Adubação nitrogenada e doses do herbicida glyphosate como regulador de crescimento em grama esmeralda
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Data
2017-03-31
Autores
Gazola, Raíssa Pereira Dinalli [UNESP]
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Universidade Estadual Paulista (Unesp)
Resumo
A adubação nitrogenada proporciona, além da nutrição, a manutenção da coloração verde intensa em gramados ornamentais, imprescindível do ponto de vista estético. Mas, o nitrogênio (N) aumenta o crescimento da parte aérea e, assim, maior será frequência de cortes, principal fator do custo de manutenção em gramados. Neste contexto, objetivou-se avaliar a adubação nitrogenada (via solo com ou sem via foliar), e o uso de doses do herbicida glyphosate em grama esmeralda (Zoysia japonica Steud.), visando reduzir o crescimento do gramado, bem como manter sua qualidade visual (verde intenso) e nutricional. O experimento foi conduzido na Fazenda de Ensino, Pesquisa e Extensão da UNESP, Campus de Ilha Solteira/SP, de agosto de 2014 a fevereiro de 2017, em um ARGISSOLO VERMELHO Eutrófico areno-argiloso. Utilizou-se o delineamento em blocos casualizados com 20 tratamentos dispostos em fatorial 5 x 4, com quatro repetições, em 10 m2 por parcela. Os tratamentos foram: testemunha (sem N); 15 g m-2 de N aplicado via solo e sem N via foliar; 30 g m-2 de N aplicado via solo e sem N via foliar; 15 g m-2 de N aplicado via solo e com N via foliar (1% de ureia) e 30 g m-2 de N aplicado via solo e com N via foliar (1% de ureia), combinados com quatro doses de glyphosate (0, 200, 400 e 600 g ha-1 do ingrediente ativo - i.a.). As doses de N via solo foram parceladas em cinco aplicações durante o ano e, portanto, corresponderam a 3 e 6 g m-2 de N a cada aplicação, respectivamente, para as doses de 15 e 30 g m-2 de N. Foram avaliados: os atributos químicos do solo, a altura e a matéria seca das folhas, a área foliar, o índice de clorofila foliar (ICF), os teores de clorofila a e b, a análise por imagem digital e a porcentagem de fitointoxicação da parte aérea, além da determinação da ocorrência de plantas daninhas e do número de inflorescências, bem como a concentração, o acúmulo de macro e micronutrientes nas folhas do gramado e as relações log-isométricas no balanço de macronutrientes nas folhas e do balanço catiônico no solo (relação log isométrica - ilr). Foi realizada também a avaliação do sistema radicular (matéria seca e concentração de macro e micronutrientes nas raízes + rizomas). Foram realizadas dez avaliações (cortes), após as quais eram aplicados os tratamentos. Os teores de K no solo aumentaram com as doses de glyphosate. Houve maior matéria seca das raízes + rizomas quando da adubação com N e diminuição desses valores com as doses de herbicida. A maior quantidade de N via solo, com ou sem N via foliar, resultou em maior crescimento da grama esmeralda, sendo o mesmo reduzido com a dose de 600 g ha-1 do i.a. do glyphosate. Todavia, esta dose do herbicida não foi adequada do ponto de vista estético – coloração verde. Concluiu-se que a adubação com 15 g m-2 de N via solo e sem N via foliar, parcelada em cinco aplicações ao ano, propiciou qualidade visual e nutricional do gramado, e que o glyphosate na dose de 400 g ha-1 do i.a. foi eficiente na redução do crescimento da grama esmeralda, sem prejuízo na sua coloração verde e também propiciou menor acúmulo de macronutrientes pelas folhas, reduzindo a necessidade de reposição pela adubação.
Nitrogen fertilization provides, in addition to nutrition, the maintenance of intense green color in ornamental turfgrasses, necessary underesthetic view point. However, nitrogen (N) increases the shoots growth and, thus, the frequency of cuts, the main factor in the cost of turfgrasses maintenance. In this context, this study aimed to evaluate nitrogen fertilization (via soil and/or foliar) and the use of rates of glyphosate in zoysiagrass (Zoysia japonica Steud.) to reduce growth and maintain the visual quality (intense green) and good nutritional quality. The research was conducted at the Experimental Station of UNESP, Ilha Solteira/SP, from August/2014 to February/2017, on an Ultisol. It was used a randomized block design with 20 treatments arranged in a factorial scheme 5 x 4 with four replications and 10 m2 per plot. The treatments was: control (without N), 15 g m-2 of N in the soil without application of foliar N; 30 g m-2 of N in the soil without application of foliar N; 15 g m-2 in the soil with foliar application of N (1% urea) and 30 g m-2 of N in the soil with foliar application of N (1% urea) combined with four rates of glyphosate (0, 200, 400 and 600 g ha-1 active ingredient (a.i.)). N rates in the soil were split in five times during the year and, therefore, corresponded to 3 and 6 g m-2 of N at each application, respectively, for the rates of 15 and 30 g m-2 of N. Were evaluated: the chemical attributes of the soil, height and dry matter of leaves, leaf area, LCI (leaf chlorophyll index), the chlorophyll a and b, the digital image analysis and the percentage of phytotoxicity of the shoot, beyond the occurrence of weed species and number of inflorescences, as well as the concentration and accumulation of macro and micronutrients by leaves of turfgrass and log-isometrics balance of macronutrients in the leaves and cationic balance in the soil (isometric log ratio - ilr). It was being also assessed the root system (dry matter and macro and micronutrients in roots + rhizomes). Ten evaluations (cuts) were carried out. The levels of K in the soil increased with the glyphosate rates. There was higher dry matter of the roots + rhizomes when N fertilization and decrease of these values with the doses of herbicide. The greater amount of N via soil, with or without N via foliar, resulted in greater growth of the zoysiagrass, being reduced with the dose of 600 g ha-1 of a.i. of glyphosate. However, this herbicide rate was not aesthetically ideal - green color. It was concluded that the fertilization with 15 g m-2 of N in the soil without foliar N, split in five times during the year, provided visual and nutritional quality of the grass, and the rate of glyphosate of 400 g ha-1 a.i. was effective in reducing zoysiagrass growth, did not sacrifice its coloration and provided less accumulation of macronutrients in the leaves, reducing the need for replenishment by fertilization.
Nitrogen fertilization provides, in addition to nutrition, the maintenance of intense green color in ornamental turfgrasses, necessary underesthetic view point. However, nitrogen (N) increases the shoots growth and, thus, the frequency of cuts, the main factor in the cost of turfgrasses maintenance. In this context, this study aimed to evaluate nitrogen fertilization (via soil and/or foliar) and the use of rates of glyphosate in zoysiagrass (Zoysia japonica Steud.) to reduce growth and maintain the visual quality (intense green) and good nutritional quality. The research was conducted at the Experimental Station of UNESP, Ilha Solteira/SP, from August/2014 to February/2017, on an Ultisol. It was used a randomized block design with 20 treatments arranged in a factorial scheme 5 x 4 with four replications and 10 m2 per plot. The treatments was: control (without N), 15 g m-2 of N in the soil without application of foliar N; 30 g m-2 of N in the soil without application of foliar N; 15 g m-2 in the soil with foliar application of N (1% urea) and 30 g m-2 of N in the soil with foliar application of N (1% urea) combined with four rates of glyphosate (0, 200, 400 and 600 g ha-1 active ingredient (a.i.)). N rates in the soil were split in five times during the year and, therefore, corresponded to 3 and 6 g m-2 of N at each application, respectively, for the rates of 15 and 30 g m-2 of N. Were evaluated: the chemical attributes of the soil, height and dry matter of leaves, leaf area, LCI (leaf chlorophyll index), the chlorophyll a and b, the digital image analysis and the percentage of phytotoxicity of the shoot, beyond the occurrence of weed species and number of inflorescences, as well as the concentration and accumulation of macro and micronutrients by leaves of turfgrass and log-isometrics balance of macronutrients in the leaves and cationic balance in the soil (isometric log ratio - ilr). It was being also assessed the root system (dry matter and macro and micronutrients in roots + rhizomes). Ten evaluations (cuts) were carried out. The levels of K in the soil increased with the glyphosate rates. There was higher dry matter of the roots + rhizomes when N fertilization and decrease of these values with the doses of herbicide. The greater amount of N via soil, with or without N via foliar, resulted in greater growth of the zoysiagrass, being reduced with the dose of 600 g ha-1 of a.i. of glyphosate. However, this herbicide rate was not aesthetically ideal - green color. It was concluded that the fertilization with 15 g m-2 of N in the soil without foliar N, split in five times during the year, provided visual and nutritional quality of the grass, and the rate of glyphosate of 400 g ha-1 a.i. was effective in reducing zoysiagrass growth, did not sacrifice its coloration and provided less accumulation of macronutrients in the leaves, reducing the need for replenishment by fertilization.
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Palavras-chave
Gramado, Zoysia japonica Steud, Nitrogênio, Nutrição foliar, Coloração verde