Tropical Grasslands-Forrajes Tropicales (2017) Vol. 5(2):66– 76 66
Research Paper
Dry matter accumulation and crude protein concentration in
Brachiaria spp. cultivars in the humid tropics of Ecuador
Acumulación de materia seca y concentración de proteína cruda en cultivares
de Brachiaria spp. en el trópico húmedo de Ecuador
JONATHAN R. GARAY1, SANTIAGO JOAQUÍN CANCINO1, PEDRO ZÁRATE FORTUNA1, MARTÍN A.
IBARRA HINOJOSA1, JUAN C. MARTÍNEZ GONZÁLEZ1, RICARDO P. GONZÁLEZ DÁVILA2 AND EUGENIA
G. CIENFUEGOS RIVAS1
1 Universidad Autónoma de Tamaulipas, Facultad de Ingeniería y Ciencias, Ciudad Victoria, Tamaulipas, Mexico.
2 Universidad Tecnológica Equinoccial, Campus Santo Domingo, Investigación y Transferencia de Tecnología, Santo Domingo de los Tsáchilas, Ecuador. www.ute.edu.ec
Abstract
Climatic conditions throughout the year and age of plants affect both yield and quality of forage grasses. In this research, we evaluated the effects of age of regrowth and seasonal conditions on dry matter accumulation and crude protein concentration in 5 cultivars of Brachiaria spp.: Señal, Xaraés, Marandú, Piatá and Mulato II, harvested at 2, 4, 6, 8 and 10 weeks after a uniformity cut, during the rainy and dry seasons. The variables were: total dry matter (TDM), leaf dry matter (LDM) and stem dry matter (SDM) yields, leaf area index (LAI), specific leaf area (SLA) and crude protein (CP) concentration. For TDM yield, in the rainy season there was no significant difference (P>0.05) among cultivars, with mean DM yield over 10 weeks of 6.34 t/ha; however, during the dry season Xaraés presented a higher (P<0.05) yield over 10 weeks than other cultivars (5.09 vs. 3.14‒3.89 t/ha). Overall, mean DM yield in the dry season was only 62% of that in the wet season. In both periods, Señal tended to have the highest SDM yields, while Xaraés had the greatest (P<0.01) LDM yields in the dry season. Mulato II tended to have the highest CP concentrations throughout, especially in the dry season. This study was conducted in plots with plants only 12 weeks old at commencement. However, it indicated that all cultivars performed well and larger-scale studies of longer duration are warranted to test these cultivars under grazing, especially Mulato II, which showed both high dry matter yield and retention of high protein concentration throughout the study.
Keywords: Brachiaria decumbens, Brachiaria brizantha, Brachiaria hybrid cv. Mulato II, leaf area index, specific leaf area.
Resumen
En la finca experimental “El Oasis” de la Escuela de Ingeniería Agropecuaria, Universidad Tecnológica Equinoccial, Campus Santo Domingo, Ecuador, en un suelo Andosol se evaluaron los efectos de la edad de rebrote y la época del año sobre la acumulación de materia seca y la concentración de proteína bruta en 5 cultivares de Brachiaria: Señal ( B. decumbens), Xaraés ( B. brizantha), Marandú ( B. brizantha), Piatá ( B. brizantha) y Mulato II ( Brachiaria híbrido), cosechados a 2, 4, 6, 8 y 10 semanas después de un corte de uniformidad, durante las estaciones lluviosa y seca.
Las variables evaluadas fueron la materia seca (MS) total, MS de hoja y de tallo, el índice de área foliar, el área foliar específica y la concentración de proteína bruta. El rendimiento de MS total a 10 semanas de rebrote (6.34 t/ha en ___________
Correspondence: E. G. Cienfuegos Rivas, Centro Universitario Adolfo
López Mateos, Edificio de Gestión del Conocimiento 4º piso. Cd.
Victoria, CP 87149, Tamaulipas, Mexico.
Email: ecienfue@docentes.uat.edu.mx
Tropical Grasslands-Forrajes Tropicales (ISSN: 2346-3775)
Brachiaria spp. evaluation in Ecuador 67
promedio) en la estación de lluvias no varió entre cultivares (P>0.05) mientras en la estación seca el cv. Xaraés presentó el mayor rendimiento (P<0.05) en comparación con los demás cultivares (5.09 vs. 3.14‒3.89 t/ha). El rendimiento de MS total en la época seca fue sólo el 62% del obtenido en la época de lluvia. En ambos períodos, el cv. Señal tendió a tener los rendimientos de MS de tallos más altos, mientras que el cv. Xaraés presentó los mayores rendimientos de MS
de hojas (P<0.01) en la estación seca. El cv. Mulato II tendió a tener las mayores concentraciones de proteína bruta en ambas épocas, especialmente en la seca. Este estudio se realizó en parcelas con plantas de sólo 12 semanas de edad al inicio. Sin embargo, indicó que todos los cultivares se comportaron satisfactoriamente y estudios a mayor escala y de mayor duración se justifican para probar estos cultivares bajo pastoreo, especialmente el cv. Mulato II que mostró tanto un alto rendimiento de MS como una retención de alta concentración de proteína a lo largo del estudio.
Palabras clave: Área foliar específica, Brachiaria decumbens, Brachiaria brizantha, Brachiaria híbrido cv. Mulato II, índice de área foliar.
Introduction
seasonal changes (Fagundes et al. 2005) on the pattern of
growth, quality and chemical composition of pasture
Poor grassland productivity is one of the most important
plants, in order to optimize their use and plan an
limitations in the dual-purpose cattle system in the
appropriate
agronomic
management
strategy
for
Ecuadorian tropics (Avellaneda et al. 2008), because most
grasslands (Avellaneda et al. 2008). Based on the above,
grazing areas are sown with forage species such as
this research aimed to evaluate the effects of plant
Brachiaria humidicola, Brachiaria decumbens and
regrowth age and seasonal conditions on the
Brachiaria brizantha (Vera 2004). These grasses have
accumulation of dry matter and crude protein
limitations in productivity, adaptability and persistence in
concentration in 5 cultivars of Brachiaria spp. in the
these environments; in addition, they are susceptible to
humid tropics of Ecuador.
the spittlebug of pastures caused by Aeneolamia spp.
(Cardona et al. 2006) and foliar fungi such as Rhizoctonia
Materials and Methods
solani, which significantly reduce productivity (Álvarez
et al. 2013). However, new cultivars of the genus
The research was conducted under field conditions from
Brachiaria have been released to the market as options to
December 2011 to November 2012, at the experimental
overcome the problems observed in traditional forages,
farm “El Oasis”, property of the Escuela de Ingeniería
thus providing better fodder options (Pizarro et al. 2013).
Agropecuaria
of
the
Universidad
Tecnológica
In Ecuador, several cultivars of Brachiaria spp. are
Equinoccial,
Campus
Santo
Domingo,
Ecuador
available that have potential for increasing the
(00°13'20' S, 79°15'39'' W; 406 masl). The experimental
productivity of existing grass production systems (Faría
site has a predominantly humid tropical climate, with
Mármol 2006; Miles 2006). Jácome and Suquilanda
annual average temperature of 23.4 °C and annual rainfall
(2014) indicated that cultivars Mulato I and Xaraés are
of 2,600‒3,500 mm with 2 seasons, defined as rainy and
well accepted by farmers because of their high nutritional
dry (SENPLADES 2015). The monthly rainfall and mean
value, adaptation to a range of soils and resistance to or
maximum and minimum temperatures during the
tolerance of pests and diseases (Cardona et al. 2006; Argel
evaluation period are reported in Figure 1.
2008).
In this research 5 Brachiaria cultivars were used:
The productive capacity of forage species can be
Señal ( B. decumbens, considered as the control since
modified by changing various factors, such as: using
it is most widely cultivated in the area); Marandú
different genotypes or cultivars; modifying the
( B. brizantha), Piatá ( B. brizantha), Mulato II ( Brachiaria
agronomic management and age of the plants at harvest;
hybrid) and Xaraés ( B. brizantha); and these were
and by weather conditions throughout the year (Zaragoza
harvested at 5 growth stages (2, 4, 6, 8 and 10 weeks after
et al. 2009; Lara et al. 2010). It is therefore important to
an initial harvest) during the rainy (March‒May) and dry
assess the dynamics of herbage accumulation of
(September‒November) seasons to monitor the rate of
different pasture species and to understand the impact of
DM accumulation over time and assess quality aspects.
Tropical Grasslands-Forrajes Tropicales (ISSN: 2346-3775)
68 J.R. Garay, S. Joaquín, P. Zárate, M.A. Ibarra, J.C. Martínez, R.P. González and E.G. Cienfuegos
35
900
800
30
700
)
C)
25
m
(°
600
m(
20
ure
500
on i
400
at
15
perat
pit
300
ci
em 10
re
T
200
P
5
100
0
0
jan feb mar apr may jun
jul aug sep oct nov dec
Precipitation
Temp. Max.
Temp. Min.
Figure 1. Monthly precipitation and mean maximum and minimum temperatures during 2012 at the Climatological Station of the Universidad Tecnológica Equinoccial, Campus Santo Domingo, Ecuador.
A randomized complete block design in an
season, observations commenced 2 weeks after each
arrangement in divided plots was used, where the large
uniformity cut to measure: accumulation of total (TDM),
plot was the cultivar and the subplots the ages of
leaf (LDM) and stem (SDM) dry matter; plant height
regrowth. On 3 December 2011, seeds of each cultivar
(PH); leaf area index (LAI); specific leaf area (SLA);
were placed in bags (3 seeds/bag) of black polyethylene
and crude protein concentration (CP). During each
with a capacity of approximately 2 kg of soil, to ensure
sampling for the relevant cutting treatment we measured
one plant survived per bag and placed in a greenhouse. At
the height of plants from ground level to ligule of the
6 weeks after seedling emergence (21 January 2012; 7
fully developed leaf and harvested the forage at 15 cm
weeks after sowing), the plants were transplanted to large
above ground level from the relevant 1 m2 subplot
plots of 5 x 5 m (25 m2), leaving an intra-row and inter-
(4 plants). The harvested forage (green matter) was
row spacing of 0.50 m. The useful area within each large
weighed on a precision scale (Model PB3002-S, Mettler
plot was 3 x 3 m, divided into 9 quadrants of 1 m2
Toledo) and 2 subsamples were taken, the first
(subplots), of which 5 subplots were randomly selected to
(approximately 200 g) to define the proportions of leaf
represent each age of regrowth (2, 4, 6, 8 and 10 weeks).
(leaf blade + sheath) and stem after separating these
The soil of the experimental site is of volcanic origin
components. Leaves from this subsample were used for
(Andosol) and a soil sample was taken using a 5-point
leaf area estimation as well. A multifunctional printer
method to 20 cm depth to provide the physicochemical
scanner (HP Photosmart D110) was employed using the
analyses shown in Table 1. All plots were fertilized after
methodology reported by Rincón et al. (2012). The
transplanting with 120 kg N/ha (as urea), 60 kg P/ha (as
second subsample (approximately 1 kg) was used to
Daphos), 70 kg K/ha (as KCl), 60 kg Mg/ha (as
determine CP concentration by the Kjeldahl method (N x
magnesium oxide) and 50 kg S/ha (as ammonium sulfate).
6.25) (AOAC 2000); CP% was determined only for 4, 6
In the sixth week after transplantation the plants
and 8 week cuttings. All samples were dried in a forced-
were 80‒100 cm tall with 45‒65 tillers/plant; senescent
air oven at 65 °C for 48 h to estimate the dry matter (DM)
material was obvious in the lower stratum, so we
concentration and calculate DM yields.
applied an initial uniformity cut on 3 March 2012 to 15
The data were analyzed in time within season by using
cm above ground level. The evaluation during the rainy
PROC GLM of SAS (SAS Institute 2010), in a complete
season then followed. At the end of this period (12 May
randomized block design in an arrangement in divided
2012), the plots were allowed to stand for 15 weeks,
plots. Tukey’s Studentized range tests (P≤0.05) were
when a second uniformity cut was applied on 1 September
performed, when treatments were significantly different
2012. The dry season evaluation then followed. In each
in each season.
Tropical Grasslands-Forrajes Tropicales (ISSN: 2346-3775)
Brachiaria spp. evaluation in Ecuador 69
Table 1. Chemical1 characteristics of the soil used in the experiment2.
pH
OM3
NH4
P
S
Fe
Cu
Zn
Mn
B
K
Ca
Mg
(%)
(mg/kg)
(cmol/kg)
5.9
2.2
41.0
6.5
6.3
42.0
5.6
1.9
2.8
0.3
0.3
8.3
2.9
1Obtained in the Chemistry Laboratory, Universidad Tecnológica Equinoccial, Campus Santo Domingo.
2The analysis to determine the phosphorus concentration in the soil was performed by the method of Olsen modified with a solution of sodium bicarbonate and EDTA adjusted to pH 8.5 with 10N NaOH.
3The organic matter (OM) analysis was performed using the method of Walkley Black, suitable for the conditions of Ecuador.
Results
with the remaining cultivars producing 3.14‒3.89 t
DM/ha. Average accumulation of TDM during the dry
Total dry matter accumulation
season was 62% of that produced in the rainy season.
Accumulation of total dry matter (TDM) followed an
Leaf dry matter accumulation
exponential pattern in both rainy and dry seasons (Table
2). There were no significant differences (P>0.05) in
Leaf dry matter (LDM) yield during the rainy season
TDM accumulation among cultivars of Brachiaria during
varied between cultivars at the various cutting ages but at
the rainy season, with yields ranging from 5.83 to 6.87 t
the tenth week, there were no significant differences in
DM/ha (mean 6.34 t DM/ha) over the 10 week period.
leaf yield between cultivars (P>0.05; Table 3). On the
However, in the dry season differences between cultivars
other hand, during the dry season, significant differences
(P<0.01) were observed in each of the regrowth periods.
(P<0.05) in leaf yield between cultivars at all ages of
While there was little consistency in which cultivars were
regrowth were observed. Towards the end of the dry
superior within particular cutting frequencies, cultivar
season (8 and 10 week cuttings) Xaraés produced more
Xaraés accumulated the greatest amount of TDM during
leaf (P<0.05) than most other cultivars. Dry season leaf
the later part of the dry season and produced the highest
yield at the 10 week cutting varied from 4.28 t DM/ha
DM yield during the dry season period (5.09 t DM/ha),
(Xaraés) to 2.50 t DM/ha (Marandú) (P<0.001).
Table 2. Total dry matter yields at different ages of regrowth of 5 Brachiaria cultivars during the rainy (March‒May) and dry (September‒November) seasons in humid tropical conditions of Ecuador.
Cultivar
Total dry matter (t/ha)
Rainy season
Dry season
Age of regrowth (weeks)
Age of regrowth (weeks)
2
4
6
8
10
2
4
6
8
10
Señal
0.24
0.96
2.96
4.02
6.87
0.16
0.39
0.75
1.98
3.69
Marandú
0.24
0.85
2.54
4.00
5.83
0.23
0.42
0.73
1.59
3.14
Mulato II
0.29
1.31
2.66
4.33
6.57
0.13
0.28
0.64
1.95
3.76
Piatá
0.28
1.13
2.36
4.36
6.14
0.13
0.41
0.91
1.93
3.89
Xaraés
0.32
1.28
3.16
4.49
6.27
0.13
0.41
0.87
2.49
5.09
Mean
0.27
1.11
2.73
4.24
6.34
0.16
0.38
0.78
1.99
3.92
LSD1
0.09
0.29
1.05
1.59
2.38
0.04
0.1
0.19
0.54
1.09
LS2
0.058
<0.001
0.177
0.812
0.686
<0.001
0.005
0.004
0.003
0.001
1Least Significant Difference (Tukey P≤0.05).
2Level of significance.
Tropical Grasslands-Forrajes Tropicales (ISSN: 2346-3775)
70 J.R. Garay, S. Joaquín, P. Zárate, M.A. Ibarra, J.C. Martínez, R.P. González and E.G. Cienfuegos Table 3. Leaf dry matter yields at different ages of regrowth of 5 Brachiaria cultivars during the rainy (March‒May) and dry (September‒November) seasons in humid tropical conditions of Ecuador.
Cultivar
Leaf dry matter (t/ha)
Rainy season
Dry season
Age of regrowth (weeks)
Age of regrowth (weeks)
2
4
6
8
10
2
4
6
8
10
Señal
0.21
0.75
1.71
1.85
3.13
0.16
0.35
0.66
1.55
2.76
Marandú
0.24
0.79
1.76
2.49
3.46
0.23
0.42
0.72
1.48
2.50
Mulato II
0.29
1.26
1.90
2.66
3.85
0.13
0.28
0.63
1.88
3.19
Piatá
0.28
0.97
1.60
2.60
3.21
0.13
0.41
0.88
1.66
3.02
Xaraés
0.32
1.20
2.45
3.50
4.18
0.13
0.41
0.87
2.34
4.28
Mean
0.27
1.00
1.88
2.62
3.57
0.16
0.37
0.75
1.78
3.15
LSD1
0.08
0.24
0.76
0.93
1.17
0.04
0.10
0.19
0.52
1.01
LS2
0.017
<0.001
0.029
0.002
0.072
<0.001
0.004
0.002
0.001
0.001
1Least Significant Difference (Tukey P≤0.05).
2Level of significance.
Stem dry matter accumulation
respectively), while Marandú and Mulato II had the least
(0.64 and 0.57 t DM/ha) (P<0.001).
As for leaf production, stem dry matter (SDM)
accumulation during the rainy season varied between
Plant height
cultivars from the second to the sixth week (P<0.01). At
the 8 and 10 week cuts cultivars Señal and Piatá tended to
During the rainy season plant height of the different
have the highest stem yields and Xaraés the lowest but
cultivars varied but by the eighth and tenth weeks Señal
differences were not significant (P>0.05; Table 4). During
was shorter than all other cultivars (P<0.001; Table 5).
the dry season, SDM accumulation followed an expo-
During the dry season Piatá, Señal and Xaraés progres-
nential pattern, with greatest stem production between the
sively showed superiority in height over the other
8 and 10 week cuts. At the 10 week cut, cultivars Señal
cultivars and by the tenth week Piatá and Xaraés were
and Piatá had the highest SDM (0.93 and 0.87 t DM/ha,
taller than all others (P<0.01).
Table 4. Stem dry matter yields at different ages of regrowth of 5 Brachiaria cultivars during the rainy (March‒May) and dry (September‒November) seasons in humid tropical conditions of Ecuador.
Cultivar
Stem dry matter (t/ha)
Rainy season
Dry season
Age of regrowth (weeks)
Age of regrowth (weeks)
2
4
6
8
10
2
4
6
8
10
Señal
0.03
0.20
1.22
1.69
2.81
-
0.04
0.09
0.41
0.93
Marandú
-
0.06
0.78
1.39
1.95
-
-
0.02
0.11
0.64
Mulato II
-
0.05
0.76
1.43
2.09
-
-
0.01
0.08
0.57
Piatá
-
0.16
0.76
1.62
2.61
-
-
0.03
0.27
0.87
Xaraés
-
0.08
0.71
1.00
1.86
-
-
0.01
0.15
0.80
Mean
-
0.11
0.84
1.43
2.26
-
-
0.03
0.21
0.76
LSD1
-
0.07
0.37
0.82
0.95
-
-
0.02
0.10
0.22
LS2
-
<0.001
0.005
0.127
0.068
-
-
<0.001
<0.001
0.001
1Least Significant Difference (Tukey P≤0.05).
2Level of significance.
Tropical Grasslands-Forrajes Tropicales (ISSN: 2346-3775)
Brachiaria spp. evaluation in Ecuador 71
Table 5. Plant height at different ages of regrowth of 5 Brachiaria cultivars during the rainy (March‒May) and dry (September‒
November) seasons in humid tropical conditions of Ecuador.
Cultivar
Plant height (cm)
Rainy season
Dry season
Age of regrowth (weeks)
Age of regrowth (weeks)
2
4
6
8
10
2
4
6
8
10
Señal
43.1
53.5
81.8
95.4
80.2
29.6
42.5
70.4
91.3
77.5
Marandú
40.3
48.8
77.2
117.1
129.8
32.4
30.0
41.5
55.0
67.8
Mulato II
47.7
57.3
83.5
108.3
129.2
32.5
31.2
43.1
57.9
75.8
Piatá
45.8
63.8
98.8
132.1
137.1
32.0
39.2
65.7
95.4
105.5
Xaraés
54.5
71.6
91.2
126.3
137.8
32.3
48.3
71.0
91.3
103.5
Mean
46.3
59.0
86.5
115.8
122.8
31.8
38.2
58.4
78.2
86.0
LSD1
9.4
10.6
14.3
10.1
19.8
10.1
9.1
16.5
16.8
23.8
LS2
0.005
0.001
0.003
<0.001
<0.001
0.879
<0.001
<0.001
<0.001
<0.001
1Least Significant Difference (Tukey P≤0.05).
2Level of significance.
Leaf area index
the lowest SLA throughout the wet season, while Señal,
Mulato II and Marandú presented the highest values. In
During the rainy season, the leaf area index (LAI)
the dry season, cultivar differences again emerged with
followed a linear pattern for all cultivars, increasing from
Mulato II, Marandú and Señal having the greatest SLA
a mean of 0.6 at week 2 to 5.3 at week 10 (Table 6). The
and Xaraés and Piatá the lowest (P<0.01).
cultivars Mulato II and Xaraés reached the highest LAI at
week 10 of 6.6 and 5.8, respectively. Throughout the wet
Crude protein concentration
season Piatá had lower LAI than most other cultivars
(P<0.001). During the dry season, LAI followed an
Data for weeks 4, 6 and 8 on whole plant samples are
exponential pattern with the highest increase from the
presented in Table 8. Differences in crude protein
sixth week. As for the wet season, Piatá showed lower
concentration (P<0.05) between cultivars were observed
LAI than Xaraés and Mulato II by week 10 (P<0.05).
in both rainy and dry seasons, where Mulato II presented
the highest concentration at most observations. In both
Specific leaf area
seasons, mean crude protein concentration decreased as
the regrowth age increased, declining from 14.1% to 9.1%
Specific leaf area (SLA) declined in all cultivars during
in the wet season and from 12.6% to 7.6% in the dry
both rainy and dry seasons (Table 7). Piatá tended to have
season.
Table 6. Leaf area index at different ages of regrowth of 5 Brachiaria cultivars during the rainy (March‒May) and dry (September‒
November) seasons in humid tropical conditions of Ecuador.
Cultivar
Leaf area index
Rainy season
Dry season
Age of regrowth (weeks)
Age of regrowth (weeks)
2
4
6
8
10
2
4
6
8
10
Señal
0.5
2.0
3.2
3.7
5.1
0.4
0.9
1.2
2.7
4.8
Marandú
0.6
1.8
3.1
4.3
5.4
0.7
1.0
1.6
2.5
4.4
Mulato II
0.8
2.6
3.8
4.7
6.6
0.3
0.8
1.4
3.6
5.8
Piatá
0.5
1.3
2.1
3.4
3.8
0.3
0.7
1.4
2.2
3.6
Xaraés
0.7
1.9
3.5
4.9
5.8
0.3
0.9
1.6
3.6
5.9
Mean
0.6
1.9
3.1
4.2
5.3
0.4
0.9
1.4
2.9
4.9
LSD1
0.2
0.4
1.0
1.1
1.2
0.2
0.2
0.3
0.9
2.2
LS2
0.001
<0.001
0.002
0.004
<0.001
<0.001
0.045
0.016
0.001
0.03
1Least Significant Difference (Tukey P≤0.05).
2Level of significance.
Tropical Grasslands-Forrajes Tropicales (ISSN: 2346-3775)
72 J.R. Garay, S. Joaquín, P. Zárate, M.A. Ibarra, J.C. Martínez, R.P. González and E.G. Cienfuegos Table 7. Specific leaf area at different ages of regrowth of 5 Brachiaria cultivars during the rainy (March‒May) and dry (September‒
November) seasons in humid tropical conditions of Ecuador.
Cultivar
Specific leaf area (cm2/g)
Rainy season
Dry season
Age of regrowth (weeks)
Age of regrowth (weeks)
2
4
6
8
10
2
4
6
8
10
Señal
229
246
181
190
151
248
232
173
163
164
Marandú
242
216
168
163
145
273
221
213
158
162
Mulato II
268
190
187
165
162
238
279
210
178
168
Piatá
156
129
125
124
112
221
173
148
125
112
Xaraés
207
148
134
130
132
237
213
170
142
129
Mean
221
186
159
154
140
243
224
183
153
147
LSD1
29
30
41
40
34
85
39
25
28
27
LS2
<0.001
<0.001
0.001
0.001
0.005
0.433
<0.001
<0.001
<0.001
<0.001
1Least Significant Difference (Tukey P≤0.05).
2Level of significance.
Table 8. Crude protein concentration at different ages of regrowth of 5 Brachiaria cultivars during the rainy (March‒May) and dry (September‒November) seasons in humid tropical conditions of Ecuador.
Cultivar
Crude protein concentration (%)
Rainy season
Dry season
Age of regrowth (weeks)
Age of regrowth (weeks)
4
6
8
4
6
8
Señal
13.4
11.2
9.0
11.6
7.3
6.5
Marandú
14.0
12.1
8.8
13.4
8.6
8.1
Mulato II
14.6
12.5
10.1
14.3
10.1
10.2
Piatá
13.8
10.9
8.9
12.2
8.3
6.8
Xaraés
14.6
11.1
8.6
11.6
7.4
6.5
Mean
14.1
11.6
9.1
12.6
8.3
7.6
LSD1
0.9
1.1
0.8
0.9
1.3
3.4
LS2
0.007
0.003
0.001
<0.001
<0.001
0.022
1Least Significant Difference (Tukey P≤0.05).
2Level of significance.
Discussion
The absence of cultivar differences in total DM
production during the rainy season in this study was
This plot study has provided useful information on the
similar to the findings of Rojas-Hernández et al. (2011)
potential of the Brachiaria cultivars for use in pastures of
for B. decumbens, B. brizantha cv. Libertad, B. hybrid
humid tropical Ecuador. While the grasses were planted
cv. Mulato I and cultivars of B. humidicola. Those authors
from seed, were only 12 weeks old at commencement of
also failed to demonstrate any significant differences in
observations and the study was in only a single year, the
total DM production. However, the differences we
excellent growth obtained and CP levels maintained
showed in proportions of leaf and stem in the different
indicate that these pastures can be very productive under
cultivars are important, as we showed higher production
these conditions. In fact, the DM yields obtained over
of leaves and higher CP concentration than Reyes-Purata
only 10 weeks in pastures that were only 12 weeks old at
et al. (2009). The reduction in growth in these cultivars
commencement are quite remarkable. Further studies
during the dry season was not surprising, as the major
under field conditions would clarify how well these
climatic factors that determine forage production are
preliminary findings can be extrapolated to commercial
precipitation and temperature (Gerdes et al. 2000;
situations.
Cuadrado et al. 2004). Rainfall in the rainy season and
Tropical Grasslands-Forrajes Tropicales (ISSN: 2346-3775)
Brachiaria spp. evaluation in Ecuador 73
hence soil moisture was much higher than in the dry
The differences among cultivars for LAI may be
season and minimum temperatures were also lower in the
because some species such as B. decumbens are shorter
dry season. The reduction in TDM yield in the dry season
than B. brizantha, and there is a positive correlation
was somewhat lower than the 50% reduction reported by
between plant height and LAI (Guenni et al. 2005). In
Benítez et al. (2007). This marked reduction in yield
addition, LAI increases as the plant grows (Gómez-
accompanied by a drop in CP concentration indicates the
Carabalí et al. 1999), and this increase is closely related
reduced carrying capacity of these pastures during the dry
to tillering of the crop and soil cover (Rincón et al. 2007;
season.
Ramírez-García et al. 2012). Therefore, as LAI of the
The differences between cultivars in leaf DM yield we
pasture increases, the amount of light that reaches the
found in this study may be due to B. decumbens and
ground will be reduced, which can prevent or retard weed
B. brizantha having different rates of elongation in leaves
growth.
(Dias-Filho and Carvalho 2000). In this regard,
Furthermore, it has been reported that SLA in
elongation rates in leaves of 2.5 and 3.5 cm/d and leaf
Brachiaria cultivars varies according to species; Baruch
percentages in total DM of 54 and 77% in B. decumbens
and Guenni (2007) reported that at 4 weeks of age SLA in
and B. brizantha, respectively, have been reported by
B. decumbens and B. brizantha were 300 and 270 cm2/g,
Guenni et al. (2005). In addition, Hare et al. (2009)
respectively. Also, it has been reported that, as the height
reported that Xaraés and Mulato II have higher foliar
and age of the plant increase, SLA decreases (Gómez et
DM yields than other Brachiaria cultivars, especially
al. 2012), as it did in our study, because there is an
during the dry season. Similarly, Gerdes et al. (2000)
increment in the thickness of the leaves. Grasses with
reported a significant decrease in the accumulation of
greater SLA have thinner leaves and higher concen-
total DM during the period of minimum precipitation,
trations of nitrogen (Pérez et al. 2004) and higher rates of
with as much as 98% of the accumulation corresponding
photosynthesis (Reich et al. 1997), while a high SLA is
to leaf DM.
related to greater palatability and consumption by animals
The pattern of stem DM accumulation during both
(Lloyd et al. 2010; Zheng et al. 2014).
periods would have been determined by environmental
The CP values obtained in this study for Señal
conditions that affected growth of the cultivars. Stem
were higher than those reported by Alvarado et al. (1990)
production during the dry season is reduced (Cab et al.
at 6 and 9 weeks of age (9.4 and 8.8%, respectively),
2008) due to stress caused by soil moisture deficiency,
while the values obtained in Mulato II were similar to
curbing the growth of the plant and reducing stem growth
those found by Castillo et al. (2006) at 3 weeks (15%).
(Cruz et al. 2011a). Cruz et al. (2011b) reported that
The values obtained in Xaraés, Marandú and Piatá were
season has a marked effect on the relative growth of leaf
similar during the rainy season to, and higher in the dry
and stem, and differences between stem elongation rates
season than, those obtained by Pérez et al. (1999) in
of 1.2, 0.8 and 0.6 mm/stem/d in Señal, Xaraés and
B. brizantha at 6 and 9 weeks (11.9 and 8.6%,
Marandú, respectively, have been reported by Paciullo et
respectively). Water deficiency stress can have a negative
al. (2011). The marked reduction in stem growth in the
effect on Brachiaria cultivars, decreasing the con-
dry season results in increases in leaf:stem ratios in this
centration of CP. In this regard, Cuadrado et al. (2004)
season as found in this study. Leaf:stem ratios also
reported that at 24 days of regrowth CP concentration in
declined significantly as plants matured and the
the wet season was higher than in the dry season for
proportion of stem in the forage increased.
Marandú (10.5 vs. 9.3%), Señal (15.4 vs. 9.2%) and
Plant height was affected to a greater extent by
Xaraés (11.5 vs. 8.2%). Increasing age of the plant also
seasonal conditions than by cultivar. Marandú has been
decreases the concentration of CP in forage because of
shown to be quite susceptible to stress caused by soil
accumulation of dry matter (resulting in dilution of
water deficiency, presenting taller plants in the rainy
nutrients), increase in stem DM and decline in the
season (67 cm) and shorter ones in the dry season (36 cm)
proportion of leaf (Juárez-Hernández et al. 2004; Reyes-
at 35 d of regrowth (Gerdes et al. 2000). On the other
Purata et al. 2009), as shown in our study. All cultivars
hand, B. decumbens presented lower height, due to its
had CP concentrations above 7% which is considered the
decumbent growth habit, which is characteristic of this
minimum, below which intake by ruminants could be
species (Pérez et al. 1999). In this study, B. brizantha
suppressed (Lazzarini et al. 2009). The choice of cultivar
cultivars were taller than the Brachiaria hybrid and B.
to use could depend on a range of factors including DM
decumbens, which agrees with what was reported by
yield of leaf, CP concentration, rate of regrowth, response
Gómez et al. (2000).
to fertilizer etc.
Tropical Grasslands-Forrajes Tropicales (ISSN: 2346-3775)
74 J.R. Garay, S. Joaquín, P. Zárate, M.A. Ibarra, J.C. Martínez, R.P. González and E.G. Cienfuegos Conclusions
Avellaneda C; Cabezas JF; Quintana G; Luna R; Montañez O;
Espinoza I; Zambrano S; Romero D; Vanegas J; Pinargote
While the dry season negatively affected the production
E. 2008. Comportamiento agronómico y composición
and nutritional value of forage of all grasses evaluated, the
química de tres variedades de Brachiaria en diferentes
edades de cosecha. Ciencia y Tecnología 1:87‒94.
most outstanding cultivars in terms of leaf yield, leaf area
index and specific leaf area were: Mulato II, Marandú and
Baruch Z; Guenni O. 2007. Irradiance and defoliation effects in
Xaraés. Xaraés certainly showed the best tolerance of dry
three species of the forage grass Brachiaria. Tropical
conditions, while performing well in terms of total DM
Grasslands 41:269‒276. https://goo.gl/ttgvtU
and leaf production in the rainy season. However, Mulato
Benítez D; Fernández JL; Ray J; Ramírez A; Torres V; Tandrón
II showed high DM yield and nutritional value over time,
I; Díaz M; Guerra J. 2007. Factores determinantes en la
which supports its further evaluation in grass production
producción de biomasa en tres especies de pastos en
systems in humid tropical conditions, especially as good
sistemas racionales de pastoreo en el Valle del Cauto, Cuba.
CP levels (11‒14%) were maintained for long periods in
Revista Cubana de Ciencia Agrícola 41:231‒235.
both rainy and dry seasons. This was a plot study and
plants were only 12 weeks old when observations
Cab F; Enríquez J; Pérez J; Hernández A; Herrera J; Ortega E;
commenced, but the results do indicate that all cultivars
Quero A. 2008. Potencial productivo de tres especies de
performed well and further evaluation of the more
Brachiaria en monocultivo y asociadas con Arachis pintoi
promising cultivars under field conditions, particularly
en Isla, Veracruz. Técnica Pecuaria en México 46:317–332.
under grazing, is warranted.
Cardona C; Sotelo G; Miles JW. 2006. Resistencia en
Brachiaria a especies de salivazo: Métodos, mecanismos y
avances. Pasturas Tropicales 28(1):30‒35. https://goo.gl/
Acknowledgments
Castillo MS; Vélez M; Rosas JC; Trabanino R. 2006.
We thank the Consejo Nacional de Ciencia y Tecnología
Producción y composición de los cultivares Mulato I y II de
(CONACYT) for the grant that made possible the stay of
Brachiaria híbrido inoculados con micorriza y Trichoderma
the first author in Ecuador. Our thanks to the Universidad
harzianum. Ceiba 47:25‒32. DOI: 10.5377/ceiba.v47i1-
Tecnológica Equinoccial, Campus Santo Domingo
(Ecuador) and the Facultad de Ingeniería y Ciencias of the
Cruz PI; Hernández A; Enríquez JF; Mendoza SI; Quero AR;
Universidad Autónoma de Tamaulipas (Mexico) for the
Joaquín BM. 2011a. Desempeño agronómico de genotipos
facilities provided to make this research possible.
de Brachiaria humidicola (Rendle) Schweickt en el trópico
húmedo de México. Revista Fitotecnia Mexicana 34:123‒
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(Received for publication 15 September 2016; accepted 02 May 2017; published 31 May 2017)
© 2017
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