Tratamento industrial e armazenamento: sementes tratadas com nematicidas e as consequências sobre a qualidade, nodulação e produção da soja

Abstract

In order to achieve significant productivity, it is necessary to efficiently manage the soybean crop, including pest and disease control. In this context, seed treatment can help protect seeds and seedlings, favoring the initial establishment of the crop. Nowadays, it is common practice to treat seeds using a variety of products, both chemical and biological, but these must not affect the quality of the seeds and there must be no incompatibility between them, especially when stored. Seed treatment and storage is especially necessary in industrial processing, for technical and logistical reasons. In the case of soybeans, one of the great challenges of industrial treatment is to find formulations that do not interfere with the viability of Bradyrhizobium and consequently nodulation (biological nitrogen fixation - BNF). Therefore, the aim of this study was to evaluate the effect of treating soybean seeds with chemical and biological nematicides on the physiological quality of stored seeds and nodulation by Bradyrhizobium. Seeds of cultivar 97R50IPROwere treated with the chemical nematicides Abamectin, Thiophanate-methyl + Fluazinam and Fluopiram and the biologicals Bacillus amyloliquefaciens, Bacillus subtilis + Bacillus licheniformis, Pasteurianishizawae + Biological biostimulant and inoculated with Bradyrhizobium. All the seeds were treated with the fungicide Picoxystrobin + Ipconazole + Oxathiapiprolim and the insecticide Chlorantraniliprole, as well as the polymer L232 and drying powder. The first experiment in the laboratory and greenhouse was carried out using a completely randomized experimental design in a 9x4 factorial scheme. The treated seeds were stored for different periods until evaluation and sowing, 0, 15, 30 and 45 days, after which they were assessed for physiological quality using the germination and accelerated ageing tests, while in the pots in the greenhouse, nodulation, dry mass of nodules and roots, volume and length of roots were assessed. Seed treatments and 45-day storage resulted in a reduction in physiological quality in the Fluopiram and Control treatments.The nematicide molecules provide different nodulation rates in soybean plants, with the influence of the storage time of the treated seeds. In the second field experiment, a completely randomized experimental design was used in a 9x3 factorial scheme. The treated and inoculated seeds were stored for 0, 15 and 30 days until sowing. The field evaluations were stand, normalized difference vegetation index (NDVI) and yield (kg.ha-1). At the longest storage time, phytotoxicity occurred in the field as measured by NDVI. For some nematicide molecules, such as Fluopiram, Abamectin and Thiophanate-Methyl + Fluazinam showed higher phytotoxicity results. Productivity was affected when using chemical nematicide molecules compared to biological nematicides.