Banca de DEFESA: GABRIELLA FRANCISCO PEREIRA BORGES DE OLIVEIRA
Uma banca de DEFESA de MESTRADO foi cadastrada pelo programa.DISCENTE : GABRIELLA FRANCISCO PEREIRA BORGES DE OLIVEIRA
DATA : 12/12/2018
HORA: 09:00
LOCAL: Sala 01 PPGF
TÍTULO:
SORPTION AND DESORPTION OF PENDIMETHALIN IN SOIL AND SUGARCANE STRAW
PALAVRAS-CHAVES:
pre-emergent, mineral oil, vegetable oil
PÁGINAS: 60
GRANDE ÁREA: Ciências Agrárias
ÁREA: Agronomia
SUBÁREA: Fitotecnia
ESPECIALIDADE: Matologia
RESUMO:
Elimination of pre-harvest burning has brought important challenges for management practices in sugarcane production. Despite of environmental and agronomic benefits associated to the permanence of straw in the soil, this production system may negatively affect herbicides efficiency in weeds control, especially those applied in pre-emergence. It occurs because sugarcane straw may work as a physical barrier and interact with molecules of the herbicides, changing their dynamics in the environment. The sorption corresponds to the main retention mechanism of the herbicides to the straw and can be favored according to the physical-chemical characteristics of the molecules of the herbicides and the chemical composition of the straw. These factors also influence the desorption process, which is associated with the release of the molecules in the soil solution. Pendimethalin is a pre-emergent herbicide widely used in the cultivation of sugarcane in Brazil to control grasses and some weeds with broad leaves. Due to its hydrophobic characteristics, it has high sorption capacity in soil colloids and straw. The use of adjuvants in pre-emergent herbicides may change their dynamics in the environment as well as improve their efficiency. The objective of this work was to evaluate sorption and desorption, in soil and sugarcane straw, of pendimethalin alone and in mixture with adjuvant. Sorption experiment was performed using pendimethalin in the EC formulation alone and in mixture with vegetable oil (Aureo®), in aqueous solution of CaCl2, with concentrations between 2.5 and 40 μg mL-1. The solutions were conditioned in teflon tubes with soil, in the proportion of 1: 2 (w /v), and with sugarcane straw, in the proportion of 1:50 (w/v), remaining in agitation for a period of 12 and 24 hours, respectively. After the centrifugation process, aliquots of the supernatant were removed for quantification of pendimethalin by high performance liquid chromatography (HPLC). Desorption experiment was performed by discarding the supernatant from teflon tubes and adding aqueous solution of CaCl2 without herbicide. The tubes were in constant agitation for 24 hours and centrifugation was performed to remove aliquot of the supernatant for quantification by HPLC. The data were submitted to analysis of variance (p ≤ 0.05) and ISOFIT software were used to obtain the isotherms parameters of the Freundlich and linear models. The linear model was the most suitable for representing the sorption and desorption isotherms. The sorption coefficient for soil was 18, 48 mL g-1 for pendimethalin in the EC formulation alone, while the coefficients for sugarcane straw were 355.52 and 27.24 mL g-1 for the EC formulation alone and for the EC + Aureo® system. In desorption experiment, the Kd values obtained were higher than the sorption values, indicating the herbicide returned to the solution. Therefore, the sorption of pendimethalin in the EC formulation alone is significantly higher when in mixture with adjuvant, indicating the addition of adjuvants in the preparation of the herbicide solution may decrease its retention in the straw and, consequently, increase the weed control efficiency.
MEMBROS DA BANCA:
Interno - 2466219 - CAMILA FERREIRA DE PINHO
Interno - 019.283.890-31 - ANA CLAUDIA LANGARO - UFRRJ
Externo à Instituição - EDIVALDO DOMINGOS VELINI - UNESP