Seed treatments with insecticides, mixture of fertilizers and sowing depths on the emergence and growth of Brachiaria grasses / Tratamento de sementes com inseticidas, mistura com fertilizantes e profundidades de semeadura na emergência e crescimento de braquiária

AUTOR(ES)
DATA DE PUBLICAÇÃO

2008

RESUMO

The mixture of seeds of forage species to fertilizers at sowing time can reduce operational costs and favour the associate cultivation of crops such as corn and beans, specially when the crop-cattle Integration System (ILP) is employed. However, the contact of the fertilizer with the seed can impair the germination, the emergence and the establishment of the forage plants. The objective of this work was to evaluate the treatments of seeds with insecticides, mixture of fertilizers and sowing depths on the mergence and growth of Brachiaria grasses. The experiments were divided into two steps, both including one part in the field and another one in the greenhouse. In the controlled environment the experiments were always carried out in a completely at random design, and in the field the design was of at random plots. In the first step four experiments were done. The first on in the greenhouse, Brachiaria grass seeds treated with the insecticides thiametoxan and fipronil and without treatment (controls) were sown in plastic boxes containing soil collected in the field, mixed to the granulate fertilizers NPK 6-30-6, NPK 8-28-16 and simple superphosphate (SFS). At 15 and 21 days after the emergence (DAE), the number of plants per box (0.112 m2) was evaluated, and together with the 21 DAE the aerial part and root dry masses of the Brachiaria plants were evaluated. The second experiment was carried out under field conditions and was constituted by the same treatments done in the greenhouse. At 30 and 60 DAE the dry mass of the Brachiaria plants was quantified. Each species of the plants (Brachiaria brizantha and Brachiaria decumbens) was an experiment. The second step was also composed by four experiments. In the first two, under field condition, two sowing methods of the seeds (in furrows and casting) were evaluated together with the seed treatments (thiametoxan, fipronil and control). At 30 and 60 DAE the number of plants by square meter was evaluated. The dry mass of the Brachiaria plants was determined at 60 DAE. In the other two experiments, in the green house, three sowing depths of Brachiaria seeds were studied (0, 3 and 6 cm), with the seed treatments (thiametoxan, fipronil and control). At 15 and 28 DAE the number of plants per box (0.112 m2) was evaluated, and at 28 DAE the aerial part and root dry masses were checked. In the first step, in the greenhouse experiment, it was observed the best result was obtained with the Brachiaria seeds sown mixed with the simple superphosphate. The fertilizers NPK (8-28-16 and (6-30-6) reduced the emergence of the Brachiaria species. Different from the results observed in the greenhouse, under the field conditions experiments, the greatest density of plants and the greatest production on dry mass were obtained with the seeds mixed with the fertilizers 8-28-16 and 6-30-6. The treatment of seeds with fipronil produced the best result both for the density of plants and for the dry mass, no matter the fertilizer used. In the second step, in the field experiments, it was observed that the seeds not treated with insecticides sown by casting showed a smaller density and smaller dry mass production. When the seeds were treated with fipronil a greater number of plants by square meter was observed. In the experiments in the greenhouse, there was no effect of the treatments of the seeds but there was an effect in relation to the sowing depths. Seed sown from 0 to 30 cm of depth showed a greater density of plants and greater production of dry mass of the aerial part ad of the roots.

ASSUNTO(S)

fitotecnia sowing method thiametoxan adubação fipronil thiametoxan fertilization método de semeadura fipronil

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