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Organic matter pools and nutrient cycling in different coffeeproduction systems in the Brazilian Cerrado
Eduardo Barros Marinho • Aline Lima de Oliveira • Daniel Basılio Zandonadi •
Luiz Eduardo Celino Benedito • Ronessa Bartolomeu de Souza •
Cıcero Celio de Figueiredo • Jader Galba Busato
Received: 5 February 2014 / Accepted: 7 June 2014 / Published online: 19 June 2014
� Springer Science+Business Media Dordrecht 2014
Abstract Agroforestry and organic systems have
been used to reduce the negative effects that conven-
tional coffee cultivation has on soils. In this work,13C-CPMAS-NMR, Fourier transform infrared spec-
troscopy, elemental composition, classical humus
fractionation and the soil fertility status were used to
evaluate the impact of these three systems on a Latosol
from the Brazilian Cerrado. Continuous input of tree
residues promoted changes to the soil organic matter
with increase in total organic carbon, humic acids
(HA) and light organic matter, mainly in the topsoil.
Available P and cation exchange capacity were also
increased and the acidity status decreased in the
agroforestry system. Moreover, HA from the agrofor-
estry were enriched in O-alkyl C, O-di-alkyl C and
alkyl C groups and the organic system resulted in
HA richer in carboxyl groups. The conventional
system resulted in greater aromatic and methoxyl
participation, and lower phenol groups. HA from the
agroforestry system were richer in easily degradable
structures and the chemical fractionation demon-
strated a decrease in both recalcitrant fractions,
allowing for a more conservative and sustainable
management of soil fertility. The modifications were
not as evident in the organic system, probably due to
the low organic fertilizer input.
Keywords Agroforestry � Organic cultivation �Humic acids � 13C-CPMAS-NMR spectroscopy
Introduction
Coffee is one of the most widely consumed food
products in the world and Brazil is the main producer
E. B. Marinho � L. E. C. Benedito � C. C. de Figueiredo �J. G. Busato (&)
Faculdade de Agronomia e Veterinaria, Universidade de
Brasılia (UnB), Campus Universitario Darcy Ribeiro -
Asa Norte, Caixa Postal 4508, Brasılia,
DF CEP 70910-970, Brazil
e-mail: jaderbusato@unb.br
E. B. Marinho
e-mail: e_barros.m@hotmail.com
L. E. C. Benedito
e-mail: leduardo420@gmail.com
C. C. de Figueiredo
e-mail: cicero@unb.br
A. L. de Oliveira
Instituto de Quımica, Universidade de Brasılia (UnB),
Campus Universitario Darcy Ribeiro - Asa Norte,
Brasılia, DF CEP 70910-970, Brazil
e-mail: aline.alo@gmail.com
D. B. Zandonadi � R. B. de Souza
Empresa Brasileira de Pesquisa Agropecuaria
(EMBRAPA), Centro Nacional de Pesquisa de Hortalicas
(CNPH), Brasılia, DF CEP 70359-970, Brazil
e-mail: daniel.zandonadi@embrapa.br
R. B. de Souza
e-mail: ronessa.souza@embrapa.br
123
Agroforest Syst (2014) 88:767–778
DOI 10.1007/s10457-014-9723-4
and exporter of green coffee, accounting for approx-
imately 35 % of the global production (Monteiro and
Farah 2012). The coffee farms are responsible for
millions of jobs and about 7 % of all Brazilian
agribusiness exports in 2012 were due the coffee
activity. However, besides its economic and social
importance, coffee cultivation strongly changes agro-
ecosystem characteristics. The loss of soil organic
matter (SOM) and decrease in nutrients levels due to
soil disturbance and runoff in conventional systems
favor the impoverishment of highly weathered soils.
Also, mineral nitrogen fertilizer inputs increase soil
acidity and enhance greenhouse gas emissions as N2O,
which has greater global warming potential than CO2
(Stehfest and Bouwman 2006; Chu et al. 2007).
Many practices have been proposed to reduce the
negative effects of coffee cultivation. Agroforestry
systems are structurally diverse compared to mono-
cropping and frequently improve the use of natural
resources by both temporally and spatially accessing
different sources of light, water and nutrients (Moreno
and Obrador 2007). Introduction of trees in agrofor-
estry systems enhances the potential energy as
biomass and results in a larger carbon stock in soils,
favoring nutrient cycling and plant growth (Khanna
1997; Hergoualc’h et al. 2012). Furthermore, trees
decrease water runoff, protecting the soil against
erosion (Cannavo et al. 2011). Organic production
systems also have been used to restore the soil quality.
Organic farming avoids the use of synthetic high
soluble fertilizers and emphasizes organic inputs as
nutrients source (Araujo et al. 2008). In Brazil
approximately 800,000 hectares are occupied by
organic crops (Willer et al. 2008), but there is a clear
increasing trend to support both great national and
international market demands.
Besides total carbon stocks and nutrient status of
soil, SOM chemical compartments are changed when
agroforestry or organic managements are established
(Aranda et al. 2011; Benbi et al. 2012; Guimaraes et al.
2013). Humic substances (HS) are the major compo-
nents of stabilized SOM and the most widespread
natural products found on the Earth’s surface. Changes
in the distribution, functionality and molecular com-
position of HS have been successfully used to assess
the impact of management on agricultural environ-
ments (Canellas et al. 2010). Humus fractionation by
chemical procedures and non-destructive spectro-
scopic techiques such as Fourier Transform Infrared
Spectroscopy (FT-IR) and cross-polarization magic-
angle-spinning nuclear magnetic resonance (13C-
CPMAS-NMR) are useful methods for the character-
ization of the HS, enabling increased knowledge on
the influence of crops on soil quality.
Based on these facts, this study was carried out to
determine the influence of agroforestry and organic
coffee systems, in comparison to conventional system,
on nutrient levels, HS content and characteristics in a
Latosol from the Brazilian Cerrado. The hypothesis
evaluated was that the combined use of tree species
and crops, or the adoption of organic crop production,
improved soil quality by increased nutrients and HS
due to a higher and efficient cycling when compared
with the conventional system.
Materials and methods
Site characterization and experimental design
The Brazilian Cerrado is the most extensive area of
savanna-type vegetation in South America, originally
covering about 2,000,000 km2. The major areas of
Cerrado are located on the Central Brazilian Plateau,
presenting annual rainfall between 1,100 and
1,600 mm, concentrated in the months of October to
April. Long-term mean temperatures of the site range
between 22 and 24 �C (Buol 2009). An experiment
involving the cultivation of coffee in agroforestry,
organic and conventional systems was established in
2007 at the Centro Nacional de Pesquisas de Hortalicas
(Embrapa Hortalicas) farm, located at 15�560700S and
48�80900W, 997 m elevation, in Brasilia—DF, Brazil
(Fig. 1). The agroforestry system consisted of planta-
tions of Gliricidia sepium (Jacq.) Steud in close
association with coffee plants (Coffea arabica L). The
organic system consisted of cultivation that received
only fertilizer permitted for organic production. Both
the agroforestry and organic systems received organic
composts at planting produced from castor meal
(300 g plant-1), lime (2 ton ha-1) and magnesium
thermophosphate (500 g plant-1). After planting, the
coffee plants received an organic fertilizer every
6 months based on cattle and chicken manure and
castor meal at the rate of 300 g plant-1. No pesticides or
chemical weed control were used at these sites. To
conventional system, lime (2 ton ha-1) and cattle
manure (5 L plant-1) were applied at planting. During
768 Agroforest Syst (2014) 88:767–778
123
the first year, 170, 100 and 300 g plant-1 of N, P2O5 and
K2O, respectively, were applied as mineral soluble
fertilizers. After the second year, mineral fertilization
consisted of 60 g plant-1 of P2O5, 80 g plant-1 of both
N and K2O per year, again using soluble sources.
Mechanical and chemical weed controls were per-
formed and as well chemical pesticides were occasion-
ally used.
Soil samples
Soil was classified as Dystrophic Red–Yellow Latosol
according to the Brazilian taxonomy system (Embrapa
2006), corresponding to a Typic Haplustox according
to the US soil taxonomy system (Soil Survey Staff
2010). In September 2012, each coffee production
system was divided into three plots of approximately
100 m2. In each plot, twenty soil sub-samples were
randomly collected to obtain a composite soil sample.
Three sampling depths were considered: 0–0.05,
0.05–0.10 and 0.10–0.20 m.
Laboratory analysis
Chemical and physical properties
The soil samples (three replicates for each system) were
transported to the laboratory in plastic bags, air dried,
sieved through a 2-mm screen and stored prior to
analysis according to Embrapa (1997). The pH was
measured in water (soil:solution relationship equal to
1:2.5); P and K? were extracted by Mehlich–1 solution;
Ca2?, Mg2? and Al3? were extracted with KCl
1 mol L-1. Total organic carbon (TOC) was deter-
mined by the modified Walkley–Black procedures
(Yeomans and Bremner 1988). Mineral particle-size
distribution was analyzed using the pipette method
(Embrapa 1997). Prior to start the experiment, the soil
presented the following chemical characteristics: 5.2 of
pH H2O; 5.1 mg dm-3 of P; 30.0 mmolc dm-3 of Al3?,
28.0 mmolc dm-3 of Ca2? ? Mg2?, 2,4 mmolc dm-3
of K?, 80.5 mmolc dm-3 of total acidity and
29.8 g dm-3 of organic matter.
Fig. 1 Location of sampling sites in agroforestry, organic and conventional coffee systems in the Brazilian Cerrado: (1) organic
system; (2) agroforestry system; (3) conventional system
Agroforest Syst (2014) 88:767–778 769
123
Organic matter fractionation
Soil samples were pre-treated with a 2 mol L-1
orthophosphoric acid solution which separated the
light organic matter (LOM) through density and also
solubilized the free fulvic acids (FFA) fractions.
Thereafter, a 0.1 mol L-1 NaOH solution was added
to residual soils (1:20, v:v), which solubilized the
fulvic acids (FA) and humic acids (HA). The insoluble
solid residue resulting from the fractioning process
was called as humins (HUM). HA were separated from
the FA through centrifugation after precipitation in
acid medium using concentrated H2SO4 to pH 1–1.5.
The carbon content of FFA, FA, HA and HUM was
determined according to Yeomans and Bremner
(1988). Light organic matter was determined using
an analytical balance.
Humic acids extraction
Soluble humic substances were extracted from the top
soil samples (0–0.05 m) by adding 200 mL of a
0.1 mol L-1 NaOH solution to 10 g soil samples,
followed by 16 h of agitation at room temperature
under N2 atmosphere. The dark colored supernatant
solution was separated from the residual fraction by
centrifugation (3,000g, 30 min). The insoluble residue
was re-suspended in 200 mL of 0.1 mol L-1 NaOH
and shaken for 4 h. Then, the solution was centrifuged
again and the previously collected supernatant was
added. This procedure was repeated until a clear
solution was obtained. The extracted alkaline solution
was acidified to pH 1.0–1.5 with concentrated H2SO4
and the HA was separated from the FA by centrifu-
gation at (5,000g, 15 min). The HA was treated with
100 mL of a dilute HF-HCl solution [5 mL HCl (36 %
m/v) ? 5 mL HF (48 % m/v)] and agitated overnight.
After centrifugation (5,000g, 15 min), the HA was
repeatedly washed with deionized water, dialyzed
against deionized water using a 12–14 kDa-cutoff
membrane (Thomas Scientific, Inc) and freeze-dried.
13C-CPMAS-NMR spectroscopy and elemental
composition
Humic acids extracted from the top soils (0–0.05 m)
were characterized by solid state carbon nuclear
magnetic resonance (13C-CPMAS-NMR) using a
Varian Mercury 300 at 75.452 MHz. Samples of the
HA were packed in zirconia rotors with Kel-F caps and
spun at 13 ± 1 kHz. To account for possible inhomo-
geneity of the Hartmann–Hahn condition at high rotor
spin rates, a 1H ramp sequence was applied in CP
experiments during a contact time (CT) of 1 ms.
Experiments were conducted at an acquisition time of
20 ms and a recycle delay of 2.0 s. The ACD/NMR
processor software was used to collect and elaborate
the spectra. The areas for different 13C resonances
were assigned into six integrating regions: 0–46 ppm
(aliphatic C; alkyl), 47–66 ppm (methoxyl C; meth-
oxyl/N-alkyl), 67–111 ppm (oxidized and/or carbo-
hydrate C; O-alkyl; anomeric C; di-O-alkyl),
112–141 ppm (unsubstituted and alkyl-substituted
aromatic C; aryl), 142–164 ppm (oxygen substituted
aromatic C from lignin and nonhydrolyzable tannins;
phenolic, O-aryl) and 165–188 ppm (aliphatic and
aromatic carboxyl C, C in amidic groups; carboxyl/
amide). Elemental composition of the HA was deter-
mined using a Perkin Elmer 2400 Series II.
Fourier Transform Infrared Spectroscopy
Fourier Transform Infrared Spectroscopy spectra of
HA were recorded on KBr pellets in the
400–4000 cm-1 wave number, with a 4 cm-1 resolu-
tion and 16 scans for each sample using a Varian 640
spectrophotometer. A mixture of 1 mg HA and
100 mg KBr was pressed to obtain the KBr pellets.
The spectra subtraction procedure was used to infer
the H2O and CO2 contaminations.
Statistical analysis
Changes in the carbon pools and soil fertility were
analyzed according to a complete randomized design.
The coffee systems and sampling depths were con-
sidered as primary and secondary effects, respectively.
Results were submitted to variance analysis and the
means were compared via the Tukey test (p \ 0.05).
The data of all variables together was subjected to
principal component analysis (PCA), based on linear
combinations of the original variables on the inde-
pendent orthogonal axes. This analysis was performed
for distinction of the different coffee production
systems, considering all the attributes together
(TOC, LOM, CFFA, CHA, CFA, CHUM, pH, Al3?,
H ? Al?3, Ca2? ? Mg2?, K?, effective CEC, CEC
(pH 7.0), SB, P, V and m). Statistical analyses were
770 Agroforest Syst (2014) 88:767–778
123
performed using the software XLSTAT 2011 (Addin-
soft 2011).
Results and discussion
Chemical properties of the soils varied significantly
among the coffee productions systems (Table 1). In
the 0–0.05 m layer, controlled soil acidity was
observed when the agroforestry or organic systems
were implanted. The soil exchange complex under the
conventional system was saturated with Al3? (mean of
15.1 % for the three depths), indicating the absence of
a residual effect from the lime after 5 years of coffee
planting. Low pH in the conventional system was
presumably due to the high doses of nitrogenous
fertilizers in the ammoniacal form. Conversion of
ammonium to nitrate in soils, as well the continued
uptake of NH4? by plants, are followed by the release
of H? ions, increasing the acidity and decreasing the
base reserves (Middleton and Smith 1979). Moreover,
the conventional system showed the lowest values for
pH, sum of bases, base saturation and (Ca2? ? Mg2?),
whereas the agroforestry and organic systems, which
did not receive mineral fertilizer applications, pre-
sented an exchange complex occupied by cations with
alkaline character and low acidity index, mainly in the
top soil. The lowest values of Al3? and H ? Al3? in
conservation tillage systems, especially under organic
management, may be the result of Al3? complexing by
low molecular weight organic acids in soils (van Hees
et al. 2001).
The organic system was particularly effective in
neutralizing acidity even in the deepest soil layer. On
the other hand, control of acidity by the agroforestry
system occurred only in the two shallowest samples
(0–0.05 and 0.05–0.10 m) and similar values to those
in the conventional system were observed at increased
depths. In forest systems, the action of low weight
molecular organic acids on aluminium complexing is
higher in the surface soil layers, decreasing with depth
(van Hees et al. 2001). Increase in soil acidity was also
observed in areas covered with tree-legumes when soil
samples were obtained at depths deeper than 0.10 m
(Schiavo et al. 2009). This behavior can be associated
with biological nitrogen fixation since when main-
taining the intracellular pH, and making the fixation
process effective, the legume species perform H?
extrusion with consequent rhizosphere acidificationTa
ble
1C
hem
ical
attr
ibu
tes
of
soil
fert
ilit
yo
nd
iffe
ren
tsy
stem
so
fco
ffee
pro
du
ctio
nin
the
Bra
zili
anC
erra
do
Cro
p
syst
em
Dep
th
(m)
pH
(H2O
)
Al3
?
(mm
ol c
dm
-3)
(H?
Al)
(mm
ol c
dm
-3)
Ca2
??
Mg
2?
(mm
ol c
dm
-3)
K?
(mm
ol c
dm
-3)
Eff
ecti
ve
CE
C
(mm
ol c
dm
-3)
CE
C(p
H7.0
)
(mm
ol c
dm
-3)
SB
(mm
ol c
dm
-3)
P (mg
dm
-3)
V(%
)m
(%)
San
d
(gdm
-3)
Sil
t
(gdm
-3)
Cla
y
(gdm
-3)
Conven
tional
0–0.0
55.3
c4.5
a80.5
a18.5
c5.9
b28.9
c104.8
b24.4
c18.0
b23.2
c15.6
a637.4
100.5
262.1
Org
anic
6.4
a0.0
c47.9
c42.0
b6.6
a48.6
b96.4
c48.6
b15.0
c50.4
a0.0
c612.9
105.9
281.2
Agro
fore
stry
6.0
b0.5
b59.0
b50.5
a3.5
c54.5
a113.0
a54.0
a22.9
a47.8
b0.9
b595.6
118.2
286.2
Conven
tional
0.0
5–0.1
05.3
c4.0
a78.4
a18.8
c5.6
a28.3
c102.7
a24.3
c17.6
a23.7
c14.1
a615.6
113.2
271.2
Org
anic
6.2
a0.0
c48.3
c40.0
a2.3
c42.3
a90.5
b42.3
a7.7
c46.7
a0.0
c602.0
110.9
287.1
Agro
fore
stry
5.7
b1.0
b65.6
b33.3
b3.4
b37.7
b102.2
a36.7
b12.0
b35.9
b2.6
b616.5
117.3
262.2
Conven
tional
0.1
0–0.2
05.4
b4.0
a76.3
a17.3
b4.4
a25.7
a98.0
a21.7
b9.4
a22.1
b15.6
b639.7
109.1
251.2
Org
anic
6.0
a0.5
b49.1
c25.0
a1.9
b27.4
a76.0
c26.9
a5.7
b35.5
a1.8
c590.2
92.7
317.1
Agro
fore
stry
5.5
b4.3
a68.1
b13.5
c1.6
c19.8
b83.1
b15.1
c2.6
c18.2
c23.0
a599.7
109.7
291.2
Sum
of
bas
es(S
B)
=C
a2?
?M
g2?
?K
?;
Eff
ecti
ve
cati
on
exch
ange
capac
ity
=S
B?
Al3
?;
Cat
ion
exch
ange
capac
ity
atpH
7.0
(CE
Cp
H7
.0)
=S
B?
(H?
Al3
?);
Bas
esa
tura
tion
(V)
=100
9S
B/T
;A
lum
inum
satu
rati
on
(m)
=100
9A
l3?
/t.
For
each
layer
,av
erag
esfo
llow
edby
the
sam
ele
tter
inth
eco
lum
nar
enot
stat
isti
call
ydif
fere
nt
(Tukey
test
,p
\0.0
5)
Agroforest Syst (2014) 88:767–778 771
123
(Marschner and Romheld 1983). Additionally, in
samples obtained from the agroforestry system at
0.05–0.10 and 0.10–0.20 m, there was decrease in the
Ca2? ? Mg2? content, probably due to absorption by
the tree which allowed for an increased soil acidity
index. The pH values of 6.4 and 6.0 for the organic and
agroforestry systems in the 0–0.10 m samples, respec-
tively, justify the absence or low level of exchangeable
Al3? in these managements (Table 1).
Available P was significantly increased in the
agroforestry system compared to the organic and
conventional systems in the top soil (Table 1). Content
of available P depends on soil management and
cropping systems, where accumulation of SOM usu-
ally results in higher levels of available P (Cardoso
et al. 2003; Busato et al. 2005; Canellas et al. 2010).
The turnover of P forms accumulated in vegetal
biomass produced in higher amounts by arborous
legume species contributed to these increased P levels.
Degraded soils re-planted with Acacia mangium also
increased the available P in a relatively short time
period (3 years) due a combined effect of nutrient
cycling and reduced P fixation resultant of the higher
SOM content (Schiavo et al. 2009). However, the
agroforestry system showed a marked decrease of P in
the samples obtained at 0.10–0.20 m. The complex
system involving trees and coffee plants influenced the
dynamics of P through the conversion of a portion of
the inorganic P into organic forms, mainly in deeper
layers (Cardoso et al. 2003). It was possible that part of
the inorganic P present in agroforestry soils was
converted to organic forms that are not reached by the
extractor used in the available P analysis (Nelson et al.
1953). Levels of organic P forms increased consider-
ably in agricultural soils when managements based on
preservation of SOM are adopted (Busato et al. 2005).
Under these conditions, diester organic phosphates
can be protected against microbial degradation in the
hydrophobic domain of SOM (Canellas et al. 2010),
forming an important reservoir for P in soils.
Total organic carbon was about 15 % higher in the
0–0.05 m layer when tree-legumes were cultivated
together with coffee plants (Table 2). Conservation
practices using leguminous cover crops and inputs of
organic amendments improve the plant biomass
production by increasing the quantities of residues
added to the soil (Guimaraes et al. 2013). The presence
of trees promoted frequent input of plant tissues,
mimicking natural systems by increasing residue
returns and minimizing C removal. In the Brazilian
Cerrado, however, carbon mineralization is particu-
larly fast due to the high temperature, rainfall and
microbial activity (Kaschuk et al. 2010). Therefore,
only managements with constant input of organic
residues enable accumulation and increase in the TOC.
The volume of compounds applied in the organic
system was not sufficient to alter the TOC, resulting in
a value similar to that observed in the conventional
system. Furthermore, no differences in the TOC were
observed between the three systems in the deeper
layers. The results are in agreement to those of
Guimaraes et al. (2013), who reported greater SOM in
the upper layer of cultivated soils using conservation
practices when compared with conventional systems,
although there was no difference for depths below
0.10 m. The absence of soil disturbance, natural
mulching and the relatively short time of agroforestry
implementation may have resulted in accumulation of
SOM on the soil surface, retaining these residues
isolated from the rest of the soil profile.
Although differences in the SOM content were
observed only in the upper layer, adoption of both
organic and agroforestry systems greatly affected the
carbon pools distribution even in the deeper layers
(Table 2; Fig. 2). In the 0–0.05 m layer, the agrofor-
estry system showed the highest LOM content, which
represented 20 % of all fractions (Fig. 2). The
conventional system showed only 5 % of LOM and
most of the organic matter (77 %) was related to the
most recalcitrant carbon form (HUM). The organic
system had 38 % more alkali-soluble forms
(HA ? FA) than the other management systems.
Increase in the LOM and soluble alkaline forms in
the agroforestry and organic systems, respectively,
were followed by decreases in the HUM fractions,
showing conversion among carbon forms. A similar
result was observed for the 0.05–0.10 m depth in
agroforestry systems, with higher LOM content and
decrease in the HUM fraction when compared to the
conventional system (Table 2). Furthermore, a slight
increase in the FFA fraction was observed. No
alterations were noticed between organic and conven-
tional systems at this depth. Even in the samples
obtained for the 0.10–0.20 m depth, the agroforestry
system showed a higher LOM fraction and lower value
for HUM. Alkali-soluble forms represented 15 % of
total carbon in the agroforestry system, while both
organic and conventional systems presented 10 and
772 Agroforest Syst (2014) 88:767–778
123
6 %, respectively. No LOM fraction was detected in
the conventional system at the deepest sampled layer.
Two principal components (PC1 and PC2) were
generated (Fig. 3). These components were created as
tools to discriminate the effects of the different coffee
production systems, considering the organic matter
fractions (TOC, LOM, CFFA, CHA, CFA and CHUM) and
chemical characteristics (pH, Al3?, H ? Al3?,
Ca2? ? Mg2?, K?, effective CEC, CEC (pH 7.0), SB,
P, V and m) together for the layers of 0–0.05 m
(Fig. 3a), 0.05–0.10 m (Fig. 3b) and 0.10–0.20 m
(Fig. 3c). The distribution of selected variables showed
cumulative variance of 87.3, 90.8 and 87.6 % for the
sum of the principal components PC1 and PC2 in the
layers of 0–0.05, 0.05–0.10 and 0.10–0.20 m, respec-
tively. For all layers, the PC1 and PC2 axes separated the
three systems: conventional, organic and agroforestry.
This distinction indicates that the managements adopted
for coffee production in weathered Latosols with
different inputs of organic material changes the chem-
ical composition, leaving a distinct soil profile as a
function of agricultural management.
Despite this general pattern of distinction, accord-
ing to the PC1 axis which is responsible for the largest
percentage of explained variance in the 0–0.05 m
layer, it may be possible to observe that conservation
systems (organic and agroforestry) differed from the
conventional system, influenced by greater accumu-
lation of organic matter fractions and cation exchange
complexes and reduction of acidity components in
conservation tillage systems. In the 0.05–0.10 m layer,
there was clear distinction between organic and
conventional systems, with the agroforestry system
presenting intermediate behavior. In this layer and also
in the 0–0.05 m layer, the organic system generally
higher levels of carbon in fractions of humified
organic matter, reduction of acidity components, and
increase in the sum of bases and exchange complexes.
In the 0.10–0.20 m layer, the three systems showed
distinct patterns. This differentiation was influenced
by the accumulation of nutrients derived from mineral
fertilizers in the conventional system by reducing the
acidity components promoted by the organic system,
as well as by increasing the acidity in the agroforestry
system, despite its high capacity to accumulate LOM
in that layer (Tables 1, 2).
Humic acids content also varied greatly among
systems. In the 0–0.10 m layer, mean HA concentra-
tions were 1.3, 1.8 and 1.5 g kg-1, respectively, for
the conventional, organic and agroforestry systems
(Table 2). Both organic and agroforestry systems were
38 and 19 % richer in HA content, respectively, as
compared with the conventional system. Elemental
composition and atomic ratios of the HA are listed in
Table 3. The C content of the HA varied from 425.0 to
481.9 g kg-1 and only slight modifications were
observed for N and H contents among the manage-
ments (from 37.3 to 40.1 and 42.6 to 44.9 g kg-1,
respectively, for N and H). A high C/N ratio is
considered to indicate a high stability of humus and
large degree of condensed structures (Stevenson
1994). Therefore, organic and conventional systems
presented HA traditionally interpreted as humic
material with an advanced humification stage.
Table 2 Total organic carbon (TOC) and carbon content in the
light organic matter (LOM), free fulvic acids (FFA), fulvic
acids (FA), humic acids (HA), humins (HUM) and humic
acids:fulvic acids ratio (CHA/CFA) in different systems of
coffee production from Brazilian Cerrado
Crop system Depth
(m)
TOC
(g kg-1)
LOM
(g kg-1)
CFFA
(g kg-1)
CHA
(g kg-1)
CFA
(g kg-1)
CHUM
(g kg-1)
CHA/
CFA
Conventional 0–0.05 23.0 b 0.8 b 0.6 b 1.3 b 0.7 b 11.7 b 1.9
Organic 22.7 b 1.5 b 1.1 a 1.8 a 1.7 a 13.8 a 1.1
Agroforestry 26.1 a 3.8 a 0.9 ab 1.5 ab 0.9 b 11.5 b 1.7
Conventional 0.05–0.10 22.9 a 0.4 b 1.1 b 1.4 a 1.7 ab 12.0 b 0.8
Organic 20.2 b 1.0 b 1.3 a 2.0 a 2.2 a 20.0 a 0.9
Agroforestry 21.9 ab 1.9 a 1.0 b 1.0 b 1.4 b 10.0 b 0.7
Conventional 0.10–0.20 21.8 a 0.0 c 0.9 b 0.6 a 0.3 b 12.1 b 2.0
Organic 19.4 b 0.5 b 0.9 ab 0.9 a 0.8 a 13.9 a 1.1
Agroforestry 19.4 b 0.9 a 1.2 a 1.5 a 1.2 a 11.5 b 1.3
For each layer, averages followed by the same letter in the column are not statistically different (Tukey test, p \ 0.05)
Agroforest Syst (2014) 88:767–778 773
123
The changes, however, were not restricted to the
amount of HA or content of C in this humic fraction,
but also the structural composition, resulting in
different spectroscopic signature when the HA from
the topsoil were analyzed by 13C-CPMAS-NMR
(Fig. 4; Table 3). HA from the agroforestry system
were enriched in O-alkyl C and O-di-alkyl C
(67–111 ppm), as well in alkyl C groups
(0–46 ppm). The conventional system resulted in
HA with greater aromatics (112–141 ppm and me-
thoxyls (47–66 ppm) and lesser participation of phe-
nols (142–164 ppm); the organic system was enriched
with HA in carboxyl groups (165–188 ppm). In the
aliphatic C region, a sharp peak centered at 30 ppm,
assigned to methylene C from waxes, lipids, cutin and
suberin polymers (Quideau et al. 2000; Keeler et al.
2006), was observed in the HA from the agroforestry
Fig. 2 Percent distribution of humidified fractions of the
organic matter from soils in 0–0.05 m (a), 0.05–0.010 m
(b) and 0.10–0.20 m (c). 100 % = FFA ? FA ? HA ?
HUM ? LOM, respectively representing the carbon content
present in the free fulvic acids, fulvic acids, humic acids, humins
and low organic matter
Fig. 3 Ordination diagram derived from the principal compo-
nent analysis of the scores of treatments under different coffee
production systems: a 0.00–0.05 m, b 0.05–0.10 m,
c 0.10–0.20 m
774 Agroforest Syst (2014) 88:767–778
123
and organic systems. These systems also showed a
signal at 47 ppm, attributed to methylene or methine C
groups in amino acids residues (Almendros et al.
2000). In the conventional system, the peak at
30 ppm was decreased and widened, typical of
humic material with a greater chemical stability.
Agroforestry exhibited various signals between 53
and 111 ppm, the region of readily degradable
aliphatic groups. On the other hand, only signals
at 56 and 74 ppm were observed in the organic
system. In turn, the conventional system showed
extended signals between 52–57 ppm, 68–74 ppm
and 107–111 ppm, typical for more humified humic
material (Preston et al. 1994). This may be a result
of the absence of new inputs of organic materials in
the conventional system, which preserved only
recalcitrant structures in HA.
Stabilized HA are usually enriched in paraffinic
structures resistant to degradation such as cutin and
suberin (C-alkyl; 0–46 ppm) and this spectral region
was slightly increased in the agroforestry system,
which could be associated with the chemical nature of
residues from Gliricidia. Extended signals between
124 and 145 ppm observed in the organic and
conventional systems are characteristic of aromatic
C-transformed and recalcitrant structures. Instead of
an extended signal, the agroforestry system showed
multiple peaks in that region (126, 132, 135, 141 and
145 ppm). Modifications of the aromatic lignin rings
decreased the signal of aromatic groups (112–
120 ppm) in the organic system and promoted the
presence of a peak near 132 ppm. All managements
presented a signal near 75 ppm, assigned to C-car-
boxyl derived polypeptides (Keeler et al. 2006). The
spectra of organic and agroforestry management
systems, however, showed an additional signal at
181 ppm, assigned to the C-carbonyl group.
Similarities between HA from the three different
managements were observed in the FT-IR spectra
(Fig. 5), especially in the regions of 3,500, 2,950,
2,800, 1,650 and 1,450 cm-1 and only slight differ-
ences were detected in the regions of 1,250 and
1,000 cm-1. The different absorption bands were
identified according to Colthup et al. (1964), Bloom
and Leenheer (1989) and Stevenson (1994). Intense
and broad band absorption around 3,500 cm-1 due to
OH stretching vibrations and NH was observed in all
managements. Absorption near to 2,950 cm-1 was
due to stretching vibrations of CH bonds (CH3
aliphatic) and that near 2,800 cm-1 can be associated
with aldehydes. Absorption at 1,650 cm-1 is due to
amides and near 1,450 cm-1 may be attributed to
deformation vibrations of aliphatic CH (CH2 and
CH3). Broad bands at 1,250 cm-1, associated with the
presence of CO carboxylic groups, ether or phenol,
were slightly more intense in the organic and conven-
tional systems. Finally, absorption near 1,000 cm-1,
intense in the agroforestry system, was due to
stretching of C–O from polysaccharides.
Conclusions
The adoption of agroforestry promoted changes in the
soil that resulted in a chemical environment more
favorable to coffee plant development, i.e., less acid
environment, more available cations and P. The
organic system decreased the effects of acidity typical
of Latosol in the Cerrado, generating a favorable
environment for proper development of coffee plants.
Table 3 Elemental
composition and 13C-
CPMAS-NMR integrated
area of humic acids in
topsoil (0–0.05 m)
extracted from different
coffee production systems
Elemental composition (g kg-1) Conventional Organic Agroforestry
Carbon 464.6 481.9 425.0
Hydrogen 42.6 44.9 43.1
Nitrogen 38.5 40.1 37.3
C/N ratio 12.1 12.0 11.413C-CPMAS-NMR integrated area (%)
0–46 ppm (Alkyls) 23.6 23.6 24.3
47–66 ppm (Methoxyls) 16.6 14.7 14.5
67–111 ppm (Carbohydrates and sugars) 23.2 23.4 25.4
112–141 ppm (Aromatics) 18.6 16.6 16.0
142–164 ppm (Phenols) 7.3 8.2 8.9
165–188 ppm (Carboxyls) 10.7 13.6 11.0
Agroforest Syst (2014) 88:767–778 775
123
Fig. 4 CPMAS 13C-NMR
spectra of humic acids
isolated from a Latosol
under different coffee
production systems:
a conventional, b organic
and c agroforestry systems
776 Agroforest Syst (2014) 88:767–778
123
However, effects of changes promoted by this system
on other soil characteristics were not so evident,
probably due to the lower organic fertilizer input,
suggesting that for weathered Latosol from the
Brazilian Cerrado the incorporation of organic mate-
rials must be constant to alter the structural properties
of the SOM. Although it is very well documented that
the HA fraction is not, quantitatively, the major
portion of humic material in soils, this fraction can be
successfully used to describe the status of soil quality
according to the management to which they are
submitted. The 13C-CPMAS-NMR showed that HA
from the agroforestry system was richer in easily
degradable structures, and chemical fractionation
showed a decrease in both recalcitrant fractions and
accumulations of other less humified fractions.
References
Addinsoft (2011) XLSTAT 2011: statistical software to MS
Excel. Addinsoft, New York
Almendros G, Dourado J, Gonzales-Vila FJ, Blanco MJ, Lankes
U (2000) 13C NMR assessment of decomposition patters
during composting of forest and shrub biomass. Soil Biol
Biochem 32:793–804
Aranda V, Ayora-Canada MJ, Domınguez-Vidal A, Martın-
Garcıa JM, Calero J, Delgado R, Verdejo T, Gonzalez-Vila
FJ (2011) Effect of soil type and management (organic vs.
conventional) on soil organic matter quality in olive groves
in a semi-arid environment in Sierra Magina Natural Park
(S Spain). Geoderma 164:54–63
Araujo ASF, Santos VB, Monteiro RTR (2008) Responses of
soil microbial biomass and activity for practices of organic
and conventional farming systems in Piauı state, Brazil.
Eur J Soil Biol 44:225–230
Benbi DK, Brar K, Toor AS, Singh P, Singh H (2012) Soil
carbon pools under poplar-based agroforestry, ricewheat,
and maize-wheat cropping systems in semi-arid India. Nutr
Cycl Agroecosystem 92:107–118
Bloom PR, Leenheer JA (1989) Vibrational, electronic, and
high-energy spectroscopic methods for characterizing
humic substances. In: Hayes MHB, McCarthy P, Malcolm
RL, Swift RS (eds) Humic substances: in search of struc-
ture. Wiley, New York, pp 410–446
Buol SW (2009) Soils and agriculture in central-west and north
Brazil. Sci Agric 66:697–707
Busato JG, Canellas LP, Velloso ACX (2005) Fosforo num
Cambissolo cultivado com cana-de-acucar por longo
tempo: I-fracionamento sequencial. Rev Bras Cienc Solo
29:935–944
Canellas LP, Busato JG, Dobbss LB, Baldotto MA, Rumjanek
VM, Olivares FL (2010) Soil organic matter and nutrient
pools under long-term non-burning management of sugar
cane. Eur J Soil Sci 61:375–383
Cannavo P, Sansoulet J, Harmand JM, Siles P, Dreyer E, Vaast P
(2011) Agroforestry associating coffee and Inga densiflora
results in complementarity for water uptake and decreases
deep drainage in Costa Rica. Agric Ecosyst Environ 140:1–13
Cardoso IM, Janssen B, Oenema O, Kuyper T (2003) Phos-
phorus pools in Latosols under shaded and unshaded coffee
systems on farmers’ fields in Brazil. Agrofor Syst 58:55–64
Chu H, Hosen Y, Yagi K (2007) NO, N2O, CH4 and CO2 fluxes
in winter barley field of Japanese Andisol as affected by N
fertilizer management. Soil Biol Biochem 39:330–339
Colthup NB, Daly LH, Wiberley SE (1964) Introduction to infrared
and Raman spectroscopy. Academic Press, New York
Empresa Brasileira de Pesquisa Agropecuaria (1997) Manual de
metodos de analises de solos. EMPRAPA, Rio de Janeiro
Empresa Brasileira de Pesquisa Agropecuaria (2006) Sistema
brasileiro de classificacao de solos. EMBRAPA, Rio de
Janeiro
Guimaraes DV, Gonzaga MIS, Silva TO, Silva TL, Dias NS,
Matias MIS (2013) Soil organic matter pools and carbon
fractions in soil under different land uses. Soil Tillage Res
126:177–182
Hergoualc’h K, Blanchart E, Skiba U, Henaultf C, Harmand JM
(2012) Changes in carbon stock and greenhouse gas bal-
ance in a coffee (Coffea arabica) monoculture versus an
agroforestry system with Inga densiflora, in Costa Rica.
Agric Ecosyst Environ 148:102–110
Kaschuk G, Alberton O, Hungria M (2010) Three decades of soil
microbial biomass studies in Brazilian ecosystems: lessons
learned about soil quality and indications for improving
sustainability. Soil Biol Biochem 42:1–13
Keeler C, Kelly EF, Maciel GE (2006) Chemical-structural
information from solid-state 13C NMR studies of a suite of
humic materials from a lower montane forest soil, Colo-
rado, USA. Geoderma 130:124–140
Khanna P (1997) Nutrient cycling under mixed-species trees in
Southeast Asia. Agrofor Syst 38:99–120
Marschner H, Romheld V (1983) In vivo measurement of root
induced pH changes at the soil-root interface. Effect of
plant species and nitrogen source. Z Pflanzenphysiol
111:241–251
Fig. 5 FT-IR spectra of humic acids isolated from a Latosol
under different coffee production systems: (A) conventional,
(B) organic and (C) agroforestry systems
Agroforest Syst (2014) 88:767–778 777
123
Middleton KR, Smith GS (1979) A comparison of ammoniacal
and nitrate nutrition of perennial ryegrass through a ther-
modynamic model. Plant Soil 53:487–504
Monteiro MC, Farah A (2012) Chlorogenic acids in Brazilian
Coffea arabica cultivars from various consecutive crops.
Food Chem 134:611–614
Moreno G, Obrador JJ (2007) Effects of trees and understorey
management of soil fertility and nutritional status of holm
oaks in Spanish dehesas. Nutr Cycl Agroecosys 78:253–264
Nelson WL, Mehlich A, Winters E (1953) The development,
evaluation, and use of soil tests for phosphorus availability.
Agronomy 4:153–158
Preston C, Newman RH, Rother P (1994) Using 13C CPMAS
NMR to assess effects of cultivation on the organic matter
of particle size fractions in a grassland soil. Soil Sci
157:26–35
Quideau SA, Anderson MA, Graham RC, Chadwick OA,
Trumbore SE (2000) Soil organic matter processes: char-
acterization by 13C NMR and 14C measurements. For Ecol
Manag 138:19–27
Schiavo JA, Busato JG, Martins MA, Canellas LP (2009)
Recovery of degraded areas revegeted with Acacia
mangium and Eucalyptus with special reference to organic
matter humification. Sci Agric 66:353–360
Soil Survey Staff—SSS NRCS (2010) Keys to soil taxonomy.
United States Department of Agriculture, Washington
Stehfest E, Bouwman L (2006) N2O and NO emission from
agricultural fields and soils under natural vegetation:
summarizing available measurement data and modeling of
global annual emissions. Nutr Cycl Agroecosyst 74:207–
228
Stevenson FJ (1994) Humus chemistry: genesis, composition,
reactions. Wiley, NY
van Hees PA, van Hees AMT, Lundstrom US (2001) Determi-
nation of aluminium complexes of low molecular organic
acids in soil solution from forest soils using ultrafiltration.
Soil Biol Biochem 33:867–874
Willer H, Sorensen N, Yussefi-Menzler M (2008) The world of
organic agriculture: statistics and emerging trends 2008.
http://orgprints.org/13123/4/world-of-organic-agriculture-
2008.pdf. Accessed 26 June 2013
Yeomans JC, Bremner JM (1988) A rapid and precise method
for routine determination of organic carbon in soil. Com-
mun Soil Sci Plant 19:1467–1476
778 Agroforest Syst (2014) 88:767–778
123