Dissertação
Número de amostra para a estimativa da densidade populacional de fitonematoides na cultura de soja (Glycine max (L.) Merrill) e dinâmica populacional em plantas de cobertura
Fecha
2021-08-12Autor
Rebelatto, Gracieli
Institución
Resumen
Soybean (Glycine max (L.) Merrill) is a crop of great economic importance. Despite numerous
advances, soybean cultivation is significantly affected by diseases and pests that cause reduced
productivity in different Brazilian regions, especially fungi and nematodes. The sampling of
nematodes has become increasingly important in modern agriculture, because through the
information obtained from the surveys, an attempt is made to develop sampling plans that are
representative, accurate and easy to carry out, and that help in the development of management
programs. Among the management strategies, the cultivation of cover plants in the off-season
has been an option in reducing the population density of nematodes in the soil. The objective
of the work is to collect information on the population dynamics of phytonematodes in
commercial soybean farming, determining the number of samples needed to quantify soil
nematodes and to assessing the population variation of those micro-organisms in different cover
plants. It will be demarcated a grid of 144 sampling points, spaced 10 x 10 m, represented in 1
hectare, in the month of September 2019 to March 2020, in the evaluation before the sowing
and R7-R8 stage of the soybean crop. The samples will be collected with the aid of a cutting
blade, at a depth of 0-20 cm. The extraction of nematodes in the soil will be performed by the
flotation-centrifugation method in sucrose solution, using 100 cm³ of the soil. The extraction of
nematodes in the roots will be performed by the blender technique, sieving and centrifugation
in sucrose solution. In the suspension obtained, the number of nematodes (1 mL) under an
optical microscope shall be estimated using a Peters slide. For sample number analysis, the data
were submitted to resampling technique, and a total of 2000 resampling with replacement was
calculated. After obtaining the data, it is concluded that nematodes have aggregate distribution
and their population density interferes in the amount of samples to be collected. Considering
the set of soil and root samples, at the R7-R8 stage, 58 sampling points are necessary to estimate
the population density of nematodes, for an estimation error of 65% of the mean and with 95%
confidence. Regarding cover plants, they present some divergences as to their effect in relation
to nematodes, being able to be promising in relation to the management and to increase or
decrease the population density of the species present in the area. The forage turnip, white oats
and black oats presented themselves as multiplying plants of the species Helicotylenchus
dihystera. For Meloidogyne javanica, the forage turnip crop increased population density,
followed by black oats and white oats. For Pratylenchus brachyurus, both black oats and white
oats and nabo forage kept the population denside between 20 and 40 specimens/100 cm³ of soil.