Capim-marandu submetido a solu??o contendo nicosulfuron por diferentes per?odos de armazenamento

Abstract

Objetivou-se com o presente trabalho avaliar o efeito de diferentes tempos de armazenamento da solu??o do herbicida nicosulfuron sob a efici?ncia no crescimento e fisiologia do capim-marandu. O experimento foi conduzido em casa de vegeta??o na UFVJM, campus JK, em Diamantina-MG. O delineamento experimental foi inteiramente casualizado, com sete repeti??es. Os tratamentos foram distribu?dos em esquema fatorial (6x5)+1, sendo seis tempos de armazenamento da solu??o do herbicida nicosulfuron (0, 6, 12, 24, 48 e 72 horas) aplicado na Brachiaria brizantha Stapf cv. marandu (capim-marandu) (syn. Urochloa brizantha), e cinco ?pocas de avalia??o 0, 7, 14, 21 e 60 dias ap?s aplica??o do herbicida (DAA), mais testemunha sem aplica??o. Avaliou-se as caracter?sticas de intoxica??o, crescimento e fisiol?gicas do capim-marandu. Observou-se redu??o do pH da ?gua ap?s a adi??o do herbicida, promovendo acidifica??o da solu??o, e quanto maior o tempo de armazenamento da solu??o do herbicida, menor foi o pH. A intoxica??o promovida pelo nicosulfuron no capim-marandu aumentou significativamente de acordo com os dias ap?s a aplica??o. J? com rela??o ao tempo de armazenamento da solu??o, constatou-se maior efeito intoxicante no tempo zero de armazenamento do herbicida, observando-se decr?scimo desses valores com o aumento do tempo de armazenamento. O n?mero de perfilhos a?reos (NPA) foi maior no tempo zero horas, reduzindo 72 horas. J? para o n?mero de perfilhos basais (NPB) ocorreu o inverso do NPA. Para as caracter?sticas fisiol?gicas como taxa de transporte de eletros (ETR) e efici?ncia do fotossistema II (Fv/Fm) foram observadas diferen?as entre as ?pocas de avalia??o. J? o CO2 consumido (?C), taxa de transpira??o (E), condut?ncia estom?tica de vapores de ?gua (Gs), taxa fotossint?tica (A) e efici?ncia no uso da ?gua (EUA) menores valores com o aumento dos dias de avalia??o e menores valores no tempo de armazenamento de zero horas quando comparamos com os tempos com mais de 48 horas de armazenamento, por?m para os valores de carbono interno (Ci) observou-se o contr?rio. O tempo de armazenamento da solu??o herbicida de nicosulfuron afeta diretamente as caracter?sticas produtivas e fisiol?gicas do capim-marandu, pois, quanto maior o tempo de armazenamento da solu??o, menor ser? a efici?ncia desse herbicida, devido a hidr?lise da mol?cula herbicida. O tempo de armazenamento da solu??o herbicida afeta diretamente no pH da ?gua, onde quanto maior esse tempo menor ser? o pH da ?gua e menor os n?veis de intoxica??o das plantas de capim-marandu, sem todavia, interferir no tamanho das plantas. O aumento do tempo de armazenamento da solu??o herbicida reduz o perfilhamento a?reo e aumenta o basal. O armazenamento da solu??o do herbicida nicosulfuron afeta os par?metros fisiol?gicos: CO2 consumido, E, A e EUA aumentando seus valores.Disserta??o (Mestrado) ? Programa de P?s-Gradua??o em Zootecnia, Universidade Federal dos Vales do Jequitinhonha e Mucuri, 2018.The objective of this work was to evaluate the effect of different storage times of the herbicide nicosulfuron under the efficiency of the growth of marandu grass. The experiment was conducted in a greenhouse at the UFVJM, JK campus, in Diamantina-MG. The experimental design was completely randomized, with seven replications. The treatments were distributed in a factorial scheme (6x5) +1, with six storage times of the herbicide nicosulfuron (0, 6, 12, 24, 48 and 72 hours) applied in Brachiaria brizantha Stapf cv. and five evaluation periods 0, 7, 14, 21 and 60 days after application of the herbicide (DAA), plus control without application. It was evaluated the intoxication, growth and physiological characteristics of the marandu grass. It was observed a reduction of the pH of the water after the addition of the herbicide, promoting acidification of the solution, and the longer the storage time of the herbicide, the lower the pH. The intoxication promoted by nicosulfuron in the marandu grass increased significantly according to the days after the application. Regarding the time of storage of the syrup, it was verified a greater intoxicating effect in the zero time of storage of the herbicide, observing a decrease of these values with the increase of the time of storage. The number of aerial tiller (NPA) was higher at time zero hours, reducing 72 hours. As for the number of basal tillers (NPB), the inverse of NPA occurred. For the physiological characteristics such as electron transport rate (ETR) and efficiency of photosystem II (Fv / Fm), differences between the epochs of evaluation were observed. On the other hand, CO2 consumption (?C), transpiration rate (E), stomatal conductance of water vapors (Gs), photosynthetic rate (A) and water use efficiency (US) values in the storage time of zero hours when compared with the times with more than 48 hours of storage, but for the values of internal carbon (Ci) the opposite was observed. The storage time of the herbicide syrup of nicosulfuron directly affects the productive and physiological characteristics of the marandu grass, because the longer the storage time of the syrup, the lower the herbicide efficiency due to the hydrolysis of the herbicide molecule. The storage time of the herbicide solution directly affects the pH of the water, where the longer the water pH, the lower the levels of intoxication of the marandu grass plants, without interfering with the size of the plants. The increase in the storage time of the herbicide syrup reduces aerial tillering and increases the basal. The storage of the herbicide nicosulfuron affects the physiological parameters: CO2 consumed, E, A and WUE increasing their values