) by stirring samples of soilwith distilled water (soil/H2O 1:20) for 24 h at room tempera-ture, centrifuging the suspension at 10,000 rpm for 10 min and,after filtration through a 0.4 mm glass fibre, determining thecarbon by dichromate oxidation titration (Ciavatta et al., 1991);

- light fraction (LF) of organic matter was separated from soilsamples by the method of Strickland and Sollins (1987) andweighed;

- light fraction carbon (LF-C) by dry combustion (induction furnace900 CS, Eltra);

- a short term (28 days) aerobic incubation was used to determinethe potential of the samples to mineralize organic C. The CO2

evolution was monitored daily between 1 and 28 days: 50 g ofsoil were placed in 250-ml glass containers closed with rubberstoppers, moistened at 50% of the maximum water holdingcapacity and incubated at 25 � 1 8C; the CO2 evolved was trappedin NaOH solution and the alkali excess was titrated with HCl (Levi-Minzi et al., 1990); sodium hydroxide reacted with carbon dioxideaccording to the reaction:

CO2þ H2O þ 2NaOH ! 2H2O þ Na2CO3

The CO2 produced, and then the C mineralized were calculatedusing the equation:

mg mineralized C

100 g soil¼ ðml NaOHblank � ml NaOHsamÞ � 0:5 � 2 � 12

2

The results, normalized with respect to time, were expressed asmg of C mineralized/100 g of dry soil.

- microbial biomass C (MB-C) content was determined accordingto Vance et al. (1987) with extraction from fumigated andunfumigated soils by 0.5 M K2SO4, measuring the organic C asdescribed by Jenkinson and Powlson (1976). An extraction

R. Cardelli et al. / Soil & Tillage Research 120 (2012) 8–1410

efficiency coefficient of 0.38 was used to convert the difference insoluble C between the fumigated and unfumigated soil inmicrobial biomass C (Vance et al., 1987);

- specific respiration of biomass (qCO2) was calculated as follows:the CO2 evolved during the 15th day of incubation was used asbasal respiration value because, after that period, the soil reacheda constant rate of CO2 production. The specific respiration ofbiomass (mgC–CO2basal h�1 mgbiomassC�1) represents the mi-crobial respiration per biomass unit (Schnurer et al., 1985);

- water-soluble phenols were determined on the same extractused for WSOC (soil:water); alkali-soluble phenols on a 2 MNaOH solution extracts (soil:solution, 1:5). The NaOH extrac-tion was performed under N2 for 16 h at room temperature;after centrifuging (6000 rpm � 15 min), the centrifuged wasfiltered on cellulose acetate (pore size 0.2 mm) and treatedwith a 10% solution of TCA to remove proteins. The water- andalkali-extracted phenols were determined using a Folin–Ciocalteu reagent, following the method of Kuwatsuka andShindo (1973);

- trolox equivalent antioxidant capacity (TEAC) was determinedon the 2 M NaOH solution extract used for phenols. Themethod (Re et al., 1999) is based on the use of ABTS+, a stablecolored radical in aqueous solution. The measurement ofantioxidant capacity is expressed as a decrease in absorbanceof the solution of ABTS+ after the addition of an antioxidant.10 ml of the extract were neutralized to a value of 7.0 � 0.2using 1 M HCl solution. The neutralization of the extracts is acrucial phase, because the antioxidant capacities of many of thephenolic acids that are likely to be present in the extracts aredemonstrated to be pH-sensitive (Labrinea and Georgiou, 2004).For the measurement of antioxidant capacity, 3 ml of a solutionof ABTS+ radical, obtained by reacting overnight an ABTS stocksolution (7 mM) with a 24.5 mM potassium persulfate solution,were placed directly in spectrophotometer cuvettes. 30 ml ofeach extract were then added and, in blank cuvette, 30 ml ofdeionized H2O. The absorbance of the blank was read with aspectrophotometer setted at a wavelength of 734 nm andconsidered optimal if it gave a value of about 0.700. Eachcuvette was then sealed with parafilm, shaken and placed toincubate in the dark at 25 8C. After exactly 60, the absorbance ofthe mixture has been newly read. The decrease in absorbance dueto the activity of soil extract on antioxidant ABTS+ radical wasexpressed as a percentage of initial absorbance. It was thereforeprepared a calibration curve using Trolox (6-hydroxy-2,5,7,8-tetramethylchroman-2-carboxylic acid) as reference substance toallow a comparison between the percentage decrease resultedfrom the extract of soil with that caused by Trolox.

- enzyme activities were assayed on fresh sieved soil stored at 4 8C,within 1 week from sampling: dehydrogenase activity (DH-ase)was determined by the method of Casida et al. (1964)(mg triphenylformazan g�1 h�1);

- hydrolysis rate of fluorescein diacetate (FDA-H) was estimated asreported by Swisher and Carroll (1980), by determining theconcentration of fluorescein released by FDA (mg g�1 2 h�1) at490 nm.

Table 1Physical and chemical properties of agricultural (HC), grassland (NG) and forest (F) soi

Land use pH TOCa (g kg�1) TNb(g kg�1) C/N CE

HC 6.1 c 18.8 c 3.0 b 6.3 c 14

NG 6.6 b 26.4 b 2.9 b 9.0 b 17

F 7.0 a 107.7 a 7.2 a 15.0 a 30

Means in the same column followed by different letters indicate significant differencea Total organic carbon.b Total nitrogen.c Cation exchange capacity.

The biochemical indexes were calculated as follows:

a) Hydrolyzing coefficient (HyC): HyC = FDA-H/FDAt, where FDAtis total fluorescein diacetate before hydrolysis (Perucci, 1992);

b) Metabolic potential (MP) (Masciandaro et al., 1998): MP = DH-ase/1�10�4 WSOC.

All data were expressed on the basis of oven-dry weight of soiland the results reported are the means of determinations made onthree replicates.

Statistical analysis of percent values was performed onangularly transformed data; differences among mean values ofreplicates for treatments were compared at 0.05 significant levelby Analysis of Variance (ANOVA) test.

A non linear least square regression analysis (Graph Pad Prism)was used to calculate parameters from cumulative data of C-mineralization. C mineralization kinetics were determined follow-ing a first-order model [Cm = C0(1 � e�kt)] (Riffaldi et al., 1996),where Cm is the cumulative value of mineralized C during t (days);C0 is the potentially mineralizable carbon and k is the rate constantof C mineralization. The coefficient of determination (R2) was usedfor the evaluation of model fit.

3. Results and discussion

Soil physical and chemical properties are reported in Table 1.Soil pH was significantly lower in HC than in NG and F soils,perhaps due to the effect of repeated use of ammonium-basedfertilizers and the release of H+ by legume roots due to excessuptake of cations over anions during N2 fixation (Tang et al., 1997).The pH value was lower in NG than in F; these findings appear tocontrast with results of Buschbacher et al. (1988) who reportedincreases in soil pH after forest cutting. However, De Moraes et al.(1996) reported that increase in soil pH was significant only in theyoungest pastures while, after the initial increase through 5 year,pH values tend to decrease as a consequence of reduction inexchangeable cations.

Data in Table 1 shows that the total organic carbon (TOC) wassignificantly affected by land use. Despite its high inorganicnutrient status, the soil under long-term vegetable production hadthe lowest TOC content (18.8 g C kg�1). Compared with theundisturbed NG and F areas, the HC soil showed a decrease byabout 29% and 82% respectively. The decline, due both to reducedsupply of organic material and an increased rate of organic matterdecomposition induced by the routine annual ploughing, ischaracteristic of that occurring when undisturbed forest isconverted to continuous arable agriculture (Haynes and Tregurtha,1999; Riffaldi et al., 1996, 2003; Saviozzi et al., 1994). For example,Hajabbasi et al. (1997) reported that deforestation and subsequenttillage practices resulted in almost a 50% decrease in organic Ccompared to an undisturbed forest soil. The lower amount of TOCin NG soil than in F soil could be due to higher inputs of plantresidues in the forest, where there are other sources of organicmatter such as undergrowth vegetation.

ls.

Cc (Cmol(+) kg�1) Available P (mg kg�1) Exchangeable K (mg kg�1)

.3 c 36 a 543 a

.7 b 14 b 302 c

.4 a 19 b 480 b

s (P < 0.05) according to LSD’F multiple test.

R. Cardelli et al. / Soil & Tillage Research 120 (2012) 8–14 11

As a consequence of the great amount of organic matter, total Nwas the highest in F soil (7.2 g kg�1) while values were similar inHC and NG soils (3.0 and 2.9 g kg�1, respectively) (Table 1). This isprobably due to the N fertilizer annually applied to HC because, asreported by Jia et al. (2005), fertilization can increase the total Ncontent in soil.

Significant changes due to land use were also present in the C/Nratio, with the lowest value in HC soil (6.3) and the largest in F soil(15.0) (Table 1). The C/N ratio, lower in HC as compared to NG andF, reflects the different rates of loss of organic C and N or, assuggested by Marinari et al. (2007), the different nature ofvegetation residues that return to soil.

Table 1 shows the decline of the cation exchange capacity (CEC)in HC as compared with NG and F, caused by the decrease inorganic matter content. Available P and exchangeable K concen-trations were significantly higher in HC soil than in the NG and Fsoils. This indicates that long-term fertilization is responsible forthe increase of available P and K content in the cultivated site.

Values of microbial biomass ranged from 650 mg g�1 of HC soilto 6620 mg g�1 of F soil (Table 2). Higher values of MB-C (from1110 mg g�1 in soil under horticultural cropping to 1740 mg g�1 insoil under natural grassland) were reported by Riffaldi et al. (2003).This difference may be due to the more favorable climaticconditions of south-eastern Sicily (Italy) environment, character-ized by a mean monthly temperature of 19.7 8C and an averageyearly precipitation of 549 mm. Smith and Paul (1990) reportedthat soils that are ploughed routinely contain less microbialbiomass than soils under no tillage, or perennial crops. Inagreement, the soil used for arable production of vegetablescontained 42% and 90% of microbial biomass C less than NG and Fsoils, respectively. As well as the absolute amounts of MB-C, theMB-C values expressed in relation to C content (as % of TOC, Table2) were significantly higher in F than in NG and HC, in this order.This suggests that microbial biomass was preferentially changedby the land use relative to the bulk of organic C. The decrease inMB-C%TOC in HC is likely due to low returns of metabolizable C insoil and/or decrease of number of bacteria, commonly found insoils treated with mineral fertilized variants (Kubat et al., 1999).The MB-C%TOC values were similar to those reported by Meleroet al. (2006) and Moscatelli et al. (2007) in studies carried out inSpain and Italy, respectively, but were generally higher than thosereported by Castillo and Joergensen (2001) in a study conducted ina tropical area with an annual precipitation rate of 1500–2200 mmand a mean annual temperature varying between 27 and 29.5 8C.This difference may be due to different climatic conditions in theMediterranean area and in tropical environment.

The light fraction (LF), consists primarily of recognizable plantresidues that have not been highly degraded by decomposers insoil (Greenland and Ford, 1964). It is characterized by the labilenature of its constituents and by the lack of protection by soilcolloids. The availability of carbon of the light fraction was found tobe associated with the basal respiration and carbon in the soilmicrobial biomass (Alvarez et al., 1998). Land use significantly

Table 2Organic matter fractions of agricultural (HC), grassland (NG) and forest (F) soils.

Land use MB-Ca

(g kg�1)

MB-C (%TOC) LFb

(g kg�1)

LF-Cc

(g kg�1)

LF-C

(%TOC)

WSOCd

(mg kg�1)

HC 650 c 3.5 c 8.0 c 204.7 a 8.5 c 236 c

NG 1120 b 4.2 b 29.5 b 135.7 b 15.3 b 330 b

F 6620 a 6.1 a 163.8 a 192.6 a 29.2 a 812 a

Means in the same column followed by different letters indicate significant differencea Microbial biomass carbon.b Light fraction.c Light fraction carbon.d Water soluble organic carbon.

affected this parameter (Table 2). The LF content was greatest inundisturbed F and lowest in HC, yearly tilled and without additionof organic residues. Other studies had already found greateramounts of LF in forest and grassland than in arable soils (Riffaldiet al., 2003). As well as for TOC, the most pronounced differences inLF content were between HC and F soils. The light fractiondecreased by about 95% in HC compared to the value of F soil, adecrease greater than that observed for TOC. The carbon content oflight fraction (LF-C) followed a different trend compared to that ofthe total content of LF, with HC and F showing the highest and thelowest in NG (Table 2). However, when the LF-C content wasexpressed on the basis of TOC, values confirmed the general trendthat sees the labile organic pools of F soil richer than those of NGand HC soils.

Water-soluble organic carbon (WSOC), composed mainly oforganic acids and soluble carbohydrates (Cook and Allan, 1992),plays an important role in both natural and modified ecosystems,as a substrate for microorganisms (Davidson et al., 1987). Theamount of WSOC in the soil used for vegetable production wassignificantly lower than in native grassland and forest soils (Table2). This agrees with the findings reported by Riffaldi et al. (2002),who found a decrease in the content of the very active organicfractions in cultivated soils, relative to undisturbed areas. Thecontent of WSOC was clearly lower than that found by Saviozziet al. (2001) in a study on soil quality of adjacent cultivated, forestand native grassland soils in a area located in the province of Siena(Italy). This may be explained by more intense leaching of solublecompounds through the soil profile, due to the much greaterrainfall in the site examined in the present study (1590 mm year�1

against 930 mm year�1).The WSOC value, expressed on the basis of TOC, was similar in

HC and NG (1.5%, Table 2). The lower amount of TOC as WSOC inthe F site (0.7%) could be due to colder soil temperature, resultingfrom greater sunlight interception by foliage, with respect to HCand NG sites. Indeed, Christ and David (1996) showed that lowtemperature decreased WSOC content in soil.

The type of vegetation and cropping systems have been foundto exert a marked influence on the amount of the phenols in soil(Riffaldi et al., 1989). The water-soluble phenols are free and nonadsorbed form, while the alkali-soluble phenols are the chemicallybound form. Table 2 shows that long-term soil cultivation caused adecline in both water- and alkali-soluble phenols, with most cleardifferences between HC and F. The lower amount of phenols in soilused for vegetable production compared to the two land usesagrees with the findings of Riffaldi et al. (2003). In particular, it canbe noted that the decrease of the water-soluble phenols in HC withrespect to F was of the same order of magnitude (by about 60%)observed for WSOC amounts in the same sites (Table 2). In parallel,the decline of alkali-soluble phenols in HC soil compared to F soilwere similar to the corresponding decline of TOC (by about 80%,Table 1). These results suggest that the decline in soluble forms dueto changes in land use is to a lesser extent than the correspondingdecrease of the total organic matter.

WSOC

(%TOC)

Phenol compounds

(H2O) (mg kg�1)

Phenol compounds

(NaOH) (mg kg�1)

Phenol compounds

(NaOH) (%TOC)

1.5 a 35 c 1021 c 54 b

1.5 a 45 b 2004 b 76 a

0.7 b 92 a 4507 a 42 b

s (P < 0.05) according to LSD’F multiple test.

R. Cardelli et al. / Soil & Tillage Research 120 (2012) 8–1412

Rimmer and Smith (2009) and Rimmer and Abbott (2011)showed that the trend of soil antioxidant capacity (TEAC) increasedwith the TOC and WSOC contents of soils. Accordingly, in thepresent study values of TEAC were directly related to both those ofTOC (Table 1) and WSOC (Table 2), and decreased in the order:F > NG > HC (Table 3). Rimmer and Smith (2009) reported thatTEAC of organic residues was greater than that of soil. This mayexplain the high TEAC of F soil (Table 3), probably due to its highamount of light fraction, made up largely of organic residues invarious stages of decomposition. This result may put in evidence adirect relationships between the amounts of LF and TEAC in soil. Tobetter evaluating the differences in TEAC between HC, NG and Fsoils, the dominant influence of soil C content was removed bynormalizing the data (Table 3). The influence of the land useremained but the normalized data, expressed on TOC basis,showed the highest TEAC in NG soil. As reported by Rimmer andSmith (2009) and Rimmer and Abbott (2011), TEAC is mainly dueto the antioxidant activity of the alkali-soluble phenols in theorganic matter. Accordingly, the highest amount of alkali-solublephenols, as %TOC, was found in NG (Table 2), due to the differentnature of plant material returned to soil.

The presence of antioxidants in soil could have a significanteffect on the dynamics of soil organic matter. Rimmer (2006)hypothesized that TEAC is able to protect the soil organic matterfrom degradation. To identify a possible influence of TEAC, relatedto the content of alkali-soluble phenols, on the rate of organic Cdecomposition, a rapid bioassay of the potential of soils tomineralize the easily decomposable organic fraction was carriedout and parameters related to C mineralization were calculated.Data reported in Table 3 show that the rate constants of Cmineralization (k) fell within a narrow range, but were signifi-cantly higher in HC and F soils (0.14 and 0.12 day�1) than in NG soil(0.10 day�1). Comparing k values to the amount of phenolcompounds and TEAC (both normalized to TOC), NG soil showedthe highest percentage of phenols, highest TEAC and, consequently,the smallest k. HC and F soils showed instead lower phenol content,lower TEAC and the highest k. No clear relationships were insteadfound between the rate constant of C mineralization (k) and eithervalues of LF-C, WSOC (Table 2) and the potentially mineralizablecarbon Co (Table 3) (all expressed as percent of TOC), theconstituents of the easily mineralizable C. This means that k

values of soils are mainly due to the antioxidant capacity ratherthan to the amounts of the labile C pools. These results seem toexplain the role of phenols as antioxidants and as controller of therate of oxidation, and then decomposition, of organic C.

The short-term mineralization under laboratory incubationconditions may also estimate changes in the amount of the easilymineralizable C (Gregorich et al., 1994). The Cm value (i.e. C

Table 3Biochemical properties of agricultural (HC), grassland (NG) and forest (F) soils.

Land

use

TEACa

(mM g�1 soil)

TEAC

(mM g�1 TOC)

Cmb

(mg kg�1)

Cm

(%TOC)

C0c

(mg kg�1)

C0

(%TO

HC 2.01 c 10.7 b 54 c 2.9 a 56 c 3.0 a

NG 3.99 b 15.1 a 88 b 3.3 a 89 b 3.4 a

F 9.21 a 8.5 c 330 a 3.1 a 339 a 3.2 a

Means in the same column followed by different letters indicate significant differencea Trolox equivalent antioxidant capacity.b Cumulative amount of mineralized carbon during 28 days of incubation.c Potentially mineralizable carbon.d Rate constant.e Quality of fit.f Specific respiration of biomass.g Dehydrogenase activity.h Metabolic potential.i Hydrolyzing coefficient.

mineralized during 28 days) was the greatest in F soil and smallestin HC soil (Table 3). The Cm value, expressed on the basis of TOC,was similar in all three soils and averaged by about 3% TOC. Thismeanings that the reductions were roughly proportional to TOClosses and indicates similar quantity of available carbon withrespect to TOC for the active microbial biomass during minerali-zation. As for Cm, the potentially mineralizable carbon (C0) was thehighest in F soil (339 mg C g�1) and the lowest for HC soil(56 mg C g�1) (Table 3). The similarity of C0 as percent TOC, byabout 3, in the soils under the three land uses confirms a similarcontent of organic matter in the form available for microbialactivity.

If the basal respiration rates were related to biomass size, thespecific respiration of biomass (qCO2) so obtained represents theCO2–C produced per unit biomass and time. The parameterindicates how efficiently the microbial biomass utilizes available Cfor biosynthesis rather than for maintenance respiration. Schnureret al. (1985) found qCO2 a sensitive indicator for estimating theinfluence of cropping on biological activity and substrate qualityand noted high qCO2 values in systems where fertilizers wereapplied. Anderson and Domsch (1993) reported that qCO2

increases when the ecosystem is stressed, polluted or in adverseclimatic conditions. Haynes and Tregurtha (1999), in a studyconcerning the effects on soil conditions of increasing periodsunder intensive cultivation for vegetable production, reported thatqCO2 remained unaffected. Moscatelli et al. (2007) reportedsignificantly higher qCO2 values in agricultural soils than in bothforest and grassland soils. In our study, the specific respirationactivity of biomass was influenced by land use and showed aninverse relation with TOC content (Table 3). The highest value ofqCO2 was in HC soil with 1.3 mg CO2–C mg biomass C�1 while F soilhad the minimum value of 0.5 mg CO2–C mg biomass C�1. The highqCO2 value of HC suggests an intense competition for the availableC made accessible after soil tillage (Paustian et al., 2000).Moreover, Islam and Weil (2000) reported that perturbed systems,such as HC, favored bacteria having low efficiency in C assimilation,while more efficient fungi are dominating in untilled or natural notstressed systems.

It is interesting to note that to the low microbial pool size of HC(Table 2) corresponded the highest level of specific respirationactivity of biomass (qCO2). Also, to a high amount of microbialbiomass of F soil corresponded the lowest qCO2. This suggests, asindicated by Nsamibana et al. (2004), the predominance of moreactive microorganisms in HC and/or an increase in the ratio fungi/bacteria caused by the different quality of available carbon in F.

Anderson and Domsch (1993) found an inverse relationbetween qCO2 and soil reaction. Accordingly, the highest qCO2

was in the most acidic soil HC, while the lowest qCO2 was in the

C)

Kd R2e qCO2f

(mgCO2–C h�1 mg

biomass C�1�102)

DH-aseg

(mgTTF g�1 h�1)

MPh HyCi

0.14 a 0.98 1.3 a 0.60 c 22 c 0.42 c

0.10 c 0.98 1.0 b 1.28 b 32 b 0.61 b

0.12 b 0.97 0.5 c 12.88 a 168 a 0.96 a

s (P < 0.05) according to LSD’F multiple test.

R. Cardelli et al. / Soil & Tillage Research 120 (2012) 8–14 13

forest soil, showing the highest pH (Table 1). This indicates that soilreaction may be responsible for the discrimination of the soilmicrobial activity in soils under forest, grassland and agriculturalmanagement.

Studies from long-term sites have shown that soil enzymeactivities, as indicators of microbial activity, may highlight theeffects due to different soil management. Dick et al. (1988)reported a decrease of dehydrogenase (DH-ase) activity followingtillage of virgin soils. Accordingly, in our study, DH-ase activity wasdepressed by long-term cultivation compared to native grasslandand forest (Table 3). According to the results of Dick (1984) andRiffaldi et al. (2003) concerning the influence of long-term tillageon soil enzyme activities, the DH-ase activity appear closely relatedto organic C concentrations in soil (Table 1).

Soil enzyme activities have been used by some authors(Masciandaro et al., 1998; Perucci, 1992) as a basis for empiricalindexes of soil quality. The metabolic potential (MP), calculated asthe ratio between DH-ase activity and WSOC (Masciandaro et al.,1998), was about 1.4 and 8 times higher in NG and F, respectively,than in HC soil (Table 3). This confirms a strong decrease inmetabolic activity occurring when virgin soil is intensivelycultivated.

The hydrolyzing coefficient (HyC) was of 0.42 in HC soil, 0.61 inNG and 0.96 in F soils (Table 3), which is the same trend of themetabolic potential. Cardelli et al. (2004) reported a similar valueof 0.35 in soil under horticultural cropping in southern Liguria(Italy). The lower value of HyC in cultivated compared touncultivated soils indicates a lower hydrolyzing capacity and,consequently, a lower soil fertility. In spite of the significantdifferences between the three sites, all the values resulted greaterthan 0.3, which is considered as an index of good fertility (Perucci,1992).

4. Conclusions

The results of this study showed that land use can significantlychange soil quality. In general, differences were more markedbetween soils under horticultural cropping and forest.

The soil used for vegetable production showed a strongdecrease of organic C, microbial biomass C, water-soluble organicC, water- and alkali-soluble phenols, dehydrogenase activity (DH-ase), metabolic potential (MP), hydrolyzing coefficient (HyC),potentially mineralizable C (C0) and C mineralized (Cm). Theorganic matter of soil under horticultural cropping showed thelowest percentage of MB-C and of light fraction carbon (LF-C),suggesting that this cropping system is detrimental to soil quality.

The specific respiration activity of biomass (qCO2) was alsoinfluenced by land use; the highest value was in the soil underhorticultural cropping and showed an inverse relation with pH,organic C and microbial biomass C contents. This indicates that themicrobial biomass in the agricultural soil was less efficient in theutilization of substrates for biomass synthesis.

A close relationship between the amount of alkali-solublephenols and the soil antioxidant capacity was observed. Theantioxidant capacity appeared to influence the rate of organic Cmineralization more than the relative contents of the easilymineralizable C pools. These results seem justify the role of phenolcompounds as controller of the rate of organic C mineralization.

References

Alvarez, C.R., Alvarez, R., Grigera, M.S., Lavado, R.S., 1998. Associations betweenorganic matter fractions and the active soil microbial biomass. Soil Biol.Biochem. 30, 767–773.

Anderson, T.H., Domsch, K.H., 1993. The metabolic quotient for CO2 (qCO2) a specificactivity parameter to assess the effect of environmental conditions, such as pH,on the microbial biomass of forest soils. Soil Biol. Biochem. 25, 393–395.

Bending, G.D., Turner, M.K., Rayns, F., Marx, M.C., Wood, M., 2004. Microbial andbiochemical soil quality indicators and their potential for differentiating areasunder contrasting agricultural management regimes. Soil Biol. Biochem. 36,1785–1792.

Buschbacher, R., Uhl, C., SemIto, A.S., 1988. Abandoned pastures in eastern Ama-zonia. II: nutrient stocks in the soil and vegetation. J. Ecol. 76, 682–699.

Canadell, J.G., Mooney, H.A., Baldocchi, D.D., Berry, J.A., Ehleringer, J.R., Field, C.B.,Gower, S.T., Hollinger, D.Y., Hunt, J.E., Jackson, R.B., Running, S.W., Shaver, G.R.,Steffen, W., Trumbore, S.E., Valentini, R., Bond, B.Y., 2000. Carbon metabolism ofthe terrestrial biosphere: a multitechnique approach for improved understand-ing. Ecosystems 3 (2), 115–130.

Cardelli, R., Levi-Minzi, R., Saviozzi, A., Riffaldi, R., 2004. Organically and conven-tionally managed soils: biochemical characteristics. J. Sustain. Agric. 25, 63–74.

Casida Jr., L.E., Klein, D.A., Santoro, T., 1964. Soil dehydrogenase activity. Soil Sci. 98,371–376.

Castillo, X., Joergensen, R.G., 2001. Impact of ecological and conventional arablemanagement systems on chemical and biological soil quality indices in Nicar-agua. Soil Biol. Biochem. 33, 1591–1597.

Christ, M.J., David, M.B., 1996. Temperature and moisture effects on the productionof dissolved organic carbon in a spodosol. Soil Biol. Biochem. 28, 1191–1199.

Ciavatta, C., Govi, M., Antisari Vittori, L., Sequi, P., 1991. Determination of organiccarbon in aqueous extract of soil and fertilizers. Commun. Soil Sci. Plant Anal.22, 795–807.

Cook, B.D., Allan, D.L., 1992. Dissolved organic carbon in old field soils: totalamounts as a measure of available resources for soil mineralization. Soil Biol.Biochem. 24, 585–594.

UNFCC.Davidson, E.A., Galloway, L.F., Strand, M.K., 1987. Assessing available carbon:

comparison of techniques across selected forest soil. Commun. Soil Sci. PlantAnal. 18, 45–64.

De Moraes, F.F.L., Volkoff, B., Cerri, C.C., Bernoux, M., 1996. Soil properties underAmazon forest and changes due to pasture installation in Rondonia, Brazil.Geoderma 70, 63–81.

Dick, W.A., 1984. Influence of long-term tillage and crop rotation combinations onsoil enzyme activities. Soil Sci. Soc. Am. J. 48, 569–574.

Dick, R.P., Myrold, D.D., Kerle, E.A., 1988. Microbial biomass and soil enzymeactivities in compacted and rehabilitated skid trail soils. Soil Sci. Soc. Am. J.52, 512–516.

Dilly, O., Blume, H.P., Sehy, U., Jimenez, M., Munch, J.C., 2003. Variation ofstabilised, microbial and biologically active carbon and nitrogen in soil undercontrasting land use and agricultural management practices. Chemosphere52, 557–569.

Gianfreda, L., Bollag, J.M., 1996. Influence of natural and anthropogenic factors onenzyme activity in soil. In: Stotzky, G., Bollag, J.M. (Eds.), Soil Biochemistry, vol.9. Marcel Dekker, NY, USA, pp. 123–193.

Greenland, D.J., Ford, G.W., 1964. Separation of partially humified organic materialsfrom soils by ultrasonic dispersion. In: Trans. Int. Congr. Soil Sci. 8th, Bucharest,Romania, pp. 137–146.

Gregorich, E.G., Carter, M.R., Angers, D.A., Monreal, C.M., Ellert, B.H., 1994. Towardsa minimum data set to assess soil organic matter quality in agricultural soils.Can. J. Soil Sci. 74, 367–385.

Gullison, R.E., Frumhoff, P.C., Canadell, J.G., 2007. Tropical forests and climate policy.Science 316, 985–986.

Hajabbasi, M.A., Jalaliant, A., Karimzdadeh, H.R., 1997. Deforestation effects on soilphysical and chemical properties, Lordegan, Iran. Plant Soil 190, 301–307.

Haynes, R.J., Beare, M.H., 1996. Aggregation and organic matter storage in meso-thermal, humid soils. In: Carter, M.R., Stewart, B.A. (Eds.), Advances in SoilScience. Structure and Organic Matter Storage in Agricultural Soils. CRC Lewis,Boca Raton, pp. 213–262.

Haynes, R.J., Tregurtha, R., 1999. Effects of increasing periods under intensive arablevegetable. Biol. Fertil. Soils 28, 259–266.

Haynes, R.H., 2004. Labile organic matter fractions as central components of thequality of agricultural soils: an overview. Adv. Agron. 45, 221–268.

Islam, K.R., Weil, R.R., 2000. Land use effects on soil quality in a tropical forestecosystem of Bangladesh. Agric. Ecosyst. Environ. 79, 9–16.

Jenkinson, D.S., Powlson, D.S., 1976. The effects of biocidal treatments on metabo-lism in soil. V: a method for measuring soil biomass. Soil Biol. Biochem. 8, 209–213.

Jia, G.M., Cao, J., Wang, G., 2005. Influence of land management on soil nutrients andmicrobial biomass in the central Loess Plateau, northwest China. Land Degrad.Dev. 16, 455–462.

Kubat, J., Novakova, J., Mikanova, O., Apfelthaler, R., 1999. Organic carbon cycle,incidence of microorganisms and respiration activity in long-term field experi-ment. Rost. Vyroba 45, 389–395.

Kuwatsuka, S., Shindo, H., 1973. Behavior of phenolic substances in the decayingprocess of plants. I: identification and quantitative determination of phenolicacids in the rice straw and its decayed products by gas chromatography. Soil Sci.Plant Nutr. 19, 219–226.

Labrinea, E.P., Georgiou, C.A., 2004. Stopped-flow method for assessment of pH andtiming effect on the ABTS total antioxidant capacity assay. Anal. Chim. Acta 526,63–68.

Levi-Minzi, R., Riffaldi, R., Saviozzi, A., 1990. Carbon mineralization in soil amendedwith different organic materials. Agric. Ecosyst. Environ. 31, 325–335.

Levi-Minzi, R., Saviozzi, A., Cardelli, R., Riffaldi, R., 2002. Relationships betweenbiological and physico-chemical characteristics in a Mediterranean agriculturalarea. Arch. Acker-Pfl. Boden. 48, 279–288.

R. Cardelli et al. / Soil & Tillage Research 120 (2012) 8–1414

Marinari, S., Liburdi, K., Masciandaro, G., Ceccanti, B., Grego, S., 2007. Humification–mineralization pyrolitic indices and carbon factions of soil under organic andconventional management in central Italy. Soil Till. Res. 92, 10–17.

Masciandaro, G., Ceccanti, B., Gallardo-Lancho, G.F., 1998. Organic matter proper-ties in cultivated versus set-aside arable soils. Agric. Ecosyst. Environ. 67, 267–274.

Melero, S., Porras, J.C., Herencia, J.F., Madejon, E., 2006. Chemical and biochemicalproperties on a silty loam soil under conventional and organic management.Soil Till. Res. 90, 162–170.

Merino, A., Perez-Batallon, P., Macias, F., 2004. Responses of soil organic matter andgreenhouse gas fluxes to soil management and land use changes in a humidtemperate region of southern Europe. Soil Biol. Biochem. 36, 917–925.

Moscatelli, M.C., Di Tizio, A., Marinari, S., Grego, S., 2007. Microbial indicatorsrelated to soil carbon in Mediterranean land use systems. Soil Till. Res. 97,51–59.

Nsamibana, D., Haynes, R.T., Wallis, F.M., 2004. Size, activity and catabolic diversityof the soil microbial biomass as affected by land use. Appl. Soil Ecol. 2, 81–92.

Parton, W.J., Schimel, D.S., Cole, C.V., Ojima, D.S., 1987. Analysis of factors control-ling soil organic matter levels in Great Plain grassland. Soil Sci. Soc. Am. J. 51,1173–1179.

Paustian, K., Elliott, E.T., Six, J., Hunt, H.W., 2000. Management options for reducingCO2 emissions from agricultural soils. Biogeochemistry 48, 147–163.

Perucci, P., 1992. Enzyme activity and microbial biomass in a field soil amendedwith municipal refuse. Biol. Fertil. Soils 14, 54–60.

Re, R., Pellegrini, N., Proteggente, A., Pannala, A., Yang, M., Rice-Evans, C., 1999.Antioxidant activity applying an improved ABTS radical cation decolorizationassay. Free Radic. Biol. Med. 26, 1231–1237.

Riffaldi, R., Saviozzi, A., Levi-Minzi, R., 1989. Phenolic compounds in soils underpermanent pasture. Agrochimica 33, 380–386.

Riffaldi, R., Saviozzi, A., Levi-Minzi, R., 1996. Carbon mineralization kinetics asinfluenced by soil properties. Biol. Fertil. Soils 22, 293–298.

Riffaldi, R., Saviozzi, A., Levi-Minzi, R., Cardelli, R., 2002. Biochemical properties of aMediterranean soil as affected by long-term crop management systems. SoilTill. Res. 67, 109–114.

Riffaldi, R., Saviozzi, A., Levi-Minzi, R., Cardelli, R., 2003. Conventional crop man-agement effects on soil organic matter characteristics. Agronomie 23, 45–50.

Rimmer, D.L., 2006. Free radicals, antioxidants, and soil organic matter recalci-trance. Eur. J. Soil Sci. 57, 91–94.

Rimmer, D.L., Smith, A.M., 2009. Antioxidants in soil organic matter and in associ-ated plant materials. Eur. J. Soil Sci. 60, 170–175.

Rimmer, D.L., Abbott, G.D., 2011. Phenolic compounds in NaOH extracts of UK soilsand their contribution to antioxidant capacity. Eur. J. Soil Sci. 62, 285–294.

Saviozzi, A., Levi-Minzi, R., Riffaldi, R., 1994. The effect of forty years of continuouscorn cropping on soil organic matter characteristics. Plant Soil 160, 139–145.

Saviozzi, A., Levi-Minzi, R., Cardelli, R., Riffaldi, R., 2001. A comparison of soil qualityin adjacent cultivated, forest and native grassland soils. Plant Soil 233, 251–259.

Saviozzi, A., Cardelli, R., Labbaci, L., Levi-Minzi, R., Riffaldi, R., 2007. Selected enzymeactivities in particle-size fractions from an organically and conventionallymanaged soil. Fresenius Environ. Bull. 16, 1195–1200.

Schnurer, J., Clarholm, M., Rosswall, T., 1985. Microbial biomass and activity in anagricultural soil with different organic matter contents. Soil Biol. Biochem. 17,611–618.

SISS Societa italiana Scienza del Suolo, 1985. Metodi normalizzati di analisi delsuolo. Edagricole, Bologna, Italy.

Smith, J.L., Paul, E.A., 1990. The significance of soil microbial biomass estimates. In:Bollag, J.M., Stozky, G. (Eds.), Soil Biochemistry, vol. 6. Marcel Dekker, NewYork, pp. 357–396.

Stevenson, F.J., 1982. Humus Chemistry. John Wiley and Sons, New York.Strickland, T.C., Sollins, P., 1987. Improved method for separating light- and heavy-

fraction organic material from soil. Soil Sci. Soc. Am. J. 51, 1390–1393.Swisher, R., Carroll, G.C., 1980. Fluorescein diacetate hydrolysis as an estimation of

microbial biomass on coniferous needle surfaces. Microb. Ecol. 6, 217–226.Tan, Z., Lal, R., 2005. Carbon sequestration potential estimates with changes in land

use and tillage practice in Ohio, USA. Agric. Ecosyst. Environ. 111, 140–152.Tang, C., McLay, C.D.A., Barton, L., 1997. A comparison of proton excretion of twelve

pasture legumes grown in nutrient solution. Aust. J. Exp. Agric. 37, 563–570.Turner, W.R., Oppenheimer, M., Wilcore, D.S., 2009. A force to fight global warming.

Nature 462, 278–279.Vance, E.D., Brookes, P.C., Jenkinson, D.S., 1987. An extraction method for measuring

soil microbial biomass carbon. Soil Biol. Biochem. 19, 403–707.van der Werf, G.R., Morton, D.C., De Fries, R.S., Olivier, J.G.J., Kasibhatla, P.S., Jackson,

R.B., Collatz, G.J., Randerson, J.T., 2009. CO2 emissions from forest loss. Nat.Geosci. 2, 737–738.

Zibilske, L.M., Bradford, J.M., 2007. Soil aggregation, aggregate carbon and nitrogen,and moisture retention induced by conservation tillage. Soil Sci. Soc. Am. J. 71,793–802.