Tropical Grasslands-Forrajes Tropicales (2017) Vol. 5(2):8593 85

DOI: 10.17138/TGFT(5)85-93

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.

www.fcav.unesp.br

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

83582002000200004

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

200004

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

1300015

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

10.1590/

S1516-35982007000900004

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.

S0100-83582007000100005

Pellegrini LG; Nabinger C; Carvalho PCF; Neumann M. 2007.

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Tropical Grasslands-Forrajes Tropicales (ISSN: 2346-3775)