1 research outputs found
Avalia??o de plantas forrageiras tropicais sob sombreamentos no outono e inverno
O presente trabalho foi realizado com apoio da Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior - Brasil (CAPES) - C?digo de Financiamento 001.Os sistemas de integra??o lavoura-pecu?ria-floresta, tamb?m conhecidos como
agrossilvipastoris, podem contribuir positivamente para os sistemas de produ??o animal e s?o
alternativas eficientes de uso da terra na recupera??o de ?reas degradadas. No entanto, a
toler?ncia de gram?neas e leguminosas ao sombreamento depende da sua capacidade
morfofisiol?gica para se adaptar a determinado n?vel de radia??o, conhecido como plasticidade
fenot?pica. O objetivo com este trabalho foi avaliar o comportamento de quatro cultivares de
plantas forrageiras tropicais sob diferentes n?veis de sombreamento e manejadas a 95% de
intercepta??o luminosa (IL), ao longo do outono e inverno de 2019. Foram realizados quatro
experimentos com quatro esp?cies forrageiras tropicais: Brachiaria spp. cv. Mavuno (capim-mavuno),
Panicum maximum Jack cv. BRS Zuri (capim-zuri), Panicum maximum cv. BRS
Tamani (capim-tamani) e Arachis pintoi cv. Amarillo (amendoim forrageiro). Cada
experimento foi realizado em delineamento inteiramente casualizado (DIC), com seis
repeti??es, submetidos aos n?veis de sombreamento artificial de 47% com radia??o
fotossint?ticamente ativa (RFA) de 353 ?mol m-2s-1, de 64% com RFA de 242 ?mol m-2s-1, 74%
com RFA de 172 ?mol m-2s-1 e o tratamento controle com as plantas cultivadas sem
sombreamento, com RFA de 668 ?mol m-2s-1. As plantas foram mantidas sob regime de corte
ao atingir 95% de IL. Durante o experimento foram realizadas avalia??es morfog?nicas para
determina??o das vari?veis-respostas: taxa de aparecimento foliar, filocrono, taxa de
alongamento foliar, taxa de senesc?ncia foliar, dura??o de vida da folha, taxa de alongamento
do colmo/caule para todas as forrageiras e tamb?m a taxa de alongamento em largura e taxa de
alongamento do pec?olo para o amendoim forrageiro. Antes do corte tamb?m foram realizadas
as avalia??es estruturais, referentes ao n?mero de folhas vivas por perfilho, comprimento final
da folha e do colmo ou caule, altura final das plantas, o ?ndice de ?rea foliar, densidade de
perfilhos e o peso m?dio dos perfilhos. Tamb?m foram realizadas an?lises fisiol?gicas
referentes aos teores de clorofila a e b, taxa fotossint?tica, condut?ncia estom?tica, taxa
transpirat?ria, efici?ncia no uso da ?gua e temperatura da folha. Posteriormente, ap?s o corte
foi determinada a composi??o morfol?gica (propor??o de folhas, colmo ou caule, material
senescente e infloresc?ncia) e a produ??o de massa seca total de cada esp?cie forrageira sob os
diferentes n?veis de sombreamento. Todos os dados foram analisados no programa estat?stico
Statistical Analysis System - SAS 9.1. As m?dias das caracter?sticas morfog?nicas,
morfofisiol?gicas e produtivas foram submetidas ? an?lise de vari?ncia e posteriormente ?
an?lise de regress?o linear e quadr?tica a 5% de probabilidade. O capim-mavuno apresentou
adapta??o aos sombreamentos de 47%, 64% e 74% ao longo do outono e inverno, visto que a
produ??o de massa seca n?o diminuiu mesmo com a restri??o luminosa imposta pelos n?veis de
sombreamentos nas plantas e houve aumentos no ?ndice de ?rea foliar, na propor??o de folhas,
no teor de clorofila a e b e na taxa fotossint?tica nos sistemas sombreados. O capim-zuri
apresenta alta adapta??o ao sombreamento de 64%, visto que nesta condi??o houve maior
produ??o de massa seca, maiores propor??es de folhas e da taxa de aparecimento foliar e
aumentos nos teores de clorofila que consequentemente proporcionaram maiores taxas
fotossint?ticas sob este n?vel de sombreamento. O capim-tamani apresentou grande toler?ncia
aos sombreamentos de 47% e 64%, aumentando a produ??o de massa seca, a taxa fotossint?tica,
a clorofila a e b, a taxa de aparecimento foliar, a propor??o de folhas e a rela??o folha/colmo da composi??o morfol?gica, quando comparado as plantas sem sombreamento. Foi verificado
tamb?m que o capim-tamani pode ser sombreado em at? 74% sem reduzir a produ??o em
compara??o com as plantas que crescem sem sombreamento. O amendoim forrageiro
apresentou grande adapta??o ao sombreamento a 47%, aumentando a produ??o de massa seca,
a taxa fotossint?tica, a propor??o de folhas e a rela??o folha/ caule quando comparado as plantas
sem sombreamento e com sombreamento de 64 e 74%. Com isso o capim-tamani quando
comparado com outros capins, apresenta maior adapta??o aos diferentes n?veis de
sombreamento durante a esta??o outono e inverno, seguido pelo capim zuri e o capim mavuno.
J? a leguminosa amendoim forrageiro durante a esta??o outono e inverno, apresenta toler?ncia
a baixos n?veis de sombreamento.Conselho Nacional de Desenvolvimento Cient?fico e Tecnol?gico (CNPq)Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior (CAPES)Funda??o de Amparo ? Pesquisa do Estado de Minas Gerais (FAPEMIG)Disserta??o (Mestrado) ? Programa de P?s-Gradua??o em Produ??o Vegetal, Universidade Federal dos Vales do Jequitinhonha e Mucuri, 2020.The crop-livestock-forest integration systems, also known as agrosilvipastoris, can contribute
positively to animal production systems and are efficient alternatives for land use in the
recovery of degraded areas. However, the tolerance of grasses and legumes to shading depends
on their morphophysiological capacity to adapt to a certain level of radiation, known as
phenotypic plasticity. The objective of this work was to evaluate the behavior of four cultivars
of tropical forage plants under different levels of shading and managed at 95% light interception
(IL), throughout the fall and winter of 2019. Four experiments were carried out with four forage
species tropical: Brachiaria spp. cv. Mavuno (mavuno grass), Panicum maximum Jack cv. BRS
Zuri (zuri grass), Panicum maximum cv. BRS Tamani (tamani grass) and Arachis pintoi cv.
Amarillo (forage peanut). Each experiment was carried out in a completely randomized design
(DIC), with six replications, subjected to artificial shading levels of 47% with
photosynthetically active radiation (RFA) of 353 ?mol m-2s-1, 64% with RFA of 242 ?mol m-
2s-1, 74% with RFA of 172 ?mol m-2s-1 and the control treatment with plants grown without
shading, with RFA of 668 ?mol m-2s-1. The plants were kept under a cutting regime when
reaching 95% IL. During the experiment, morphogenic evaluations were performed to
determine the response variables: leaf appearance rate, phyllochron, leaf elongation rate, leaf
senescence rate, leaf life duration, stem / stem elongation rate for all forages and also the rate
of elongation in width and the rate of elongation of the petiole for forage peanut. Before cutting,
structural evaluations were also carried out, referring to the number of live leaves per tiller,
final length of the leaf and stem or stem, final height of the plants, the leaf area index, tiller
density and the average weight of tillers. Physiological analyzes were also carried out regarding
the levels of chlorophyll a and b, photosynthetic rate, stomatal conductance, transpiratory rate,
water use efficiency and leaf temperature. Subsequently, after cutting, the morphological
composition (proportion of leaves, stem or stem, senescent material and inflorescence) and the
production of total dry mass of each forage species were determined under the different levels
of shading. All data were analyzed using the statistical program Statistical Analysis System -
SAS 9.1. The means of the morphogenic, morphophysiological and productive characteristics
were subjected to analysis of variance and subsequently to the analysis of linear and quadratic
regression at 5% probability. The mavuno grass showed adaptation to the shading of 47%, 64%
and 74% throughout autumn and winter, since the production of dry mass did not decrease even
with the light restriction imposed by the levels of shading in the plants and there were increases
in the index leaf area, leaf proportion, chlorophyll content a and b and photosynthetic rate in
shaded systems. Zuri grass has a high adaptation to shading of 64%, since in this condition there
was greater production of dry mass, higher proportions of leaves and the rate of leaf appearance
and increases in chlorophyll contents which consequently provided higher photosynthetic rates
under this level of shading. Tamani grass showed great tolerance to shading of 47% and 64%,
increasing dry mass production, photosynthetic rate, chlorophyll a and b, leaf appearance rate,
leaf proportion and leaf / stem ratio of the morphological composition, when compared to plants
without shading. It was also found that tamani grass can be shaded by up to 74% without
reducing production compared to plants that grow without shading. Forage peanuts showed
great adaptation to shading at 47%, increasing the dry matter production, the photosynthetic
rate, the proportion of leaves and the leaf / stem ratio when compared to plants without shading
and with shading of 64 and 74%. As a result, tamani grass, when compared to other grasses, shows greater adaptation to different levels of shade during the autumn and winter season,
followed by zuri grass and mavuno grass. The forage peanut legume during the autumn and
winter season, tolerates low levels of shading