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Bioassays and application of olive pomace composton emmer: effects on yield and soil properties inorganic farmingMariangela Diacono a , Donato Ferri a , Corrado Ciaccia b , Fabio Tittarelli b , FrancescoCeglie c , Vincenzo Verrastro c , Domenico Ventrella a , Carolina Vitti a & FrancescoMontemurro da CRA – SCA, Research Unit for Cropping Systems in Dry Environments, Bari, Italyb CRA – RPS, Research Centre for the Soil–Plant System, Roma, Italyc CIHEAM – MAIB, Mediterranean Agronomic Institute of Bari, Valenzano (BA), Italyd CRA – SSC, Research Unit for the Study of Cropping Systems, SS 106 Jonica Km 448.2,75010, Metaponto (MT), Italy

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To cite this article: Mariangela Diacono, Donato Ferri, Corrado Ciaccia, Fabio Tittarelli, Francesco Ceglie, VincenzoVerrastro, Domenico Ventrella, Carolina Vitti & Francesco Montemurro (2012): Bioassays and application of olive pomacecompost on emmer: effects on yield and soil properties in organic farming, Acta Agriculturae Scandinavica, Section B -Soil & Plant Science, DOI:10.1080/09064710.2012.663785

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ORIGINAL ARTICLE

Bioassays and application of olive pomace compost on emmer: effectson yield and soil properties in organic farming

MARIANGELA DIACONO1, DONATO FERRI1, CORRADO CIACCIA2,

FABIO TITTARELLI2, FRANCESCO CEGLIE3, VINCENZO VERRASTRO3,

DOMENICO VENTRELLA1, CAROLINA VITTI1 & FRANCESCO MONTEMURRO4

1CRA � SCA, Research Unit for Cropping Systems in Dry Environments, Bari, Italy, 2CRA � RPS, Research Centre for the

Soil�Plant System, Roma, Italy, 3CIHEAM � MAIB, Mediterranean Agronomic Institute of Bari, Valenzano (BA), Italy,4CRA � SSC, Research Unit for the Study of Cropping Systems, SS 106 Jonica Km 448.2, 75010, Metaponto (MT), Italy

AbstractComposting olive oil pomace could solve the problem of disposal, by recycling this organic waste for agricultural purposes.Furthermore, application of composted organic waste could be a way to sustain both soil fertility and production, especiallyin organic farming. Therefore, the aim of this research was to evaluate the phytotoxicity and the effects of application of olivepomace composts on emmer performance and soil properties. Two types of olive pomace composts, with a different initialC/N ratio, were stopped at the active phase and processed until maturation. The obtained four olive pomace composts werecompared with a commercial fertilizer in a two-year field experiment. Before the field trial, a bioassay was performed toassess phytotoxicity both for the raw pomace and the not-stabilized composts. Growing and yielding data for emmer weredetermined during the two-year period and soil characteristics were measured at the start and at the end of the experiment.

The composts were not phytotoxic (germination index was higher than 90%) and their total organic carbon content wasalways higher than the minimum values established by the Italian fertilizers legislation. The emmer protein contentwas significantly higher in the matured compost treatment with low C/N, than in the other compost treatments. Its valuewas comparable with that of the commercial fertilizer, suggesting a good performance on crop yield quality. Although notsignificant, this compost showed an increase of 9.8% in grain yield compared with commercial fertilizer treatment. On thewhole, it can be suggested that repeated compost application might preserve the soil organic carbon content and supplymacronutrients to a crop.

Keywords: Compost maturation, olive pomace, organic farming, organic wastes, phytotoxicity.

Introduction

Intensive cropping systems and inadequate replace-

ment of nutrients removed in harvested materials or

lost through erosion, leaching and gaseous emis-

sions, degrade soil physical, chemical and biological

properties, thus intensifying global warming (Diaco-

no and Montemurro 2010). On the contrary, ac-

cording to Montemurro et al. (2008), crop rotation,

introduction of leguminous plants in cropping sys-

tems and organic amendments could improve soil

fertility, so attaining a sustainable agricultural pro-

duction. Organic wastes can be used as amend-

ments, since they are important sources of nutrients

for growing crops. Their re-use in agriculture can

also contribute to closing the natural ecological

cycles (Montemurro and Maiorana 2008). It can

be assumed that the benefit of organic wastes

recycling occurred only when they are applied

according to best agronomical practices. In particu-

lar, Van-Camp et al. (2004) pointed out the im-

portance of suitable time, specific plan of

fertilization, needs of the soil�plant system and the

climatic conditions.

In many Mediterranean countries, the olive oil

agro-industrial sector generates, yearly and in a

limited period, organic residues both liquid and

solid, depending on the system of oil extraction

Corresponding authors: Mariangela Diacono and Francesco Montemurro, Via Celso Ulpiani 5, 70125, Bari, Italy. Fax: �39 080 5475023.

E-mails: mariangela.diacono@inwind.it and francesco.montemurro@entecra.it

Acta Agriculturae Scandinavica Section B � Soil and Plant Science

2012, 1�9, iFirst article

(Received 31 October 2011; revised 31 January 2012; accepted 1 February 2012)

ISSN 0906-4710 print/ISSN 1651-1913 online # 2012 Taylor & Francis

http://dx.doi.org/10.1080/09064710.2012.663785

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(Alburquerque et al. 2009). In particular, the

modern two-phase centrifugation system produces

a moist olive pomace (OP) with a doughy texture

and low porosity. This material is rich in polyphe-

nolics, unextracted oil and organic acids (Niaounakis

and Halvadakis 2006). Millions of tons of OP are

produced every year, most of them in southern

regions of the Mediterranean area. In these regions,

the concentration of organic matter in soil is

extremely low and climatic conditions and intensive

agricultural practices have led to severe soil degrada-

tion (Cayuela et al. 2010).

According to Roig et al. (2006), a gradual OP

accumulation and its incorrect disposal may have a

damaging environmental impact, due to phytotoxic

and antimicrobial effects both of phenolic com-

pounds and lipid fraction. Most of the factors that

determine phytotoxicity can influence seed germina-

tion simultaneously and it is very difficult to assess

which parameter has the greatest weight (Said-Pull-

icino et al. 2007). Phytotoxicity is one of the most

important criteria for evaluating the suitability of

organic materials as OP for agricultural purposes,

and it can be tested by using bioassays. The Zucconi

et al. (1981) method can be used to assess phyto-

toxicity of this semi-solid residue, by combining the

measurements of seeds germination and roots elon-

gation of cress (Lepidium sativum L.).

The OP generally contains a large proportion of

organic matter and valuable nutrients which could

be recycled by composting, in accordance with the

basic agro-ecological principles of organic farming

(Alfano et al. 2008, Sellami et al. 2008). However,

the use of OP for fertilizing soils may require

technologies for processing the raw material, in order

to prevent soil contamination from some toxic

organic compounds (Van-Camp et al. 2004). Com-

post is a humified and sanitized product of aerobic

exothermic biodegradation reactions, which are

carried out by a microbial community on a mixture

of organic substrates (Insam and de Bertoldi 2007).

Although OP has unsuitable physical characteristics

that makes aeration difficult, its composting can be

feasible by using complementary residues as bulking

agents, such as olive leaves, cereal straw or pruning

wastes (Canet et al. 2008). Hence, a waste material

could become a farm resource.

Soil fertility management relies on crop rotation,

cropping systems, green manuring and recycling of

organic wastes according to best agronomical prac-

tices. Within this context, the organic production of

cereals is not only important for feed and food, but

also for contribution to soil fertility. Emmer is an

underutilized ancient cereal suitable for development

in marginal rural areas and particularly fit for organic

production because of its great adaptability (Giuliani

et al. 2009).

Our hypothesis was that the addition of manure

(nitrogen source) and pruning wastes (bulking

agents) to OP matrix would obtain a balanced soil

amendment for organic cultivation of emmer. There

is a large literature relating to the influence of

composted OP both on soils and different crops

(Montemurro et al., 2006a, 2008, Altieri and

Esposito 2010), although there is a lack of informa-

tion on its application on minor cereal crops in

organic farming.

Therefore, the objectives of this two-year field trial

were: (i) to evaluate the phytotoxicity of both the raw

and the composted materials; (ii) to investigate the

agronomic performance of four types of OP compost

as amendments on emmer crop, cultivated under

organic farming management; (iii) to evaluate the

short-term effects of compost application on soil

properties.

Materials and methods

Compost mixtures and composting set-up

The OP was collected from two-phase centrifugation

olive oil milling factories in Apulia region (southern

Italy). Two composting mixtures were made with the

same organic residues (i.e. OP, pruning wastes and

cattle manure) in 2008 and 2009, in the experi-

mental facility of CIHEAM-IAMB (Valenzano, Bari,

Italy). In particular, the following two mixtures were

prepared: (i) with a high C/N ratio equal to 45 (A);

(ii) with a lower C/N ratio equal to 30 (B). The olive

oil processing waste was composted with the follow-

ing proportion of raw materials in the two mixtures

(on a fresh-weight basis): (i) in A, 53.7% OP mixed

with 38.5% olive pruning wastes and 7.9% cattle

manure; (ii) in B, 10.5% OP mixed with 43.0% olive

pruning wastes and 46.5% cattle manure.

The proportion of the raw materials was the same

in the two years, showing low and not significant

difference in the values.

The two mixtures were processed in bio-contain-

ers of 25 m3 of net volume (Le Coccinelle†

technology, Entsorga Italia, Tortona). The process

of bio-oxidation and ventilation was monitored by an

automated system provided with the bio-container.

This system measures the temperature of the bio-

mass and, consequently, controls both the air flow

and the irrigation in the bio-container.

At the end of the active phase, each mixture was

removed from the container, put outdoors and split

in two heaps. One heap of each mixture was sun-

dried in a thin layer (2.5 cm) to obtain A1 and B1

composts. The second heap for each mixture was led

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to maturation as a turned windrow, so obtaining A2

and B2 composts. The bio-oxidative phase was

considered finished when the temperature was

stable, close to the external value, and reheating

did not occur. This phase required about 120 and 80

days for A2 and B2, respectively. Therefore, four

olive pomace composts (OPCs) were obtained: (i)

A1, with a high initial C/N ratio, stopped at the

active phase and (ii) A2 processed until maturation;

(iii) B1, with a low initial C/N ratio, stopped at the

active phase and (iv) B2 processed until maturation.

Compost sampling, analytical determinations and

bioassays

At the end of the processes some analytical determi-

nations were made on compost samples. These

samples were obtained by mixing six sub-samples

from six sites of each heap and pooled in three

compost sub-samples each year. Since no difference

was found between years, the results are presented as

averages. The main chemical characteristics of OPCs

are shown in Table I.

Electrical conductivity and pH were measured in

1:10 (w/v) water-soluble extraction at 2491 8C. The

conductivimeter used was a CRISON 524 and

the pH-meter was a CRISON microTT 2050. The

moisture content was determined by drying each

sample at 105 8C until the constant weight was

reached. The total organic carbon (TOC) was

measured by dichromate oxidation and the total

nitrogen (N) by the Kjeldahl method. Total P was

determined by Inductively Coupled Plasma-Optical

Emission spectrometry (ICP-OES) after digestion in

HNO3 65%, in a pressurized microwave.

Phytotoxicity for both the raw OP and the A1 and

B1 composts was evaluated by modifying the original

method of Zucconi et al. (1981). We analysed A1

and B1 composts since they were potentially phyto-

toxic due to the incomplete bio-oxidation. Deionized

water was added to the fresh OP and composts

samples to attain a moisture content equivalent to

85% (wet weight). Then, after a contact period of 2

h, the aqueous extracts were obtained by centrifuga-

tion and filtration through a membrane filter. Three

dilutions (25, 50 and 75% in deionized water) as well

as the concentrated extract for OP (100% extract)

were used as germination media. A Whatman filter

paper (Number 542) placed inside 90 mm diameter

Petri dishes was wetted with 1 mL of each germina-

tion solution and 10 cress seeds were placed on each

paper. Pure deionized water was used as a control.

Five replicates were set out for each treatment. The

dishes of each treatment were wrapped together with

a polyethylene bag to prevent desiccation and were

kept in an incubator (RUMED 4101, Mod.

G†Therm) in the dark, for 2 d at 2092 8C and

90% humidity.

After the incubation period the number of germi-

nated seeds and their primary root length were

measured and expressed as a percentage of the

control as follows:

GI ¼ 100xSt

Sc

� �x

Lt

Lc

� �(1)

where GI �germination index (%); St �number of

germinated seeds for treatment samples; Sc �num-

number of germinated seeds for control; Lt �aver-

average root length of seedlings for treatment

samples; Lc �average root length of seedlings for

control.

Finally, the GI (%) of OP and the composts were

obtained as an average of the GI calculated from

each dilution with equation (1).

Site of study, experimental treatments and measurements

Within a two-year emmer�chickpea rotation, the

research on emmer (Triticum dicoccum L.) was

carried out in the Experimental Farm of the CRA,

Research Unit for Cropping Systems in Dry Envir-

onments at Foggia � southern Italy (41827?N,

3804?E, 90 m a.s.l.). The experimental trial was

conducted during 2008�2009 and 2009�2010 (in-

dicated as 2009 and 2010, respectively) under

organic farming management. The climatic condi-

Table I. Characteristics (mean9standard error) of composts obtained from a mixture with C/N �45 (A1, stopped at the active phase; A2,

processed until maturation) and of composts obtained from a mixture with C/N �30 (B1, stopped at the active phase; B2, processed until

maturation). Results for the two years, expressed on a dry weight basis.

Parameters A1 A2 B1 B2

Moisture (%) 10.5390.17 47.8997.86 9.8094.24 44.5093.29

pH 7.1990.21 7.4890.33 7.3690.25 8.5190.39

Electric conductivity (dS m�1) 0.6390.19 0.5690.23 1.3790.25 1.3690.28

Total organic carbon (g kg�1) 395.89192 382.59179 381.69134 363.09135

Total N (g kg�1) 13.8493.31 17.9194.23 16.2893.36 19.2993.62

Total P (g kg�1) 3.2690.79 3.9490.84 6.0291.21 6.2891.32

C/N 28.60 21.35 23.44 18.82

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tions were those of a typical Mediterranean environ-

ment, characterized by temperatures that can range

from below 0 8C in winter to above 40 8C in

summer. The rainfall is unevenly distributed during

the year, being concentrated mainly in the winter

season. The soil, typical of the flat land of Apulian

Tavoliere (South Italy), is silty-clay of alluvial origin,

classified as a Fine, Mesic, Typic Chromoxerert by

Soil Taxonomy-USDA.

The experimental field was prepared by plough-

ing the soil during late summer and disk harrowing

to prepare the seedbed. Emmer was sown at the

end of December in both years in a randomized-

block design with three replications, on plots of 40

m2 (5�8 m). The following five treatments were

compared, to allow an application of 80 kg ha�1 of

N in accordance with the fertilization local prac-

tices: (i) two OPCs from a starting mixture with

high C/N ratio (A1 and A2); (ii) two OPCs from a

starting mixture with a lower C/N ratio (B1 and

B2); and (iii) a commercial organic mineral fertili-

zer (OM). The four types of composts were

uniformly applied in one solution, about 1 month

before sowing, and buried with a rotary hoe. The

OM was applied at two times: 1/3 N at sowing as

organo-mineral fertilizer (Granosano, ILSA, with:

4% organic N, 15% P2O5; 33% organic matter)

and 2/3 N as organic fertilizer (Fertil, ILSA, with:

12.5% organic N; 70% organic matter) at the end

of tillering, corresponding to Stage 29 of Zadoks

scale (Zadoks et al. 1974).

In both years, during the cropping cycle, 0.5 linear

meter samples were randomly harvested from each

elementary plot at 68, 108 and 158 days after sowing

(DAS) in 2009 and at 70, 98 and 147 DAS in 2010.

These sampling corresponded to tillering, flag leaf

sheath extending and dough development stage,

respectively (Stages 25, 41 and 80; Zadoks et al.

1974). At these DAS, leaf area index (LAI) was

determined on such samples and the plants collected

were weighed and dried for 48 h at 70 8C to obtain

biomass dry weight. Before these determinations,

leaf green index (SPAD, Minolta 502) readings were

measured at mid-length on fully expanded leaves

from 9 plants for each replication.

At harvest, which occurred at 202 and 197 DAS

for 2009 and 2010, respectively, the grain (at 13% of

humidity) and the straw yield, the harvest index (HI)

and the fertile spikes m�2 were determined in the

middle of each plot on about 20 m2. Total N

contents of grain and straw (Fison CHN elemental

analyser mod. EA 1108) were also determined,

allowing the calculation of total N uptake (N

content�biomass dry weight). Moreover, for the

agronomic quality assessing, the grain protein con-

tent was obtained by multiplying the grain N content

by 5.70 (Baker 1979). On the basis of these

measurements, the following N efficiency indices

were calculated: N utilization efficiency (NUE)

(ratio of grain weight to N uptake, in kg kg�1) and

N harvest index (NHI) (ratio of N uptake by the

grains to N uptake by the plants, in%) (Montemurro

et al. 2006b).

Soil characteristics determination

At the beginning (t0) and at the end of the

experiment (tf), three soil sub-samples (0�40 cm

layer) were taken from each elementary plot, pooled

in one sample for replication and treatment, air

dried, ground to pass a 2-mm sieve and then

analysed. The data at t0 were the mean of every

treatment, since the replications were pooled in one

sample. On all samples the following soil character-

istics were determined: pH in a 1:2.5 (w/v) soil/water

mixture; electrical conductivity in 1:10 (w/v) water-

soluble extraction; TOC and total N using the same

methodologies reported for compost samples; avail-

able P by the Olsen and Sommers method (Olsen

and Sommers 1982); exchangeable K, Ca, Mg and

Na extracted by BaCl2 and triethanolamine accord-

ing to Page et al. (1982) methodologies, and assayed

by Inductively Coupled Plasma-Optical Emission

spectrometry ICP-OES. Total extracted carbon

(TEC) and humified organic carbon (HA�FA)-C

were also calculated, according to the Springer and

Klee method, modified by Sequi et al. (1986).

Statistical analysis

The data obtained in the two-year trial period were

subjected to analysis of variance (ANOVA), using the

SAS software package (SAS Institute 1990). In

the ANOVA, the years were considered as a random

effect, whereas fertilizing management as a fixed one.

The differences among the experimental treatments

were compared using the Student�Newman�Keuls

(SNK) tests at the p 5 0.05 probability level. The

differences found with the SNK test for different

main effect and interaction comparisons were calcu-

lated using the appropriate standard error term.

Finally, the arccosine transformation of data was

used to evaluate statistical differences among vari-

ables expressed as percentages.

For clearness of exposition, only the main effects

of experimental treatments are presented in

this paper, because the large part of the interactions

were not significant. In particular, no interaction was

found between years and fertilization treatments,

therefore the results shown in tables and figures do

not include this interaction and they are presented as

average of the main effects.

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Results

Characteristics of the experimental composts

At the end of the active phase and after sun-drying,

A1 and B1 showed lower moisture percentage (by

78% in both composts) than the matured composts

(Table I). The A1, A2 and B1 composts, presented

almost the same values of pH (7.19, 7.48 and 7.36,

respectively), whereas the B2 showed a significantly

higher level (8.51). Because of the different initial

proportion of raw materials in the composting

mixtures, the values both of EC and total P were

greater in B composts than in A ones. The TOC

content of all composts was always higher than the

minimum values of 250 g kg�1 established by the

Italian fertilizers legislation. The C/N ratio was

above the threshold of 25 only for the A1, as a

consequence of a reduced level of total N (13.84 g

kg�1).

Potential phytotoxicity of raw and composted olive

pomace

Figure 1 shows the GI (%) (average of two years)

which indicates the phytotoxicity of raw OP, A1 and

B1 to cress, at increasing dilutions and as an

average of dilutions. The influence of water extract

concentration on the phytotoxicity level was differ-

ent between the pure OP (100%) and the com-

posted OP. The pure OP was highly toxic to the

germinating cress seeds, since it showed very low

germination percentage (10%). Furthermore, the

OP samples showed a high toxicity (43% GI) even

with the medium dilution (50%). The most diluted

medium inhibited seeds germination by about 37%

compared with the control. On the whole, the

phytotoxicity of raw OP increased from 25 to

75% dilution (thus, the GI decreased from 73 to

29%, respectively).

As far as composts are concerned, GI was not

affected by concentration of the germination

medium. The GI average of the three dilutions

was equal to 91.3 and 92.7% for A1 and B1,

respectively.

Effects of fertilizer treatments on emmer yield, quality

and N management

Table II shows the effects of the fertilizer treatments

on emmer yields (grain and straw), HI, yield

components and quality parameters (average of the

two years). Significant differences were only ob-

served in grain protein content. A deeper analysis

of the results obtained is reported hereafter, although

the results are not significantly different from each

other.

The grain yield ranged from 2.80 t ha�1 of B

treatments to 2.55 t ha�1 both of A1 and OM

treatments. The straw yield ranged from 4.45 t ha�1

of B2 to 3.65 t ha�1 of A1 treatment. Moreover, the

mean values of HI were not notably different among

treatments, although the B2 showed the lowest

absolute value. The fertile spikes per m2 ranged

from about 387 for OM to 320 of B1 treatment.

No significant difference was found between B2

and the commercial fertilizer in protein content,

which is the most important grain quality parameter.

This parameter was significantly higher by 22.25%

in B2 than in A2. Furthermore, protein content

pointed out an inverse relationship with grain yields

for the A2 and OM treatments. The grain protein

content in OM was significantly higher by 22.75%

than A2. Finally, no significant differences were

found among OM and the other three composts.

Figure 1. Germination index (GI%) for various dilutions of olive pomace (OP) and composts stopped at the active phase: A1 (from a

composting mixture with C/N ratio of 45) and B1 (from a composting mixture with C/N ratio of 30). Mean of dilutions (25, 50, 75%, and

also 100% extract for OP); average of two years (SE bars are shown).

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Table III shows the effects (average of the two

years) of treatments on SPAD, LAI and N utilization

parameters. No significant differences between com-

post treatments and OM were found for SPAD

readings. Moreover, LAI ranged from 2.38 for B2

to 1.81 for the A2 treatment even if these results

were not significantly different from each other.

Although statistically significant differences were

not found for NHI, this index ranged from about

70% of B1 to about 66% of OM treatment. The

NUE indicates the grain yield per unit of absorbed

nutrient. Its mean value reached the lowest absolute

value in OM. Moreover, A1 and A2 showed sig-

nificantly highest values as compared with OM (by

24.41 and 26.96%, respectively). No significant

correlations between NUE (or NHI) and yield was

found.

Effects of fertilizer treatments on soil characteristics

Table IV shows the chemical properties of the soil at

the start (mean of the treatments), and at the end of

the two-year trial period, divided by treatment. The

composts treatments showed an average increase of

3.21% (mean of the four treatments) compared with

t0 for the TOC, despite no significant differences

having been found. The TEC decreased in OM

compared with the other treatments as well as with

t0 value, although no significant differences were

found among treatments. The extracted and humi-

fied organic carbon in the OPC treatments increased

by 7.5 and 3.2%, respectively, compared with the

OM treatment.

The OM treatment also showed a reduction in

soil-available P, at the end of the two-year field

experiment, compared with the initial level. No

statistical differences among treatments were found

for exchangeable cations, even if the OM presented

the lowest value of exchangeable K compared with

both OPCs treatments and t0.

Discussion

Our findings suggested that the addition to olive

pomace both of manure, as a nitrogen source, and

pruning wastes, as a bulking agent, may produce

organic amendments suitable for the organic cultiva-

tion of emmer crop.

The pH of the OPCs was in the range allowed by

Italian law for agricultural compost applications

which is 6�8.5 (Decree n. 217, 2006). The total N

and P contents of the four OPCs were quite

different, suggesting that the composition of ma-

trices and their percentage may be responsible for

the nutrients content of amendments. The composts

derived from B mixture showed, on average, N and P

contents higher by 12 and 71%, respectively, than

those derived from the A mixture, probably due to

the highest cattle manure matrix in B. Montemurro

et al. (2010) indicated that nutrient content influ-

ences amendments in agronomical performance.

Zucconi et al. (1985) proposed that a germination

index of more than 60% could be an index of lack of

phytotoxicity in composts. This was the threshold

considered also in our study. The high germination

index values confirmed a complete absence of

phytotoxicity for OP composts, even for the not-

stabilized ones. McEachin et al. (2008) suggested

that maturity is a term used to indicate the level of

phytotoxic substances in composts and product

Table II. Emmer grain yield (at 13% humidity), straw yield,

Harvest Index (HI), fertile spikes and grain quality (protein

content) as an average of two years. A1 and A2: composts

obtained from a mixture with C/N �45, stopped at the active

phase and processed until maturation, respectively; B1 and B2:

composts obtained from a mixture with C/N �30, stopped at the

active phase and processed until maturation, respectively; OM:

commercial organic fertilizer. The values in each column followed

by a different letter are significantly different according to SNK at

p 50.05.

Parameters

Treatments

Grain

yield

(t ha�1)

Straw

yield

(t ha�1) HI

Fertile

spikes

(m�2)

Grain

protein

(%)

A1 2.55 3.65 0.41 370.7 10.64 ab

A2 2.75 3.90 0.41 363.0 10.02 b

B1 2.80 4.05 0.42 320.1 11.64 ab

B2 2.80 4.45 0.38 376.2 12.25 a

OM 2.55 4.20 0.39 387.2 12.30 a

Mean 2.69 4.05 0.40 363.4 11.37

Table III. Chlorophyll index (SPAD), leaf area index (LAI), N

harvest index (NHI), N utilization efficiency (NUE), determined

at tillering, flag leaf sheath extending and dough development

stage, as average of the two years. A1 and A2: composts obtained

from a mixture with C/N �45, stopped at the active phase and

processed until maturation, respectively; B1 and B2: composts

obtained from a mixture with C/N �30, stopped at the active

phase and processed until maturation, respectively; OM: com-

mercial organic fertilizer. The values in each column followed by a

different letter are significantly different according to SNK at

p 50.05.

Parameters

Treatments SPAD LAI

NHI

(%)

NUE

(kg kg�1)

A1 37.67 1.98 68.32 38.53 a

A2 37.89 1.81 68.99 39.32 a

B1 36.45 2.10 70.16 34.41ab

B2 37.04 2.38 66.78 31.49 b

OM 37.17 2.06 66.43 30.97 b

Mean 37.24 2.07 68.14 34.94

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suitability for plant growth. The composts assayed in

this research can be defined as mature, even if

stopped at the active phase in bio-containers. These

findings are consistent with previous research in

similar environments (Alburquerque et al. 2007).

The yield results obtained by applying the OPCs

are consistent with the findings reported by other

authors in other crops (Altieri and Esposito 2010,

Montemurro et al. 2010), who found that traditional

fertilization could be substituted by organic fertili-

zers without reducing yield performance. Moreover,

the commercial fertilizer was applied by splitting the

total dose in two times, while in OPCs only one

application was carried out one month before sow-

ing, thus reducing the distribution costs.

No significant difference was recorded on grain

yield between A1 and OM, despite A1 not being a

stabilized compost. This compost showed the lowest

absolute values of grain and straw yield (2.55 and

3.65 t ha�1, respectively), probably due to the lowest

N content and the highest C/N ratio, which may

induce N immobilization in soil (Diacono and

Montemurro 2010). Despite the absence of a

significant difference between composts and OM,

the fertile spikes number per square metre was

higher in OM than in compost treatments. This

was probably a consequence of a higher and prompt

N release by OM, compared with composts, which

improved the tillering and, consequently, the spikes

number.

The grain protein content suggested an inverse

relationship with grain yields for OM and A2

treatments, suggesting that qualitative performances

may have an opposite pattern compared with pro-

ductive ones. This result confirms the Gan et al.

(2003) findings. The grain protein values were the

highest for B2 and OM treatments and they were

similar between them. Moreover, these two treat-

ments obtained grain yields not statistically different.

The findings of a comparison between the A2 and

B2 results provided some evidence that the initial

organic materials proportion can play a role in

compost performance on yield quantity and quality.

The absence of significant difference between or-

ganic amendments and OM for SPAD readings,

suggested both the absence of phytotoxicity and the

validity of OPCs in the emmer crop cultivation.

Similar results were found by Montemurro et al.

(2006a) on cocksfoot. The high value for LAI in B2

could probably be the reason for high grain and

straw yield values.

The NHI results would appear to indicate a good

ability to N translocation in yielding components,

also when a compost stopped at the active phase was

used. Furthermore, the values of NHI were similar

to those observed in other research, on maize and

barley crops, in the same environment (Montemurro

et al. 2006b). Although Montemurro et al. (2006b)

found significant correlations between NUE (or

NHI) and yield, we did not find similar correlations.

The NUE mean value reached the lowest absolute

value in OM which was significantly different from

A1 and A2. These results indicated that commercial

fertilization did not increase the efficiency of the

translocation of absorbed N in the yield components,

in comparison with organic amendments. Similar

observations have been made on durum wheat by

Montemurro and Maiorana (2008), who tested

municipal solid waste compost.

Albiach et al. (2001) reported that after repeated

organic matter applications there was a significant

increase in humified substances in the soil, whereas

the commercial amendment did not produce any

significant change. In the present study, the results

Table IV. Influence of compost amendments on soil characteristics pH, electric conductivity (EC), total organic carbon (TOC), total

extracted carbon (TEC); humified organic carbon ((HA�FA)-C), total nitrogen (N), available phosphorus (P Olsen), exchangeable bases

(K, Na, Ca, and Mg) at the start (t0) and at the end (tf) of the two-year field experiment. The values in each row followed by a different

letter are significantly different according to SNK at the p 50.05 probability level.

tf

Treatments

Parameters Units t0 A1 A2 B1 B2 OM

pH 7.87 7.77 7.73 7.76 7.72 7.72

EC (dS m�1) 0.33 0.24 0.27 0.26 0.26 0.28

TOC (g kg�1) 16.49 16.54 17.32 17.32 16.90 16.27

TEC (g kg�1) 10.58 10.33 10.68 10.80 10.97 9.95

(HA�FA)-C (g kg�1) 8.55 8.62 8.71 9.01 9.38 8.65

Total N (g kg�1) 1.31 1.47 1.40 1.63 1.23 1.30

P Olsen (mg kg�1) 28.65 13.33 22.87 22.13 26.87 16.17

K (meq 100g�1) 3.65 3.52 3.97 3.69 3.70 3.45

Na (meq 100g�1) 0.11 1.08 1.07 1.07 1.06 1.05

Ca (meq 100g�1) 31.76 33.87 33.92 33.75 33.91 33.17

Mg (meq 100g�1) 1.95 2.03 2.04 2.04 2.06 1.93

Bioassays and application of olive pomace compost on emmer 7

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suggested the positive effect also of OPCs applica-

tion to preserve the organic carbon content in the

soil. Even if not significant, the extracted and

humified organic carbon in the OPCs treatments

showed an increase of 7.5 and 3.2% compared with

the OM one. Our findings about total N, total P and

exchangeable K in soil would seem to show that the

composts obtained from olive pomace may supply

macronutrients to a crop. This outcome could be

especially confirmed after repeated composts distri-

bution on the same site (Diacono and Montemurro

2010).

The results obtained suggest that the biodegrada-

tion process could be a feasible alternative to recycle,

for agricultural purposes, olive oil pomace. This

byproduct is a waste abundant in Mediterranean

areas and its agricultural utilization could contribute

to solve the disposal problem of the specific agro-

industrial factories. The application of OP composts

is a sustainable option, which can be particularly

promoted in organic farming and on a minor cereal

crop.

However, the two-year trial period is not sufficient

to draw general conclusions on the findings ob-

served. More data are needed to assess the possible

long-term effects of composts application, as sug-

gested by Diacono and Montemurro (2010).

Acknowledgements

The research has been supported by Italian Ministry

of Agriculture, Food and Forestry Policies in the

frame work of CONSSABIO (Compost di qualita per

la conservazione del suolo e la sostenibilita delle produ-

zioni in agricoltura biologica) research project (DM

297/7303/06). The authors thank Franco Fornaro

and A. Vittorio Vonella for their skilful technical

assistance.

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