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Effects of Lime and Wood Ash on Soil-solutionChemistry, Soil Chemistry and NutritionalStatus of a Pine Stand in Northern GermanyBernard Ludwig a , Sabine Rumpf b , Michael Mindrup b , Karl-Josef Meiwes b

& Partap K. Khanna ca Institute of Soil Science and Forest Nutrition , University of Göttingen ,Büsgenweg 2, Göttingen, D-37077, Germanyb Forest Research Institute of Lower Saxony , Grätzelstr. 2, Göttingen,D-37079, Germanyc CSIRO Forestry and Forest Products , P. O. Box E4008, Canberra, KingstonACT, Australia , 2604Published online: 05 Nov 2010.

To cite this article: Bernard Ludwig , Sabine Rumpf , Michael Mindrup , Karl-Josef Meiwes & Partap K.Khanna (2002) Effects of Lime and Wood Ash on Soil-solution Chemistry, Soil Chemistry and NutritionalStatus of a Pine Stand in Northern Germany, Scandinavian Journal of Forest Research, 17:3, 225-237, DOI:10.1080/028275802753742891

To link to this article: http://dx.doi.org/10.1080/028275802753742891

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Scand. J. For. Res. 17: 225–237, 2002

Effects of Lime and Wood Ash on Soil-solution Chemistry, SoilChemistry and Nutritional Status of a Pine Stand in NorthernGermany

BERNARD LUDWIG1, SABINE RUMPF2, MICHAEL MINDRUP2, KARL-JOSEF MEIWES2

and PARTAP K. KHANNA3

1Institute of Soil Science and Forest Nutrition, University of Gottingen, Busgenweg 2, D-37077 Gottingen, Germany,2Forest Research Institute of Lower Saxony, Gratzelstr. 2, D-37079 Gottingen, Germany, and 3CSIRO Forestry and ForestProducts, P.O. Box E4008, Kingston ACT 2604, Canberra, Australia

Ludwig, B.1, Rumpf, S.2, Mindrup, M.2, Meiwes, K.-J.2 and Khanna, P. K.3 (1Institute of SoilScience and Forest Nutrition, University of Gottingen, Busgenweg 2, D-37077 Gottingen,Germany, 2Forest Research Institute of Lower Saxony, Gratzelstr. 2, D-37079 Gottingen,Germany, and 3CSIRO Forestry and Forest Products, P.O. Box E4008, Kingston ACT 2604,Canberra, Australia). Effects of lime and wood ash on soil-solution chemistry, soil chemistry andnutritional status of a pine stand in northern Germany. Received November 2, 2000. AcceptedNovember 6, 2001. Scand. J. For. Res. 17: 225–237, 2002.

Lime and wood ash may be useful to improve acidic forest soils. A � eld experiment wasconducted in a pine stand on a sandy podzol at Fuhrberg, Germany, which involved anapplication of dolomitic lime (3 t ha¼1) with three replications or wood ash (4.8 t ha¼1) withoutreplications on the forest � oor. During the 2 yr study period, lime affected the soil solutioncomposition only slightly. Ash had a marked effect on solution chemistry of the mineral soilat 10 cm and the pH values dropped temporarily from 3.7 to 3.1. Nineteen months after thetreatments, exchangeable calcium in the organic layer and mineral soil increased by 222 (limeaddition) or 411 kg ha¼1 (ash addition) and exchangeable magnesium increased by 101 (limeaddition) or 39 kg ha¼1 (ash addition). After ash addition, no marked change in heavy metalcontent was found below 4 cm of the organic layer. In the ash treatment, the potassiumconcentration of the 1-yr-old pine needles increased from 5.6 to 5.9 g kg¼1. This study suggeststhat ash from untreated wood may be recommended for amelioration of forest soils. Key words:dolomite, exchangeable cations, heavy metals, nutrients, soil acidity.

Correspondence to: B. Ludwig, e-mail: bludwig@gwdg.de

INTRODUCTION

Addition of lime on acidic forest soils increases pHand base saturation, and improves biotic conditionsin soils (for overviews see Huttl & Zottl 1993,Kreutzer 1995). For instance, Aldinger (1983) investi-gated 50 limed Norway spruce and silver � r stands ofthe Black Forest, Germany, which received limestoneapplications (2.5–3 t ha¼1) 10–20 yrs before thestudy. He found increased pH values and a change inthe humus forms. Before the liming the mor humusaccounted for 55% and the mull layers for 18% of thearea, whereas after liming the mor humus layers andmull layers accounted for 15 and 61%, respectively.

A cheaper alternative to lime might be the use ofash produced in wood-processing mills or frompower plants using wood chips. Presently, ash mustbe disposed at city disposal places, although somestudies have reported bene� cial effects on soil condi-tions when wood ash was used as a liming material.For example, application of wood ash (equivalent to

6 t CaCO3 ha¼1) to an acidic forest spodosol underbeech and birch stands altered soil-exchange chem-istry favourably after 2 yrs without seriously affectingthe soil-solution chemistry. However, at additions\6 t ha¼1, soil exchange sites were unable to retainentirely the nutrient cations released from the ash(Kahl et al. 1996). Addition of granulated wood ash(at rates of 1–6 t ha¼1) to podzolic soils under pineand spruce stands in Sweden showed that changes incation exchange capacity (CEC), pH and base satura-tion in the upper part of the humus layer werepositively related to the amount of ash added(Eriksson 1998a). Lundkvist (1998) found for twospruce stands in Sweden that the earthworm popula-tion increased after the application of wood ash.

Application of lime to forest soils may have ecolog-ical and environmental risks associated with an in-crease in decomposition of soil organic matter,nitrate leaching, displacement of heavy metal ionsand a stimulation of root development in the surfacesoil layers, increasing the susceptibility to frost,

© 2002 Taylor & Francis. ISSN 0282-7581

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B. Ludwig et al.226 Scand. J. For. Res. 17 (2002)

drought and windthrow (Huttl & Zottl 1993,Kreutzer 1995, Meiwes 1995). Use of ash as a limingmaterial can potentially have some additional nega-tive effects on the soil chemistry and nutritionalstatus of forests, especially related to the accumula-tion or mobilization of heavy metals or other traceelements (Adriano et al. 1980, Carlson & Adriano1993, Wolfer 1996). Eriksson (1998b) investigated thedissolution of hardened wood ashes in a columnexperiment and found that the heavy metals werereleased relatively slowly and most of them werebound in non-exchangeable form in the mor layer.He suggested that the greatest risk of increased con-centrations of heavy metals appears to involve atemporary mobilization of part of the mor layer’sreserve of heavy metals as a result of the salt effect ofthe ashes.

A generalization about effects of ash additions isdif� cult, because the chemical composition of differ-ent ashes can vary considerably, depending on theorigin of the material, combustion conditions, ef� -ciency of particulate removal, pretreatment (harden-ing and granulation), degree of weathering before� nal disposal and the various fractions of ash (Adri-ano et al. 1980, Etiegni & Campbell 1991, Carlson &Adriano 1993). For example, � y ash is substantiallymore enriched in trace elements than is bottom ash(Adriano et al. 1980). Wood ashes may contain con-siderably smaller quantities of trace elements than docoal � y ashes (Someshwar 1996). Dinkelberg (1999)reported that wood ash contained less chromium(Cr), mercury (Hg) and nickel (Ni), but more cad-mium (Cd), lead (Pb), copper (Cu) and zinc (Zn) thanlignite ash.

The objective of the present study was to assess theeffects of lime and wood ash on soil-solution chem-istry, soil chemistry and nutritional status of a pinestand in northern Germany.

MATERIALS AND METHODS

Site and soil

The study was carried out at Fuhrberg (LuneburgerHeide) in northern Germany. The site has an eleva-tion of 38 m a.s.l. and receives 650 mm mean annualprecipitation, and the mean annual temperature is8.4°C (Otto 1989). The site carries a 50-yr-old pinestand (Pinus sylvestris) (diameter at breast height:21.9 cm; height of trees: 17.8 m). The groundwatertable at the site is 220–350 cm below the surface. The

soil is a podzol (FAO) which has developed in Pleis-tocene valley sands. The texture ranges from � nesand to medium sand. The organic layer is 10 cmthick with horizons Oi (10–8 cm), Oe (8–4 cm) andOa (4–0 cm). The mineral soil horizons are Ae (0–20cm) and Bs (20–66 cm). pHCaCl2

(0.01 M) values inthe organic layer range from 3.6 (10–8 cm above themineral soil) to 2.7 (2–0 cm) and from 2.7 to 2.9 inthe Ae horizon (mineral soil) (Table 1). Aluminium(Al3») is the dominant exchangeable cation in themineral soil, with values ranging from 65.7 kg ha¼1

(0–5 cm) to 164.9 kg ha¼1 (10–20 cm, Table 1). Thebulk deposition for the period 1996–1997 was (in kgha¼1 yr¼1): calcium (Ca) 3.2, magnesium (Mg) 0.9,potassium (K) 1.7, sodium (Na) 8.1, hydrogen (H»)0.3, ammonia (NH4

»-N) 8.1, nitrate (NO3¼-N) 6.3,

chlorine (Cl¼) 13.7 and sulfate (SO4-S) 8.7 (Rumpf &Buttner 1998).

Experimental design

For the � eld experiment, three blocks were estab-lished. In each block, there was a control plot (nolime or ash added) and a plot with 3 t dolomitic lime[dry weight (DW) ha¼1 added. In one block, an extraplot with addition of 4.8 t ash (DW) ha¼1 wasestablished. Each of the seven plots had an area of0.48 ha. Lime or ash was added to the surface of theforest � oor by hand to ensure an even distributionduring 28–30 April 1996. The amount of elementsadded in the experiment with lime was Ca (619 kgha¼1), Mg (365 kg ha¼1) and K (2 kg ha¼1) andwith wood ash was Ca (1131 kg ha¼1), Mg (61 kgha¼1) and K (105 kg ha¼1).

Dolomitic lime was obtained from Scharzfeld(Lower Saxony, Germany). Its carbonate content was63% and elemental composition (in g kg¼1 DW) wasCa (206), Mg (122), K (1) and Na (1). The content ofheavy metals in the lime (in mg kg¼1 DW) was lowand decreased in the order Zn (16)\Cr (3)\Cu(2)¾Pb (2)\Ni (1). Particle size classes were B2mm (6%), 2–6 mm (6%), 6–20 mm (17%), 20–60 mm(4%), 60–200 mm (14%), 0.2–0.6 mm (23%) and0.6–2 mm (29%).

Wood ash consisted of bottom ash plus cyclone � yash from a furnace used by a veneer company. Forthe furnace untreated wood was used. Ash had aninitial carbonate content of 7.9%. To decrease itsalkalinity and to stabilize it, ash was left outdoors inan open container for 50 days. Then, it was homoge-nized and sieved through a 10 mm sieve. It had awater content of 30% and a carbonate content of 39%

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Effects of lime and wood ash on soil chemistryScand. J. For. Res. 17 (2002) 227

Tab

le1.

pHC

aC

l 2,

C,

Nan

dex

chan

geab

leca

tion

sin

the

orga

nic

laye

ran

dm

iner

also

ilof

the

thre

eco

ntro

lpl

ots

take

n19

mon

ths

afte

rth

ebe

ginn

ing

ofth

eex

peri

men

t

CE

CD

epth

CN

Ca

Mg

KN

aA

lF

eM

nH

pHC

aC

l 2(c

m)

Hor

izon

(tha

¼1)

(kg

ha¼

1)

(km

olc

ha¼

1)

Oi

10–8

3.6

7.8

218

35.8

6.4

24.2

2.9

0.1

0.1

3.0

0.3

3.5

3.4–

3.9

(1.7

)(4

2)(3

.7)

(0.4

)(2

.8)

(0.2

)(0

.0)

(0.0

)(0

.2)

(0.2

)(0

.3)

Oe

8–6

3.2

11.4

344

48.3

5.6

12.7

4.0

0.7

0.1

1.8

2.2

5.7

3.0–

3.5

(2.4

)(7

2)(2

.1)

(0.6

)(0

.9)

(0.5

)(0

.4)

(0.1

)(0

.6)

(0.9

)(1

.1)

6–4

2.9

13.5

405

48.6

5.2

11.1

4.8

3.8

0.2

1.1

3.8

7.6

2.7–

3.1

(2.5

)(1

06)

(2.1

)(0

.1)

(2.1

)(1

.0)

(2.7

)(0

.1)

(0.6

)(1

.5)

(1.9

)O

a4–

22.

816

.548

549

.04.

49.

06.

18.

40.

20.

45.

59.

82.

7–2.

9(1

.9)

(49)

(0.4

)(0

.6)

(2.5

)(1

.3)

(5.2

)(0

.1)

(0.2

)(1

.4)

(2.0

)2–

02.

716

.548

747

.54.

27.

36.

912

.40.

10.

26.

511

.12.

7–2.

8(1

.6)

(24)

(4.3

)(0

.4)

(2.2

)(1

.2)

(4.9

)(0

.1)

(0.0

)(1

.0)

(1.8

)A

e0–

52.

723

.767

142

.84.

06.

99.

765

.714

.40.

015

.826

.52.

6–2.

9(6

.4)

(160

)(9

.8)

(0.6

)(0

.8)

(5.6

)(1

3.5)

(1.6

)(0

.0)

(3.5

)(5

.3)

5–10

2.8

21.8

600

31.2

3.0

5.1

9.9

81.1

12.4

0.1

15.3

27.0

2.7–

2.9

(5.1

)(1

11)

(7.4

)(0

.3)

(0.5

)(0

.9)

(14.

9)(0

.7)

(0.1

)(3

.4)

(4.4

)10

–20

2.9

22.8

662

26.1

3.6

7.5

17.6

164.

919

.30.

017

.839

.32.

7–3.

2(8

.0)

(163

)(4

.6)

(0.4

)(1

.8)

(1.8

)(8

3.3)

(9.7

)(0

.0)

(5.8

)(1

4.2)

Dat

aar

em

eans

(SE

)(n

¾3)

.F

orpH

CaC

l 2,

the

min

ima

and

max

ima

are

give

nin

stea

dof

the

SE.

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B. Ludwig et al.228 Scand. J. For. Res. 17 (2002)

(DW). The elemental composition of the ash (in gkg¼1 DW) was Ca (236), K (22), Mg (13), S (7), P (5)and Na (3). The content of heavy metals in the ash(in mg kg¼1 DW) was Zn (346), Cu (115), Cr (66),Pb (42), Ni (35), Co (8) and Cd (3). Particle sizes ofthe ash were B0.1 mm (24%), 0.1–0.2 mm (16%),0.2–0.63 mm (32%), 0.63–1 mm (8%), 1–2 mm(14%) and 2–10 mm (6%).

Soil and needle-chemistry studies

Soil samples (n¾6 for the plot with addition of 4.8 tash ha¼1 and n¾3 for the other plots) were obtainedat random from each plot before lime or ash additionand 19 months later. The organic layer was separatedfor 2 cm depth intervals and the mineral soil for0–2.5, 2.5–5, 5–10 and 10–20 cm depths. Results for0–5 cm depths are given as weighted means for thesurface soil layers. Needle samples (1- and 2-yr-oldneedles) were collected in December 1995 and thenagain in December 1997 (two growing seasons aftertreatments). For each plot, six trees were sampled inthe upper third of their crown following BML (1994).Half of the trees were chosen on a north–southtransect, the other half on an east–west transect. Thesame trees were used for both sampling dates. Thetrees sampled were not within a speci� c site class. Thebranches sampled were taken from all four directions.All 1- and 2-yr-old needles were sampled from allshoot parts of the sample branches. Each sampleconsisted of 100 needles. Dried (at 60°C for 5 days)and ground samples of the organic layers and needleswere digested using the HNO3 pressure technique(Konig & Fortmann 1996). For the needles, the di-gests were analysed for Ca, Mg, K, Na, Al, Fe, Mnand P (atomic emission spectroscopy), and for theorganic layers, for Zn, Cu, Cr, Pb, Co, Ni and Cd(atomic absorption spectroscopy) (Konig & Fort-mann 1996). Soil pHCaCl2

was determined in a 0.01 MCaCl2 solution (soil to solution ratio 1:3). Totalorganic C and total N content were determined in thesoil and needle samples by an automated C and Nanalyser (Heraeus vario EL).

Soil -solution chemistry

Soil-solution chemistry was investigated at 0 (mineralsoil surface), 10 and 100 cm depth for 24 months(April 1996 to April 1998) using ceramic P80 cups(Staatliche Porzellanmanufaktur , Berlin, Germany).Ceramic cups were rinsed before installation with 0.1N HCl and then with distilled water. One-hundred

ceramic cups were installed at each depth and plot,giving a total of 2100 cups in the experiment. Cupswere conditioned in the � eld by discarding the � rst200 ml of the solution obtained. After the condition-ing, a continuous suction of 50 kPa was applied. Soilsolution samples were obtained once every 2 weeksand stored at 4°C. Samples were bulked on amonthly basis and analysed for pH using a glasselectrode and for Na, K, Mg, Ca, Mn, Al, Fe and S(interpreted as SO4

2¼) using atomic ICP emissionspectroscopy. Concentrations of Cl¼, NH4

» andNO3

¼ were determined colorimetrically (Konig &Fortmann 1996).

Exchangeable cations

Mineral soil samples (2.5 g, air-dried and sieved B2mm) were leached slowly (6 h) at a constant percola-tion rate with 100 ml of 1 M NH4Cl, and cations (Ca,Mg, K, Na, Al, Fe and Mn) were then measured inthe extract using atomic absorption spectroscopy(Konig & Fortmann 1996). For organic layer sam-ples, 12 g of � eld moist samples were leached slowly(10 h) at a constant percolation rate with 600 ml of0.2 M CsCl, and cations were measured in the extractusing atomic emission spectroscopy (Konig & Fort-mann 1996). Organic layer samples which were col-lected 19 months after addition of lime or ashcontained residual ash or lime. To separate the ex-changeable cations in the extracts from those releasedfrom residual ash or lime, a sequential leachingmethod as described by Konig & Fortmann (1996)and Meiwes et al. (2002) was employed. A prerequi-site for this determination is that the release of Ca,Mg and K from the alkaline substance is a � rst-orderreaction. This was successfully tested by leachingmixtures of lime and quartz (Meiwes et al. 2001) andof ash and quartz (data not shown). Exchangeablecations in the ash- or lime-treated organic layers wereobtained by subtracting the amounts of Ca, Mg andK released from the residual lime (or ash) from thetotal amounts extracted (Konig & Fortmann 1996,Meiwes et al. 2001). In all cases, exchangeable H»

was obtained from the decrease in pH of NH4Cl afteraccounting for H» released on hydrolysis of ex-changeable Al3» (Konig & Fortmann 1996).

Statistical analysis

For the solid-phase samples from the lime and con-trol treatments, statistical analysis was carried out bycalculating a standard normal distribution. A two-way anova with the factors ‘‘treatment’’ and ‘‘spatial

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Effects of lime and wood ash on soil chemistryScand. J. For. Res. 17 (2002) 229

replication’’ was done. The factor ‘‘spatial replication’’was considered to be a random factor. Differencesbetween treatment means were compared in an F-test.No statistical analysis was carried out for the soil-so-lution data, since for most sampling times there wereinsuf� cient replications.

RESULTS

Changes in soil solution

After the addition of 3 t dolomitic lime ha¼1, maxi-

mum Ca concentrations were 130 mM (0 cm), 140 mM(10 cm) and 80 mM (100 cm) and maximum Mgconcentrations were 70 mM (0 and 10 cm) and 90 mM(100 cm) (Fig. 1). Mg concentrations continued to behigh at the end of the measurement period in thelime-treated plot compared with the control. pH valuesincreased slightly at all depths, but spatial variabilitywas considerable (Fig. 2). Liming had a considerableeffect on NO3

¼ concentrations (most pronounced at 10cm depth); maximum values were 300, 450 and 220 mMat 0, 10 and 100 cm, respectively (Fig. 3).

Fig. 1. Concentrations of Ca andMg at different depths. Mean valuesand SEs for the control ( n ), plotwith lime addition ( ) and plot withash addition ( ). The treatmentswere started on 28 April 1996.

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B. Ludwig et al.230 Scand. J. For. Res. 17 (2002)

Fig. 2. Concentration of K(mean values and SEs) and pHvalues (mean, minima andmaxima) at different depthsfor the control ( n ), plot withlime addition ( ) and plotwith ash addition ( ). Thetreatments were started on 28April 1996.

The effect of addition of 4.8 t wood ash ha¼1 onsoil solution chemistry was more pronounced thanthat of the lime treatment. After the addition of woodash, Ca concentrations in the soil solutions collectedat the mineral soil surface (0 cm) were elevated for 15months, with a maximum value of 430 mM after 6months (Fig. 1). The increase in Ca concentration at10 cm was less pronounced and lasted for 9 months(maximum concentration was 170 mM after 7months). No marked increase in Ca concentrations

was found at 100 cm (Fig. 1). The considerable Kcontent of the ash (22 g kg¼1) increased the soil-solu-tion concentration at 0 and 10 cm throughout thestudy period of 2 yrs and was still elevated at the endof the study period. The peak concentration values(730, 750 and 180 mmol K l¼1 at 0, 10 and 100 cm,respectively) were observed within the � rst year afterthe ash application and decreased continuously dur-ing the second year (Fig. 2). Compared with theeffects of ash additions on K concentrations, changes

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Effects of lime and wood ash on soil chemistryScand. J. For. Res. 17 (2002) 231

Fig. 3. Concentrations ofNO3

¼ and SO42¼ at different

depths. Mean values and SEsfor the control ( n ), plot withlime addition ( ) and plotwith ash addition ( ). Thetreatments were started on 28April 1996.

in Mg concentrations (due to release of Mg from theash and cation-exchange reactions) were less pro-nounced (Fig. 1).

Large amounts of SO42¼ were released from the ash

during the � rst year after ash addition; maximumconcentrations were 1300 mM at 0 cm and 1400 mMat 10 cm (Fig. 3). At the end of the study period, theconcentration of SO4

2¼ was higher at all depths (0, 10and 100 cm) in the ash-treated plot than in thecontrol plots, indicating that a considerable amountof cations was continuously being leached in the

ash-treated plot compared with the control plots. Thecations accompanying SO4

2¼ during percolationthrough the soil had undergone ion-exchange pro-cesses resulting in the desorption of H» [or of Al3»

followed by Al(OH)3 precipitation]. A pronounceddecrease in solution pH (minimum value of 3.1) at 10cm was observed for 1 yr after ash addition (Fig. 2).At 100 cm, changes in pH and SO4

2¼ concentrationsdue to ash addition were less pronounced. The pHvalues at 100 cm were generally 0.1 unit lower andSO4

2¼ concentrations were generally 1.3–2.6 times

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B. Ludwig et al.232 Scand. J. For. Res. 17 (2002)

higher in ash-treated soil than those for the control(Fig. 3). Addition of ash increased Al concentrationsat 10 cm, which remained high from the fourth to theseventh month after addition (a maximum concentra-tion of 220 mM was observed 4 months after treat-ment) (Fig. 4). In the second year after ash addition,Al concentrations in 100 cm were generally 60 mM

higher than for the control, for which an Al concen-tration of 250 mM was observed (Fig. 4).

In the ash treatment, NO3¼ concentrations in-

creased in soil solutions collected from all depths andthe maximum values were 270, 110 and 90 mM at 0,10 and 100 cm, respectively (Fig. 3).

Changes in the organic layer and mineral soil dueto addition of dolomitic limestone

Addition of dolomitic limestone resulted in highercontents of exchangeable Mg (corrected for the re-lease of Mg from dolomitic limestone) in the organiclayer (2–8-fold) and the mineral soil (2-fold) com-pared with the results for the control (Table 2).However, differences between the results of the treat-ments were signi� cant (pB0.05) only for 8 to 6 cmand 4–2 cm depths. Exchangeable Ca (corrected forthe release of Ca from dolomitic limestone) was2–3-fold higher at some depths, but changes wereonly statistically signi� cant (pB0.05) for 8–6 cmdepth. In the Oi layer (10–8 cm) and Oe layer (at 6–4cm), CEC of the lime-treated plots was signi� cantly(pB0.05) higher than that of the control (Table 2).The increase in pHCaCl2

values occurred in the surfaceOi and Oe layers (10–4 cm). However, lime caused asmaller increase in pH than did ash.

Thirty six per cent of the Ca added (222 kg ha¼1,Table 3) and 27% of the Mg added (101 kg ha¼1)were present in exchangeable form in the organiclayer and mineral soil (0–20 cm) 19 months after limeaddition. On a molar basis, the ef� ciency of dolomiticlimestone to change exchangeable Ca and Mg wasslightly less than that of wood ash: the sum ofexchangeable Ca and Mg in the organic layer andmineral soil from the lime accounted for 17 and 3kmolc ha¼1, respectively.

Changes in the organic layer and mineral soil due toash addition

Nineteen months after ash addition, pHCaCl2values

were increased in the surface 8 cm of the organiclayer and the values were: 5.9 (10–8 cm), 5.4 (8–6cm), 4.0 (6–4 cm) and 2.9 (4–2 cm). Amounts ofexchangeable Ca and Mg (corrected for the release ofCa and Mg from the ash) were 2–5-fold higher in theentire organic layer (except for Mg in the Oi layer)compared with the results for the control. Exchange-able Mg in the surface mineral soil (0–5 cm) was2-fold higher (Tables 1, 2). After ash addition, a2-fold higher content of exchangeable K in the min-eral soil (0–20 cm) (Table 2) was observed. Ex-

Fig. 4. Concentration of Al at different depths. Meanvalues and SEs for the control ( n ), plot with lime addition( ) and plot with ash addition ( ). The treatments werestarted on 28 April 1996.

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Effects of lime and wood ash on soil chemistryScand. J. For. Res. 17 (2002) 233

Tab

le2.

Exc

hang

eabl

eca

tion

sin

the

orga

nic

laye

rsan

dm

iner

also

ilsfo

rth

eex

peri

men

tsw

ith

addi

tion

of3

tlim

eha

¼1

(n¾

3)an

d4.

8t

ash

ha¼

1(n

¾1)

afte

r19

mon

ths

CN

Ca

Mg

KN

aA

lF

eM

nH

CE

CD

epth

(tha

¼1)

(kg

ha¼

1)

(km

olc

ha¼

1)

Hor

izon

pHC

aC

l 2(c

m)

3t

lime

ha¼

1

49.5

14.6

13.4

Oi

2.4

0.6

0.0

1.0*

0.0*

4.3*

10–8

4.9

6.0

176

(13.

3)(6

.5)

(4.6

)(0

.6)

(0.5

)(0

.0)

(0.4

)(1

8)(0

.0)

(0.6

)(1

.3)

4.6–

5.4

95.5

*44

.0*

14.7

3.6

0.2

0.0*

1.6

0.2*

Oe

9.2

8–6

4.1

10.2

331

(19.

7)(7

.0)

(2.7

)(0

.6)

(0.2

)(0

.0)

(0.6

)(2

6)(0

.2)

(1.4

)(0

.8)

3.9–

4.5

24.7

837

128.

639

.919

.37.

65.

30.

21.

23.

414

.5*

6–4

3.1

(49.

8)(1

1.6)

(7.2

)(2

.1)

(2.3

)(0

.1)

(0.7

)(2

02)

(0.6

)(3

.1)

(5.7

)2.

9–3.

461

.614

.2*

10.1

4.9

4.6

0.2

0.4

4.0

Oa

9.2

4–2

2.8

16.4

530

(18.

2)(2

.6)

(2.2

)(0

.6)

(1.4

)(0

.1)

(0.1

)(9

1)(0

.7)

(0.4

)(2

.9)

2.6–

3.1

649

72.6

9.1

9.3

6.8

9.8

0.2

0.2

7.2

13.1

2–0

2.7

20.6

(9.1

)(1

.3)

(2.0

)(0

.4)

(1.4

)(0

.1)

(0.1

)(8

9)(1

.4)

(1.9

)(2

.5)

2.6–

3.0

684

Ae

55.0

6.5

6.6

8.5

62.3

20.9

0.1

15.4

26.8

0–5

2.6

23.8

(3.6

)(1

03)

(16.

2)(1

.6)

(0.9

)(4

.9)

(11.

8)(9

.4)

(0.0

)(2

.4)

(2.8

)2.

6–2.

733

.83.

44.

77.

260

.012

.60.

046

611

.816

.721

.35–

102.

7(1

5.1)

(1.1

)(1

.1)

(1.0

)(1

0.3)

(2.7

)(0

.0)

(1.8

)(2

.8)

2.6–

2.7

(0.8

)(3

3)54

.15.

48.

617

.415

7.8

26.5

0.0

906

20.3

42.7

34.3

2.8

10–2

0(3

4.7)

(1.1

)(1

.8)

(0.3

)(4

4.6)

(2.4

)(0

.0)

(5.4

)(1

1.6)

2.7–

3.0

(8.7

)(2

18)

4.8

tas

hha

¼1

69.5

6.0

19.2

2.1

0.3

0.1

1.1

0.3

4.9

Oi

10–8

5.9

6.5

165

197.

910

.718

.73.

90.

00.

11.

124

80.

011

.48.

65.

48–

6O

e12

.037

616

7.8

11.8

14.5

4.2

0.2

0.0

1.2

0.3

10.3

6–4

4.0

99.5

23.0

19.9

5.6

2.4

0.1

0.9

547

4.2

2.9

12.1

15.9

Oa

4–2

804

82.1

8.3

10.4

8.7

16.0

0.0

0.1

8.7

15.8

2–0

2.7

26.7

61.3

7.4

12.6

11.9

86.4

13.5

0.1

24.1

38.5

Ae

0–5

2.6

31.1

819

30.7

3.7

8.5

10.5

84.5

7.6

0.0

660

18.7

25.5

30.7

5–10

2.7

31.5

4.5

13.3

21.3

235.

024

.00.

023

.553

.510

–20

2.8

49.7

1363

Dat

aar

em

eans

(SE

).D

ata

for

the

cont

rol

plot

sar

egi

ven

inT

able

1.*S

igni

�can

tdi

ffer

ence

sbe

twee

nth

eco

ntro

lan

dlim

etr

eatm

ents

(pB

0.05

).E

xcha

ngea

ble

Ca,

Mg

and

Kw

ere

corr

ecte

dfo

rth

eam

ount

rele

ased

from

resi

dual

ash

and

lime.

For

pHC

aC

l 2,

the

min

ima

and

max

ima

are

give

nin

stea

dof

the

SE.

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B. Ludwig et al.234 Scand. J. For. Res. 17 (2002)

Table 3. Fate of the elements of the lime and the ash 19 months after the treatments

Mg KCa(kg ha¼1)

3 t lime ha¼1

619 365 2Added in lime96 (26%) 3 (150%)Exchangeable in the organic layer (10–0 cm) 179 (29%)5 (1%) 0 (0%)43 (7%)Exchangeable in the mineral soil (0–20 cm)

264 (72%) 0 (0%)Rest (in insoluble forms; plant uptake or transport below 20 cm soil depth) 397 (64%)

4.8 t ash ha¼1

1131 61 105Added in ash34 (56%) 18 (17%)388 (34%)Exchangeable in the organic layer (10–0 cm)

23 (2%)Exchangeable in the mineral soil (0–20 cm) 5 (8%) 15 (14%)720 (64%) 22 (36%) 72 (69%)Rest (in insoluble forms; plant uptake or transport below 20 cm soil depth)

The amounts of exchangeable cations in the organic layer and mineral soil were calculated from the changes inexchangeable cations after additions of lime and ash (Tables 1, 2). Values in parentheses give the percentage of the addedamounts.

changeable Al and H decreased in the surface organiclayer (8–2 cm) and decreases in exchangeable Fe(6–0 cm) and Mn (10–6 cm) were also observed(Table 2). The CEC of the organic layer (correctedfor the release of Ca, Mg and K from the ash) at 8–6cm was 2-fold higher than for the control (Table 2).

Nineteen months after ash addition 34% (388 kgha¼1) and 2% (23 kg ha¼1) of the Ca added werepresent in the exchangeable form in the organic layerand mineral soil, respectively (Table 3). Most of Caadded (720 kg ha¼1) remained in an insoluble formin the organic layer, assuming that plant uptake andleaching of Ca below 20 cm accounted for a smallamount only (a few kilograms per hectare). Sixty-fourper cent of Mg and only 31% of the K added wereretained as exchangeable in the organic layer andmineral soil (Table 3). A considerable amount of K(72 kg ha¼1, Table 3) was not accounted for.

Changes in heavy metal content of the organiclayer due to ash addition were mainly con� ned to thesurface organic layer (10–6 cm) (Table 4) because ofthe low mobility of the heavy metals. An exceptionwas Pb, for which the concentration decreased at10–4 cm and increased below this level (4–0 cm). Zncontent increased in the surface organic layer (10–6cm) and also in the 2–0 cm layer (Table 4).

Changes in needle contents

The nutritional status of the 1-yr-old pine needlesfrom control plots was low for Mg and Mn, low tomedium for P and Ca, and medium for K, N and Fe(Table 5) (cf. Block et al. 1991, Huttl 1992). Neitherliming nor ash addition had a marked effect on the

nutritional status of the 1-yr-old (Table 5) and 2-yr-old (data not shown) needles which were sampled 19months after the treatments. However, an increase inthe K content was observed for the 1-yr-old pineneedles in the ash treatment, which had 5.9 g K kg¼1

compared with 5.6 g K kg¼1 in the needles fromcontrol plot.

DISCUSSION

In this study, the effects of lime addition on soil andsoil-solution chemistry were studied on three plots,whereas no replications were carried out for the studyof the effects of ash addition. Thus, the results for theash treatment are only indicative.

Nineteen months after the addition of lime andash, an increase in the CEC was observed in theorganic layer. This increase in CEC was the result ofchange in pH and was primarily associated with anincrease in exchangeable Ca. The increases in CECand exchangeable cations were higher in ash-treatedplots than in lime plots. Kahl et al. (1996) reported a2.5-fold higher CEC of the organic layer 2 yrs afterthe addition of wood ash (equivalent to 6 t CaCO3

ha¼1) to an acidic forest spodosol. However, this sitecomparison is not straightforward as, for example,Kahl et al. (1996) did not mention the thickness (oramount) of the organic layer or the texture of thewood ash used, and did not account for elementsreleased from the ash during the determination ofexchangeable cations. Accounting for elements re-leased from the ash during the determination ofexchangeable cations has been done in only a fewstudies (Ludwig et al. 1998, 1999a ).

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Effects of lime and wood ash on soil chemistryScand. J. For. Res. 17 (2002) 235

Table 4. Heavy metal content in the organic layers for the different treatments after 19 months

Cu CrDepth Pb Ni Co CdZn(kg ha¼1)(cm)

Control0.13 (0.02) 0.04 (0.01) 0.23 (0.07) 0.03 (0.01)0.93 (0.13) 0.01 (0.00)10–8 0.01 (0.00)

1.29 (0.19)8–6 0.25 (0.06) 0.11 (0.04) 0.96 (0.41) 0.08 (0.02) 0.01 (0.00) 0.01 (0.00)0.43 (0.18) 0.25 (0.13) 3.24 (1.86) 0.16 (0.07) 0.04 (0.02) 0.02 (0.00)6–4 1.90 (0.65)0.53 (0.14) 0.33 (0.12) 4.15 (1.92) 0.19 (0.05)2.49 (0.57) 0.05 (0.02) 0.02 (0.00)4–20.54 (0.05) 0.38 (0.08) 5.36 (1.75) 0.22 (0.02) 0.06 (0.01)2–0 0.03 (0.00)2.59 (0.46)

4.8 t ash ha¼1

1.1810–8 0.22 0.08 0.16 0.06 0.01 0.010.49 0.23 0.59 0.141.88 0.038–6 0.02

1.316–4 0.36 0.16 1.31 0.11 0.02 0.022.36 0.65 0.37 4.96 0.23 0.05 0.034–2

0.96 0.79 9.98 0.384.82 0.112–0 0.06

Data are means (SE) (n¾1 for the ash treatment or n¾3 for the control). Added amounts of ash components (in kg ha¼1)were 1.66 (Zn), 0.55 (Cu), 0.32 (Cr), 0.20 (Pb), 0.17 (Ni), 0.04 (Co) and 0.01 (Cd).

Table 5. Concentrations (g kg¼1) of elements in 1-yr -old needles for different treatments after 19 months

C:N P Ca Mg K Fe MnTreatment N

33.6 (1.1) 1.5 (0.0) 2.8 (0.2) 0.9 (0.1)Control 5.6 (0.0) 0.1 (0.0) 0.2 (0.0)15.8 (0.5)15.7 (0.4) 33.7 (0.6) 1.6 (0.1) 2.7 (0.2) 0.9 (0.0) 5.4 (0.0) 0.1 (0.0) 0.1 (0.0)3 t lime ha¼1

37.7 1.5 2.1 0.8 5.9 0.1 0.14.8 t ash ha¼1 14.2

Data are means (SE) [n¾1 (addition of 4.8 t ash ha¼1) or n¾3]. Differences between the control and lime treatment arenot signi� cant (pB0.05).

The calculations of the fate of the elements addedin the lime and ash indicated that 19 months aftertheir addition, most of the Ca added remained in aninsoluble form in the organic layer. Insoluble formsof Ca could be CaCO3, magnesium calcites and et-tringite [Ca6Al2(SO4)3(OH)12½26 H2O] (Steenari &Lindqvist 1997). Only 31% of K added in the ash wasretained as exchangeable in the organic layer andmineral soil, but a signi� cant amount of K may havebeen present in insoluble forms owing to its incorpo-ration into silicates and the formation of microcline(KAlSi3O8) (Steenari & Lindqvist 1997). Dependingon the type of ash, more than 40% of the total K inthe ash may be present in sparingly soluble forms(Khanna et al. 1994). By assuming an average con-centration of 0.25 mmol K l¼1 at 10 cm during the 19months after ash addition (cf. Fig. 2) and a water � uxof 150 mm yr¼1, 23 kg ha¼1 of K would haveleached below 10 cm soil depth. Plant uptake mayhave accounted for a few kilograms of K, Ca and Mgper hectare.

The results of this study showed that addition oflime only slightly affected the soil-solution composi-

tion during the � rst 24 months, especially at soildepths greater than 10 cm. The changes in pH andion concentrations in seepage water due to lime addi-tion reported in this study are similar to previous� ndings. For instance, Wenzel (1989) studied theeffect of additions of different lime materials (6 tha¼1) on the soil-solution chemistry at Solling sprucesite and found elevated concentrations of Ca (up to190 mM), Mg (up to 160 mM) and NO3

¼ (generallyaround 500 mM; maximum: 1250 mM) at 100 cmthroughout the study period of 2 yrs.

Ash had a marked effect on soil-solution chemistryat 0 and 10 cm during the � rst year after addition,with maximum concentrations (in mM) of 1400(SO4

2¼), 110 (NO3¼), 750 (K) and 170 (Ca) at 10 cm.

Even greater changes in solution chemistry were re-ported by Wolfer (1996), who found maximum con-centrations (in mM) of 5300 (SO4

2¼), 860 (NO3¼), 170

(K) and 1800 (Ca) at 15 cm during the � rst year afteraddition of 5 t � uidized bed boiler ash ha¼1 to anacidic forest soil. Such large changes were due to thehigh S content of 46 g kg¼1 of the � uidized bedboiler ash (Wolfer 1996). In the present study, as well

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B. Ludwig et al.236 Scand. J. For. Res. 17 (2002)

as in the study by Wolfer (1996), SO42¼ concentra-

tions decreased considerably with soil depth on theash-treated plots, which may result from its reten-tion in association with an increase in pH, as de-scribed by Ludwig et al. (1999b).

A long period of increased K concentrations at 0and 10 cm was observed in this study, which canprobably be assigned to releases of soluble K saltsfrom the ash into solution and exchangeable phasesin the � rst few months, followed by cation-ex-change reactions (adsorption of Ca from the ashand desorption of K) in the subsequent months. Arelease of K from slowly dissolving phases (micro-cline (KAlSi3O8); Steenari & Lindqvist 1997) maybe of less signi� cance initially but may contributeto some extent in the long term. In the presentstudy, after ash addition the pH values in soil solu-tions dropped temporarily from 3.7 to 3.1 at 10 cmdepth. Similarly, Lehnardt (1998) reported that theaddition of 5 t lime ha¼1 to different forest siteson cambisols in Hesse (Germany) did not lead to asigni� cant pH increase in seepage water at 50 and100 cm in subsequent years. In some cases, a de-crease in pH values by 0.1–0.2 units and an in-crease in Al concentrations was found at 100 cm(Lehnardt 1998).

In the present study, concentration changes of allelements due to ash addition at 100 cm were muchless pronounced than the changes at 10 cm. Nitrateconcentrations at 100 cm depth were well below theGerman legal limit of 807 mM in the drinking water(TrinkwVO 1990). The increase in NO3

¼ concentra-tion due to ash addition found at all depths studiedpoints to an increase in nitri� cation and an excessof mineral N in the soil which cannot be taken upby the vegetation. During the process of nitri� ca-tion, additional protons are produced in the soil.

The SO42¼ concentrations at 100 cm remained

high at the end of the study period. However, sinceSO4

2¼ concentrations at 10 cm decreased consider-ably after the initial peak, it may be assumed thatincreased SO4

2¼ concentrations at 100 cm (and thusincreased cation leaching) would decrease withinmonths.

Addition of ash did not increase heavy metalcontent below 4 cm of the organic layer, with theexcep tion of a slight translocation of Pb which wasprobably related to enhanced complexation due toincreased dissolved organic carbon (DOC) concen-trations (Konig et al. 1986). Marked changes in Zncontent were expected in the entire organic layer

because of high levels of Zn in the ash (346 mgkg¼1), its high mobility in sandy soils (Korte et al.1976) and the low pH value at the study site (thethreshold pH value, below which Zn shows highmobility, is 5.3; Hornburg & Brummer 1993). How-ever, changes in Zn content were only slight andspatial variability was high. It has been argued thatrecycling of waste products and their addition tosoils may lead to a sustained enrichment of heavymetals in soils and will eventually result in unac-ceptable amounts (Kloke 1999). However, thepresent short-term study suggests that if the ash islow in heavy metal content (untreated wood, possi-bly with a low � y-ash component) it can safely bedeposited at modest doses in pine forests. It will,however, be essential to de� ne the quality of theash for nutrients and heavy metal content, becauseash composition can be highly variable, dependingon the combustion conditions and other factors.

ACKNOWLEDGEMENTS

This study was � nancially supported by the Facha-gentur fur Nachwachsende Rohstoffe, Gulzow, Ger-many. B. Ludwig acknowledges the � nancialsupport received by the Deutsche Forschungsge-meinschaft (Heisenberg scholarship). We wish todedicate this paper to Prof. Dr Dr h.c. B. Ulrichon his 75th birthday and express our appreciationfor his forming many of the ideas which are thebasis of this and other research projects.

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