Banca de QUALIFICAÇÃO: GABRIELLA FRANCISCO PEREIRA BORGES DE OLIVEIRA

Uma banca de QUALIFICAÇÃO de DOUTORADO foi cadastrada pelo programa.
STUDENT : GABRIELLA FRANCISCO PEREIRA BORGES DE OLIVEIRA
DATE: 18/12/2020
TIME: 14:00
LOCAL: vídeo conferência
TITLE:

Influence of Lithothamnium calcareum on dynamics of atrazine and S-metolachlor herbicides in soil and absorption of nutrients by corn crop.

KEY WORDS:

liming; sorption; leaching, persistence; pre-emergent.

PAGES: 30
BIG AREA: Ciências Agrárias
AREA: Agronomia
SUMMARY:

Weeds can cause considerable economic damage, because they interfere in the cultivation areas by competition for water, light and nutrients between them and crops, as well as hosting pests and diseases and making harvesting difficult. Herbicides are the main method of weed control, compared to the others, such as mechanical, physical and cultural methods, combining efficiency, speed and low cost. Atrazine and S-metolachlor herbicides are widely recommended for weed control in corn crop. They act in inhibition of photosystem II and inhibition of nucleic acid and protein synthesis, respectively. Different processes may occur with herbicides molecules when they are applied in the environment, such as sorption / desorption, chemical and biological degradation, runoff, leaching, photolysis, absorption by plants and volatilization. These phenomena are strongly influenced by management practices, soil characteristics, climatic conditions and physicochemical properties of herbicides. Liming is a common management practice in cultivated areas and can alter herbicides dynamics in soil. Dolomitic and magnesian calcareous are generally used, bringing positive effects, such as significant increase in calcium and magnesium contents in leaves dry matter and greater grain production. The seaweed called Lithothamnium calcareum presents itself as an alternative to traditional products, being composed mainly of calcium carbonate deposited in the form of hexagonal rhombohedral crystal of calcite between cell walls and magnesium carbonate and other minerals in minor extent. The objective of this work is to elucidate the influence of Lithothamnium calcareum on the dynamics of atrazine and S-metolachlor herbicides, considering, mainly, sorption, leaching and persistence processes in soil; as well as its influence in absorption of calcium and magnesium by corn crop. The experiments will be developed in an experimental area and laboratories at the Federal Rural University of Rio de Janeiro. In total, two pre-tests and four main experiments will be carried out. The first pre-test consists of determining the amounts of dolomitic calcareous and Lithothamnium calcareum necessary to reach three different pH levels, while the second consists of determining the most suitable bioindicator plants to detect presence of atrazine and S-metolachlor herbicides in soil. Experiment 1 will correspond to analysis of nutrient absorption by corn plants and there will be no use of herbicides. There will be seven treatments corresponding to the sources of calcium, using the pre-defined quantities of dolomitic calcareous and Lithothamnium calcareum and soil without an additional source of calcium, in order to verify if there is a difference in absorption of nutrients by the corn plants. Subsequently, using the common condition of maximum absorption between the two sources of calcium, three experiments will be considered for each herbicide. Experiment 2 will correspond to the sorption bioassay, experiment 3 will correspond to leaching and experiment 4 will correspond to persistence in soil. Experiment 2 will be conducted in pots using two substrates to determine sorption curve, they are soil and washed sand, considered an inert substrate, as well as bioindicator plants. The factors will be calcium source and herbicides doses. Experiment 3 will be arranged in subdivided plots, with the plots corresponding to the calcium source and the subplots to depths in PVC columns, in order to verify the ability of herbicides to percolate in soil. The factors in experiment 4 will be calcium sources and time of soil collect, including untreated. Samples will be collected from the pots and stored in a freezer for analysis. Experiments 3 and 4 will be evaluated qualitatively, using bioindicator plants, and quantitatively by high performance liquid chromatography. Bioindicator plants will be periodically evaluated for phytotoxicity and, after collection at 28 days after emergence, analysis of dry mass of aerial part, dry mass of root and height of aerial part will be carried out. Data will be submitted to analysis of variance (p <0.05) and average test or regression analysis will be performed, when pertinent. It is expected to demonstrate the differences regarding the nutrient absorption processes of corn plants, as well as the sorption, leaching and persistence of atrazine and S-metolachlor herbicides according to calcium source.

BANKING MEMBERS:
Externa ao Programa - 2466219 - CAMILA FERREIRA DE PINHO
Externo à Instituição - DANIEL VALADÃO - UFERSA
Presidente - 2213075 - EVERALDO ZONTA
Externo ao Programa - 1282206 - JULIANO BAHIENSE STAFANATO