Decomposition Coffee Mendonga

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Characteristics and decomposition rates of pruning residues from a

shaded coffee system in Southeastern Brazil

E.S. Mendona1,2,*and D.E. Stott1

1USDA Agricultural Research Service, National Soil Erosion Research Laboratory, IN 47907-1196 WestLafayette, USA; 2Departamento de Solos, Universidade Federal de Viosa, 36570-001 Viosa, Minas Gerais,

Brazil; *Author for correspondence (e-mail: [email protected] fax: 31-38992648)

Received 8 April 2002; accepted in revised form 30 December 2002

Key words:Century simulation, Lignin, Nitrogen, Shaded perennial system, Tropical trees

Abstract

In the Zona da Mata Mineira of Southeastern Brazil the development of sustainable land requires the integration

of crops with trees. The objectives of this study then were to (i) characterize prunings from the main tree speciesin an agroforestry system; (ii) determine the effects of the physical and chemical characteristics of the prunings

on their decomposition patterns in the laboratory; (iii) assess the effect of mixing leaves of different species on

decomposition rates; and (iv) propose a decomposition index for the residues studied. The study was carried out

with pruning residues fromCajanus cajan, Solanum variable, Cassia ferruginea, Piptadenia gonoacantha, Cro-

ton urucurana, andMelinis multiflora. The materials were characterized for total C, N, P, Ca, Mg and K con-

tents; lignin, cellulose, hemicellulose and soluble polyphenols contents. The pruning residues had high polyphe-

nols and lignin contents, high C:N and C:P ratios, and low contents of Ca, Mg, and K. The low decomposition

rates of the prunings were related to the P, K, hemicellulose and polyphenol contents. The rates of N mineral-

ization from most of the residues indicate that there is a potential to supply the needs of a crop of maize. The

residues of some species, if decomposed alone, would not supply sufficient nutrients, and need to be mixed with

leaves of other species.

Introduction

The Zona da Mata Mineira in Southeastern Brazil is

characterized by a hilly, rolling landscape. The soils

are highly weathered and acidic, with low natural fer-

tility. At present, its agricultural sector is character-

ized by the use of traditional non-mechanized man-

agement systems with little or no additions of

fertilizer and low food production. Under these con-

ditions, the development of sustainable land use

seems to demand erosion control and an integration

of crops to increase soil biology and chemical char-

acteristics (Franco et al. 1994). Hence, agroforestry

systems may present the potential to solve part of the

regions agricultural problems of the farmers since it

can contribute to reduce soil erosion and increase nu-

trients and carbon cycle.

The aims of agroforestry systems in highland ar-

eas are to increase physical protection against soil

erosion and improve soil fertility. With crops, such as

coffee, agroforestry may improve soil structure and

increase soil organic matter content and plant-avail-

able nutrients (Palm 1995; Sanchez 1995). The suc-

cess of an agroforestry system is related to the amount

and quality of the tree prunings, the amount of nutri-

ents released from the prunings during the decompo-

sition process, and how the amount and timing of the

released nutrients satisfy the needs of the crop.

Several attempts have been made to quantify plant

residue quality and its relation to the decomposition

process (Palm and Sanchez 1991; Constantinides and

Fownes 1994a; Tian et al. 1995; Handayanto et al.

1995). Residue quality is usually defined in relation

to its chemical composition. The C, N, P, lignin, and

polyphenolic contents, along with their interrelations,

117Agroforestry Systems 57: 117125, 2003.

2003Kluwer Academic Publishers. Printed in the Netherlands.


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are the most common measurements (Sinsabaugh and

Moorhead 1994; Vanlauwe et al. 1997). Residues

with high decomposition and N-mineralization rates

are usually considered to be of high quality. However,

if the main aim of an agroforestry system is to keepthe soil surface covered for erosion control, the con-

cept of low quality residues should be reconsidered.

The focus of the residue quality measurements should

be on determining the dynamics of the decomposition

process and nutrient cycling in different ecosystems

and relating the quality with the goals of each situa-

tion. Palm (1995) pointed out that agroforestry spe-

cies with high N, lignin, and polyphenolic contents

may provide nutrient release patterns that more

closely match the demands of crops for nutrients, es-

pecially N.

Despite increasing experience with agroforestry

systems in the tropics, there is still a lack of informa-

tion about the characteristics and decomposition dy-

namics of prunings from tropical trees and bushes in

our region. Most published studies dealing with resi-

due decomposition in agroforestry systems consider

only the leaves, and ignore other parts of the plant.

Therefore, the objectives of this study were to: (i)

characterize the prunings from the main plants of an

agroforestry system in southeastern Brazil; (ii) deter-

mine the effect of the characteristics of the pruning

residues on their decomposition patterns as measured

in a laboratory incubation study; (iii) assess the effect

of mixing leaves from different species on the decom-position rate since in the field the plants are in the

same area and the mixture of residues may change the

decomposition pattern; and (iv) propose a decompo-

sition index for the residues studied.

Material and methods

Pruning residues

Pruning residues were obtained from two farms inApril 1997. The farms used agroforestry systems,

with coffee as the main crop. The farms of Paulo-Vi-

cente and Joo dos Santos, were located within 2 km

of one another, at 203959S latitude, 423115W

longitude, and 900 m altitude. The main soil on the

farms was classified as a Latossolo Vermelho-Ama-

relo (Red-Yellow Latosol) in the Brazilian taxonomic

system and as a Typic Haplustox in the U.S. soil tax-

onomic system (Table 1).

Pruning residues from four tree species were col-

lected from both sites: Cajanus cajan (common

name: guandu) of theCaesalpinoideae, Solanum var-

iable(capoeira branca) of theSolanaceae, Cassia fer-

ruginea (cana fistula) of the Caesalpinoideae, and

Piptadenia gonoacantha(jacare) of theMimosoideae.

Pruning residues from two other species were also

collected at the Santos farm: Croton urucurana

(adrago) of theCaesalpinoideae, and a tall grass,Me-

linis multiflora(capim gordura) of theGramineae.

The residues were divided into their component

parts: leaves, the stems attached to the leaves (peti-

oles), and the small stems (diameter


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tion, Ca and Mg contents were determined using an

atomic absorption spectrophotometer (GBC, Model

908AA, Victoria, Australia) and K content was deter-

mined using a flame spectrophotometer.

Water potential of the residues at given water con-

tents were measured with a thermocouple psychrom-

eter (Tru Psi model SC10X, Decagon, Inc., Pullman,WA) (Myrold et al. 1981). To measure the water po-

tential of the residues at various water contents, air-

dried leaves, petioles and stems were cut in 0.50 to

1.0-cm lengths. Samples were wetted with double

deionized water to contents of 100, 200, 300, 400,

500, and 600%, by weight. The samples were allowed

to equilibrate in closed plastic vials at room tempera-

ture for 24 h before measurement.

Lignin, cellulose and hemicellulose content were

determined by the acid-detergent fiber method (Goer-

ing and Van Soest 1970). Sub-samples were placed in

hot (80 C) 50% aqueous methanol for 1 h to extract

soluble polyphenols. A 2 mg mL1 plant tissue: ex-tractant ratio was used (Constantinides and Fownes

1994b). The final concentrations were determined

colorimetrically using the Folin-Denis reagent with

tannic acid as a standard (Anderson and Ingram

1989). Carbohydrates were determined by the acid

hydrolysis method. All residue data are reported on

an oven dry, ash-free basis.

Incubation procedure

The 120-d incubation experiment was conducted to

determine the amount of CO2evolved and mass lostfrom the pruning residues. Pruning residues were

chopped into 4 to 5 cm long pieces. Each of six treat-

ments consisted of the leaves, petioles, and stems

from a single species mixed in the same ratio as the

original, uncut sample. Three additional treatments

consisted of mixtures of the six types of leaves. Mix-

ture 1 contained equal portions of leaves fromC. ca-

jan, S. variable, C. fernuginea, andP. gonoacantha;

Mixture 2 included leaves, in equal portions, fromC.

cajan, S. variable, C. fernuginea, P. gonoacantha, and

C. urucurana; and Mixture 3 contained equal

amounts of leaves fromC. cajan, S. variable, C. fer-

nuginea, P. gonoacantha, andM. multiflora.

The soil used for the incubation experiment was a

Typic Haplustox collected from the 0 to 15 cm depth

(Table 1). The soil was sieved (


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Results and discussion

Characteristics of pruning residues

Leaves, petioles, and stems varied in their chemical

composition (Table 2). The elemental concentrations

were low and followed the general trend of leaves >

petioles > stems. The amount of N in the leaves

ranged from 26 (C. fernuginea) to 47 g kg1 (C. ca-

jan) in the leaves and from 11 (C. fernuginea) to 24

g kg1 (S variable) in the petioles. TheM. multiflora

blades had lower N concentrations than the tree

leaves, 19 g kg1. The N in the stems was about the

same for all species, ranging from 9 to 13 g kg1. The

P contents of the tree leaves of all species varied from

1 to 2.4 g kg1

. Among the trees,S. variablehad thehighest K (120 mg kg1) and Ca (120 mg kg1) con-

tents in the leaves. TheM. multiflorablades had lower

Ca concentrations when compared to the tree leaves,

and the K concentration was similar to the highest K

concentrations in the tree leaves. The Mg content was

about the same in all the leaves, petioles, and stems.

The concentration of N and P in the leaves (Ta-

ble 2) of the pruning residues, assuming an input of

10 t ha1 yr1 of dry matter what is the dry matter

normally produced in the areas, is potentially enoughto meet the amount of nutrients required to produce 2

t of maize (Palm 1995). The residues with the lower

concentrations of Ca, Mg or K, would not supply

sufficient amounts of these nutrients to meet the nu-

trient demands for the next maize crop.

Leaves generally had lower contents of lignin, cel-

lulose and hemicellulose and higher amounts of

polyphenols than the petioles and stems (Table 2).

Petioles showed the same trend when compared with

stems. Amongst all the species, lignin contents ranged

from 74 to 111, 96 to 139, and 129 to 203 g kg 1 in

the leaves, petioles, and stems, respectively. Celluloseconcentrations ranged from 150 to 304, 275 to 473,

and 412 to 496 g kg1 in the leaves, petioles, and

stems, respectively. Contents of hemicellulose in the

leaves varied from 121 to 307 g kg1, while contents

in the petioles and stems ranged from 161 to 191 and

from 161 to 216 g kg1, respectively. Total carbohy-

Table 2. Initial chemical and physical characteristics of the tree- and bush-pruning residues from the shaded coffee system in southeastern

Brazil

Plant species Plant part Relative proportiona C N P Ca Mg K LGb CLc HCd CRe PPf WCh

------------ g kg1 ------------ g g1

C. cajan Leaf 0.45 540 47 2.4 0.08 0.02 0.10 111 194 121 406 88 8.22

Petiole 0.35 510 16 0.7 0.04 0.01 0.07 124 418 191 755 12 11.03Stem 0.20 510 13 0.6 0.02 0.01 0.05 129 466 215 838 09 22.45

S. variable Leaf 0.33 500 39 1.2 0.12 0.03 0.12 75 224 176 521 37 6.04

Petiole 0.37 490 24 0.8 0.08 0.03 0.15 96 335 189 644 13 7.23

Stem 0.30 510 13 0.2 0.05 0.01 0.06 146 466 207 829 08 12.28

C. fernuginea Leaf 0.38 550 26 1.2 0.06 0.03 0.06 90 168 137 430 193 8.31

Petiole 0.34 520 11 0.4 0.05 0.02 0.06 139 473 180 802 82 10.12

Stem 0.28 530 09 0.3 0.04 0.01 0.03 157 496 161 790 33 36.26

P. gonoacantha Leaf 0.35 510 38 1.3 0.09 0.03 0.09 106 181 156 426 151 8.73

Petiole 0.40 510 17 0.7 0.05 0.01 0.08 138 409 165 706 14 8.07

Stem 0.42 520 14 0.5 0.04 0.01 0.05 147 473 216 840 10 7.41C. urucurana Leaf 0.29 520 35 1.0 0.10 0.03 0.06 84 150 146 401 189 12.80

Petiole 0.29 480 15 0.4 0.14 0.03 0.07 98 275 161 586 131 18.94

Stem 0.42 510 12 0.4 0.03 0.01 0.03 203 412 168 738 33 27.90

M. multiflora Leaf 1.00 490 19 1.0 0.03 0.02 0.11 74 304 307 764 35 5.54

aThe proportion of the harvested residue of a plant species that is leaf, petiole, or stem. bLG = lignin; cCL = Cellulose; dHC = Hemicellulose;eCR = Carbohydrates; fPP = Polyphenols; gWC = Water Content of the residues at 0.33 MPa. The standard deviation for C, N, P, Ca, Mg,

and K ranged from 5 to 10%, and ranged from 5 to 15% for all other analyses.

120


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drate concentrations varied from 401 to 764, 586 to

802, and 738 to 840 g kg1 in the leaves, petioles, and

stems, respectively.

Concentrations of polyphenolics in the plant ma-

terial varied from 35 to 193, 12 to 131, and 8 to 33

g kg1 in the leaves, petioles, and stems, respectively.

The polyphenolic contents of the leaves were in the

same range as that found by Constantinides and

Fownes (1994b) for tropical plant leaves.

All the pruning residues displayed similar water

sorption patterns (Figure 1). At the same water con-

tents, the stems had the highest water potential, fol-

lowed by petioles and leaves. Among the trees, S.

variablepresented the lowest and C. urucuranathe

highest water potential at a given water content for

the leaves and petioles. For the thick stem compo-

nents, P. gonoacantha presented the lowest and C.

fernugineathe highest values. This information was

used to determine the water content necessary to

bring the residues to a water potential of 0.33 MPa

for the incubation experiments (Table 2), which will

have influence on the biomass activity that decom-

pose the residues.

Laboratory Incubations

During the first 21-d of the 120-d incubation experi-

ment, C evolved as CO2at exponential rates from all

residue samples. After 21 days, the rate of CO2evo-

lution proceeded linearly. The total amounts of C

mineralized and loss of mass were low and were in-

fluenced by the species of plant (Table 3). Among the

trees,C. fernugineaproduced the lowest andS. vari-

able the highest cumulative C evolved as CO 2 and

loss of mass, respectively, after 120-d of incubation.

Mixing leaves of different species together signifi-

cantly increased the total C evolved as CO2, whencompared to single species residues ofC. fernuginea,

and decreased when compared toS. variable, C. ca-

jan, orM. multiflora.

For five residue samples, the N concentration in

the residues increased during the incubation, while

the concentration decreased in 3 samples and re-

mained unchanged in one leaf mixture (Table 3). The

total N in theC. fernuginearesidue was low, less than

17 g kg1 when the leaves, petioles and stems were

combined in normal ratios, so if this were the only

residue present, net N immobilization would occur for

relatively long periods. The total N present in the

residues of the other plant species was sufficient toresult in net mineralization.

Thirty-nine percent or less of the N in the residues

was mineralized during 120 days of incubation (Ta-

ble 3). The amount of N mineralized was calculated

from the initial and final N concentrations and resi-

due mass. From 2.5 to 39% of the N was mineralized

during the 120-d incubation, withS. variableresidues

showing the highest N mineralization potential andC.

fernugineathe lowest. Several laboratory decomposi-

tion studies using leaves from leguminous trees re-

covered less than 50% of the initial N content (Palm

and Sanchez 1991; Tian et al. 1992; Constantinidesand Fownes 1994a). The net N mineralization of the

pruning residues was correlated with N to (lignin +

polyphenol) ratio, withr= 0.77 (P< 0.01), this ratio,

developed by Palm and Sanchez (1991), increases as

the total net mineralization decreases.

Comparing the average daily rate of CO2evolved

as C during the first 21-d and the initial elemental and

chemical concentrations of the residue (Table 4),

there were statistically significant correlations with P

(r= 0.92), K (0.61), hemicellulose (0.63), polyphe-

nols (0.76), and carbohydrates (0.56). When corre-

lated with the rate of C-CO2evolved per day, aver-

aged over the 120-d incubation, or with the total

cumulative amount of C evolved as CO2, P (r= 0.87),

K (0.70), hemicellulose (0.63), and polyphenol

(0.68) contents were significantly related. Initial el-

emental and chemical concentrations that were signif-

icantly related to the mass remaining at the end of

Figure 1. Water potential curves for the different components of

theCajanus cajanpruning residues from the shaded coffee system

in southeastern Brazil.

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120-d included P (r= 0.82), K (0.72), and polyphe-

nols (0.58).

The concentrations of hemicellulose in the resi-

dues used for the incubations ranged from 147 g kg 1

in leaf mixture 2 to 307 g kg 1 inM. multiflora. For

carbohydrates, the concentrations range from 431

g kg1 in leaf mixture 2 to 695 g kg1 inP. gonoa-

cantha. Polyphenol contents varied from 19 g kg1 in

S. variableto 132 g kg1 in leaf mixture 2. There is

some evidence in the literature that C, after the rela-

tively available C is utilized, becomes limiting the

microorganisms activity (Stott et al. 1989). Diack

Table 3. C and N concentration in the tree- and bush-pruning residues from the shaded coffee system in southeastern Brazil before and after

the 120-d incubation at 25 C, and the total amount of N mineralized during the residues incubation

Plant species C content of residue N content of residue Mineralized Nb

Initial Final Initial Final N Lost Portion of Initial N

------------ g kg1residue ------------ %

C. cajan 520 20

a

500 11 29 2 27 1 8.8 30.0S. variable 500 11 470 24 24 3 20 2 9.5 39.4

C. fernuginea 530 30 490 13 16 1 19 1 0.4 2.5

P. gonoacantha 520 22 470 11 23 1 29 2 0.8 3.5

C. urucurana 500 11 480 32 19 2 22 1 2.5 13.2

M. multiflora 490 12 450 24 19 1 21 2 3.9 20.4

Mixture 1 520 32 500 11 37 4 41 4 6.4 17.3

Mixture 2 520 13 480 12 36 2 35 3 8.9 24.7

Mixture 3 520 22 490 32 33 1 33 1 8.3 25.2

aNumbers represent the mean value with standard deviation, and are based on the contents of the leaves, petioles and stems in the ratios

found at harvest. bCalculated from the initial and remaining N contents of the residue.

Table 4. Correlation coefficient (r) between the initial chemical composition of the tree- and bush-pruning residues from the shaded coffee

system in southeastern Brazil, with leaves, petioles, and stems in the ratios found at harvest, and the average rate of C evolved as CO 2during

the first 21 days of decomposition, the average rate of C evolved as CO2during the entire 120-day incubation, and the cumulative amount

of C lost as CO2during the 120 day incubation

Average Rate of C-CO2

Evolution During the

Initial chemical characteristics First 21-d of incubation Full 120-d incubationa Mass remaining after 120-d

------------ r------------

C 0.57* 0.53* 0.48

N 0.16 0.02 0.19

P 0.92** 0.87** 0.82**

K 0.61* 0.70** 0.72**

Ca 0.22 0.19 0.02

Mg 0.22 0.14 0.01

Lignin (LG) 0.37 0.47 0.45

Cellulose (CL) 0.06 0.09 0.20

Hemicellulose (HC) 0.63** 0.63** 0.49

Polyphenols (PP) 0.76** 0.68** 0.58*

Carbohydrates (CR) 0.56* 0.44 0.33

C:N 0.12 0.28 0.44

C:P 0.90** 0.88** 0.89**

N:LG 0.02 0.21 0.33

N:PP 0.68** 0.60* 0.58*

N/(LG+PP) 0.57* 0.67** 0.72**

(C:N)*LG/CR0.05 0.46 0.61* 0.70**

*,** Significant atP < 0.05 andP < 0.01, respectively. aCorrelations are the same as for the total cumulative C evolved as CO2.

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(1994) observed a strong correlation between hemi-

cellulose and carbohydrate contents and the degrada-

tion of a wide variety of residues from the temperate

zone. The negative correlation of polyphenol concen-

trations and their associated rates of degradation have

been noted by Palm and Sanchez (1991).

Correlations between the decomposition rates at 21and 120-d, as well as the mass of residue remaining

after 120-d, and the residue quality indices found in

the literature (Palm and Sanchez 1991; Constan-

tinides and Fownes 1994a; Handayanto et al. 1995;

Gijsman et al. 1997) (Table 4) were mixed. The N

content of the residues was not correlated with the

decomposition rates in this study, the lignin concen-

tration was only weakly correlated, and the C to N

and N to lignin indices did not correlated well. The N

to polyphenol and N to (lignin + polyphenol) indices

were moderately correlated, but the correlations were

not nearly as strong as polyphenol alone. The [C to

N*lignin]/ carbohydrate 1/2 index was also moder-ately correlated with the rates of decay, but there was

a strong correlation with mass loss (r= 0.70), basi-

cally due to the weak C to N correlation being ne-

gated by the weak lignin correlation.

The C to P ratio was high, ranging from 931(C.

fernuginea) to 321 (M. multiflora), reflecting the low

P availability in the strongly P-sorbing Latosols (Ox-

isols) of the region. The high C:P ratio in the residues,

along with the somewhat high C to P ratio (43) of the

incubation soil, likely resulted in the immobilization

of P by the soil microbial community during the ini-

tial stages of decomposition (Ofori-Frimpong andRowell 1999). Along with the initial P concentrations,

the C to P index, correlated well with the decompo-

sition rates (r= 0.90,r= 0.88) and mass remaining (r

= 0.89), indicating that P was a controlling nutrient

within the incubation system. P availability has a

strong impact on litter decomposition in tropical, P-

deficient soils. In these soils, residues decayed slowly,

with soil microbes expending relatively more meta-

bolic energy to acquire the deficient nutrient rather

than to produce the lignocellulases necessary to de-

cay the residues to obtain C (Sinsabaugh and Moor-

head 1994).

The C to N ratio, ranging from 14.0 for the Leaf

Mixture 1 to 33.1 for the C. fernuginea, was poorly

correlated with the decomposition rates (r= 0.12,

0.28) and the amount of mass remaining at the end

of 120-d (r= 0.44). There was, probably, enough N,

or nearly so, to supply the needs of the microbial

population involved in the decay process. This is in

some conflict with the studies of Vitousek et al.

(1994) and Gijsman et al. (1997), however, C to N

ratios of the residues in those studies were somewhat

higher ranging from, 98 to 130, and 24 to 137, re-

spectively.

CENTURY model simulation

The initial chemical composition and mass data for

the pruning residues and the incubation conditions

were used as input for the CENTURY model. For the

first run of CENTURY using these data, and the de-

fault value of 14.8 for the maximum surface meta-

bolic decomposition rate, the model overestimated the

amount of decomposition after 120 days (Table 5).

This overestimation was most likely to the low nutri-

ent status and high polyphenol content of the pruning

residue, due to of the inclusion of petioles and small

stems. The default value was therefore adjusted to8.8, resulting in a simulated rate of C-CO2evolution

similar to the experimental data. CENTURY works

with lignin:N and C:N ratios to determine the amount

of plant parts that go to the metabolic and structural

compartments. However, some works have pointed

out the importance of polyphenols content on the ini-

tial stage of plant decomposition (Palm and Sanchez

1991; Constantinides and Fownes 1994a), and the in-

fluence of P content and others nutrients on the plant

decomposition rate (Vitousek et al. 1994). Therefore,

our data suggest that some adjustments, i.e. including

polyphenols and P contents, should be made in theCENTURY when working with tropical plant since

the decomposition rate of tropical pruning species is

mainly influenced by the (lignin+polyphenol):N ratio

and P content.

Conclusion

Our study shows that the plants used in the tropical

agroforest presents very high polyphenols and low P

contents, indicating that they are the controlling com-

pounds within the incubation system and inducing

low decomposition rates of the prunings. The species

used in the studied agroforestry system present a great

potential to prevent soil erosion and rebuilt soil C

content. But, most of the residues, if decompose

alone, would not supply sufficient nutrients, and need

to be, therefore, mixed with leave of other species.

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Acknowledgements

We thank Paulo do Amaral Lopes, Donizete Lopes

and Joo dos Santos for allowing us access to their

farms for this study. We also thank Jos Braz Junior

for expending extra time preparing samples and do-

ing part of the pruning characterization. We would

like to thank Dr. William Parton for discussions re-

garding CENTURY, and Ms. Robin H. Kelly for her

technical assistance with CENTURY. This study was

supported by a grant from CAPES, Brazilian Post-

Graduate Federal Agency. The mention of specific in-

struments or products is for the readers information

only, and does not imply endorsement by the USDA-ARS or the Universidade Federal de Viosa.

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Table 5. Mean percentage of added C evolved as CO2of the tree- and bush-pruning residues from the shaded coffee system in southeastern

Brazil, the mass remaining after 120 days of incubation at 25 C, and the results of a CENTURY model simulation using the same initial data

Plant species % C-CO2Evolved Mass remaining (% of original)

Experimental Simulated MDsc

= 14.8

Simulated MDsc

= 8.8

Experimental Simulated MDsc

= 14.8

Simulated MDsc

= 8.8

C. cajan 13.7 0.9

a

c

b

19.0 14.0 74.8 3.0 b,c 54.7 74.3S. variable 14.2 0.9 b 21.5 15.4 72.7 2.3 c,d 50.9 71.1

C. fernuginea 10.9 0.5 f 17.3 10.3 82.2 4.6 a 58.1 80.3

P. gonoacantha 12.6 0.7 e 18.0 13.0 76.8 4.4 b 55.1 75.5

C. urucurana 13.3 0.8 c,d 18.5 13.8 75.0 3.3 b,c 54.5 74.6

M. multiflora 15.0 1.0 a 20.8 15.4 72.0 1.8 d 51.6 71.1

Mixture 1 13.1 0.8 d,e 18.7 13.7 74.6 2.9 b,c 54.4 74.2

Mixture 2 12.6 0.7 e 18.6 13.5 77.3 4.1 b 53.9 74.3

Mixture 3 13.0 0.8 d,e 18.6 13.7 74.8 2.8 b,c 54.0 74.1

aNumbers represent the mean value with standard deviation. bMeans within a column with different letters indicates a significant different at

theP< 0.05 level (n= 6). cMDsis the constant representing the maximum surface metabolic decomposition rate.

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Decomposition Coffee Mendonga