Aplicação foliar de sílicio em algodoeiro herbáceo em função da disponibilidade de água
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Data
2019-05-21
Autores
Nocchi, Raiana Crepaldi de Faria
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Universidade Estadual Paulista (Unesp)
Resumo
O silício tem papel importante nas relações planta-ambiente, pois pode dar às culturas melhores condições para suportarem adversidades climáticas, edáficas e biológicas, tendo como resultado aumento e a melhora nas condições fisiológicas da planta. Objetivou-se, com este trabalho, estudar o efeito da adubação silicatada via foliar (silicato de cálcio) na cultura do algodoeiro herbáceo (Gossypium hirsutum L. raça latifolium Hutch), sobre suas características fisiológicas e agronômicas, visando avaliar sua resposta com a diminuição da disponibilidade hídrica através de análises fisiológicas e bioquímicas, bem como a anatomia, biometria e a constituição histoquímica do limbo foliar. Foram realizados dois experimentos. O 1° experimento foi realizado em casa de vegetação, o delineamento experimental utilizado foi o interamente casualizado (DIC), com seis repetições, no esquema fatorial 6 x 2, sendo os fatores: 5 concentrações de silicato de cálcio (50;100;150;200 e 400 mg L-1) e a testemunha (sem aplicação), e 2 níveis de água no solo (capacidade de campo (CC) e 1/3 da capacidade de campo (1/3 CC)). O Si foi aplicado em três períodos, aos 30, 45 e 60 dias após a emergência (DAE). Concluiu-se que a altura da planta, o diâmetro do caule, o número de nós, o número de ramos reprodutivos e número de estruturas reprodutivas foram afetados, de maneira negativa pelo déficit hídrico e positiva para o irrigado. A fotossíntese, condutância estomática, transpiração e conteúdo interno de CO2 foram reduzidos com a utilização de doses de silício. O algodoeiro mostrou-se uma planta que acumulou Si conforme se aumenta as doses na aplicação, sendo os maiores teores na folha, seguida do caule. O 2° experimento foi realizado em condições de campo, na região de Cerrado, cujo delineamento experimental adotado foi o de blocos ao acaso, em esquema fatorial 6x2 totalizando 12 tratamentos, com 4 repetições, perfazendo um total 48 parcelas. Os tratamentos foram constituídos por 5 doses de Si (50, 100, 150, 200 e 400 g ha-1) e as plantas testemunhas (0,0 sem Si) e dois sistemas de cultivo (sequeiro e irrigado). As aplicações das doses de Si foram realizadas via foliar e parcelado em duas aplicações realizadas aos 50 e 70 dias após a emergência (DAE). As irrigações foram realizadas por um sistema de aspersão convencional fixo. A altura da planta, diâmetro do caule e número de nós foram afetados de maneira negativa pelo déficit hídrico ao qual o algodoeiro foi submetido. O tratamento sem déficit hídrico (irrigado) promoveu maiores altura, diâmetro do caule e número de nós na planta de algodão.A fotossíntese, condutância estomática, transpiração e conteúdo de CO2 foram reduzidos com a utilização de doses de silício. O sistema de irrigação proporcionou uma maior solubilidade para os macronutrientes e uma melhor absorção dessas nutrientes pelas plantas. Houve uma relação positiva do Si com o Fe, havendo uma maior absorção de Fe pelas plantas pois a liberação de Silicio dos óxidos e hidróxidos de ferro. O Si mostrou que espessou as camadas de epiderme da folha, houve uma maior turgescência da folha nas plantas irrigadas do que a que estavam em sequeiro. A produtividade do algodoeiro foi maior nas plantas irrigadas. Para os parâmetros para a qualidade de fibra, observou-se que resistência da fibra, reflectância, teor de amarelamento e índice de maturidade foram maiores no sistema irrigado e o grau de folhas foi significativo as aplicações de doses de Si. A dose recomendada de Si seria a de 100 kg.ha-1 , pois apresentou uma maior média na maioria dos parâmetros analisados.
The silicon plays an important role in plant-environment relationships, as it can give crops better conditions to withstand climatic, edaphic and biological adversities, resulting in increased and improved physiological conditions of the plant. The objective of this work was to study the effect of leaf silica fertilization (calcium silicate) on the herbaceous cotton (Gossypium hirsutum L. breed latifolium Hutch), on its physiological and agronomic characteristics, in order to evaluate its response with the decrease of water availability through physiological and biochemical analyzes, as well as the anatomy, biometry and histochemical constitution of the leaf blade. Two experiments were carried out. The first experiment was carried out in a greenhouse, and the experimental design was a randomized (DIC), with six replications, in the factorial scheme 6 x 2, with the following factors: 5 calcium silicate concentrations (50, 100, 150 (Field capacity (CC) and 1/3 of the field capacity (1/3 CC)) and the control (without application), and 2 levels of water in the soil. Si was applied in three periods, at 30, 45 and 60 days after emergence (AED). It was concluded that the plant height, stem diameter, number of nodes, number of reproductive branches and number of reproductive structures were negatively affected by water deficit and positive for irrigated. The photosynthesis, stomatal conductance, transpiration and internal CO2 content were reduced with the use of silicon doses. The cotton showed a plant that accumulated Si as the doses increase in the application, being the highest contents in the leaf, followed by the stem. The second experiment was carried out under field conditions in the Cerrado region. The experimental design was a randomized block design, in a 6x2 factorial scheme, with a total of 12 treatments, with 4 replications, making a total of 48 plots. The treatments consisted of 5 doses of Si (50, 100, 150, 200 and 400 g ha-1) and the control plants (0.0 without Si) and two cultivation systems (dry and irrigated). The applications of Si doses were performed via foliar and split in two applications at 50 and 70 days after emergence (AED). Irrigations were performed by a fixed conventional sprinkler system. Plant height, stem diameter and number of nodes were negatively affected by the water deficit to which the cotton was submitted. The treatment without water deficit (irrigated) promoted higher height, stem diameter and number of nodes in the cotton plant. Photosynthesis, stomatal conductance, transpiration and CO2 content were reduced with the use of silicon rates. The irrigation system provided greater solubility for the macronutrients and a better absorption of these nutrients by the plants. There was a positive relation of Si with Fe, with a higher Fe absorption by the plants as the release of Silicon from the iron oxides and hydroxides. The Si showed that it thickened the layers of the epidermis of the leaf, there was a greater turgescence of the leaf in the irrigated plants than the one that were in the dry one. Cotton yield was higher in irrigated plants. For the parameters for the fiber quality, it was observed that fiber strength, reflectance, yellowing content and maturity index were higher in the irrigated system and the degree of leaves was significant the applications of Si rates. The recommended rate of Si would be 100 kg.ha-1, as it presented a higher mean in most of the analyzed parameters.
The silicon plays an important role in plant-environment relationships, as it can give crops better conditions to withstand climatic, edaphic and biological adversities, resulting in increased and improved physiological conditions of the plant. The objective of this work was to study the effect of leaf silica fertilization (calcium silicate) on the herbaceous cotton (Gossypium hirsutum L. breed latifolium Hutch), on its physiological and agronomic characteristics, in order to evaluate its response with the decrease of water availability through physiological and biochemical analyzes, as well as the anatomy, biometry and histochemical constitution of the leaf blade. Two experiments were carried out. The first experiment was carried out in a greenhouse, and the experimental design was a randomized (DIC), with six replications, in the factorial scheme 6 x 2, with the following factors: 5 calcium silicate concentrations (50, 100, 150 (Field capacity (CC) and 1/3 of the field capacity (1/3 CC)) and the control (without application), and 2 levels of water in the soil. Si was applied in three periods, at 30, 45 and 60 days after emergence (AED). It was concluded that the plant height, stem diameter, number of nodes, number of reproductive branches and number of reproductive structures were negatively affected by water deficit and positive for irrigated. The photosynthesis, stomatal conductance, transpiration and internal CO2 content were reduced with the use of silicon doses. The cotton showed a plant that accumulated Si as the doses increase in the application, being the highest contents in the leaf, followed by the stem. The second experiment was carried out under field conditions in the Cerrado region. The experimental design was a randomized block design, in a 6x2 factorial scheme, with a total of 12 treatments, with 4 replications, making a total of 48 plots. The treatments consisted of 5 doses of Si (50, 100, 150, 200 and 400 g ha-1) and the control plants (0.0 without Si) and two cultivation systems (dry and irrigated). The applications of Si doses were performed via foliar and split in two applications at 50 and 70 days after emergence (AED). Irrigations were performed by a fixed conventional sprinkler system. Plant height, stem diameter and number of nodes were negatively affected by the water deficit to which the cotton was submitted. The treatment without water deficit (irrigated) promoted higher height, stem diameter and number of nodes in the cotton plant. Photosynthesis, stomatal conductance, transpiration and CO2 content were reduced with the use of silicon rates. The irrigation system provided greater solubility for the macronutrients and a better absorption of these nutrients by the plants. There was a positive relation of Si with Fe, with a higher Fe absorption by the plants as the release of Silicon from the iron oxides and hydroxides. The Si showed that it thickened the layers of the epidermis of the leaf, there was a greater turgescence of the leaf in the irrigated plants than the one that were in the dry one. Cotton yield was higher in irrigated plants. For the parameters for the fiber quality, it was observed that fiber strength, reflectance, yellowing content and maturity index were higher in the irrigated system and the degree of leaves was significant the applications of Si rates. The recommended rate of Si would be 100 kg.ha-1, as it presented a higher mean in most of the analyzed parameters.
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Palavras-chave
Gossypium hirsutum L. raça latifolium Hutch, Adubação silicatada, Estresse hídrico, Nutrição de plantas, Gossypium hirsutum L. var. Latifolium Hutch, Silicate fertilization, Water stress, Plant nutrition