52a Reunião Anual da Sociedade Brasileira de
Zootecnia
Zootecnia: Otimizando Recursos e Potencialidades
Belo Horizonte – MG, 19 a 23 de Julho de 2015
Relação entre altura de dossel com índice de área foliar e interceptação luminosa em Brachiaria decumbens
Stapf. sob monocultivo e em sistemas silvipastoris
Diego de Lima Coêlho2, Alexandre Carneiro Leão de Mello3, Márcio Vieira da Cunha3, José Carlos Batista
Dubeux Júnior4, Erinaldo Viana de Freitas5, Amanda Maria Gallindo dos Santos6, Janerson José Coelho7
1
MS thesis of the first author, funded by CNPq
MS student. Post Graduation Program in Animal Science – UFRPE, Recife, Brazil, CNPq scholar. e-mail:[email protected]
3
Teacher. Department of Animal Science - UFRPE, Recife. Brazil, CNPq scholar
4
Teacher. University of Florida, North Florida Research and Education Center, Mariana, USA
5
Research. Agronomic Institute of Pernambuco – IPA, Itambé, Brazil
6
PhD student. Integrated PhD Program in Animal Science – UFRPE, Recife, Brazil, FACEPE scholar
7
MS in Animal Science – UFRPE, Recife, Brazil
2
Resumo: O objetivo deste estudo foi avaliar a relação entre interceptação luminosa (IL) e índice de área foliar
(IAF), estimados indiretamente a partir de três equipamentos com altura de dossel de Brachiaria decumbens Stapf.
em monocultivo e em sistemas silvipastoris na Zona da Mata de Pernambuco. Os tratamentos experimentais
consistiram em B. decumbens em monocultivo; B. decumbens + M. caesalpiniifolia Benth. e B. decumbens + G.
sepium, em delineamento experimental casualizado em blocos, com três repetições. Correlações de Pearson foram
testadas utilizando o SAS 9.3. Correlações significativas (P<0.01) entre altura do dossel de B. decumbens e IAF
foram obtidas nos tratamentos estudados, com uso de AccuPAR e LAI-2000. Correlações significativas entre altura
de dossel e IL foram encontradas (P<0.01 e ≤0.05, respectivamente) quando utilizou-se LAI-2000 e AccuPAR, em
todos os tratamentos experimentais. A maior parte das correlações existentes entre altura de dossel com IAF e IL,
nos equipamentos, foram moderadas ou fracas.
Palavras–chave: AccurPar , CI-120, LAI-2000, pastagens
Relationship between canopy height with leaf area index and light interception in Brachiaria decumbens
Stapf. under monoculture and silvopastoral systems
Abstract: The objective of this study was to evaluate the relationship between light interception (LI) and leaf area
index (LAI) measured indirectly using three equipment, with canopy height of Brachiaria decumbens Stapf. in
monoculture and in silvopastoral systems in Pernambuco Forest Zone. The experimental treatments were
Brachiaria decumbens under monoculture; B. decumbens + M. caesalpiniifolia Benth. and B. decumbens + G.
sepium, in randomized block design with three replications. Pearson’s correlations were tested using SAS 9.3.
Significant correlations (P<0.01) between canopy height of B. decumbens and LAI were obtained in the treatments
studied, using AccuPAR and LAI-2000. For correlations between canopy height and IL there were significance
(P<0.01 and ≤0.05) when using LAI-2000 and AccuPAR, in all experimental treatments. Most of the correlations
between canopy height with LAI and LI in the equipment were moderate or weak.
Keywords: AccurPAR, CI-120, LAI-2000, pastures
Introduction
Brachiaria spp. occupies about 70% of the cultivated areas of the grasslands in Brazil. Among these species,
Brachiaria decumbens Stapf. is the most used for grazed pastures in Brazil, due to some specifics productive and
ecological characteristics, such as, the potential to produce under acidic soils and low soil P concentration. It also is
easily propagated by seeds and shade tolerant (Dias, 2007). Therefore, this specie is an excellent option to use in
silvopastoral systems in the tropics. In these systems, some legume trees have been used in combination with
herbaceous forage grasses. Sabiá (Mimosa caesalpiniifolia Benth.) and gliricídia [Gliricidia sepium (Jacq.) Steud.]
are trees recognized for their N2-fixing capacity, nutritional value, and other uses. Pasture structure characterization
is important for a better understanding of plant responses to environment and management. Interrelationships
between plant and environment are governed by sward characteristics and its interaction with the surrounding
environment, and light plays an important role in plant growth (Norman & Campbell, 1989). Light interception (LI)
and Leaf Area Index (LAI) are two important factors to consider when managing forage species, however LI and
LAI are characteristic difficult to measure at the farm level, due to the high cost of the equipment, and technical
feasibility of the process. The aim of this research was to evaluate the relationship between LI and LAI, estimated
indirectly, with canopy height of Brachiaria decumbens Stapf. growing under monoculture and silvopastoril
systems in Pernambuco Forest Zone.
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52a Reunião Anual da Sociedade Brasileira de
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Zootecnia: Otimizando Recursos e Potencialidades
Belo Horizonte – MG, 19 a 23 de Julho de 2015
Material and Methods
The experiment was carried out at Experimental Station of Itambé, Itambé district, Pernambuco – Brazil
(7º23’S e 35º10’W), using as experimental area forage plots measuring 1,0 ha (43,5 x 230,0 m), with water trough
and mineral salt available. Experimental treatments were Brachiaria decumbens under monoculture; B. decumbens
+ M. caesalpiniifolia Benth. (sabiá) and B. decumbens + [Gliricidia sepium (Jacq.) Steud.] (gliricídia), in
randomized block design with three replications. The pastures were grazed by cattle (Bos Taurus/Bos indicus) until
the appropriate time. The canopy height (cm) was measured using graduated ruler, on the average height of the
curvature of the leaves. Light interception (%) and leaf area index were estimated indirectly by three techniques
based on radiation transmittance in the plant canopy: i) canopy analyzer LAI-2000 ((LI-COR®) coupled to a "view
cap" 270°, with readings in proportion of one measure above (1 meter vertical distance from the ground) for two
measures under the sward; ii) Digital Plant Canopy Imager, model CI-120 (CID Bio-science®), by hemispherical
images captured below the sward and iii) AccuPAR Linear PAR/LAI ceptometer, Model LP-80, which has 80
photosensitive sensors coupled to a single control, operated according to the manufacturer's specifications
(DECAGON Devices). Measurements were taken along six months (September/2014 to February/2015) in 28-d
intervals, totaling six evaluations. The samples were taken in five points, ranging from near the trees to the midsection of the pasture. Paired data (270 points) of canopy height with the respective value of (LAI/LI) were
collected in B. decumbens exclusive, 240 points in B. decumbens + gliricídia and 100 points of B. decumbens +
sabiá. The differences in the number of samples among treatments were due to the non-existence of canopy height
of B. decumbens in some points near the trees in the silvopastoral system (dry season). Correlation analyses were
performed using PROC CORR in SAS 9.3 software, and null hypothesis (no correlation) was tested for 1 and 5% of
probability. Classification of correlations magnitude followed parameters based on (Franzblau, 1958), where: if | r
|<0.20 nonexistent correlations; if 0.20<| r |<0.40 weak correlations; 0.40<| r |<0.60 moderate correlations; 0.60<| r
|<0.80 strong correlations; if | r |> 0.80 very strong correlations.
Results and Discussion
Significant correlations (P<0.01) between canopy height of B. decumbens and LAI (Table 1) were obtained
in the treatments studied, using AccuPAR and LAI-2000. For CI-120 this correlation occurred only in B.
decumbens + sabia treatment. For correlations between canopy height and LI there was significance (P<0.01) when
LAI-2000 was used, for all experimental treatments. When AccuPAR was used, this correlation was significant
(P<0.01) for B. decumbens in monoculture and (P≤0.05) in the silvopastoral systems. For CI-120 that correlation
was significant (P<0.01) only in the Brachiaria decumbens + sabiá. Coêlho et al. (2014) observed few significant
correlations for relationship between canopy height with LAI and LI, when measured with CI-120 in some tropical
grasses with different growth habits. Pedreira et al. (2007) considered canopy height a good predictor of LI in
Brachiaria brizantha swards. Most correlations between canopy heights of B. decumbens with LAI were moderate
or weak. This might be related to the fact that, indirect methods also measure other canopy structures, such as the
stems and senescent material and not only photosynthetically active leaves (Bréda, 2003). Correlations with
variables such as forage mass are encouraged in order to give a better understanding of the relationship between
sward characteristics with LAI and LI.
Table 1. Correlations between canopy height with LAI and LI (%) of Brachiaria decumbens in monoculture and in
silvopastoral systems in Pernambuco Forest Zone.
Equipment/variables
Treatments
AccuPAR
Brachiaria exclusive
Brachiaria + gliricídia
Brachiaria + sabiá
Canopy height x LAI
Canopy height x LI
0,55**
0,34**
0,35**
0,20*
0,34**
0,21*
-0,001NS
0,10NS
0,06NS
0,06NS
0,34**
0,38**
0,37**
0,31**
0,28**
CI-120
Canopy height x LAI
Canopy height x LI
LAI-2000
Canopy height x LAI
Canopy height x LI
0,25**
0,24**
** = (P<0.01); * = (P≤0.05); NS = no significant
0,25**
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52a Reunião Anual da Sociedade Brasileira de
Zootecnia
Zootecnia: Otimizando Recursos e Potencialidades
Belo Horizonte – MG, 19 a 23 de Julho de 2015
Conclusions
Most of the correlations between canopy height of Brachiaria decumbens Stapf. with LAI and IL were
moderate or weak, either in monoculture or in silvopastoral system. Measurements of others sward structures and
characteristics, such as herbage mass or height compressed with disk settling, may be an alternative for future
studies seeking for correlations between sward with IAF and LI in tropical grasses.
Acknowledgements
Financial support from CNPq and FACEPE, and field support from IPA.
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