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Soil Biology & Biochemistry 39 (2007) 1383–1390

Trace and nutrient elements in manure, dung and compost

samples in Austria

Manfred SagerÃ

Austrian Agency for Food and Health Safety, Competence Centre for Elements, SpargelfeldstraX e 191, A-1226 Vienna, Austria

Available online 26 December 2006

Abstract

In Austria, farm animals are estimated to produce about 20Â 106

ton of excrements annually. In order to predict possible changes of the inorganic compositions of the target soils from various organic fertilizers, mean compositions of excrements, composts and sewage

sludges have been compiled on a dry weight basis. Although the high amounts of K and P were beneficial, there were some high

concentrations of Na in biogas residues and pig manures. Intense additions of Cu, Zn, and Se are reflected in high loads in the respective

excrements, and these amounts in some instances exceeded the threshold limits for soil contamination. Selenium addition to arable soils

can be regarded as beneficial, however, as Austria is a low Se area. Composts and sewage sludges were higher in Al and lithophilic trace

elements than were the excrements. Factor analysis traced phosphates as the main source of Cd. Cr in processed matrices was

significantly higher, and abrasion from tools should be considered in future investigations. Other unwanted trace elements, like Ni, Pb,

As and Hg, were found at a rather low concentration.

r 2006 Elsevier Ltd. All rights reserved.

Keywords: Organic fertilizers; Excrements; Composts; Microelements; Animal farming

1. Introduction

Austria has currently about 8Â 106 inhabitants, and

2.75Â 106 live in rural areas. Some areas house a lot of

foreign tourists. In addition, about 2Â 106 cattle, 3.2Â 106

pigs and 12Â 106 chickens are annually produced, as well

as lesser amounts of other farm animals. This results in

about 20.4Â 106 ton of excrements annually (Table 1).

These might be either deposited as waste, incinerated, used

for fertilization, or for biogas production with subsequent

use for fertilization.

Since the Stone Age, manure and dung have been used toimprove soil quality and to recycle phosphorus (P), carbon

(C) and nitrogen (N). Animal manure and compost

addition increases soil organic matter content, soil aggre-

gate stability, water holding capacity, water infiltration and

hydraulic conductivity. When a molli-gleyic fluvisol of pH

7.6 and 2.07% organic carbon (OC) content was fertilized

for six consecutive years either with compost or with

mineral fertilizers at the same phosphate input amount, no

significant differences in pH, carbonate content, and water-

extractable phosphate was observed. Compost treatment,

however, increased cation exchange capacity, OC content,

and water extractable chloride more than did mineral

fertilization (Bartl et al., 2002).

Besides maintaining high OC amounts in soils, organic

fertilization practice helps the lowering of the eutrophica-

tion of surface waters, and saves in the energy for the

synthesis of N-compounds needed to stimulate the growth

of valuable crops. An effective use of animal waste

resources might provide a contribution in reducing netCO2 emissions. Less fossil energy is needed for the

industrial production of fertilizers, although some fossil

energy is needed for transport and drying (Ceotto, 2005).

The main disadvantages are in the entry of toxicants and

pathogens to the arable soils. Whereas organic compounds

are more or less microbially degradable, metal salts persist

and are sparingly transported to deeper layers (Tables 2–4).

Commercial feedstuffs are frequently enriched with

essential elements copper (Cu), manganese (Mn), iron

(Fe), zinc (Zn), cobalt (Co), molybdenum (Mo) and

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selenium (Se) to promote optimum nutrient supply and

thus optimum growth rates (Tables 2 and 3). For pigs,

the minimum requirement of Cu in the feedstock is in the

range 5–10 mg kgÀ1, but higher amounts stimulate growth.

Zinc deficiencies may occur in high calcium (Ca) and high

phytic acid diets. In intense pig farming, the amount of

Cu eliminated through the animal faeces corresponds to

72–80% of the amount ingested, and this proportion

can be as high as 92–96% for Zn (Mantovi et al., 2003).

Manures from Germany contained more Cu and Zn

than all types of mineral fertilizers. In particular, pig

manure contained extraordinary amounts of nickel (Ni).

Similarly, in sewage sludges and composts, mean contents

of lead (Pb), Cu, chromium (Cr), Ni, and Zn were higher

than in mineral fertilizers with respect to nutrient contents.

Within the years 1986–1988, arable soils in Lower Saxony

received more inputs of Cu and Zn from various manures,

but less inputs of arsenic (As), Cr, and cadmium (Cd)

with respect to equivalent mineral fertilization. A tendency

towards higher inputs of Pb, Ni, and Se from manures

was noticed (Severin et al., 1990). In pig slurry, Pb, Ni,

and Cr were below the concentrations encountered in

arable soils. In 1998, a change of feeding habits in

Baden–Wu ¨ rttemberg led to a mean reduction of 30%

for Cu and 20% of Zn in pig slurry, compared to the

similar data for 1995 (Siegfried, 1998). In Northern Italy,

10–15 years of fertilization with manure from intense

pig or cattle farming led to significant enrichments of Cu

and Zn in arable soils. In the Mantova area (Italy), pig

slurries can be expected to contain 250–800 mg kgÀ1 Cu

and 600–1000 mg kgÀ1 Zn, and calf slurries to contain

30–60 mg kgÀ1 Cu and 600–1100 mg kgÀ1 Zn (dry weight).

These amounts of Cu and Zn can lead to values of 50–220

and 90–150 mg kgÀ1, respectively, in arable soils (Mantovi

et al., 2003).

ARTICLE IN PRESS

Table 1

Estimation of excreta loads annually produced in Austria

Animal Production

(106 kg yÀ1)

Estimated excreta

annually produceda

103 t yÀ1

Cattle 2.05 9000 kg per animal (per

500 kg of animal weight)

18,468

Pigs 3.25 550 kg per pig and

fattening period (3 pigs at

1 place)

1785

Sheep 0.33 1000 kg per 7 sheep (per

500 kg of animal weight)

47

Chickens 12.35 6 kg per broiler chicken 74

Turkeys 0.55 30 kg annually per place (3

turkeys at 1 place)

5.5

aExcreta load values based on wet weight.

Table 2

Concentration of copper in commercial feedstuffs in Austria in the period

2002–2004: medians of samples taken by the public control authorities

Animal Cu (mg kgÀ1)a

Single feeds Supplementary

feeds

Mineral

components

Premixes

Piglets 119 535 2970

Pigs 37 110 868

Sows 166 759

Calves 87 243

Bulls 37 950

Lactating cows 50 950

Horses 38 560

Sheep 10.3 60

Poultry 18.4 281 13,200

Laying hens 1925

aValues estimated as dry weight. The samples have been taken as

supplied, but for reasons of stability, the water content of these

commercial feedstuffs ranges from about 4% to 8%, with a maximum

of 12%.

Table 3

Concentration of zinc in commercial feedstuffs in Austria in the period

2002–2004; medians of samples taken by the state public authorities

Animal Zn (mg kgÀ1)a


feeds

Mineral

components

Premixes

Piglets 153 467 3690

Pigs 119 740 3300

Sows 405 2990

Calves 1787 2450

Bulls 193 5450

Lactating cows 313 5200

Horses 341 3150

Sheep 60 5789

Poultry 1975 92,000

Laying hens 9800




of 12%.

Table 4

Concentrations of selenium in commercial feedstuffs in Austria in the

period 2002–2004; medians of samples taken by the state public authorities

Animal Se (mg kgÀ1)a


feeds

Mineral

components

Premixes

Piglets 0.38 1.75 10.5

Pigs 0.42 1.79 14.9

Sows 1.44 11.3

Calves 4.41 14.3

Bulls 0.63 27.5Lactating cows 0.68 27.6

Horses 0.50 14.7

Sheep 18.8

Poultry 2.57 11.8 563

Laying hens 46.5




of 12%.

M. Sager / Soil Biology & Biochemistry 39 (2007) 1383–13901384

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The primary concern associated with land application of

sludges centres on the mobility and utilization rates of

potassium (K) and P reaching high concentrations.

Because the organic phosphates of composts are miner-

alized during composting, the direct P utilization rates are

lower compared with mineral P, and the respective inputs

should be considered only in long-term nutrient balances(Pfundtner and Hoesch, 2003). Higher trace metal, sodium

(Na) and K amounts from composts do not necessarily

lead to higher plant uptake, because plant availability is

lower. In particular, Cd transfer to crops has been shown

to be significantly higher from mineral fertilizers than from

composts (Bartl et al., 2002). Also, Cu and Zn transfer to

edible parts of crops was low from soils contaminated with

pig slurries. Cu uptake increased from maize to sugar beet

to lucerne, and Zn uptake increased from sugar beet to

maize to lucerne (Mantovi et al., 2003).

In pig slurry, one-third of the Cu and of Zn contents

were found to be bound to macromolecules of 450 kDa.

After 3 d of contact with an acid soil, however, the

molecular size distribution of Cu-associated moities had

changed in favour of lower molecular sizes, and in favour

of higher molecular sizes in the cases of the Zn species.

Thus, these species were not in equilibrium, but were

involved in microbial metabolic processes (Del Castilho

et al., 1993).

Mobility changes of trace and nutrient elements have

been tested via processing of the additives. Upon dilution,

the composting of wastewater sludge with about equal

amounts of wood chips reduced the extractability of Ni,

Pb, and P into 92 mM acetic acid (20:1 ratio), whereas the

extractability of Cu and of Mo was increased. Mixing withCaO to pH 12.3, in order to extract ammonium, increased

the amounts extractable with acetic acid, except in the case

of P. Incineration at 800 1C for at least 4 h increased the

mobility of Cu and Mo, but decreased that of Cr, Co, Pb,

and Zn (Richards et al., 1997).

Austria, a country of rather small structured agricultural

units and climatic zones, considers itself to be a rather

clean area. Substantial and increasing amounts of crops are

obtained from organic farming. A recent compilation of

data has been made to document current element

concentrations encountered in Austria in various sub-

stances utilized for organic fertilization. This provides

detailed information to the user and gives background

amounts in the cases of samples obtained from more

contaminated areas.

2. Materials and methods

Within the last few years, in order to match the

application rates in the field with the needs of the plant

cover, many manure, dung, and sludge samples from

Eastern Austria have been analyzed for their nutrient

contents in our laboratory.

The digests were obtained after drying and ashing of

representative weights sample (about 4 g of dry weight) in

600 ml glass beakers within a muffle furnace for 6 h at

560 1C, and then dissolving the ash in HCl. When Se and

sulphur (S) were needed, drying and ashing was carried out

in the presence of excess Mg-nitrate. The digests were run

for multi-element analysis on the ICP-OES in at least three

dilutions (e.g., 1+24, 1+4 and pure) to meet the optimum

calibration ranges, and to trace matrix effects. Watercontents were determined in aliquots at 110 1C, and all data

were finally calculated with respect to concentrations on a

dry weight basis. Some data can be compared with a

previous study carried out in 1992–1993, to trace trends

which happened within the last 10y due to changing

farming practices, or to changing emissions into the

environment. The data from 1992 to 1993 were obtained

after a similar sample decomposition procedure, but flame

AAS was used. For some other elements, which are easily

determined simultaneously using ICP-OES, no previous

data are available. Whereas solid dung samples from cattle

were used in 1992–1993, in the present study liquid cattle

manure was used, due to obvious changes in farming

practices, which may complicate comparisons.

3. Results

Respective data from soil inventory and river sediment

inventory studies are quoted for comparison in order to

interpret the current datasets (Tables 5 and 6) with respect

to possible accumulations, both at a global scale and for

local arable soils and river sediments. Unfortunately, soil

and sediment data cannot be fully compared. The

sediments were sieved at 180 mesh ($0.08mm) and

underwent HF digestion (Pirkl and Kralik, 1988), whereasthe soils were sieved at o 2 mm, and were digested with

aqua regia (Danneberg, 1999) (Tables 5 and 6).

3.1. Main and nutrient elements

The mean abundance of K in the Earth crust (which

averages down to a depth of 35 km below the continents

and to 10–13 km below sea level in the large oceans) has

been estimated at about 26 g kgÀ1 (Mason and Moore,

1982). Because K is mainly bound to silicates such as

muscovite and feldspars, it is sparingly bioavailable.

Within this dataset, the highest K concentrations, at

50–80 g kgÀ1, were encountered in pig manure and biogas

manure. The amounts of K decreased in the order pig

manure 4 cattle manure 4 pig dung 4 poultry dung 4

compost. Na from pig manure and biogas residues easily

reached more than 20g kgÀ1, which is an order of

magnitude higher than from compost, and may have

caused salt stress. Similarly, the Na/K ratio proportion was

significantly higher in pig manure than in cattle manure

and compost.

In contrast, Ca was lower in the excrements than in

compost, and it was highly variable in poultry dung.

Poultry feeds may contain much more Ca than for other

farm animals to ensure sufficient stability of egg shells.

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Mg in pig manure and in pig dung was as high as in

compost, whereas Mg was lower in cattle manure, poultry

manure, and in biogas manure. Thus, the Ca/Mg ratios

were higher in poultry dung and compost than in cattle

manure.

The quasi total Al (i.e., the Al that is soluble without HF

digestion) was significantly higher in the composts than in

the animal products. In other words, whereas Al and Mg in

composts were about equal, Al was much less in excreta.

The quasi-total Al/Fe ratio varied within the same broad

range for all matrices investigated, and contrary to

geological samples, did not indicate any special meaning.

Sulphur was at about the same concentration for excreta,

sludges and composts, and well above mean crust amounts.

Mean occurrence of P in the Earth crust is about

1.05g kgÀ1, which includes mineral phosphates and also

metamorphic apatites. P amounts in all excreta were

higher, and top concentrations were reached in pig dung

and pig manure, although still less than present in most

mineral NPK fertilizers. The K/P ratio was highest in cattle

manure, and lowest in pig and poultry dung. The excreta of

herbivore cattle significantly differed from the plant-

derived composts in K/P and Ca/Mg ratios.

3.2. Essential trace elements

In stream sediments, Zn is a good indicator of

anthropogenic inputs. Likewise, all excreta investigated,

and sludges and composts were above the mean crust

amounts of 70 mg kgÀ1 for soils. Arable soils of Austria

have mean values between 56 and 89 mg kgÀ1. For Zn,

300 mgkgÀ1 is considered to be the soil contamination

threshold. Sewage sludges may contain some Zn from the

abrasion of Zn-plated metals and roofs, but the Zn

contents found in pig excreta and poultry manure were

even higher. Whereas the mean concentration in sediments

of moderately polluted rivers in the lowlands around

Vienna was within 100–200 mg kgÀ1 (Pirkl and Kralik,

1988), the mean in this work for pig manure was almost

1200 mg kgÀ1

, and that falls within the category of

ARTICLE IN PRESS

Table 5

Median content of some nutrients and aluminum in organic fertilizers with respect to mean Earth crust concentrationa

Element (g kgÀ1) Cat tle man ure Pi g manu re Pig dun g Pou ltry du ng Bio gas manu re Compo st Sew age s ludg e Me an cr ust

Na 3.59 2.08 2.68 2.04 16.3 0.62 2.25 28.3

K 44.7 75.5 18.6 15.0 67.1 6.2 6.8 25.9

Ca 20.6 32.1 36.2 50.5 31.0 83.6 53.3 36.3

Mg 9.3 14.4 11.9 6.8 7.6 15.6 17.4 20.9

Al 1.67 0.70 0.76 0.45 2.2 15.1 18.9 81.3

Fe 1.97 2.08 2.68 1.25 3.6 21.9 45.1 50.0

P 8.4 28.0 29.0 19.1 13.5 5.3 10.9 1.05

S 5.1 — b 6.0 3.5 4.6 — 5.5 0.26

aData expressed as dry weight.bNot determined.

Table 6

Median content of some micronutrients and heavy metals in organic fertilizers with respect to mean Earth crust concentrationa

Element (mg kgÀ1) C attle ma nur e Pig manur e Pig dun g Pou ltry du ng B ioga s ma nure C ompost Se wag e slu dge Me an cr ust

Co 2.1 4.0 2.3 1.7 2.4 7.5 12.8 25

Cu 51 282 84 66 94 100 166 55

Mn 180 358 317 339 289 447 265 950

Mo 3.5 5.3 2.1 3.3 4.9 1.3 1.3 1.5

Se 0.59 3.37 1.35 1.40 0.80 — b 2.08 0.05

Zn 164 1156 399 314 349 267 683 70

Ba 46 24 42 41 35 182 163 425

Be 0.16 0.16 0.16 0.17 0.30 1.91 2.30 2.8

Li 3.2 3.5 1.4 2.1 7.2 15.9 33.3 20

Sr 59 47 53 60 48 151 136 375

V 2.9 4.2 6.0 7.8 5.4 24.7 27.7 135

As 0.33 0.88 0.51 0 .12 — 7.0 11.2 1.8

Cd 0.27 0.46 0.33 0.43 0.56 0.43 0.82 0.2

Cr 6.6 6.9 7.8 10.7 22.3 38.3 30.6 100

Hg — — — — — 0.33 0.58 0.08

Ni 6.3 12.5 8.9 8.5 14.1 25.7 25.6 75

Pb 4.1 1.9 2.6 5.4 7.7 43.4 38.3 13

aData expressed as dry weight.bNot determined.


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hazardous waste. Metal enrichments in the target soil

should thus be taken into consideration.

For Cu, the mean abundance in the entire Earth crust

has been estimated at 55 mg kgÀ1, and the threshold limit

for contamination in soils is 100 mg kgÀ1. In Austria, a lot

of uncontaminated river sediments are around the mean

crust concentration, but due to contaminations, up to332mgkgÀ1 were found in the local rivers Triesting and

Piesting (Pirkl and Kralik, 1988). Median Cu in Austrian

arable soils was around 20 mg kgÀ1 (Danneberg, 1999).

Whereas cattle excreta were at mean crust concentrations,

composts were slightly higher, and sewage sludges were

significantly higher. Cu was found to be extremely enriched

in pig and poultry manure, and even more so than in

sewage sludges, and concentrations varied within a broad

range. This may be the result of feeding farm animals with

the essential element Cu at the upper tolerance limit (Table

2). For all kinds of farm animals, manure samples were

higher than for the corresponding dung samples.

For a long time Mo has been accumulating in biota and

coals. It was found mainly at above mean crust concentra-

tions of 1.5 mg kgÀ1, except in the cases of composts, which

were within the range commonly found in green plants. In

Austrian soils, medians of Mo concentrations ranged

between 0.2 and 0.7 mg kgÀ1. As some crops may have

requirements for Mo, addition of Mo to the soil seems

beneficial. The contamination limit of 5 mg kgÀ1 is hardly

reached, however.

Mean Se in Austrian soils was determined to be

0.23 mg kgÀ1, which is quite low with respect to the needs

for animal and human nutrition. All types of excreta and

sewage sludges were above this concentration. As wasfound for Cu, Zn and P, Se concentrations were highest in

pig manure, at a median of 3.4 mg kgÀ1. No data were

available for the compost samples (Table 7).

For the essential trace elements, it may be worthwhile to

consider also the elemental ratios Cu/Se, Mn/Se, and Zn/

Se, because these pairs might act as antagonists in cell

metabolism. The Cu/Se ratios between different organic

waste types were largely overlapping. These, due to low Se,

were highest in biogas residues, whereas due to high Se,

they were lowest in sewage sludges. Zn/Se elemental ratios

were widely overlapping and within the range encountered

in soils. The S/Se ratios were significantly lower in excreta

than in cereals, mainly because of low Se concentrations in

the cereals. Among the excreta, S/Se was higher in biogas

residues than in pig and poultry manures, possibly because

of gaseous losses of Se. Unfortunately, no Se data were

available in the cases of compost samples, and there were

no data for S for the manure and dung samples.Due to low Mn contents in animal tissues, the mean

abundance in the Earth crust of 950 mgkgÀ1 was not

reached in manures and dung samples, and barely in

composts. It varied widely in sewage sludges. Cattle

manure was lowest. In case high Mn is needed, Mn

concentrations in composts will be increased from addi-

tions of tree barks.

3.3. Elements of low biological significance

Elements of low or even non-existent fertilizer require-

ments are met by organic fertilizers far below their

abundance in the roughly 35 km deep continental global

shell, such as Al, Ba, Be, lithium (Li), Sr, and vanadium

(V). Composts and sewage sludges contained more Sr and

Ba than excreta. Correlations with Ca, which would be

geochemically feasible, were not found.

For Li, the mean crust abundance is 20 mg kgÀ1, but

major parts are bound to silicates and are thus not soluble

without HF digestion. As in many feedstuffs and tissues, Li

was minor, 5 mg kgÀ1, in the excreta, and was thus very

low. It may be higher in biogas residues, and reach around

20mgkgÀ1 in composts, which resembles the amounts met

in limestones and sandstones.Whereas Be in composts was approximately close to the

mean Earth crust amount, it was very low and rather

constant in all types of excreta.

Most excreta had of the order of 10 mg kgÀ1 of V, and

that value was very low compared with the mean crust

abundance of 135mg of V kgÀ1. V was not investigated in

the soil inventory, but in river sediments it varied between 5

and 142 mg kgÀ1. Although V in most green plants is in the

range of 0.1–0.2 mg kgÀ1, the amounts in composts and

sewage sludges were significantly higher than in the excreta,

at about 30 mg kgÀ1. Appreciable amounts, however, might

ARTICLE IN PRESS

Table 7

Some nutrients and ratios among elements found in organic fertilizersa

Element Cattle manure Poultry dung Pig dung Biogas residue Sewage sludge Pig manure

Cu (mgkgÀ1) 51 (8–117)b 66 (28–182) 108 (23–211) 94 (1–360) 166 (10–612) 282 (27–642)

Mn (mg kgÀ1) 180 (40–312) 339 (91–807) 307 (74–481) 289 (4–1530) 265 (21–1941) 358 (93–907)

Se (mg kgÀ1) 0.59 ( 0.12– 0.84) 1.40 ( 0.54– 3.19) 1.35 ( 1.08– 1.42) 0.80 ( 1.15– 3.36 ) 2.08 (0. 27–13. 1) 3. 37 (2. 01–3. 57)

Zn (mgkgÀ1) 164 (49–405) 314 (92–739) 710 (48–1439) 349 (14–1715) 683 (45–1575) 1156 (214–1693)

Cu/Se ratio 92 (61–189) 75 (21–175) 79 (44–140) 132 (54–336) 58 (4–482) 76 (15–441)

Mn/Se ratio 397 (67–1245) 482 (287–1538) 297 (244–310) 307 (87–2895) 131 (15–485) 137 (28–554)

Zn/Se ratio 470 (82–780) 226 (163–693) 448 (279–1015) 537 (281–1154) 320 (30–2891) 325 (64–1751)

aData expressed as dry weight.bValues in parentheses refer to minimum and maximum values found, respectively.


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not dissolve in the HCl extracts of the ashes, compared to

incomplete recovery from aqua regia digests.

3.4. Unwanted trace elements

Cadmium has been a favourite indicator element for

anthropogenic pollution sources, and thus it is very ofteninvestigated. Although the geochemical Cd/Zn ratio is within

the range of 1:300–1:1000, the main Cd sources in agriculture

are not Zn salts but certain phosphate ore deposits, because

Cd can substitute for Ca in the apatite lattice. Whereas the

median Cd concentrations found in Austrian soils are at the

same concentration as the mean of the outer shell of the

planet Earth itself of 0.2 mgkgÀ1, many organic fertilizer

samples are higher, but still below 1 mgkgÀ1, which is

regarded as the threshold of contamination. Local river

sediments also contained 0.2–0.9 mg kgÀ1.

Like Cd, Pb has been indicative of anthropogenic inputs

since prehistoric times. Medians of Pb in arable Austrian

soils ranged between 6 and 33 mg kgÀ1, but 12–466 mg kgÀ1

were found in local river sediments. Excreta were far below

the mean Earth crust concentrations of 18 mg kgÀ1. Biogas

residues contained around 8 mg kgÀ1, which is the range for

limestone. Composts and sewage sludges were above mean

crust amounts. Higher Pb concentrations in composts may

result from atmospheric precipitation on plant leaves.

Arable soils usually get a much higher Pb load from

atmospheric precipitation than from fertilizers (Sager,

1997; Sager and Scholger, 2002). The Pb/Cd ratio in

composts was within the range expected from the

respective mean abundances, whereas due to high Cd and

low Pb, the ratio was low in the excreta. This ratio wasintermediate in sewage sludges. All Pb/Cd ratios were

similar to the Fe/Mn ratios; that may have been fortuitous,

and no reason can be given for it at this time.

Local river sediments contained 16–286 mg kgÀ1 total

Cr. For soils and sediments, only 30% of the Cr is soluble

in aqua regia. This discrepancy is much lower for composts

and sludges, which do not contain chromites, garnets and

other Cr-bearing minerals. Cr in excreta was about

10mgkgÀ1 and thus rather low; among the excreta, it

was highest in poultry dung. Abrasion from chromium-

containing cages might be a possible source, but that

should be considered in further studies. Chromium variedwidely in biogas residues, possibly due to abrasions from

mixing tools. Composts and sewage sludges contain more

Cr than manure and dung samples, but still less than the

mean Earth crust level.

Thresholds set for Ni in agriculture have been close to

the mean Earth crust abundance of 75 mg kgÀ1, and that

concentration was not reached in any of the applications.

Medians in arable soils were within 8–29 mg kgÀ1, but

contaminated river sediments contained up to 163 mg kgÀ1

.Whereas Ni in green plants is usually in the range of

1–2 mgkgÀ1, it was at about 26mgkgÀ1 in the composts,

and that is within the same range as in sewage sludges.

Among the excreta, Ni was higher in pig manure and

biogas residues, but still lower than in the sewage sludges

and composts. Significant amounts of V, as well as Cr and

Ni, may also be derived from the abrasion of tools used in

the production of composts or biogas.

Mercury (Hg) was determined only in compost and

sewage sludge samples, and it appeared to be contained

only at a moderate amount.

3.5. Statistical evaluations

For statistical evaluations, the datasets were grouped in

poultry + pig dung samples, cattle + pig manure samples,

residues from biogas production, and composts. The

correlation patterns seem quite different. In the excreta,

nutrient trace elements tend towards higher, whereas

lithogenic elements tend towards lower numbers of

significant correlations; this was not the case for composts.

In poultry + pig dung samples, many binary correla-

tions were found for Se, Ni, and Fe (12, 11, and 10

correlations from a total of 23 possible ones). This

comprises some siderophilic and lithophilic elements. Justone significant binary correlation was found for Cd, K,

Mg, Mn and Na, which would thus seem to enter the dung

accidentally. With respect to correlations in cattle + pig

manure samples, Cu(11), Ca(10) and Zn(9) were linked

most. No significant binary correlations were found for Al,

Cr, Li, Pb, and Sr in the manures.

The residues from biogas production are mainly of cattle

or pig origin. Biogas production should not change most

elemental proportions, as most of the inorganic matrix is

not volatile during methane production. Within the given

dataset, the maximum number of significant binary

correlations were obtained for Ni, V, and Se (11 out of 23 possibles). None, or just one correlation emerged for Al,

Ba, Fe, Mg, Mn, Na, and Pb.

ARTICLE IN PRESS

Table 8

Factor weights 40.7 obtained from factor analysis, after rotation

Organic fertilizers Factor 1 Factor 2 Factor 3 Factor 4 Factor 5 Factor 6

Poultry + pig dung Pb–Se–Ba–Fe–Ni Al–Co–Be–Li Mn–P–Cd Sr–As–Mg Cr–Mn — a

Cattle + pig manure Mn–Mo–Ca–Co–Zn–Cu Cd–P–V– Na–As–Se Cr–Li Sr Pb

Biogas residues Se–Co–Mo–Zn–Cu–Ni–P–V–Cd–S Li–Cr Fe–Be Ba–Al Mn Mg–Pb

Composts P–Zn–Al–Cu–Mo–Fe–Cd–Ca Mg–Ni–Cr–V Pb–Ba–Li Na–Mn–K — —

aNo value.


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In order to recognize common components and possible

differences, the four groups of data were separately

submitted to factor analysis. After rotation, almost all

elements had at least one factor weight in one component

larger than 0.6; only in the case of the biogas residues, Ca,

K and Na were not distinctly assigned. This may reflect

their heterogenous origins (Table 8).In all cases, Cd and P were found together, indicating

that Cd enters the food chain via the phosphates. The

essential trace elements Cu–Co–Mo–Zn also appeared

together, except for the poultry + pig dung. In the latter

case, some occasional inputs of ‘misplaced soil’ might have

nullified this connection. Lithophilic combinations, like

Fe–Ni, Al–Be–Li, Sr–Mg, Cr–Mn in poultry and pig dung

support this hypothesis. Nickel–Cr–V might have a

common source in the composts, i.e., the abrasion of

tools. In contrast to the composts, Na–K were not together

in the animal waste samples. Unwanted contaminants

Pb and As, and also Mn, were found in different factors in

the subsets, which indicates that they were randomly

distributed.

3.6. Long term trends

Whereas outputs from cattle remained at the about the

same amounts, a slight trend towards higher concentra-

tions was observed in pig and poultry dungs. When the

data sets get assorted for elements, Cd decreased, but some

flyers may still occur. Lead, Cr and Ni remained at about a

constant level. Copper and Zn showed a tendency to

increase (Tables 9 and 10).

4. Discussion

In organic farming practices, it is necessary to supply the

plant needs for the maintenance of steady growth by the

addition of composted plant residues. In Austria, domesticanimals are considered to produce more than 20t of

excreta annually, and it is worthwhile to consider possible

accumulations of unwanted elements in the treated arable

soils, and in the crops produced on them. In regions

without animal production, a lot of compost of presumably

plant origin can be generated. Thus a compilation of the

respective data should serve as a fundamental tool of risk

assessment.

Excreta are expected to introduce more Na, K, and P, but

less Ca and Al to the soil than composts. They are still lower

in P and in K than most mineral fertilizers, although

significantly lower than most composts. P deficiencies are at

best overcome with pig and poultry dung, whereas cattle

manure yields the highest input of K with respect to other

main elements. To satisfy plant needs for high Mg, compost

would seem preferable, as pig manure and dung also

introduce a lot of Na to the soil. There was no difference

between any type of organic fertilizer within this range of

materials with regard to requirements to meet high S needs.

5. Conclusions

As well as the known contamination sources such as

mining, industry, and traffic, high additions of essential

elements to the commercial feeds used in modern animal

ARTICLE IN PRESS

Table 9

Comparison of current data of cadmium, cobalt, and chromium compared

with values found in 1992/1993a

Organic fertilizer 1992/1993 2003–2005

Cd (mgkgÀ1)

Cattle manure 0.48 (0.10–2.95)b 0.27 (0.18–0.44)

Pig manure 0.86 (0.22–2.08) 0.46 (0.02–0.64)

Poultry dung 0.26 (0.08–0.82) 0.43 (0.19–0.93)

Pig dung 0.17 (0.04–0.67) 0.33 (o 0.02–0.38)

Cattle dung vs. manurec 0.21 (0.08–0.55) 0.27 (0.18–0.44)

Co (mgkgÀ1)

Poultry dung 2.10 (1.23–3.89) 1.71 (1.00–3.43)

Pig dung 1.2 (0.6–1.6) 2.27 (1.75–3.07)

Cattle dung vs. manure 2.4 (1.1–3.4) 2.1 (0.7–6.5)

Cr (mgkgÀ1)

Poultry dung 4.6 (2.9–6.0) 10.7 (1.6–23.1)

Pig dung 6.7 (1.6–16.1) 7.8 (4.9–13.2)

Cattle dung vs. manure 8.7 (2.8–39.5) 6.6 (2.5 – 7.4)

aData expressed as dry weight.bValues in parentheses refer to minimum and maximum values found,

respectively.cExplanation of the term ‘‘cattle dung vs. manure’’; no cattle dung was

available from 2003 to 2005, thus cattle dung from 1992 to 1993 had to be

compared with cattle manure from 2003 to 2005.

Table 10

Comparison of current data of copper, nickel, lead, and zinc vs. values

found in 1992/1993a

Organic fertilizer 1992/1993 2003–2005

Cu (mgkgÀ1)

Poultry dung 41 (23–69)b 66 (38–182)

Pig dung 75 (14–177) 62 (23–211)

Cattle dung vs. manurec 34 (13–100) 51 (8–117)

Ni (mg kgÀ1)

Poultry dung 5.2 (3.8–7.1) 8.5 (3.4–19.2)

Pig dung 4.5 (1.1–7.5) 8.9 (6.2–10.3)

Cat tle du ng vs. man ure 5. 7 (2.0 –15. 6) 6 .3 (3. 9–8. 6)

Pb (mgkgÀ1)

Poultry dung 5.0 (1.0–7.5) 5.4 (0.2–19.3)

Pig dung 3.0 (0.4–6.2) 5.0 (1.9–11.9)

Cattle dung vs. manure 3.2 (0.6–8.1) 4.1 (0.4–6.0)

Zn (mgkgÀ1)

Poultry dung 280 (176–400) 314 (92–739)

Pig dung 290 (112–944) 399 (48–1439)

Cattle dung vs. manure 148 (41–235) 164 (97–405)

aData expressed as dry weight.bValues in parentheses refer to minimum and maximum values found,

respectively.cExplanation of the term ‘‘cattle dung vs. manure’’; no cattle dung was

available from 2003 to 2005, thus cattle dung from 1992 to 1993 had to be

compared with cattle manure from 2003 to 2005.


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production processes may also pose threats of metal

accumulations in organically fertilized soils. Thus, in

general, the amounts of Cu, Zn, Mo and Se in all types

of excreta were generally above the means of occurrence in

the Earth crust of about 35km thickness below the

continents. Some inputs of Se will be beneficial for low

Se areas, like Europe. Residues from biogas production arerather new for Austrian users. These residues also

contained amounts of Cu, Mo, Zn, and Se above the

general soil concentrations. Among the unwanted trace

elements, Cd and Hg have been found to be enriched with

respect to their mean abundance in the entire Earth crust,

but at tolerable ambient amounts. For purposes of control,

it might be more reasonable to look for Cu and Zn, as well

as for Cr from abrasions of tools, and for high Na in

certain manures, than for the classical elements Cd, Pb,

and Hg, which seem to be under good control.

Although controls of metal contents have been in place

for many years, and the main industrial emission sources

are kept under control in Austria, the occurrence of some

heavily contaminated samples (termed as ‘‘flyers’’) justify a

steady and continuous level of monitoring. Whereas the

trends of general metal contaminations went down within

the last decade, surprisingly, upward trends were noted for

some metal amounts in manure and dung samples.

Acknowledgments

We acknowledge and greatly appreciate the help of Ing.

Jozo Orec for preparing most of the digests, Mrs. Gabriele

Furian for help in the operation of the ICP-OES, DI ErwinPfundtner for collecting many of the manure and dung

samples and DI Gerhard Burdicek for collecting the

compost samples.

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