Changes in chemical properties by use and management of an oxisol in the amazon biome

Abstract

The proper soil use and management are essential for a sustainable production, thus the pursuit for systems that minimize damages to the environment and improve soil fertility is continuous. The objective of this study was to evaluate changes in soil fertility by the use and management of an Oxisol (Latossolo Vermelho-amarelo, SiBCS) in the Amazon biome. The soil uses and management systems evaluated were native forest, native pasture, minimum tillage system and conventional tillage system. The chemical atributes of the soil layers 0.00-0.10, 0.10-0.20, 0.20-0.30 and 0.30-0.40 m were evaluated. The soil pH (CaCl2) and the contents of organic matter, available phosphorus and exchangeable potassium, calcium, magnesium and aluminum were evaluated and the saturation by Al, effective cation exchange capacity and soil potential were determined. The highest pH values were found in the native pasture area, and the highest exchangeable aluminum contents were found in the layers 0.00-0.10 and 0.10-0.20 m of the conventional tillage system. The highest phosphorus availability was found in the layer 0.00-0.10 m of the native forest area. The highest potassium availability was found in the minimum tillage system. The lowest calcium and magnesium values were found in the layers 0.00-0.10 and 0.10-0.20 m of the conventional tillage system. The highest soil organic matter content was found in the layer 0.00-0.10 m of the native forest area. The nutrient availability for plants decreases in soils managed using the conventional tillage system. Soil uses and management systems of little soil disturbance are recommended to minimize environmental degradation in the Amazon biome. © 2016, Universidade Federal Rural do Semi-Arid. All rights reserved.

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Rev. Caatinga, Mossoró, v. 30, n. 2, p. 278 – 286, abr. – jun., 2017
Universidade Federal Rural do Semi-Árido
Pró-Reitoria de Pesquisa e Pós-Graduação
http://periodicos.ufersa.edu.br/index.php/sistema
ISSN 0100-316X (impresso)
ISSN 1983-2125 (online)
278
CHANGES IN CHEMICAL PROPERTIES BY USE AND MANAGEMENT OF AN
OXISOL IN THE AMAZON BIOME1
MARCOS RODRIGUES2*, FLÁVIO HENRIQUE SILVEIRA RABÊLO3, HEBER AUGUSTO DE CASTRO4,
DELMONTE ROBOREDO4, MARCO ANTONIO CAMILLO DE CARVALHO4, CASSIANO GARCIA ROQUE5
ABSTRACT – The proper soil use and management are essential for a sustainable production, thus the pursuit
for systems that minimize damages to the environment and improve soil fertility is continuous. The objective of
this study was to evaluate changes in soil fertility by the use and management of an Oxisol (Latossolo
Vermelho-amarelo, SiBCS) in the Amazon biome. The soil uses and management systems evaluated were
native forest, native pasture, minimum tillage system and conventional tillage system. The chemical atributes of
the soil layers 0.00-0.10, 0.10-0.20, 0.20-0.30 and 0.30-0.40 m were evaluated. The soil pH (CaCl2) and the
contents of organic matter, available phosphorus and exchangeable potassium, calcium, magnesium and
aluminum were evaluated and the saturation by Al, effective cation exchange capacity and soil potential were
determined. The highest pH values were found in the native pasture area, and the highest exchangeable
aluminum contents were found in the layers 0.00-0.10 and 0.10-0.20 m of the conventional tillage system. The
highest phosphorus availability was found in the layer 0.00-0.10 m of the native forest area. The highest
potassium availability was found in the minimum tillage system. The lowest calcium and magnesium values
were found in the layers 0.00-0.10 and 0.10-0.20 m of the conventional tillage system. The highest soil organic
matter content was found in the layer 0.00-0.10 m of the native forest area. The nutrient availability for plants
decreases in soils managed using the conventional tillage system. Soil uses and management systems of little
soil disturbance are recommended to minimize environmental degradation in the Amazon biome.
Keywords: Brachiaria brizantha. Minimum tillage. Conventional tillage. Environmental degradation.
Sustainable management.
ALTERAÇÕES NOS ATRIBUTOS QUÍMICOS DO SOLO PELO USO E MANEJO EM LATOSSOLO
NA AMAZÔNIA
RESUMO – O uso e manejo do solo adequados são fundamentais para a produção sustentável, sendo constante
a busca por sistemas que minimizem os danos causados ao ambiente e que melhorem a fertilidade do solo.
Objetivou-se avaliar as alterações nos atributos de fertilidade em decorrência do uso e manejo em Latossolo
Vermelho-Amarelo (LVA) na Amazônia. Os seguintes sistemas de uso e manejo do solo num LVA foram
avaliados: floresta nativa, pastagem nativa e áreas preparadas por sistema de cultivo mínimo e cultivo
convencional. As avaliações dos atributos químicos do solo foram realizadas nas profundidades de 0 -0,10,
0,10-0,20, 0,20-0,30 e 0,30-0,40 m. Foram avaliados o pH do solo (CaCl2), o teor de matéria orgânica do solo,
os teores de fósforo disponível e potássio trocável, cálcio, magnésio e alumino trocáveis, sendo ainda
determinados a saturação por Al, a capacidade de troca catiônica efetiva e potencial do solo. Os valores de pH
mais elevados foram verificados no sistema de pastagem nativa e os maiores teores de alumínio trocável nas
profundidades de 0-0,10 e 0,10-0,20 m foram verificadas no sistema de cultivo convencional. O sistema de
floresta nativa apresentou a maior disponibilidade de fósforo na profundidade de 0-0,10 m. As maiores
disponibilidades de potássio foram verificadas no sistema de cultivo mínimo. Os menores valores de cálcio e
magnésio nas profundidades de 0-0,10 e 0,10-0,20 m ocorreram no sistema de cultivo convencional. O sistema
de floresta nativa apresentou o maior teor de matéria orgânica do solo na profundidade de 0-0,10 m. A
disponibilidade de nutrientes para as plantas é reduzida em solos manejados em sistema de plantio
convencional. Os sistemas de uso e manejo de menor revolvimento do solo são indicados para minimizar a
degradação ambiental na Amazônia.
Palavras-chave: Brachiaria brizantha. Cultivo mínimo. Cultivo convencional. Degradação ambiental. Manejo
sustentável.
____________________
*Corresponding author
1Received for publication in 08/18/2014; accepted in 07/29/2016.
Paper accepted from the third author's undergraduate thesis.
2Department of Soil Science, Escola Superior de Agricultura “Luiz de Queiroz”, Piracicaba, SP, Brazil; rodrigues.m@usp.br.
3Laboratory of Mineral Nutrition of Plants, Centro de Energia Nuclear na Agricultura, Piracicaba, SP, Brazil;
flaviohsr.agro@yahoo.com.br.
4Department of Agronomy, Universidade do Estado de Mato Grosso, Alta Floresta, MT, Brazil; heber.augusto.c@hotmail.com,
roboredo@gmail.com, marcocarvalho@unemat.br.
5Department of Agronomy, Universidade Federal do Mato Grosso do Sul, Chapadão do Sul, MS, Brazil; cassiano.roque@ufms.br.

CHANGES IN CHEMICAL PROPERTIES BY USE AND MANAGEMENT OF AN OXISOL IN THE AMAZON BIOME
M. RODRIGUES et al.
Rev. Caatinga, Mossoró, v. 30, n. 2, p. 278 – 286, abr. – jun., 2017 279
INTRODUCTION
Seventy-two million hectares of the Brazilian
Amazon biome was deforested in recent decades, of
which fifty-six millions are converted into pastures
and more than half are in advanced degradation state
(DE SOUZA BRAZ; FERNANDEZ; ALLEONI,
2013; SILVA NETO et al., 2012), due mainly to
inadequate soil and crop managements. Inadequate
soil managements potentially contribute to
environmental degradation, since it negatively
changes the soil physical, chemical and biological
characteristics (SILVA NETO et al., 2011). This
processes are even more serious in the Amazon
region, in which the conversion into pastures occurs
often after the use of burning practices
(TOWNSEND; COSTA; PEREIRA, 2010) and soil
tilling by plowing and harrowing, causing
destruction of aggregates, decrease of organic matter
content in the soil surface layers and increase of
water erosion (BAYER; BERTOL, 1999;
MOREIRA; MALAVOLTA, 2004; SATO et al.,
2012). Thus, the soil uses in this region must be
carefully planned, implementing soil conservation
practices from the beginning, in order to preserve the
soil productive potential (MULLER et al., 2001).
The minimum tillage system is an alternative
to minimize the impacts to the environment, whose
adoption aims to disrupt compacted layers, increase
water infiltration and reduce soil disturbances
(SASAKI; GONÇALVES; BENTIVENHA, 2005).
The intensity of soil tilling and incorporation of crop
residues carried out for soil management, promote
changes in pH, ion dynamics, organic matter content
and cation exchange capacity (CEC) of the soil,
which are intensified with the time of use of the area
(MARCOLAN et al., 2007). Falleiro et al. (2003)
assessed the effect of tillage systems (no-tillage,
minimum tillage and conventional tillage) on soil
chemical properties and found that the values of pH,
calcium, magnesium, phosphorus, organic matter and
effective CEC of the soil, under conventional tillage
system, decreased compared with the other
management systems, decreasing soil fertility and
causing early soil degradation process. Santos et al.
(2008) also reported the use of conservationist
systems (no-tillage and minimum tillage) resulting in
better soil fertility than the conventional system after
20 years of use.
Soil management is essential for agricultural
sustainability in high weathered soils, such as the
Oxisol in the Amazon biome, since it affects the
dynamics of the soil organic matter
(VALLADARES; BATISTELLA; PEREIRA, 2011),
which is the main nutrient source in this ecosystem
(SILVA; SILVA JÚNIOR; MELO, 2006). Changes
in soil organic matter content have direct and indirect
consequences on the soil chemical characteristics,
thus, studying the effects of tillage systems on soil
fertility is strategic for environmental preservation
(BAYER; BERTOL, 1999; CUNHA et al., 2007).
According to Luizão (2007), the conversion of
forests into pasture and crops, changes the organic
matter dynamics and nutrient cycling in the Amazon
biome, decreasing the soil productive capacity with
time, depending on the management established.
Thus, the objective of this work was to identify and
evaluate the main changes in soil fertility properties
resulting from the use and management of an Oxisol
(Latossolo Vermelho-amarelo, SiBCS) in the
Amazon biome, aiming the mitigation of degradation
in this agroecosystem.
MATERIAL AND METHODS
The experiment was conducted in the
Veridiana Farm (10º02'29''S; 56º06'41''W), Alta
Floresta, northern Mato Grosso State, Brazil, in the
Amazon biome. The region climate is tropical rainy
with a dry season, according to the Köppen
classification, with temperatures of 20-38°C and
annual average precipitation of 2700 mm, and has
average altitude of 320 m.
The soil uses and management systems
evaluated were conducted in an Oxisol (Latossolo
Vermelho-amarelo, SiBCS) of medium texture,
however, it was adjacent to a soil of sandy texture
(with clay content of 120-160 g kg-1 at 0.40 m).
Pasture areas prepared with minimum tillage
and conventional tillage systems were implemented
for evaluation. Native pasture and native forest areas
were also evaluated, both were adjacent to the
systems with mechanical preparation (Table 1). A
completely randomized experimental design was
used, with seven replications and plot areas of 70 m².
The species Brachiaria brizantha cv.
Marandu was used for planting and the areas were
conducted for beef cattle under extensive pasture
system, with an average of 2.4 animal unit (450 kg)
ha-1. Five single soil samples were randomly
collected, using a Dutch auger, in the areas one year
after the implementation of the pastures with
minimum tillage and conventional tillage systems.
The single samples were homogenized to form a
composite sample in each repetition of the different
soil uses and managements. The layers 0.00-0.10,
0.10-0.20, 0.20-0.30 and 0.30-0.40 m were sampled.
The sampled soil was air-dried for 72 hours and
passed through a 2 mm-mesh sieve, in order to
obtain the air-dried ground soil (ADGS) for further
analysis.

CHANGES IN CHEMICAL PROPERTIES BY USE AND MANAGEMENT OF AN OXISOL IN THE AMAZON BIOME
M. RODRIGUES et al.
Rev. Caatinga, Mossoró, v. 30, n. 2, p. 278 – 286, abr. – jun., 2017 280
The air-dried ground soil (ADGS) sampled
from each plot were used to assess the chemical
properties of soil fertility, evaluating the pH (CaCl2),
exchangeable P and K (Mehlich-1), exchangeable
Ca, Mg and Al (KCl 1 mol L-1) and organic matter
(DONAGEMA et al., 2011). The aluminum
saturation, sum of bases, base saturation, effective
cation exchange capacity (CEC) and potential CEC
were also evaluated.
The data were subjected to analysis of
variance and the means were compared by the
Tukey's test at 1% of significance, using the
statistical software SISVAR® (FERREIRA, 2011).
The Pearson's correlation was also applied to the
variables, considering the entire data set
(28 evaluations of each treatment, resulting from 7
replications in 4 sampled depths).
RESULTS AND DISCUSSION
The highest pH values in all soil layers
evaluated were found in the native pasture area
(Table 2). However, these values are within the
range class of acid soils. The minimum tillage had
higher pH values than the conventional tillage
system in the layers 0.00-0.10 and 0.10-0.20 m. The
minimum and conventional tillage systems showed
no significant difference in the layers 0.20-0.30 and
0.30-0.40 m. The pH of the native forest and native
pasture areas decreased with depth, while the
minimum tillage system had a pH decrease only in
the layer 0.30-0.40 m, and the conventional tillage
area showed no pH change with depth.
The highest pH values of the native pasture
area are related to the characteristics of the organic
matter from the litterfall deposition and dead roots,
which mineralize, contributing to the increase of
negative charges and soil pH (SARMENTO et al.,
2008). Franchini et al., (1999) found a decrease in
pH values with depth in native forest and native
pasture areas, as found in the present study.
Valladares, Batistella and Pereira (2011) evaluated
the effect of land use on chemical properties of soils
of the Amazon biome and found higher pH in
pasture areas, compared with native forest areas.
Bayer and Bertol (1999) found no significant
difference in soil pH depending on the management
systems (minimum tillage and conventional tillage).
Table 1. Description of the experimental areas (treatments).
Table 2. pH values, Al3+ contents and aluminum saturation (m%) of an Oxisol in the Amazon biome, depending on soil uses
and management systems.
Soil uses and management systems
Description
Native forest
Dense forest with absence of human intervention, used as a reference
Native pasture
Grass vegetation with predominance of Brachiaria brizantha cv. Marandu
since 1989, conducted without any soil chemical management. The native
vegetation was deforested and burned for land clearance and seeds were
broadcast for the pasture implementation.
Minimum tillage system
Rice and soybeans crops were conducted from 2003 to 2007 using the
conventional tillage system. A subsoiling to a depth of 35 cm was carried
out for the implementation of the last annual crop in 2006. Brachiaria
brizantha cv. Marandu was planted after the 2007 crop. A liming was
performed (1 Mg ha-1) during the grain crops. Nitrogen fertilizers (120 kg
ha-1) were applied for the rice crops.
Conventional tillage system
Rice and soybeans crop were conducted from 2003 to 2007 using the
conventional tillage system. Disk plow and harrow leveling to a depth of
20 cm depth was used for the implementation of the last annual crop in
2006. Brachiaria brizantha cv. Marandu was planted after the 2007 crop.
A liming was performed (1 Mg ha-1) during the grain crops. Nitrogen
fertilizers (120 kg ha-1) were applied for the rice crops.
1
Means followed by different letters in the rows differ by the Tukey's test at 1% significance.
Layers
Soil uses and management systems
(m)
Native forest
Native pasture
Minimum tillage
Conventional tillage
pH (CaCl2)
0.00-0.10
4.1 c
4.7 a
4.4 b
3.9 d
0.10-0.20
4.1 c
4.7 a
4.3 b
3.9 d
0.20-0.30
4.0 b
4.7 a
4.0 b
4.0 b
0.30-0.40
3.9 b
4.5 a
4.0 b
4.0 b
1

CHANGES IN CHEMICAL PROPERTIES BY USE AND MANAGEMENT OF AN OXISOL IN THE AMAZON BIOME
M. RODRIGUES et al.
Rev. Caatinga, Mossoró, v. 30, n. 2, p. 278 – 286, abr. – jun., 2017 281
Table 2. Continuation.
The highest exchangeable aluminum contents
were found in the soil layers 0.00-0.10 and
0.10-0.20 m of the conventional tillage system, while
the layer 0.30-0.40 m was different only from the
natural pasture, with lower Al3+ contents, compared
with other management systems (Table 2), due to the
its low acidity (higher pH) with depth. The minimum
tillage system had lower aluminum contents, with
higher pH values, compared with the conventional
tillage. Aluminum contents increased with depth,
except for the conventional tillage system, which
presented uniform contents along the soil profile.
The increase in pH usually decreases the
solubility of the toxic aluminum in the soil, while the
organic matter causes the complexation of this
element (FALLEIRO et al., 2003). Silva Neto et al.
(2011) evaluated the land use in a Cerrado-Amazon
transition area and found aluminum contents 3-fold
higher in the native forest area compared with a
pasture area. Bayer and Bertol (1999) found no
differences in aluminum contents between minimum
and conventional tillage systems.
The minimum tillage system had aluminum
saturation lower than the conventional tillage
(Table 2), which is related to its lower toxic
aluminum content. The aluminum saturation
increased with depth, except in the conventional
tillage system, which had uniform saturation along
the soil profile. On the other hand, Lourente et al.
(2011) found higher aluminum saturation in pasture
areas compared with native forest and conventional
tillage areas.
The native forest and minimum tillage had
higher phosphorus availability in the layer
0.00-0.10 m (Table 3). The soil uses and
management systems showed no significant
differences in phosphorus availability in the other
layers. Only the native forest showed decrease in
phosphorus availability at depths below 0.10 m. The
absence of tilling and maintenance of forest residues
on the soil surface in the native forest area probably
contributed to increase the phosphorus availability in
the surface layer (FALLEIRO et al., 2003). Lourente
et al. (2011) found higher phosphorus availability in
the native forest area comparing with pasture and
conventional tillage areas.
The highest potassium availabilities, in all
soil layers evaluated, were found in the minimum
tillage system (Table 4). All soil uses and
management systems showed a decrease in
potassium availability with depth. Potassium moves
in the soil predominantly by diffusion and its
availability is generally higher in systems of little
soil disturbance, since greater organic matter
contents are found in surface layers (ERNANI;
ALMEIDA; SANTOS, 2007), contributing to the
cation exchange capacity (CEC) of the soil surface
and, consequently, to a greater nutrient retention and
lower leaching rate. The results found in the present
work confirm those found by Lourente et al. (2011),
who found similar potassium availability in native
forest and native pasture areas, and by Bayer and
Bertol (1999), who found higher potassium
availability in a minimum tillage compared with a
conventional tillage system.
The lower values of calcium, magnesium and
the sum of bases were found in the layers 0.00-0.10
and 0.10-0.20 m of the conventional tillage, while
the other systems showed no significant differences
(Table 3). The soil layers 0.20-0.30 and 0.30-0.40
showed higher values in the native pasture, while the
others soil uses and management systems showed no
significant differences. The values of calcium,
magnesium and sum of bases decreased with depth,
except for the conventional tillage system, which
showed uniform values along the soil profile.
Means followed by different letters in the rows differ by the Tukey's test at 1% significance.
Layers
Soil uses and management systems
(m)
Native forest
Native pasture
Minimum tillage
Conventional tillage
Al3+ (cmolc dm-3)
0.00-0.10
0.3 b
0.1 c
0.2 c
0.6 a
0.10-0.20
0.5 a
0.2 b
0.2 b
0.6 a
0.20-0.30
0.6 a
0.3 b
0.5 ab
0.5 ab
0.30-0.40
0.6 a
0.3 b
0.5 a
0.5 a
m%
0.00-0.10
13 b
6 b
7 b
40 a
0.10-0.20
21 b
9 c
13 bc
46 a
0.20-0.30
46 a
16 b
36 ab
44 a
0.30-0.40
56 a
20 b
41 ab
48 a

CHANGES IN CHEMICAL PROPERTIES BY USE AND MANAGEMENT OF AN OXISOL IN THE AMAZON BIOME
M. RODRIGUES et al.
Rev. Caatinga, Mossoró, v. 30, n. 2, p. 278 – 286, abr. – jun., 2017 282
Table 3. Available phosphorus, potassium, calcium and magnesium, sum of bases and base saturation of an Oxisol in the
Amazon biome, depending on soil uses and management systems.
Means followed by different letters in the rows differ by the Tukey's test at 1% significance.
The calcium and magnesium contents are
commonly higher in conditions of deposition of
organic residues, as in the native forest and native
pasture areas, and conditions of little soil
disturbance, as in the minimum tillage, compared
with systems of high soil disturbance, because the
recycling of nutrients by the plants, which
contributes to increase the sum of bases (FALLEIRO
et al., 2003). The organic matter content is lower at
greater depths (ERNANI; ALMEIDA; SANTOS,
2007), causing loss of potassium, calcium and
magnesium by leaching, decreasing the sum of bases
(CAIRES et al., 1998).
De Souza Braz, Fernandes and Alleoni (2013)
found higher calcium and magnesium contents in
pasture areas, contributing to increase the sum of
bases, compared with native forest areas. Bayer and
Bertol (1999) found higher calcium contents in the
soil surface layer in a minimum tillage system
compared with a conventional tillage, and attributed
this result to the nutrient cycling by the phytomass
deposition on the soil surface. These authors found
no significant differences in magnesium contents
between the areas, in the soil surface layer.
Layers
Soil uses and management systems
(m)
Native forest
Native pasture
Minimum tillage
Conventional tillage
Available P (mg dm-3)
0.00-0.10
2.3 a
0.9 b
1.5 ab
1.1 b
0.10-0.20
0.9 a
0.7 a
0.9 a
1.0 a
0.20-0.30
0.6 a
0.6 a
0.5 a
0.3 a
0.30-0.40
0.5 a
0.5 a
0.4 a
0.2 a
Potassium (cmolc dm-3)
0.00-0.10
0.21 b
0.21 b
0.28 a
0.15 b
0.10-0.20
0.15 b
0.15 b
0.21 a
0.13 b
0.20-0.30
0.08 c
0.11 b
0.16 a
0.11 b
0.30-0.40
0.06 c
0.09 b
0.15 a
0.08 bc
Calcium (cmolc dm-3)
0.00-0.10
1.5 a
1.2 a
1.2 a
0.5 b
0.10-0.20
1.2 a
1.0 a
0.9 a
0.4 b
0.20-0.30
0.4 b
0.9 a
0.4 b
0.3 b
0.30-0.40
0.3 b
0.7 a
0.3 b
0.3 b
Magnesium (cmolc dm-3)
0.00-0.10
0.8 a
0.9 a
0.9 a
0.3 b
0.10-0.20
0.7 a
0.7 a
0.6 a
0.2 b
0.20-0.30
0.3 b
0.7 a
0.3 b
0.2 b
0.30-0.40
0.2 b
0.4 a
0.3 b
0.2 b
Sum of bases (cmolc dm-3)
0.00-0.10
2.5 a
2.2 a
2.3 a
1.0 b
0.10-0.20
2.0 a
1.9 a
1.7 a
0.7 b
0.20-0.30
0.7 b
1.7 a
0.8 b
0.7 b
0.30-0.40
0.6 b
1.2 a
0.7 b
0.6 b
Base saturation (%)
0.00-0.10
25.1 b
37.7 a
31.2 ab
15.1 c
0.10-0.20
21.6 b
36.8 a
24.0 b
11.9 c
0.20-0.30
10.8 b
32.9 a
13.8 b
12.6 b
0.30-0.40
9.5 b
26.2 a
12.0 b
11.7 b
1

CHANGES IN CHEMICAL PROPERTIES BY USE AND MANAGEMENT OF AN OXISOL IN THE AMAZON BIOME
M. RODRIGUES et al.
Rev. Caatinga, Mossoró, v. 30, n. 2, p. 278 – 286, abr. – jun., 2017 283
The highest values of base saturation were
found in the soil layers 0.10-0.20, 0.20-0.30 and
0.30-0.40 m of the native pasture area (Table 3). The
layer 0-0.10 m of the native pasture also showed
higher base saturation, compared with the native
forest and the conventional tillage systems. The
minimum tillage area had base saturations higher
than the conventional tillage in the layers 0.00-0.10
and 0.10-0.20 m. The base saturation of the native
forest and minimum tillage systems decreased with
depth, the first only in the layer 0.30-0.40 m; and the
conventional tillage showed uniform values of base
saturation along the soil profile.
These values are related to the changes in
aluminum, potassium, calcium and magnesium
contents in the soil profile of each soil use and
management system, which directly affects the base
saturation values, as pointed out by Araújo et al.,
(2011). De Souza Braz, Fernandes and Alleoni
(2013) also found higher base saturation in pasture
areas, compared with a native forest area, as well as
Pereira et al. (2009) who found higher base
saturation in a minimum tillage system, compared
with a conventional tillage.
The minimum tillage area had higher organic
matter content (Table 4) than the conventional
tillage, in the layers 0-0.10, 0.10-0.20 and
0.20-0.30 m. The organic matter content reduced
with depth in all soil uses and management systems.
The continuous deposition of plant material
and lack of soil tilling in native forest areas strongly
contribute to increase the organic matter content in
the soil (ARAÚJO et al., 2011; SATO et al., 2012).
The soil tilling in conventional tillage contributes to
the organic matter exposure and oxidation, thus,
systems that have the less intense soil tilling, such as
minimum tillage, contribute to increase the soil
organic matter contents (BAYER; BERTOL, 1999).
Lourente et al. (2011) reported higher organic matter
contents in a native forest area compare with a native
pasture. Santos and Tomm (2003) found higher
organic matter content in the soil layer 0.00-0.10 m
of a minimum tillage area compared with a
conventional tillage area.
Table 4. Soil organic matter, effective cation exchange capacity (CEC) and potential CEC in an Oxisol in the Amazon
biome, depending on soil uses and management systems.
Means followed by different letters in the rows differ by the Tukey's test at 1% significance.
The soil layer 0.00-0.10 m of the
conventional tillage system had the lowest effective
CEC values (Table 4), while the others soil uses and
management systems showed no significant
differences. The native forest and native pasture
areas showed higher effective CEC values in the
layer 0.10-0.20 m, while the native pasture showed
higher value in the layer 0.20-0.30 m. The soil uses
and management systems had no significant
differences in the layer 0.30-0.40 m regarding the
effective CEC. The effective CEC values reduced
with depth in all soil uses and management systems.
The effective CEC values found are related to
the pH values and organic matter content of the soil
uses and management systems, since the pH and
organic matter directly affect the effective CEC.
These results are also related to the marked
contribution of variable charges in the mineral
fraction, which are found mainly in weathered
tropical soils (MENDONÇA; ROWELL, 1996). The
Layers
Soil uses and management systems
(m)
Native forest
Native pasture
Minimum tillage
Conventional tillage
Soil organic matter (g kg-1)
0.00-0.10
22.9 a
16.4 c
20.5 b
16.1 c
0.10-0.20
19.6 a
11.5 b
17.8 a
13.9 b
0.20-0.30
12.0 ab
8.7 c
13.5 a
9.3 bc
0.30-0.40
11.4 a
8.0 b
10.9 ab
8.6 b
Effective CEC (cmolc dm-3)
0.00-0.10
2.8 a
2.4 a
2.5 a
1.6 b
0.10-0.20
2.5 a
2.1 b
2.0 b
1.3 c
0.20-0.30
1.4 b
2.0 a
1.3 b
1.2 b
0.30-0.40
1.2 a
1.5 a
1.2 a
1.1 a
Potential CEC (cmolc dm-3)
0.00-0.10
9.7 a
6.1 c
7.5 b
6.3 c
0.10-0.20
9.1 a
5.1 d
7.1 b
6.0 c
0.20-0.30
6.8 a
5.0 c
6.0 b
5.2 c
0.30-0.40
5.9 a
4.6 b
5.8 a
4.7 b
1

CHANGES IN CHEMICAL PROPERTIES BY USE AND MANAGEMENT OF AN OXISOL IN THE AMAZON BIOME
M. RODRIGUES et al.
Rev. Caatinga, Mossoró, v. 30, n. 2, p. 278 – 286, abr. – jun., 2017 284
organic matter also contributes to balance negative
charges and decrease the hydrogen activity (H+),
which is also affected by cations in the soil solution
(FALLEIRO et al., 2003). The results found in the
present work differ from those found by De Souza
Braz, Fernandes and Alleoni (2013), who found
higher effective CEC in a pasture compared with a
native forest area, and by Pereira et al. (2009), who
found no significant differences in CEC values
between minimum tillage and conventional tillage
systems.
The highest potential CEC values were found
in the soil layers 0.00-0.10, 0.10-0.20 and
0.20-0.30 m of the native forest area (Table 4). The
native forest and minimum tillage areas had higher
potential CEC values in the layer 0.30-0.40 m. The
minimum tillage system had higher potential CEC
values than the conventional tillage and native
pasture in all soil layers evaluated. These results
were mainly due to the effect of the organic matter
content, which is responsible for much of the soil
negative charges (BAYER; BERTOL, 1999). De
Souza Braz, Fernandes and Alleoni (2013) also
found higher potential CEC in a native forest area
compared with a pasture area.
The phosphorus showed no significant
correlation with any chemical property of soil
fertility in the native forest, unlike the others soil
management systems (Table 5).
The native pasture area showed no correlation
between pH values and contents of phosphorus,
potassium and soil organic matter. All indicative
parameters of soil fertility showed correlation with
each other in the minimum tillage system. The
conventional tillage showed no correlation between
pH values and aluminum contents; calcium and
magnesium contents; and magnesium and soil
organic matter contents.
According to the correlations between
chemical properties of soil fertility in the different
soil managements, the system with greater soil
disturbances (conventional tillage) showed no
significant correlations between pH values and
nutrients, differing from the other soil uses and
managements. On the other hand, the correlations
between the nutrient and organic matter contents
showed proportional and highly significant
correlations (>0.79) between SOM and available P
and exchangeable K. This result may be related to
the capacity of the organic matter in maintaining soil
fertility, even in the most fragile systems
(conventional tillage), from the soil conservation
point of view.
According to the results, the soil uses and
management systems affected the soil chemical
properties, soil pH and the contents of organic
matter, Al3+, P, K+, Ca2+ and Mg2+. Therefore,
changes in these properties must be taken into
account for a proper soil management, in order to
increase the agricultural efficiency and reduce
environmental degradation.
Table 5. Pearson's correlation coefficient between chemical properties of soil fertility of an Oxisol in the Amazon biome,
depending on soil uses and management systems1.
Native forest
pH
Al3+
P-Mehlich
K+
Ca2+
Mg2+
SOM
pH
1
-
-
-
-
-
-
Al3+
-0.89**
1
-
-
-
-
-
P-Mehlich
0.11NS
-0.26NS
1
-
-
-
-
K+
0.74**
-0.72**
0.28NS
1
-
-
-
Ca2+
0.92**
-0.84**
0.17NS
0.75**
1
-
-
Mg2+
0.89**
-0.82**
0.18NS
0.82**
0.88**
1
-
SOM
0.73**
-0.71**
0.24NS
0.87**
0.70**
0.86**
1
Native pasture
pH
Al3+
P-Mehlich
K+
Ca2+
Mg2+
SOM
pH
1
-
-
-
-
-
-
Al3+
-0.55**
1
-
-
-
-
-
P-Mehlich
0.28NS
-0.48**
1
-
-
-
-
K+
0.25NS
-0.53**
0.75**
1
-
-
-
Ca2+
0.64**
-0.65**
0.54**
0.56**
1
-
-
Mg2+
0.58**
-0.65**
0.61**
0.64**
0.75**
1
-
SOM
0.24NS
-0.48**
0.80**
0.83**
0.54**
0.61**
1
1
*Significant at 5%. **Significant at 1%. NS= not significant. SOM= soil organic matter. 1Values referring to the analysis
of the entire data set (seven replications of the layers 0.00-0.10, 0.10-0.20, 0.20-0.30 and 0.30-0.40 m).

CHANGES IN CHEMICAL PROPERTIES BY USE AND MANAGEMENT OF AN OXISOL IN THE AMAZON BIOME
M. RODRIGUES et al.
Rev. Caatinga, Mossoró, v. 30, n. 2, p. 278 – 286, abr. – jun., 2017 285
Table 5. Continuation.
*Significant at 5%. **Significant at 1%. NS= not significant. SOM= soil organic matter. 1Values referring to the analysis
of the entire data set (seven replications of the layers 0.00-0.10, 0.10-0.20, 0.20-0.30 and 0.30-0.40 m).
CONCLUSIONS
The fertility of the Amazonian Oxisol were
changed by the soil uses and management systems.
The soil acidity in the surface layer
(0.00-0.20 m) was higher when the implantation of
pasture (Brachiaria brizantha cv. Marandu) was
conducted using the conventional tillage system,
compared with the minimum tillage system.
The nutrient availability for the plants was
reduced with the use of soil conventional tillage,
compared with the minimum tillage system.
The tendency of increasing pH and,
consequently, nutrient exchangeable contents was
not maintained under the conventional tillage
system. The effect of the organic matter, in this case,
was more evident.
Soil uses and management systems of little
soil disturbance, such as the minimum tillage system,
are recommended to minimize environmental
degradation in the Amazon biome.
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0.46*
0.36NS
1
1

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