Bioresource Technology 97 (2006) 635–640

Effect of organic amendments on some physical, chemicaland biological properties in a horticultural soil

Laura Ferreras a,*, Elena Gomez b, Silvia Toresani b, Ines Firpo c, Rossana Rotondo c

a Catedra de Edafologıa, Facultad de Ciencias Agrarias, Universidad Nacional de Rosario,

Campo Experimental J. Villarino, 2125 Zavalla, Argentinab Catedra de Microbiologıa Agrıcola, Facultad de Ciencias Agrarias, Universidad Nacional de Rosario,

Campo Experimental J. Villarino, 2125 Zavalla, Argentinac Catedra de Horticultura, Facultad de Ciencias Agrarias, Universidad Nacional de Rosario,

Campo Experimental J. Villarino, 2125 Zavalla, Argentina

Received 5 July 2004; received in revised form 21 March 2005; accepted 22 March 2005

Available online 17 May 2005

Abstract

The aim of the present work was to assess the response of selected soil physical, chemical and biological properties, after two

applications of different organic amendments to a soil with an extended horticultural use. Vermicompost from household solid waste

(HSW) and from horse and rabbit manure (HRM), and chicken manure (CM) were applied at rates of 10 and 20 Mg ha�1. The

proportion of water stable soil aggregates (Ws) was significantly higher (p < 0.05) in HSW, HRM and CM at 20 Mg ha�1. The

proportion of ethanol stable soil aggregates (Es) was significantly higher in HSW, HRM and CM at 20 Mg ha�1, and CM at

10 Mg ha�1. After the first amendment application, HSW and HRM at 20 Mg ha�1 resulted in higher soil organic carbon

(SOC), while all the treatments showed a significant increase after the second amendment application. Linear relationships were

found between Ws and Es with SOC. An increment in microbial respiration in all the amended plots was observed with the exception

of HRM at the rate of 10 Mg ha�1.

� 2005 Elsevier Ltd. All rights reserved.

Keywords: Organic amendment; Soil organic carbon; Soil structural stability; Soil microbial respiration

1. Introduction

One of the major environmental concerns is land deg-

radation, since there is an increasing awareness that soil isa critical component of the biosphere, not only by the

production of food but also by the maintenance of envi-

ronmental quality (Marcotea et al., 2001). Inappropriate

production technologies have resulted in soil quality dete-

rioration, leading to soil organic matter losses and struc-

ture degradation, affecting water, air and nutrient flows,

and consequently plant growth (Golchin et al., 1995). Soil

0960-8524/$ - see front matter � 2005 Elsevier Ltd. All rights reserved.

doi:10.1016/j.biortech.2005.03.018

* Corresponding author. Address: Italia 647, Piso 9, Dpto. B, 2000

Rosario, Argentina. Tel.: +54 341 4970080; fax: +54 341 4970085.

E-mail address: lferrera@fcagr.unr.edu.ar (L. Ferreras).

organic matter decline in many agroecosystems occurs

because losses of carbon through oxidation and erosion

by intensive cropping are not compensated by carbon in-

puts through the return of plant biomass (Grant, 1997).Organic matter reduction is, in turn, associated with the

soil structure degradation (Albiach et al., 2001).

Soil application of compost from organic residues,

such as animal manures, sewage sludges, household

wastes, represents a management strategy that could

counteract depletion of organic matter in soils. Besides,

organic residues recycling and further use in soils repre-

sents an attempt to alleviate the serious environmentalproblems caused by residue accumulation (Marcotea

et al., 2001; Tejada and Gonzalez, 2003). The use of com-

post in soils requires that it achieves an adequate degree

636 L. Ferreras et al. / Bioresource Technology 97 (2006) 635–640

of maturity, which implies a stable organic matter con-

tent and the absence of phytotoxic compounds and plant

or animal pathogens (Bernal et al., 1998; Gomez, 1998).

Conventional horticultural cropping, due to continuous

soil removal and intensive use of pesticides and fertilizers,

is a main activity leading to deterioration of soil physical,chemical and biological properties (Albiach et al., 2000).

Mineral fertilization provides readily available nutri-

ents for plant growth; however, it does not contribute to

improve soil physical condition. Organic matter inputs

through organic amendment, in addition to supplying

nutrients, improve soil aggregation, and stimulate mic-

robial diversity and activity (Shiralipour et al., 1992;

Carpenter-Boggs et al., 2000). Improvement of soilaggregation through its effects on soil water content,

temperature, aeration and mechanical impedance influ-

ences root development and seedling emergence (Fer-

reras et al., 2000).

Since crop management systems generally have a

strong influence on soil structural characteristics, aggre-

gate stability is considered as a key indicator to assess

soil quality. Improvement of soil structure through or-ganic matter input has been found to be of primary

importance in the type of soil where the study was con-

ducted. Vertic Argiudolls with mineralogical composi-

tion consisting of illitic type clay minerals and silt

fraction with more than 50% of phytoliths, has lead to

a soil structure compacted in situ. This structure has

high susceptibility to degradation by the action of water

or tillage despite the fact that these soils have more than50% total porosity (Gomez et al., 2001). The aim of the

present work was to assess the response of some soil

physical, chemical and biological properties after two

applications of different organic amendments at two

rates, to a soil with an extended horticultural use.

2. Methods

2.1. Site and experiment description

The study was carried out in a Vertic Argiudoll

located in Zavalla, Argentina (32�43 02700 S; 60�55 01800

Table 1

Amendment composition: vermicompost from source separated household so

chicken manure (CM)

Amendment Ca (g kg�1) Nb (g kg�1) C/N Ash (g kg�1) W

HSW 255 14.1 18.1 540 5

HRM 188 15.1 12.4 660 4

CM 428 13.4 31.9 230 1

a C: organic carbon (ignition; Rodrıguez et al. (1995)).b N: total nitrogen (Kjeldahl; Bremner and Mulvaney (1982)).c W: water content.d EC: electrical conductivity.e AHM: aerobic heterotrophic microflora.

W). The main characteristics of the soil in the 0–15 cm

surface layer were: clay 260 g kg�1, silt 680 g kg�1,

organic matter 32.7 g kg�1, total N 2.23 g kg�1, pH in

water (1:2.5) 5.9. The soil possessed a high water storage

capacity and was moderately well drained.

Before the beginning of the study, the experimentalsite had been under horticultural cropping for more

than 20 years, with a conventional management (mold-

board plowing, rotovator, two or three crops a year, fer-

tilization with urea, without amendment incorporation).

Irrigation was performed with water having an electrical

conductivity 2.3 dS m�1 and sodium adsorption ratio

14.37.

In May 2001 and February 2002, amendment appli-cations were performed with: vermicompost from source

separated household solid waste (HSW), vermicompost

from horse and rabbit manure (HRM) and chicken

manure (CM). The HSW was obtained from the food

fraction separated at their houses by people from a small

town. The amendments were applied at rates of 10 and

20 Mg ha�1 on an oven dry basis (105 �C), D10 and

D20, respectively. The treatments were replicated threetimes in a complete randomized block design, with con-

trol plots without any amendment (C), previously to a

broccoli (Brassica oleracea var. Italica L.) and lettuce

(Lactuca sativa L.) crop, respectively. Amendment com-

position is shown in Table 1.

Samples composed by 15 sub-samples were collected

with a spade to the depth of 0–15 cm, fractured into

aggregates by hand pressure, air dried and sieved(<2 mm) in April 2001, November 2001 and August

2002. The same soil type without disturbance was sam-

pled as reference. The undisturbed site is an area adja-

cent to the trial that has never been cultivated and

remains with native herbaceous plant cover.

2.2. Soil measurements and statistical analysis

2.2.1. Structural stability

The proportion of aggregates that were stable to

water (Ws) and ethanol (Es) was determined by Henin

et al. (1972). Briefly, the samples are pre-treated with

water and ethanol. The fraction of aggregates that re-

lid waste (HSW); vermicompost from horse and rabbit manure (HRM);

c (g kg�1) pH (1:5) ECd (dS m�1) AHMe (CFU g�1)

18 6.88 1.9 3.7 · 107

12 6.82 0.4 5.6 · 107

13 8.10 6.8 2.5 · 109

0

5

10

15

20

25

C HSW HRM CM

Wat

er s

tabl

e ag

greg

ates

(%

)

D10 D20

cc

ab

bc

a

bc

a

Fig. 1. Percentage of water stable aggregates in plots after two

applications of vermicompost from source separated household solid

waste (HSW); vermicompost from horse and rabit manure (HRM);

chicken manure (CM) at the rate of 10 and 20 Mg ha�1 and control

plots (C). Means followed by different letters indicate significant

differences (Duncan p < 0.05), n = 3.

0

10

20

30

40

50

60

70

C HSW HRM CM

Eth

anol

sta

ble

aggr

egat

es (

%)

D10 D20

c

c

a

bc

aab

a

Fig. 2. Percentage of ethanol stable aggregates in plots after two

applications of vermicompost from source separated household solid

waste (HSW); vermicompost from horse and rabit manure (HRM);

chicken manure (CM) at the rate of 10 and 20 Mg ha�1 and control

plots (C). Means followed by different letters indicate significant

differences (Duncan p < 0.05), n = 3.

L. Ferreras et al. / Bioresource Technology 97 (2006) 635–640 637

mained in the sieve greater than 0.25 mm after shaking

(30 handle rotations; 1 rotation s�1) the samples sub-

merged in water with the apparatus of Feodoroff

(1960), was weighed. Sample pre-treatments with water

and ethanol allow the evaluation of two of the main

factors involved in structural stability, which are soiltextural characteristics and organic matter content (De

Orellana and Pilatti, 1994). The pre-treatment with

water, since it do not allow air expulsion from the aggre-

gate, indicated that aggregate disruption due to the

wetting process occurred. The ethanol facilitated the

expulsion of air inside the aggregate; thus the pre-treat-

ment with ethanol avoids aggregate disruption, allowing

the evaluation of cohesive forces between particles. Elec-trical conductivity (EC) and pH were measured in a

1:2.5 (soil:water) aqueous extract.

2.2.2. Organic carbon (SOC)

Soil organic carbon was determined by oxidizing or-

ganic matter in soil samples with K2Cr2O7 in concen-

trate sulphuric acid for 30 min followed by titration of

the excess of K2Cr2O7 with ferrous-ammonium sulphate(Nelson and Sommers, 1982).

2.2.3. Total nitrogen (TN)

Total N was determined by sulphuric acid digestion

using Se, CuSO4 and K2SO4 as catalyst. Nitrogen in

the digest was determined by a previously described

Kjeldahl distillation method (Bremner and Mulvaney,

1982).

2.2.4. Microbial respiration (MR)

The production of CO2 was measured as indicator of

soil microbial activity. Soil samples (100 g) at 75% of

water holding capacity were incubated in hermetic flasks

(600 cm3) in layers of approximately 25 mm during 7

days at 25 �C. The CO2 produced was trapped in excess

of 0.5 N NaOH. The alkali was titrated to the phenol-phthalein with HCl in the presence of BaCl2. The CO2

evolved was calculated by difference between samples

and blanks without soil (Frioni, 1990).

2.2.5. Aerobic heterotrophic microflora (AHM)

Tenfold dilution series from soil suspensions (soil

10 g, sterile deionized water 100 ml, shaken for 1 h) were

performed and aliquots of 1 ml were plated on tryptic soyagar (Difco Lab, Detroit, MI). Counts were done after 5

days of incubation at 25 �C and results expressed as col-

ony forming units (CFU) g�1 soil (on a dry-weight basis).

For all parameters, data were analyzed by analysis of

variance (ANOVA) procedure for a randomized com-

plete block design with three replications. Comparison

of means was performed by the Duncan multiple range

test at 95% level of probability. The occurrence of rela-tionships between Ws and SOC, and Es and SOC was

assessed by means of simple linear regressions. All statis-

tical analysis was performed using SAS (SAS Institute,

1990, version 6.12).

3. Results

The proportion of water and ethanol stable aggre-

gates after two amendment applications is shown in

Figs. 1 and 2, respectively. There were no differences

(p > 0.05) in the percentage of Ws between the control

plots and plots amended with HSW, HRM and CM at

the rate of 10 Mg ha�1. The proportion of Ws was sig-

nificantly higher in plots amended with HSW, HRM

and CM at the rate of 20 Mg ha�1. The proportionof Es did not differ (p > 0.05) between the control plots

and plots amended with HSW and HRM at the rate of

10 Mg ha�1, while it was significantly higher (p < 0.05)

y = 4.8883x - 41.741

R2 = 0.62

0

10

20

30

40

50

60

70

12 14 16 18 20 22

Soil organic carbon (g kg-1)

Eth

anol

sta

ble

aggr

egat

es (

%)

Fig. 5. Relationship between ethanol stable aggregates and soil

organic carbon estimated after two applications of vermicompost

from source separated household solid waste (HSW); vermicompost

from horse and rabit manure (HRM); chicken manure (CM) at the rate

of 10 and 20 Mg ha�1 and control plots (C), n = 21.

250

300

350

il

a

abbb

638 L. Ferreras et al. / Bioresource Technology 97 (2006) 635–640

in plots amended with CM at the rate of 10 Mg ha�1.

However, applications of HSW, HRM and CM amend-

ments at 20 Mg ha�1 significantly increased the Es

(p < 0.05). Plots at the beginning of the experiment

(April 2001), had a 4.3% of water stable aggregates

and 47% of ethanol stable aggregates. After two amend-ment applications, the proportion of Ws was increased

between 1% and 14.5%, while Es was increased between

3.8% and 15%. Values from both Ws and Es in plots

amended at the rate of 20 Mg ha�1 were closer to the

undisturbed soil (21.2% Ws, and 70.5% Es, respectively).

There were significant differences (p < 0.05) in soil or-

ganic carbon between HSW and HRM at the higher rate

with respect to the control after the first amendmentapplication. After the second amendment application,

all the treatments showed a significant increment in

SOC with respect to the control plots (Fig. 3). The

regression functions of Ws on SOC and Es on SOC indi-

cated linear relationships, with R2 = 0.64 and 0.62,

respectively (Figs. 4 and 5). In both sampling dates after

10

12

14

16

18

20

22

C HSW HRM CM HSW HRM CM C HSW HRM CM HSW HRM CM

Nov. 2001 Aug. 2002

Soi

l org

anic

car

bon

(g k

g-1)

D10 D20

b

ab abab

a

ab

a

c

ab ab

b

aba

ab

Fig. 3. Soil organic carbon in plots amended with vermicompost from

source separated household solid waste (HSW); vermicompost from

horse and rabit manure (HRM); chicken manure (CM) at the rate of

10 and 20 Mg ha�1 and control plots (C). Means followed by different

letters in each sampling date indicate significant differences (Duncan

p < 0.05), n = 3.

y = 2.5012x - 34.77

R2 = 0.64

0

4

8

12

16

20

12 14 16 18 20 22

Soil organic carbon (g kg-1)

Wat

er s

tabl

e ag

greg

ates

(%

)

Fig. 4. Relationship between water stable aggregates and soil organic

carbon estimated after two applications of vermicompost from source

separated household solid waste (HSW); vermicompost from horse

and rabit manure (HRM); chicken manure (CM) at the rate of 10 and

20 Mg ha�1 and control plots (C), n = 21.

0

50

100

150

200

C HSW HRM CM HSW HRM CM C HSW HRM CM HSW HRM CM

Nov. 2001 Aug. 2002

µgC

O2

g-1so

D10 D20

c

dcd

b

c

aac

cd cd

Fig. 6. Soil microbial respiration in plots amended with vermicompost

from source separated household solid waste (HSW); vermicompost

from horse and rabit manure (HRM); chicken manure (CM) at the rate

of 10 and 20 Mg ha�1 and control plots (C). Means followed by

different letters in each sampling date indicate significant differences

(Duncan p < 0.05), n = 3.

amendment applications, an increase in microbial respi-ration in all the amended plots was observed with re-

spect to the controls, with the exception of HRM at

both rates in November 2001 and HRM at 10 Mg ha�1

in August 2002 (Fig. 6). The seasonal effect of lower

winter temperatures was indicated by a reduction in

the amount of CO2 produced in August 2002 with re-

spect to November 2001. Soil pH, EC, NT and AHM

were not significantly affected after the two applicationsof organic amendments to soil (Table 2).

4. Discussion

The structure stabilization is related to organic mat-

ter inputs (Caravaca et al., 2002), thus, a significant in-

crease in the proportion of water stable aggregates wasattained with the highest application rate of amend-

ments. The higher structural stability observed in the

pre-treatment with water indicated an improvement in

Table 2

Soil variables measured in plots amended with vemicompost from source separated household solid waste (HSW); vermicompost from horse and

rabit manure (HRM); chicken manure (CM) at the rate of 10 and 20 Mg ha�1 and control plots (C)

Amendment pH (1:2.5) EC (dS m�1) NT (g kg�1) AHM (CFU g�1)

November 2001 August 2002 November 2001 August 2002 November 2001 August 2002 November 2001 August 2002

C 7.17 7.30 0.66 0.43 0.95 1.24 1.8 · 109 8.7 · 106

HSW10 7.07 7.57 0.98 0.67 1.12 1.48 6.5 · 108 1.5 · 107

HCM10 7.21 7.27 0.94 0.63 1.03 1.56 2.5 · 108 8.6 · 106

CM10 7.17 7.50 0.76 0.57 1.05 1.55 2.8 · 108 6.4 · 106

HSW20 7.30 7.27 0.90 0.60 1.23 1.50 3.7 · 109 8.9 · 106

HCM20 7.09 7.23 0.66 0.63 1.13 1.45 2.3 · 108 7.2 · 106

CM20 7.19 7.40 0.83 0.70 1.08 1.49 7.4 · 109 2.8 · 107

L. Ferreras et al. / Bioresource Technology 97 (2006) 635–640 639

pore size distribution due to an increased number of soil

macropores. Several authors have previously reported

that organic matter from amendment incorporation im-

proved pore size distribution (Giusquiani et al., 1994;

Marinari et al., 2000; Tejada and Gonzalez, 2003). An

increase in pore size and the continuity of pore

space, eases root penetration and flow of water and

gases, directly related to plant growth (Marinari et al.,2000).

The increase in the proportion of ethanol stable

aggregates was a consequence not only of organic mat-

ter input, but also of the mineralogical composition of

the soil, consisting of 26% of illitic type clay minerals.

Organic matter acts as a cementing factor, necessary

for flocculated soil particles to form stable aggregates,

which importance depends on their abundance in soil.The input of organic matter to soil trough amendment

incorporation increased the cohesion of aggregates; this

effect was more significant for plots amended at the rate

of 20 Mg ha�1. A higher cohesion due to the binding

forces between mineral particles and organic poly-

mers decreases the wettability of aggregates and thus

the extent of slaking (Sullivan, 1990; Spaccini et al.,

2004).The use of amendments has been reported previously

to increase soil organic matter, provide nutrients and

improve microbial activity (Lee et al., 2004). The results

are conditioned by the composition of amendment, the

rate of application and the soil type (Albiach et al.,

2001; Tejada and Gonzalez, 2003). In our experiment,

soil organic carbon was significantly increased in plots

amended with HSW and HRM after the first amend-ment incorporation at 20 Mg ha�1 rate. A second

amendment application significantly increased SOC at

both rates. In a sandy silty loam soil, Albiach et al.

(2001) found significant increases in soil organic matter

after applying during four years compost from munici-

pal solid waste and sewage sludge, and ovine manure

at a rate of 24 Mg ha�1.

Organic matter from the amendments associated tothe soil mineral complex may explain the linear positive

relationships found between soil organic carbon and

both water and ethanol stable aggregate fractions. Beni-

to and Diaz-Fierros (1992), and Chenu et al. (2000)

previously reported a significant correlation between

soil aggregate stability and the organic matter

concentration.

Soil microbial respiration, measured through carbon

dioxide production is a direct indicator of microbial

activity, and indirectly reflects the availability of organic

material (Parkin et al., 1996; Gomez et al., 2001).Amendment applications stimulated in general soil

microbial respiration, in line with what reported by

Marinari et al. (2000), who explained their results as

probably due to a synergic effect of soil and amendment

microorganisms or to a stimulation of microbial growth

by organic substrates added with the amendments. The

highest values of microbial respiration were found in

plots amended with CM. Most of the carbon suppliedby this amendment comprises partially decomposed

material, easily degradable to be used as energy and

nutrient source for soil microorganisms, resulting in an

increased soil microbial respiration (Stevenson, 1986).

Despite this amendment exhibiting the highest organic

carbon content in its composition, a lower soil organic

carbon content were found in plots amended with

CM. However, the organic carbon fraction in the vermi-composts (HSW and HRM) is fundamentally as humi-

fied compounds, that contribute to the stabilization of

the organo-mineral complex when incorporating to the

soil (Li et al., 2000). The adsorption of these compounds

to the clay protects them from microbial oxidation (Gol-

chin et al., 1995).

With respect to crop yields, there were no significant

differences between the amended plots and with respectto control plots in broccoli crop, which produced in

average 0.990 kg m�2. In the lettuce crop, significant dif-

ferences were found for all plots amended at a rate of

20 mg ha�1 with respect to the 10 mg ha�1 rate, which

yielded in an average 1.93 kg m�2 and 1.3 kg m�2,

respectively.

Provided that soil structure stability, organic carbon

and microbial activity were improved after twoamendment applications, repeated applications would

be recommended in the long-term as a sustainable

management practice. Also, future research combining

640 L. Ferreras et al. / Bioresource Technology 97 (2006) 635–640

amendments with mineral fertilizers, which provide eas-

ily available inorganic nutrients for crops, would yield

useful information.

Acknowledgement

We thank Dr. H. Busilachi and Municipality of

Chabas for providing source separated household solid

waste compost.

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