Vol.4, No.11 A, 26-36 (2013) Agricultural Sciences
http://dx.doi.org/10.4236/as.2013.411A004
Influence of the rainfall in the conte nt of nutrients in
litter in agroforestry systems managed with burning
and without burning in Amazon
Rosecélia Moreira Da Silva Castro1*, Maria De Lourdes Pinheiro Ruivo2, Jorge Luiz Piccinin2,
Eraldo Ferreira Rodrigues3
1Federal University of Rural Amazonia, Institute Sciences Agricultural, Belém, Brasil;
*Corresponding Author: rmsilva@museu-goeldi.br
2Emilio Goeldi Pará Museum, Coordination of Earth Sciences and Ecology, Belém, Brasil
3Brazilian Company of Agricultural Research, Statistical Department, Belém, Brasil
Received 4 September 2013; revised 5 October 2013; accepted 16 October 2013
Copyright © 2013 Rosecélia Moreira Da Silva Castro et al. This is an open access article distributed under the Creative Commons
Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is
properly cited.
ABSTRACT
This study evaluated the nutrient content of the
litter, testing different treatments with burning
and no burning, of the vegetation, to identify
which one provides better efficiency in opera-
tion and production of nutrients in different sea-
sonal conditions. The study area is located on
the property of the family farmer, initially se-
lected by a diagnosis socioeconomic, commu-
nity Benjamin Constant, in northeastern Para.
Litter was collected during tw o periods: dry sea-
son (November) and rainy (March) in 2009. For
the collection of litter samples, we used collec-
tors measuring (0.25 × 0.25 m2), which were
placed directly on the soil surface. The collected
material was stored in paper bags and taken to
the laboratory for Chemical Analysis of the Bra-
zilian Agricultural Research Corporation (EM-
BRAPA), which was determined by analyses of
macronutrients (N, P, K, Ca, Mg, Na) and micro-
nutrients (Fe, Cu, Mn, Zn). The highest concen-
trations of macronutrients were found in N for
agroforestry systems with and without burning
in two seasons (wet and dry). All macronutrient s
showed influence of seasonality, which was
verified by the wide variation in nutritional be-
havior. The decreasing concentration of nutri-
ents was presented N > Ca > Mg > Na > K > P in
agroforestry system with burning, with maxi-
mum values of all nutrients in the rainy season,
and N, P, K, Ca, Na in higher concentrations in
agroforestry system without burning, and show-
ed only the Mg peak in agroforestry system with
burning. The behavior of the concentration of
nutrients was opposite to that observed one, for
all elements analyzed showed a reduction in the
concentrations of nutrients in the dry season.
The decreasing concentration of nutrients was
presented Fe > Mn > Zn > Cu.
Keywords: Forest; Management; Ecosystem;
Seasonality; Litterfall
1. INTRODUCTION
The use of agroforestry systems has been considered
as an optimization alternative to the use of land, because
it conceals the forestry production with the aliments,
conserving the soil, decreasing the impact caused by ag-
ricultural practices and favoring the cycle of nutrients
through a higher contribution of litter.
The litter decomposition is the main way of transfer-
ence of the nutrients to the soil, and it can make possible
their re-absorption by the living vegetables [1] through
the nutrients cycling, which is responsible for the ele-
ments exchange between living beings and the environ-
ment around them, focused on the relationship between
vegetation and the soil [2].
The litter involves the more superficial surface in
agroforestry environments, being made by leaves, bran-
ches, reproductive organs and residual deposits that de-
velop several functions to the harmony and the dynamic
of these ecosystems. The litter, besides other functions,
protects the soil against high temperatures, deposits in its
content a great quantity of seeds ready to germinate or in
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R. M. Da Silva Castro et al. / Agricultural Sciences 4 (2013) 26-36 27
dormancy state, shelters a great fauna composed by mi-
cro and macro invertebrates that act directly in the proc-
ess of decomposing these materials and fertilizing. The
information generation about the litter deposition and the
analysis of its content is an important tool to the com-
prehension and conservation of these areas, as well as its
inter relationships with the environment.
The agroforestry systems (SAFs), even though im-
planted after the slashing and burning actions suffered by
the forests, have been proposed as an alternative to the
recovery of degraded areas [3] and the litter produced by
the different systems is one of the promoting agents of
this recovery. The study of the mineral nutrients cycle is
fundamental to know the structure and the function of
ecosystems. Part of the organic and nutrients matter re-
turns to the forestry soil, and is considered the most im-
portant mean of essential elements transference from the
vegetation to the soil [4].
Several studies have been applied in Brazil and in the
world objecting the contribution to a better knowledge
about the nutrients cycle and the forestry ecosystems
dynamic, and even in homogeneous plantations of for-
estry and agricultural specimens [5] longing to determine
the patterns of every vegetable typology and present for
this process the differences between them, to create the
possibility of a better understanding of the environment
mechanism and answers to the anthropic modifications
applied in it, and the study of litter production has con-
tributed to a better understanding of the vegetation and
soil function in these systems.
The agroforestry systems (SAFs) have been recom-
mended to tropical regions due to environment, eco-
nomic and social benefits. These benefits are generally
related to the carbon kidnap capacity from the atmos-
phere, adequate water and nutrients cycle, and the devel-
opment of the soil quality in comparison to annual or
perennial mono agriculture [6]. According to the compo-
sition and treatment of SAFs, these systems can also
keep high diversity of fauna and flora, compared to oth-
ers agricultural systems.
The importance of micro climate factors in the litter
decomposition and production was verified by [7], when
it was showed that the light, the temperature, the soil hu-
midity and the nutrients availability are capable of suf-
fering alterations due to the deposited litter quantity. A
realized research with the litter production in agrofor-
estry system [8] observed that, although the highest pro-
duction has had a coincidence with the drought season
ending, it couldn’t be found a significant correlation be-
tween the analyzed climate variations, the same result
found by [9] when he realized a study of the climate
variation influences on primary forest litter.
The seasonal pattern of litter deposition in the agro-
forestry system, with a higher production in the end of
the drought season, is typical of semideciduous forests,
where the leaves deposition peaks, during this period of
the year, and happens as an answer of the vegetation to
the seasonal climate; data were obtained of total and
fractional litter production which are similar to the ones
found in semideciduous forests in the southeast of Brazil,
what allows to affirm that the system has presented the
behavior of a native forest in terms of litter dynamic.
Researchers contemplate the eucalypt consortium with
leguminous trees in Brazil. It is clear that the infinity of
combinations that the tropical biodiversity offers to work
in favor of a sustainable development of the planted for-
est [10] studied the litter dynamic and the N transference
capacity to the soil in eucalypt plantations. The planta-
tion of Eucalyptus grandis and Pseudosamanea gua-
chapele in sandy soils should be incentivized, because,
when it is compared to the eucalypt plantation only, the
N quantity contribution to the soil and the speed of min-
eralization of the waste are increased, which may repre-
sent future earnings in terms of fertility and timing of
Eucalyptus nutrient demand. Moreover, the productivity
of eucalyptus is slightly higher in mixed stands com-
pared to pure crop species, where the number of plants is
twice bigger than the component crops.
The highest quantity of litter accumulated in eucalypt
plantations (16.6 t·ha1) shows that the high contribution
of timber (branches) to the produced litter may be in-
creasing the mean residue decomposition in soil. This
fact was probably influenced by the higher N contribu-
tion through leguminous litter, increasing the decomposi-
tion rate of existing waste on the soil from both legumes
and eucalyptus.
Aiming to answer the questions about what types of
land use systems have better functioning of soil and nu-
trient production, when submitted to different types of
slashing and burning vegetation treatments associated to
climate seasonality, this research has an objective to
evaluate the nutrients content dynamic in different for-
estry and agroforestry systems in the city of Bragança,
State of Pará.
2. MATERIALS AND METHODS
2.1. Study Site
The research was developed in the location of Benja-
min Constant, city of Bragança, occupying Tijoca and
Urumajó river valleys, and it was located in the east of
the Bragantine zone and 25 km southeast of the city of
Bragança [11] on geographical coordinates of 01˚11ʹ22ʺ
south latitude and of 46˚40ʹ41ʺ west Greenwich longi-
tude.
The studied area presents on its surroundings secon-
dary forests of different ages, as well as areas with recent
history of deforestation and similar use. Benjamin Con-
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R. M. Da Silva Castro et al. / Agricultural Sciences 4 (2013) 26-36
Copyright © 2013 SciRes.
28
stant community, belonging to smallholders, which was
defined Land Unity 1 (UA) and is about 40 years old,
contains a total area of 150 ha. These unities were previ-
ously selected through social-economic diagnosis per-
formed in 1999, in five cities of the region. They are
from successive cycles of slashing and burning, cropping
and fallowing procedures with cotton cultivation (Gos-
sypium hirsutum), rice (Oryza sativa), beans (Phaseolus
vulgares), tobacco (Nicotiana tabacum), cassava (Mani-
hot esculento) and corn (Zea mays) (Figure 1).
minimum of 77% and a maximum of 91%. The annual
rainfall varies between 2.200 mm to 3.000 mm. The in-
solation is about 2.200 to 2.400 hours/year. There is a
predominant direction of winds at the N or NE and an
average annual evaporation of 50.1 mm [12].
It can be observed the existence of two periods with
different characteristics regarding the distribution of rain-
fall, with a rainy station, which goes from January to
June, and another dry station, which goes from July to
December. On this study, February to June represented
the rainy station and August to December the dry station.
2.2. Characterization of the Physical
Environment In the city of Tracuateua (part of the Bragantina micro
region, in the northeast of Pará) closer to Bragança by
the distance of 17 km, is located a meteorological tower
of 25 m high, which belongs to INMET/Pará where daily
data are collected on precipitation and temperature.
These data meteorological were provided to this work.
2.2.1. Climatology of the Region
According to Climatological Normals of the Meteor-
ology National Institute (INMET, 1992), the climate
classification based on Thornthwaite and Mather (1955)
to Bragança features an AwA’a’ climate-type: in other
words, a super humid megathermal climate with moder-
ate water deficit during the August-December period.
The air temperature presents a small annual variation in
the Bragantina micro region. The daily temperature
ranges may be higher than 10˚C, mainly during the
drought season of the region. The average monthly rela-
tive humidity is always high, with a variation between a
2.2.2. Soil and Topography
Bragança is located on a plain area, formed by recent
sediments, softly undulating, and has the maximum slope
of 26 m. The main river of the area is Caeté (Rocque
1982). The soils are acid and strongly acid, of good
drainage because they are permeable and it presents low
fertility because they are Yellow Latosol [12]. The preva-
(Source: UAS, Emílio Goeldi Pará Museum, September 2010).
Figure 1. Location map of Benjamin Constant, city of Bragança—PA.
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R. M. Da Silva Castro et al. / Agricultural Sciences 4 (2013) 26-36 29
lence is upland soil, which also shows some mangrove,
hydromorphic and alluvial soils near the coast.
2.2.3. Characterization of the Vegetation
Nowadays, the main original vegetation types of the
Bragantina zone, primary forest land, forest and perma-
nently flooded lowland, upland fields and wetlands, have
a very sparse occurrence, limited to a few places. The
main landscape is characterized by a secondary vegeta-
tion with different ages and different degrees of plant
succession, agricultural crops and grazing areas [10],
from successive cycles of slashing and burning, cropping
and fallowing procedures. According to [11], the type of
vegetation in the region is secondary tropical rain forest.
The vegetation of Benjamin Constant community is
similar to the vegetation of the coastal plain of the city of
Bragança. In this location, “capoeiras” are at different
stages of succession, buritizais, Açai Palm and vegetation
characteristic of floodplains flooded. For the agricultural
communities of Bragança, the “capoeiras” represents
79% of land use for the subsistence, while 6% of the
stream, 13% of crop (whether annual, semi and perennial)
and 2% of grasslands are used as other forms of income
[13].
2.3. Agroforestry in Areas of Secondary
Forest Managed with Burning
This enrichment study of capoeira with fruit (açaí, cu-
puaçu) paricá and legume cover was deployed in the area
of family producer, which is constituted of 30-year-old
secondary vegetation, and it was previously used with
subsistence farming system with slashing and burning
procedures.
The agroforestry system from secondary forest areas,
where there have been slashing and burning procedures
of the secondary vegetation since 1999, was determined
as agroforestry systems with burning and it was used the
preparation area with traditional slashing and burning
procedures practiced by the local producer, so the sec-
ondary vegetation was slashed to and burned to imple-
ment paricá (Schizolobium amazonicum Huber ex Duc-
ke), Açaí (Euterpe oleracea Mart), Cupuaçu (Theobroma
grandiflorum Schum). Paricá plants and açaí were im-
planted with a 3 m × 3 m space, and cupuaçú with a 8 m
× 8 m space.
2.4. Agroforestry System in Areas of
Secondary Forest without Burning
Procedures
The agroforestry system, inside the Secondary Forest
area were no burning procedure was performed, was de-
termined as agroforestry systems without burning
(SAFSQ), and the area preparation occurred during the
same period and consisted of thinning the secondary
vegetation to implant Paricá (Schizolobium amazonicum
Huber ex. Ducke), Açaí (Euterpe oleracea Mart), and
Cupuaçú (Theobroma grandiflorum Schum). Then it was
proceeded with green manure cover Chamaecrista rupens,
which was cut at the time of its flowering process, leav-
ing the plant biomass on soil. Paricá plants and açaí were
implanted with a 3 m × 3 m space, and cupuaçú with a 8
m × 8 m space.
2.5. Collection and Treatment of Litter
The collection of litter was made during the months of
March (wet season) and November (dry season) 2009
using square collectors (0.25 × 0.25 m2) put directly on
the soil and stored in paper bags on the field. Then sam-
ples were placed in an oven at a temperature of 80˚C
during 72 h. After drying, this material was crushed sepa-
rately in a Wiley type mill, wrapped in plastic and stored
in a dry place. Subsequently, the material was sent to
EMBRAPA/CPATU/PARÁ Laboratory of Soil and Plant
Tissue and Chemical Analysis Laboratory Emilio Goeldi
Pará Laboratory, LAQ/GOELDI, where the samples were
chemically analyzed for macro and micro nutrient con-
tent.
2.6. Determination of the Analysis
The samples were taken to the lab and reunited in 12
groups, and each group of samples with three repetitions
was separated and homogenized to contain a sample. 1 g
samples of vegetal material were weighted for the chemi-
cal analysis.
The determination of nitrogen was based on the
method of micro-Kjeldahl, described in [14] which con-
sists, basically, in steam distillation and titration using
boric acid and sulfuric acid 0.05 N dye (fixative). It was
added 2 ml of digesting solution (2 g selenium powder to
1 liter of H2SO4) at the temperature of 400˚C, during 60
min, until the obtainment of the clear digested. After be-
ing cold, put 10 ml of boric acid solution (distilled water
and 80 g of boric acid) and add 5 drops of methyl red. In
the still, add 10 ml of soda, and when the sample reaches
the blue coloration it can be taken out of the distiller.
Lead elemeyer to the automatic burette, where titration is
done for reading, until the color pink is achieved.
For the calculation of nitrogen, we used the following
equation:
0.14VgPB F

Vg = amount spent; PB = test blank; F = factor; 0.14 =
constant.
The determination of phosphorus, potassium, calcium,
magnesium, sodium, copper, manganese, iron and zinc
was performed by acid digestion of the samples, and it
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R. M. Da Silva Castro et al. / Agricultural Sciences 4 (2013) 26-36
30
was used 8 ml of nitric acid and 2 ml of perchloric acid,
with the temperature of 180˚C during 45 min to obtain
the clear digested. After the acid digestion and the steps
of the distilled water process, it was used 2 ml solution
of ammonium vanadate and ammonium molybdate in a
1:1 ratio.
After pipetting 8 ml of the mineralized extract and 8
ml of each point on the curve (0, 2.5, 5, 7.5 and 10), the
reading of the phosphorus is made using a spectropho-
tometer at a wavelength of 440 nm. For the determina-
tion of sodium and potassium in a flame spectropho-
tometer, it is implemented a pattern of 10 ml of sodium
and 10 ml of potassium in the same flask to measure with
distilled water.
The readings of calcium, magnesium, copper, manga-
nese, iron and zinc were determined by atomic absorp-
tion (Spectr AA-220-Atomic Absortion Spectrometer)
following the methodology [15].
For the determination of calcium was added to 2 ml of
solution of lanthanum in 0.2 ml of digested extract,
where the analysis is done by electronic absorption, and
it was used as a reference point for the gas mixture, the
standard point of 2 ppm of calcium. For determination of
magnesium was added to 8 ml of lanthanum, and it was
added 0.2 ml of the diluted sample, so it was used as a
reference for the gas mixture the standard point of 0.5
ppm of magnesium, when the analysis was done by
atomic absorption.
The analysis for iron, manganese, copper, and zinc by
atomic absorption equipment were made by direct de-
termination of the elements in nitric-perchloric extract in
an atomic absorption spectrophotometer without inter-
ference problems or ionization using the hollow cathode
lamp of the element [16]. It is recommended to analyze
the standard curve previously for each quoted item. To
The determination of the curves of iron and manganese
was added 20 ml of the standard of 100 ppm of iron and
20 ml of the standard of 100 ppm of manganese. Pipette
0, 1, 2, 3, 4, 5 ml of the standard of 100 ppm of manga-
nese in six 100 ml flasks. Ascertain with demineralized
water. The curve points are for both iron and manganese
to 0, 1, 2, 3, 4 and 5 ppm.
To the determination of the curves of copper and zinc
and manganese was added 20 ml of the standard of 100
ppm of copper and 20 ml of the standard of 100 ppm of
zinc. Pipette 0, 1, 2, 3, 4, 5 ml of the standard of 100
ppm of copper in six 100 ml flasks. Ascertain with de-
mineralized water. The curve points are for both the
copper and zinc, 0, 0.1, 0.2, 0.3, 0.4, and 0.5 ppm.
3. STATISTICAL ANALYSIS
The statistical analysis of data obtained from the labo-
ratory results were subjected to analysis of variance, av-
erage test and Tukey test at 5% probability, using SAS
software version 8.2.
4. RESULTS AND DISCUSSION
4.1. Concentration of Macronutrients in
Litter
Nitrogen (Figure 2(a)) was the element with the high-
est concentration of all the nutrients analyzed, with a
maximum value of 18.95 g·Kg1 followed by calcium
(Figure 3(a)) showed that the maximum value of 10.76
g·Kg1, both in the rainy season. These elements were
also the only ones who did not show significant differ-
ences between treatments with burning in the rainy sea-
son and dry without burning in the rainy and dry seasons.
Statistical differences were presented (Tukey’s test, p <
0.05), especially between agroforestry systems with
burning for the elements phosphorus (Figure 2(b)), mag-
nesium (Figure 3(b)), potassium (Figure 4(a)), and so-
dium (Figure 4(b)) as presented differences in the same
treatment during different time periods. Considering the
two systems, the nutrient concentration was observed in
decreasing order: N > Ca > Mg > Na > K > P, all with
maximum values during the rainy season, with the ex-
ception of Mg with the highest concentration in the dry
season.
There were significant differences in nitrogen and
phosphorus (Figures 2(a) and (b)) between treatments
with and without burning during the dry and rainy, with
highest value observed in the rainy season agroforestry
systems agroforestry systems and agroforestry systems
with burning, 18.95 g·Kg1 and 0.35 g·Kg1, respectively.
However, magnesium (Figure 3(b)) was significantly
higher in agroforestry systems with burning in the dry
season (7.45 g·Kg1), we observed a significant reduction
of 60% in the magnesium concentration. The elements
phosphorus and potassium (Figures 2(b) and 4(a))
showed lower concentrations in both treatments agrofor-
estry systems with burning and without burning and two
seasons (dry and rainy ), with a maximum value of 0.35
g·Kg1 and 0.5 g·Kg1, respectively, both in the rainy
season.
Were observed between treatments with burning and
without burning in the dry season and rainy that there
was no statistically significant difference in calcium con-
centrations observed in (Figure 3(a)), with a variation in
the range of (7.34 g·Kg1 to 10.76 g·Kg1). All elements
showed high concentrations significantly different (p <
0.05) with the exception of Ca, which was the only ele-
ment that did not show statistically significant differ-
ences for all treatments and periods, it can be said that
this element did not vary as a function seasonal climate.
It was observed in (Figure 4(b)), which showed a
higher sodium concentration agroforestry systems with
burning in the dry season and the rainy season in agro-
Copyright © 2013 SciRes. OPEN A CCESS
R. M. Da Silva Castro et al. / Agricultural Sciences 4 (2013) 26-36
Copyright © 2013 SciRes.
31
(a) (b)
▀▀ ASWB1 Rainy; ▀▀ ASWB2 Rainy; ▀▀ ASWB1 Rainy; ▀▀ ASWB2 Rainy; ▀▀ ASWB1 Dry; ▀▀ ASWB2 Dry; ▀▀ ASWB1 Dry; ▀▀ ASWB2 Dry.
Means followed by lowercase lines, do not differ statistically by F test and Tukey at 5% probability. N = nitrogen, P = phosphorus. Agroforestry systems
with burning—ASWB1. Agroforestry systems without burning—ASWB2.
Figure 2. Concentration N (a) and P (b), in litter under agroforestry systems managed with burning and no burning, community
Benjamin Constant, Bragança—PA for the year 2009.
(a) (b)
▀▀ ASWB1 Rainy; ▀▀ ASWB2 Rainy; ▀▀ ASWB1 Rainy; ▀▀ ASWB2 Rainy; ▀▀ ASWB1 Dry; ▀▀ ASWB2 Dry; ▀▀ ASWB1 Dry; ▀▀ ASWB2 Dry.
Means followed by lowercase lines, do not differ statistically by F test and Tukey at 5% probability. Ca = calcium, Mg = magnesium. Agroforestry sys-
tems with burning—ASWB1. Agroforestry systems without burning—ASWB2
Figure 3. Concentration Ca (a) and Mg (b), in litter under agroforestry systems managed with burning and no burning, com-
munity Benjamin Constant, Bragança—PA for the year 2009.
forestry systems without burning, both treatments de-
creased significantly by 37% and 32%, respectively.
However, magnesium (Figure 3(b)), also showed the
same pattern in nutrient concentration was higher in with
burning in the dry season and without burning in the
rainy season, the two treatments showed significant re-
duction of 48% and 46% respectively. Potassium showed
higher concentration with burning during the dry period
and agroforestry systems without burning during the
rainy season , with maximum values of 1.90 and 1.96
g·Kg1 and minimum values 0.5 g·Kg1 one and 0.74,
respectively.
Considering only one type of treatment agroforestry
systems with burning, with the exception of calcium, all
elements analyzed showed reduction in the concentra-
tions of nutrients in the rainy season, except calcium.
There was a reduction of the nitrogen of 18.95 to 14.39
g·Kg1; phosphorus decreased from 0.35 to 0.22 g·Kg1;
potassium decreased from 1.9 g·Kg1 to 0.5 g·Kg1;
magnesium reduced from 7.45 to 3.59 g·Kg1 and sod-
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R. M. Da Silva Castro et al. / Agricultural Sciences 4 (2013) 26-36
32
(a)
(b)
▀▀ ASWB1 Rainy; ▀▀ ASWB2 Rainy; ▀▀ ASWB1 Rainy; ▀▀ ASWB2
Rainy; ▀▀ ASWB1 Dry; ▀▀ ASWB2 Dry; ▀▀ ASWB1 Dry; ▀▀ ASWB2
Dry. Means followed by lowercase lines, do not differ statistically by F test
and Tukey at 5% probability. K = potassium, Na = sodium. Agroforestry
systems with burning—ASWB1. Agroforestry systems without burning—
ASWB2.
Figure 4. Concentration K (a) and Na (b), in litter under agro-
forestry systems managed with burning and no burning, com-
munity Benjamin Constant, Bragança—PA for the year 2009.
dium of 5.85 g·Kg1 and 2.14 g·Kg1.
Agroforestry systems without burning in the concen-
tration of nutrients was opposite to that observed in agro-
forestry systems with burning because all elements ana-
lyzed showed a reduction in the concentrations of nutri-
ents in the dry season. A reduction in nitrogen of 18.95 to
17.38 g·Kg1; phosphorus decreased from 0.35 to 0.27
g·Kg1, potassium decreased from 1.96 to 0.74 g·Kg1;
calcium decreased from 10.28 to 7.34 g·Kg1 magnesium
decreased from 5.25 to 2.44 g·Kg1, and sodium de-
creased from 6.91 to 2.24 g·Kg1, with differences shown
(Tukey, p < 0.5).
Treatment agroforestry systems without burning rainy
and dry season had the highest concentrations of nutri-
ents from litter, for the elements: N, P, K, Mg, Na, and
the only element with the highest concentration in the
treatment agroforestry systems with burning was rainy
calcium.
4.1.2. Influence of Seasonality
The average annual rainfall (Figure 5) showed higher
values in May (849.7 mm) and lowest values in October
and November, months when there was no rainfall (0
mm), and the annual average was (2.323 mm), consider-
ing the year of the experiment and the average of the last
20 years. Precipitation was a variable that was shown to
have influenced the concentration of these nutrients. In
the rainy season the highest levels of rainfall in the re-
gion were observed in the months of February, March,
April and May, with a high peak in May, presented dif-
ferently in rainfall over the last 10 years, and in 1995
presented the highest value registered in rainfall (657.20
mm), and the average for the month of May for the last
20 years is (347.6 mm).
Although rainfall make the incorporation of nutrients
in plants, for agroforestry systems with burning, it was
observed that the reduction in concentration of these nu-
trients in the rainy season. The litter is characterized by
presenting a greater quantity of production during the dry
period, the decomposition rate and nutrient concentra-
tions are lower. The monthly average temperature showed
higher values in December (27.7˚C) and lowest values in
April (25.2˚C), with an annual average of 26.42˚C.
The results of the analysis of macronutrients in the lit-
ter are presented in (Table 1). The average values for
nitrogen (N) presented in the area of agroforestry system
with burning procedures agroforestry systems with burn-
ing was (15.94 g·Kg1), and without burning procedures
in the agroforestry system without burning ranged from
(17.38 g·Kg1), so the average nitrogen (N) was higher
during the rainy season. No statistical difference between
the periods considered occurred. For the analysis of the
average litter the average of the nutrient phosphorus (P)
and potassium (K) were (0.35 and 1.90 g·Kg1), respec-
tively. Considering the same area there was statistical
difference in different periods for potassium (K), how-
ever, the agroforestry systems with burning and the agro-
forestry systems without burning for the same period had
no difference. Phosphorus (P) and potassium (K) had
higher concentrations of nutrients during the rainy season,
in the area agroforestry systems without burning.
The variation analysis of calcium (Ca) was (7.34
g·Kg1 to 10.76 g·Kg1), and there was no differ between
areas and periods. Magnesium (Mg) and sodium (Na),
showed differences between areas, periods, but consid-
ering the different areas during the dry season and the
rainy season, there was no difference.
The data analysis of macronutrients in the litter, on a
Copyright © 2013 SciRes. OPEN A CCESS
R. M. Da Silva Castro et al. / Agricultural Sciences 4 (2013) 26-36 33
Tab le 1 . Concentrations of nutrients from litter in agroforestry
system with burning and agroforestry system without burning
in the rainy season and the dry season, the community Benja-
min Constant, Bragança—PA for the year 2009.
Elemento N P K Ca Mg Na
(g/Kg)
N 1
P 0.391632 1
K 0.518017 0.800401* 1
Ca 0.25408 0.21573 0.06653 1
Mg 0.13698 0.131755 0.118806 0.197858 1
Na 0.310008 0.174853 0.541457 0.237893 0.3512541
Figure 5. Monthly variation of precipitation and temperatures
during the studied period (2009), 17 km distant tower of the
studied area. Data provided by the Meteorology National In-
stitute INMET/PARÁ.
gener alway, presented a higher average total in the
agroforestry system area without burning procedures with-
out burning for N, P, K, Ca, Na, respectively, 30.24 g·Kg;
0.57 g·Kg, 2.40 g·Kg, 21.11 g·Kg, 7.99 g·Kg; and the
agroforestry system with burning procedures, for N, P, K,
Ca, Na, except for the magnesium (Mg), which presented
the total amount of (11.04 g·Kg). Considering the rainy
and dry seasons, only calcium showed a higher content of
nutrients in the two periods, and the content of (Mg) and
sodium (Na) was higher only during the dry season.
The average concentrations of nitrogen, phosphorus,
potassium, magnesium and sodium were significantly
higher during the rainy season in the agroforestry system
without burning procedures agroforestry systems without
burning except for the calcium. During the drought pe-
riod were significantly higher only the average values for
concentrations of nitrogen and potassium: for nitrogen
17.38 g·Kg1 and potassium 0.61 g·Kg1. After all the
macro nutrients studied, the highest concentrations were
of nitrogen and for the two systems agroforestry with
burning and without burning, in both periods (dry season
and rainy season), as (Table 1).
4.1.3. Interaction between Macronutrients Litter
in an Agroforestry System Managed with
Burning and without Burning
In general, among all the elements analyzed, only the
Phosphorus and Potassium showed high positive and sig-
nificant correlation (Figure 6) in the concentration of nu-
trients in the litter (r = 0.80) in agroforestry systems with
burning. It is observed that with increasing phosphorus
concentration increased there was a potassium concen-
tration, as well as nitrogen, these elements are also re-
quired in larger quantities by plants.
4.1.4. Concentration of Micronutrients in Litter
The elements Cu and Zn (Figures 7(a) and 8(b))
showed the lowest concentrations and did not show any
significant variation in treatment, with the following or-
der of concentration: Fe (1051.3 mg·Kg1) > Mn (273.62
mg· K g 1) > Zn (33.87 mg·Kg1) > Cu (28.78 mg·Kg1).
For Cu and Mn, agroforestry systems without burning,
with higher concentrations during drought and agrofor-
estry systems without burning, higher concentrations in
the rainy season. For the elements Fe and Zn, in with
burning showed higher concentrations in the rainy season
and without burning only Fe showed higher concentra-
tions in the dry season. The wide range of micronutrients
found between higher and lower amount of nutrients in
this study was (19.59 mg·Kg1 to 1051.3 mg·Kg1) in the
elements Cu and Fe, respectively.
Analyzing the concentrations of nutrients in general
scale, it is observed that copper and iron had the highest
concentrations in agroforestry systems without burning
in drought, and agroforestry systems with burning had
higher nutrient concentrations in the rainy season the
element copper and manganese, zinc showed no seasonal
variation. Although had the highest concentrations, the
elements Mn and Fe showed significant differences only
between the different treatments and not between periods,
the elements copper and zinc did not differ between
treatments and periods (Figures 7(a) and (b)).
Some authors together bibliographical review in dif-
ferent forests of the world, on the nutrient content of the
litter and concluded that the availability of soil water
increases the concentration of nutrients in forest, but in
agroforestry systems precipitation removes nutrients. In
this study, the rainy season had the highest concentra-
tions of nutrients in the litter. Litter production varies
between fractions, perhaps this interferes with nutrient
content (Figure 8).
According [17], the decomposition rate is highest in
the shoot and the greater availability of water in the soil
higher decomposition. In this study, the greatest amount
of litter collected in agroforestry, were branches or twigs,
which have a lower decomposition rate of the resistance
of the plant material, thus being able to influence the
Copyright © 2013 SciRes. OPEN A CCESS
R. M. Da Silva Castro et al. / Agricultural Sciences 4 (2013) 26-36
34
Figure 6. Correlation between soil P and K nutrient concentra-
tions in litter in agroforestry systems and burns without burn-
ing, community Benjamin Constant Bragança—Pará.
(a)
(b)
▀▀ ASWB1 Rainy; ▀▀ ASWB2 Rainy; ▀▀ ASWB1 Rainy; ▀▀ ASWB2
Rainy; ▀▀ ASWB1 Dry; ▀▀ ASWB2 Dry; ▀▀ ASWB1 Dry; ▀▀ ASWB2
Dry. Means followed by lowercase lines, do not differ statistically by F test
and Tukey at 5% probability. Cu=copper; Mn = manganese. Agroforestry
systems with burning—ASWB1. Agroforestry systems without burning—
ASWB2.
Figure 7. Concentration Cu (a) and Mn (b), in litter under
agroforestry systems managed with burning and no burning,
community Benjamin Constant, Bragança—PA for the year
2009.
(a)
(b)
▀▀ ASWB1 Rainy; ▀▀ ASWB2 Rainy; ▀▀ ASWB1 Rainy; ▀▀ ASWB2
Rainy; ▀▀ ASWB1 Dry; ▀▀ ASWB2 Dry; ▀▀ ASWB1 Dry; ▀▀ ASWB2
Dry. Means followed by lowercase lines, do not differ statistically by F test
and Tukey at 5% probability. Fe = iron; Zn = zinc. Agroforestry systems
with burning—ASWB1. Agroforestry systems without burning—ASWB2
Figure 8. Concentration Fe (a) and Zn (b), in litter under
agroforestry systems managed with burning and no burning,
community Benjamin Constant, Bragança—PA for the year
2009.
total quantity of nutrients produced by the burlap. Then
the N, the element Ca showed the highest amount of nu-
trients in the two treatments, as the fraction of branches
had the highest content of Ca [14] this large amount of
Ca found in this study may be a consequence of the large
amount of branches that was collected in this system.
The high mobility of N, P and K may have contributed to
high concentrations in the rainy season, influenced by
seasonality. The highest concentration of K presented in
the rainy season in without burning can be explained by
the fact that this element be returned mainly by rainfall
in the litter. This result may be due to the low mobility of
calcium, due to its limited redistribution in the plant. The
nutrient content of litter in this study followed the se-
quence: N > Ca > K > Mg > P, similar to that observed
Copyright © 2013 SciRes. OPEN A CCESS
R. M. Da Silva Castro et al. / Agricultural Sciences 4 (2013) 26-36 35
by [18].
According [19] in a study conducted in an agroforestry
system, the high concentrations found in leaves potas-
sium inhibit calcium concentration, for this work the po-
tassium concentration was lower than in calcium, besides
differing from this result, it can to evaluate the low con-
centration of potassium may be due to low production of
sheets that have been collected .
Agroforests system in the use of forest species or fruit,
contributes beyond the regular cycling of other elements,
also to increase the amount of nitrogen in the soil [20],
this may explain the high concentration of nitrogen also
found in this study, in which deployment was with fruit
species.
In general, this study showed higher concentration of
nutrients in the litter during the period of heavy precipi-
tation. For [21] during periods of heavy precipitation
could favor the absorption of certain nutrients by placing
them fully available in all parts of the plants. For [12] in
summer, due in part to the greater the physiological ac-
tivity, increase the rates of allocation of nutrients, which
contributes to the growth of the plant during that period
and consequently increases the transport of nutrients
within the plant.
Phosphorus is regarded as a very mobile plant, and in
some species with senescence characteristics, there trans-
location from 40% to 60% of the leaves to other plant
organs prior to leaf abscission [22], thus allowing this
nutrient to be redistributed and used in the formation of
new tissue. This mechanism is essential to ensure contin-
ued productivity in poor soils [23], as this study and the
vast majority of tropical soils.
5. CONCLUSION
The total amount of macronutrients evaluated, is high-
er in agroforestry system without burning. In the rainy
season the concentration of nutrients has greater seasonal
variation between systems. The system where there was
the burning seems to have been favored as the increase in
the concentration of nutrients, but their concentrations in
this system were presented in the dry season. The con-
centration of micronutrients has no seasonal influences.
6. ACKNOWLEDGEMENTS
To the National Council of Scientific and Technological Develop-
ment/CNPq; the scholarship granted by the Postgraduate course in Ag-
ricultural Sciences/Federal Rural University of Amazon/UFRA; Emilio
Goeldi Pará Museum (MPEG); and to the FAPESPA project/Edital
17/2008.
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