Tropical Grasslands-Forrajes Tropicales (2017) Vol. 5(2):85– 93 85
Research Paper
Weeds alter the establishment of Brachiaria brizantha cv. Marandu
Malezas afectan el establecimiento de Brachiaria brizantha cv. Marandu
SIDNEI R. DE MARCHI1, JOSÉ R. BELLÉ1, CELSO H. FOZ1, JUCILENE FERRI1 AND DAGOBERTO MARTINS2
1 Universidade Federal de Mato Grosso, Barra do Garças, MT, Brazil. www.ufmt.br
2 Universidade Estadual Paulista, Faculdade de Ciências Agrárias e Veterinárias, Jaboticabal, SP, Brazil.
Abstract
The present study evaluated the effects of different periods of coexistence among the main weeds and Marandu brachiaria grass ( Brachiaria brizantha, now Urochloa brizantha) in newly sown pasture. The experiment was conducted in a randomized block with 4 replications, with treatments being 8 coexistence periods: 0, 15, 30, 45, 60, 75, 90 and 120 days after emergence. A phytosociological assessment of the weed community was carried out at the end of the coexistence periods, and weeds were eliminated from the appropriate treatment using herbicide. Key morphogenic parameters of the forages were assessed at the end of the experimental period and dry matter production was determined. Results indicated that the presence of weeds had negative impacts on the main morphogenic components, such as plant height, number of tillers and production of leaf and stem dry matter. The presence of weeds reduced productivity in Marandu, with 15 days competition being sufficient to reduce forage production by approximately 50%, suggesting that weed control measures should be adopted within 15 days following emergence of seedlings of Marandu and weeds.
Keywords: Dry matter, interference, pasture renovation, weed competition.
Resumen
En un latosol localizado en Sinop, Mato Grosso, Brasil se evaluaron los efectos de la infestación de las principales malezas de la zona ( Hyptis suaveolens, Senna obtusifolia y Sida rhombifolia), en diferentes edades después de la siembra, en la producción y algunas características morfogénicas de la gramínea forrajera Brachiaria brizantha (ahora: Urochloa brizantha) cv. Marandu. Los tratamientos fueron dispuestos en un delineamiento experimental de bloques al azar con 4
repeticiones y consistieron en los períodos de convivencia: 0, 15, 30, 45, 60, 75, 90 y 120 días después de la emergencia de la gramínea. Al finalizar cada uno de estos períodos se realizó una evaluación fitosociológica de la comunidad infestante y se eliminaron las malezas utilizando un herbicida. Al término del período experimental se evaluaron los principales parámetros morfogénicos del pasto, así como la producción de materia seca. Los resultados mostraron un efecto negativo de las malezas en la altura de planta y el número de rebrotes, así como en la producción de materia seca de hojas y tallos. La presencia de las malezas redujo la producción del pasto en todos los tratamientos, variando de 50%
(competencia durante los primeros 15 días) hasta 74% (120 días). Por tanto las medidas de control de las malezas deben ser adoptadas durante las 2 primeras semanas de convivencia con el pasto Marandu.
Palabras clave: Competencia, interferencia, materia seca, renovación de pasturas.
___________
Correspondence: S.R. de Marchi, Universidade Federal de Mato
Grosso, Av. Valdon Varjão 6390, Barra do Garças CEP 78600-000,
MT, Brazil.
Email: sidneimarchi.ufmt@gmail.com
Tropical Grasslands-Forrajes Tropicales (ISSN: 2346-3775)
86 S.R. de Marchi, J.R. Bellé, C.H. Foz, J. Ferri and D. Martins
Introduction
and can reach 20,000 kg DM/ha (Benett et al. 2008). It is
considered an excellent source of good quality feed when
Historically, the livestock production model practiced by
appropriately
fertilized
and
managed.
However,
most South American ranchers has a strong extractive
nutritional value declines rapidly following flowering
aspect with little concern for protecting and renewing the
(Valle et al. 2000).
natural resources. This absence of the use of technical
All studies we found in the literature on weed control
criteria in the utilization of natural resources results in
in pastures focused on studying the effects of herbicides
accelerated degradation of pasture areas, where
on controlling unwanted plants (Silva et al. 2005; Santos
degradation is mainly characterized by loss in the
et al. 2007; Trigueiro et al. 2007). Practically no attention
productive capacity of the forage grass due to the severe
has been given to the study of interference relations
loss of soil fertility and the increase in weed infestation
between weeds and grasses, especially with regards to
(Lima and Pozzobon 2005). Renewal of the area is the
productivity and carrying capacity of the pasture.
most rational solution when a pasture becomes degraded.
This work sought to study the effects of increasing
Renewal consists basically of destroying the old
periods of weed presence on the initial development of
vegetation, correcting soil fertility and planting the
Brachiaria brizantha cv. Marandu forage.
appropriate forage species for the local conditions,
usually an exotic (introduced) species (Macedo 2009).
Materials and Methods
The process of renovating the degraded pasture, however,
is ineffective in removing the seeds left by weeds, so weed
The experimental phase of this work was conducted in a
and pasture seeds germinate together, which initiates a
pasture renewal area in the municipality of Sinop, Mato
new degradation cycle (Martins et al. 2007).
Grosso, Brazil, (11º11’29’’ S, 55º15’13’’ W), where,
Brachiaria grass ( Brachiaria brizantha, now Urochloa
according to the Köppen (1948) classification, the climate
brizantha) is one of the most cultivated forages in the
is of type Aw. Rainfall data and average, minimum and
warm regions of South America and supports a large
maximum temperatures recorded during the experimental
portion of the cattle herd. It has high forage yield,
period are shown in Figure 1. The average annual
persistence, good capacity for regrowth and relative
temperature is 27 ºC, varying between 17 and 40 ºC.
tolerance to attacks from spittlebugs such as Deois sp. The
Average annual precipitation is 1,500 mm, varying from
average annual productivity is 4,000‒8,000 kg DM/ha
1,200 to 1,800 mm.
35
600
30
500
25
400
C)
)
o (
m
e 20
r
m(
u
t
l
300
l
a
a
r
f
e 15
n
p
ia
m
R
e
200
T 10
100
5
0
0
Oct/10
Nov/10
Dec/10
Jan/11
Feb/11
Mar/11
Rainfall
T average
T minimum
T maximum
Figure 1. Average monthly rainfall and temperature during the experimental period.
Tropical Grasslands-Forrajes Tropicales (ISSN: 2346-3775)
Weeds affect establishment of Marandu 87
Representative soil samples (latosol) were collected
DeR = (De/Dt) x 100 (%), where: De is the density of each
and sent for laboratory analysis, which revealed the
weed species and Dt is the total weed density; DoR refers
following chemical characteristics: pH (H2O): 3.9; soil
to the relative dominance of each species and is estimated
organic matter: 18.45 g/dm3; P: 0.04 g/dm3 (Mehlich-1);
by the formula: DoR = (DMe/DMt) x 100 (%), where:
K+: 0.04 cmmol/dm3; Ca2+: 0.09 cmmol/dm3; Mg2+: 0.03
DMe is the dry matter of each weed species and DMt is
cmmol/dm3; Al3+: 0.3 cmmol/dm3 (KCl 1 mol/L); base
the total dry matter accumulated by the weed community;
saturation: 0.16 cmmol/dm3; and effective CEC of 21%.
and RF refers to the relative frequency of each species and
Physical analysis indicated 866 g sand/kg, 39 g silt/kg and
is estimated by the formula: RF = (FAe/FAt) x 100 (%),
91 g clay/kg, characterizing the soil as having a sandy
where: FAe is the absolute frequency of each species
texture. Based on these results, calcium lime was applied
calculated by the expression: FAe = (NAe/NAt) x 100,
in the third week of September 2010 at rates of 2,000
where: NAe indicates the number of samples for a
kg/ha, while 62.5 kg P/ha (as single superphosphate), 25
determined species; NAt is the total number of samples
kg N/ha (as urea) and 37.5 kg K/ha (as KCl) were
obtained; and FAt is the sum of the absolute frequencies
broadcast on all areas in the first week of November 2010.
of all species of the weed community (Mueller-Dombois
Existing forage was removed from the experimental
and Ellenberg 1974).
area by herbicide application (glyphosate at 2.5 L/ha)
All weeds were removed from the respective plots at
followed by mechanical tillage of soil before the study
the end of each period of coexistence by spraying with
commenced in November 2010. The area was fenced to
exclude animals for the duration of the study. Seed of cv.
herbicide, and thereafter any emerging weeds were
Marandu with 70% maximum germination was broadcast
removed by applying 1.5 L/ha of herbicide formulated
on the area at a rate of 6.0 kg/ha. Seedling emergence
with 40 g acid equivalent/L of aminopyralid and 320 g
commenced in 7 days and complete emergence occurred
acid equivalent/L of 2,4-D post-emergence.
by 10 days. The experimental area was divided into 32
The grass was evaluated only at the end of the
plots, each of 16 m2 (4.0 x 4.0 m) with the central 9.0 m2
experimental period, corresponding with 120 days after
of each plot used as the sampling area. The experimental
emergence of the seedlings, when the first grass
design was a complete randomized block, with 8
inflorescences emerged. At this time plant height, number
treatments representing different periods of coexistence
of tillers per plant and number of plants per square meter
between forage and weed species (0, 15, 30, 45, 60, 75,
were measured. Forage samples were collected by cutting
90 and 120 days after emergence) and 4 replications.
the plants to 10 cm from the ground within the area
Assessments of the pasture communities for each
enclosed by the 1.0 m2 metal square, cast randomly in the
treatment were performed at the end of the coexistence
sampling area of the experimental unit.
period for that treatment with the aid of a 1.0 m2 metal
The samples were sent to the laboratory and sorted into
square randomly cast within the sampling area of each
green leaves, green stems and dead matter. The green
plot. All weed species within the metal square were
inflorescences present were considered as part of the
separately identified, counted, cut at stem base and taken
stem. The various fractions were duly packed in properly
to the laboratory, where they were placed in properly
labeled and perforated paper bags and dried in a forced-
labeled and perforated paper bags to be dried in a forced-
air circulation oven at 60‒63 ºC for 72 hours. Dry matter
air oven at 60‒63 ºC for 72 hours. After this procedure,
(DM) yields for the different fractions [green leaf dry
the dry weight of the stems and leaves of each collected
matter (GLDM), green stem dry matter (GSDM), dead
species was determined by using a 0.01 g precision
material dry matter (DMDM) and total dry matter (TDM)]
balance.
were calculated. Dry matter yields for the different
The relative importance (RI) of the weeds was
treatments were compared with those for the 0 days
calculated by the formula:
treatment (control, = weed-free throughout) to determine
RI = (IVIe/IVIt) x 100 (%), where: IVIe refers to the
the suppression in yield by exposure to weeds for the
importance index of a determined species; and IVIt
various times according to the formula:
signifies the sum of the importance indices of all
ROF = [(MST – MSPC)/MST] x 100, where: ROF is
components of the community. The importance index of
the reduction in forage offering in percent; MST is the
each species is estimated by the formula:
total DM produced by the forage species that remained
IVI = DeR + DoR + RF, where: DeR refers to the rela-
weed-free for 120 days; and MSPC is the DM produced
tive density of each species, estimated by the formula:
by treatments with differing periods of weed infestation.
Tropical Grasslands-Forrajes Tropicales (ISSN: 2346-3775)
88 S.R. de Marchi, J.R. Bellé, C.H. Foz, J. Ferri and D. Martins
The values obtained were submitted to analysis of
Results
variance by the F-test and the effects of the treatments
were compared by the Scott-Knott test at 5% probability.
Only 3 weed species emerged during the experimental
The average values of total DM produced by Marandu and
period: Hyptis suaveolens (L.) Poit. (Lamiaceae) (local
observed at 120 days were also adjusted according to the
name: cheirosa), Senna obtusifolia (L.) H.S. Irwin &
Barneby (Leguminosae – Caesalpinioideae) (local name:
Boltzmann model for better understanding of the effects
fedegoso) and Sida rhombifolia L. (Malvaceae) (local
of coexistence, as used by Kuva et al. (2001). This model
name: guanxuma). Senna obtusifolia accumulated the
conforms to the following equation:
greatest amount of DM up to 45 days after emergence
(DAE), but was the only species that showed a reduction
(A
Y =
1 − A2)
+ A
in DM accumulation at 120 DAE (Figure 2). Over the full
1 + e(x− x
2
0)/dx
120 days, H. suaveolens showed the highest DM accu-
mulation with rapid growth from 45 to 120 DAE; DM
where: Y is the estimated DM yield of the forage in g/m2;
accumulation was almost 2.5 times that of S. obtusifolia
x is the upper limit of the coexistence period or control
(Figure 2).
considered; A1 is the estimated yield obtained in the
Sida rhombifolia produced little growth up to 90 DAE,
plots maintained clean throughout the cycle; A2 is the
when compared with the other 2 species, but
minimum estimated production obtained in the units
accumulation of DM increased considerably from 90
maintained with weeds throughout the cycle; xo is the
DAE. At 120 DAE total DM produced by the weeds was
upper limit of the control or coexistence period
288 g/m2 (Figure 2).
corresponding to the intermediate value between
The relative importance, obtained from density,
maximum and minimum production; and dx is the
dominance and frequency of each of the 3 species, was
parameter that indicates the velocity loss or production
relatively equal throughout the experimental period
gain (tg α at point xo).
(Figure 3).
180
150
²)
Senna obtusifolia
Hyptis suaveolens
Sida rhombifolia
120
(g/m
re
90
attm
y
60
Dr
30
0
15
30
45
60
75
90
120
Coexistence period (days)
Figure 2. Dry matter accumulated by the weeds in their coexistence periods.
Tropical Grasslands-Forrajes Tropicales (ISSN: 2346-3775)
Weeds affect establishment of Marandu 89
100
)
% 80
RI (
Senna obtusifolia
Hyptis suaveolens
Sida rhombifolia
-
60
tance
or
p 40
im
20
lative
Re
0
15
30
45
60
75
90
120
Coexistence period (days)
Figure 3. Relative importance (%) of the weed species in their respective coexistence periods.
The height of Marandu was significantly altered by
of Marandu plants did not differ between treatments
coexistence with the weeds; height of the control forage
(P>0.05) with a mean of 37.3 plants/m2 at 120 days post
at 120 days was 62 cm compared with a mean of 38 cm
emergence (Table 1). The production of green leaf, stem
for the remaining treatments (Table 1).
and total forage dry matter was significantly reduced by
Similarly, exposure to weeds for periods of >15 days
the presence of weeds in the sward, even for as little as 15
significantly reduced the number of tillers per plant (4.2
days (P<0.05; Table 2). After 120 days of growth,
and 3.8 for 0 and 15 days, respectively, vs. a mean of 2.7
total DM production was suppressed by 50%, when
for the remaining treatments; P<0.05) (Table 1). Density
weeds remained in the pasture for as little as 15 days
Table 1. Effects of duration of weed competition in a Marandu pasture on height, number of tillers per plant and density of Marandu plants at 120 days after emergence.
Days of coexistence
Height
Number of tillers
Density
(cm)
(No./plant)
(No. of plants/m2)
0
61.7a1
4.2a
40.4
15
42.7b
3.8a
30.3
30
40.5b
3.0b
42.8
45
32.5b
3.0b
32.5
60
30.2b
2.7b
40.5
75
49.0b
2.5b
32.5
90
38.0b
2.3b
38.0
120
32.5b
3.0b
41.5
F Days
3.84*
4.80*
0.86NS
F Block
0.19NS
4.08*
0.14NS
C.V. (%)
26.11
19.23
27.97
1Means followed by the same letter within columns do not differ by the Scott-Knott test at 5% probability.
Tropical Grasslands-Forrajes Tropicales (ISSN: 2346-3775)
90 S.R. de Marchi, J.R. Bellé, C.H. Foz, J. Ferri and D. Martins
Table 2. Effects of duration of weed competition on the production (kg/ha) of green leaf dry matter (GLDM), green stem dry matter (GSDM), dead material dry matter (DMDM) and total dry matter (TDM) of Marandu and reduction in forage offering (ROF) at 120
days after emergence.
Days of
GLDM
GSDM
DMDM
TDM
ROF1 (%)
coexistence
0
1,543a2
1,632a
256
3,431a
-
15
790b
710b
210
1,710b
50.2
30
610b
790b
165
1,565b
54.4
45
470b
480b
136
1,086b
68.3
60
460b
410b
193
1,063b
69.0
75
420b
490b
100
1,010b
70.6
90
530b
340b
111
981b
71.4
120
430b
350b
110
890b
74.1
F Days
5.35*
5.96*
1.41NS
6.01*
-
F Block
0.32NS
0.83NS
0.84NS
0.31*
-
C.V. (%)
49.82
54.02
58.68
47.06
-
1Reduction in forage offering relative to the control (0 days).
2Means followed by the same letter within columns do not statistically differ by the Scott-Knott test at 5% probability.
after emergence. This reduction in yield had increased to
The relationship between total DM yield and number
74% when weeds remained in the pasture for the full 120
of days that weeds remained in the pasture is presented in
days (Table 2), but there were no significant differences
Figure 4. Accordingly the suppressant effects of weeds on
between yields for the differing times that weeds
pasture growth had been expressed by 45 days after
remained in the pasture.
emergence.
3000
3,000
Y = [2,942.3/(1 + e(x-11.0738)/6))] + 890.0
)
Y = ((2942,3) / (1 + e(x-11,0738) / 6)) + 890,0*
-1
R2 = 0.8129
a) ha
R2 = 0,8129
h g (k
2000
2,000
(kg/ ld
r ie
te yats
m s
a
y m
1000
1,000
Dr ry
D
0
0
15
30
45
60
75
90
105
120
Coexi
Coe sten
xistence
ce p
per
e i
r od
iod (d
ay)
(days)
Figure 4. Relationship between forage DM yield of Marandu and duration of weed growth in the pasture.
Tropical Grasslands-Forrajes Tropicales (ISSN: 2346-3775)
Weeds affect establishment of Marandu 91
Discussion
results with most rapid growth of this species between 75
and 120 DAE. It is significant that DM yields of this
This study has shown that weeds can provide severe
species at 120 days were equal to those of Marandu in the
competition for freshly sown stands of Marandu, which
unweeded plots. Sida rhombifolia, despite the low DM
reduces DM production of the grass, even if weeds are
accumulation during virtually the entire period, began
present only for a short period initially, e.g. as little as 15
to show greater vegetative growth only after 90 DAE,
days. It could be concluded that this is due to competition
which is in agreement with findings of Bianco et al.
for available resources, especially nutrients, sunlight and
(2014). When analyzing growth and mineral nutrition of
moisture.
S. rhombifolia, these authors found that the species
Interference of the weeds was most evident on the
actually has slow vegetative growth up to 80 DAE, with
height and number of tillers generated by Marandu plants.
peak DM accumulation occurring after 140 DAE.
Nepomuceno et al. (2007) reported that plant height is not
However, the authors also found that, although initial
an adequate characteristic to evaluate the competition
growth is slow, this species has a high capacity for
between species, since plants subjected to competition
absorbing nutrients from about 35 DAE and has a
prioritize height growth in search of light rather than the
comparatively higher capacity to absorb nutrients than
accumulation of total DM. Vilela (2011) commented that
other weeds. It is important to note that S. obtusifolia and
tillering is a predominant feature in most grasses, and in
H. suaveolens are annuals and S. rhombifolia is a
the case of a pasture, the success of its production is
perennial species. Annual species grow more quickly than
related to good tillering and the consequent occupation of
perennials and this was probably the main factor
spaces between plants, thereby complicating the
suppressing growth of Marandu.
establishment of weed species. In this study the opposite
The different patterns of DM accumulation of the 3
was observed, i.e. the weeds dominated the spaces and
weed species help to explain the similarity of the relative
adversely affected the emergence of tillers in the forage,
importance obtained for the various coexistence periods
even when present for only 15 days. In addition grass
used in this study. This behavior may be correlated with
plants subjected to competition from weed plants for only
competitiveness and the consequent coexistence of the 3
15 days showed lower vertical growth than those free of
weed species in the area. In other words, the weed species
weed competition and failed to compensate when weeds
complement one another, with S. obtusifolia having
were removed.
greater competitive ability in the early growth stages,
Both S. obtusifolia and H. suaveolens are annual
while H. suaveolens and S. rhombifolia are able to grow
weeds and grow rapidly early in life, growing much more
slowly during this period, being more prominent as Senna
rapidly than Marandu and the perennial S. rhombifolia.
matures (Gravena et al. 2002).
This may explain why the main suppressant effect of
With this complementary growth, there was always at
weeds on Marandu growth happened in the first 15 days
least one weed species exerting competitive pressure on
following emergence. These weeds are native to the
Marandu, resulting in similar suppression of grass growth
American continent with wide distribution in South
regardless of when weeds were removed. It must be
America, especially in Brazil, and often infest areas of
remembered that the annual weeds are more adapted to
annual crops, perennials and pastures (Fleck et al. 2003;
the environmental conditions, have characteristics that
Souza et al. 2011). Besides the competition for
make better use of the light, and are more efficient in the
environmental resources such as water, light and
use of nutrients, since they are native in the region, while
nutrients, they can also be toxic to animals if ingested
the majority of forage grasses are exotic in South America
during grazing (Pellegrini et al. 2007; Braga et al. 2012).
(Peron and Evangelista 2004; Benett et al. 2008). Most of
We found that S. obtusifolia grew most rapidly
them are also perennials with slow growth initially.
between 21 and 91 DAE, in agreement with the findings
It is noteworthy that the main broadleaf weed control
of Erasmo et al. (1997), after which growth rate decreased
method in grazing areas is the application of specific
significantly. Those authors suggested that the reduction
selective herbicides. This represents a significant
in growth was due to the natural senescence process of the
operating expense. Our study provides an indication of
species, with resources at that time being directed to
the possible reduction in pasture growth as a result of
reproduction. Studies performed by Gravena et al. (2002)
weed infestation, which may aid a farmer in making a
demonstrated that H. suaveolens accumulated only 31%
decision to spray weeds or to let them grow. It seems that,
of total DM up to 45 DAE, with most rapid growth
if the weeds are not treated early after emergence, it is not
between 60 and 140 DAE. Our findings support these
worth treating them in terms of the effects on pasture
Tropical Grasslands-Forrajes Tropicales (ISSN: 2346-3775)
92 S.R. de Marchi, J.R. Bellé, C.H. Foz, J. Ferri and D. Martins
growth in that season, as they will still have a depressant
Planta Daninha 20:189‒196. DOI: 10.1590/S0100-
effect on pasture growth, even if removed. There is a
small window of opportunity to take action. The decision
Köppen W. 1948. Climatología. Gráfica Panamericana, Buenos
then becomes one of preventing seed set to reduce the soil
Aires, Argentina. https://goo.gl/vqr3vV
seed bank of the weeds for subsequent seasons. Our
Kuva MA; Gravena R; Pitelli RA; Christoffoleti PJ; Alves
PLCA. 2001. Períodos de interferência das plantas daninhas
results show that the reduced growth of Marandu from
na cultura da cana-de-açúcar. II – Capim-braquiária
weed competition was a function not of fewer grass plants
( Brachiaria decumbens). Planta Daninha 19:323‒330. DOI:
but reduced growth of the same number of plants, through
10.1590/S0100-83582001000300003
reduced numbers of tillers and reduced vertical growth.
Lima D; Pozzobon J. 2005. Amazônia socioambiental.
We are not aware of similar findings being reported in the
Sustentabilidade ecológica e diversidade social. Estudos
scientific literature.
Avançados 19:45‒76. DOI: 10.1590/S0103-40142005000
We consider that the regression equation obtained in
this study should be of assistance to all professionals
Macedo MCM. 2009. Integração lavoura e pecuária: O estado
involved in the livestock production chain, especially the
da arte e inovações tecnológicas. Revista Brasileira de
meat production chain, in which the productivity of a
Zootecnia 38:133‒146. DOI: 10.1590/S1516-3598200900
forage area is heavily dependent on the presence or
absence of weeds. It should be used as a component when
Martins D; Triguero LRC; Domingos VD; Martins CC; Marchi
making decisions about weed control measures to ensure
SR; Costa NV. 2007. Seletividade de herbicidas aplicados
that the decision is soundly based economically.
em pós-emergência sobre capim-braquiária. Revista
Brasileira de Zootecnia 36:1969‒1974. DOI:
However, delaying a decision to treat weeds could have
long-term consequences, especially in terms of additional
Mueller-Dombois D; Ellenberg H. 1974. Aims and methods of
seed added to the soil seed bank. As this study lasted for
vegetation ecology. Willey & Sons Inc., New York, USA.
only 120 days, it is difficult to forecast the productivity of
Nepomuceno M; Alves PLCA; Dias TCS; Pavani MCMD.
the pasture over subsequent years. Longer-term studies
2007. Períodos de interferência das plantas daninhas na
are needed to determine how the suppression of growth of
cultura da soja nos sistemas de semeadura direta e
the grass observed here is reflected over the complete life
convencional. Planta Daninha 25:43‒50. DOI: 10.1590/
of the pasture.
Pellegrini LG; Nabinger C; Carvalho PCF; Neumann M. 2007.
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