Soybean seed treatment to maximize productivity

The use of quality genetic material, with excellent physiological and health characteristics, without contamination, is an extremely important component for soybean producers to maximize productivity results. And seed treatment with insecticides+fungicides is an ally to assist in this process.

To be considered high quality, soybean seed must have physiological and sanitary characteristics, such as high rates of germination vigor and health, as well as guarantee of physical and varietal purity, and not contain weed seeds (KRZYZANOWSKI, 2004) . In order to avoid possible losses resulting from the action of soil and aerial pests and diseases, which damage seeds and young seedlings, the alternative is the use of insecticides and fungicides in seed treatment (MARTINS et al. 2009). According to Menten (2005), seed treatment with insecticides and fungicides is a practice that in most cases makes it possible to reduce the number of chemical product applications after the crop emerges.

The tests used to analyze seeds must carefully follow the prescriptions of the Rules for Seed Analysis (BRASIL, 2009), with the aim of standardizing the procedures for installing, conducting and evaluating germination tests. Thus, it is expected to minimize errors, obtaining uniform and comparable results. Germination and vigor tests are essential in the quality control of seed production companies, aiming to identify batches with a greater or lesser probability of performing well in the field or during storage (MARTINS et al. 2002).

With the aim of evaluating the vigor and germination percentage of soybean seeds after treatment with fungicides and insecticides, work was carried out in the Seed Laboratory of the Agronomy course at the State University of Maranhão (UEMA), in the municipality of Imperatriz, Maranhão. 138,12g of soybean seeds from the BRS 9090 RR cultivar, batch: 024/13 for commercial use with 95% vigor were used, produced at the Embrapa unit located in the same municipality.  

Seed treatment was carried out with commercial products, such as fungicides from the chemical group: acylalaninate and phenylpyrrole; chemical composition: (metalaxyl – M and fludioxonil), insecticide from the chemical group: neonicotinoid; chemical composition: (thiamethoxam), and the insecticide belonging to the chemical group: pyrazole; chemical composition: (fipronil).

The treatments were: Witness T0 - no treatment; T1 Treatment - fungicide (metalaxil – M and fludioxonil) in the recommendation of 3,47 ml of the product for 500ml of water, to treat 200 seeds, that is, 34,42g of seed; T2 Treatment - fungicides + insecticides (metalaxyl – M and fludioxonil and thiamethoxam) in which 3,5 ml of the two products were used dissolved in 100 ml of water, to treat 200 seeds, which corresponds to 34,55g of seed; T3 Treatment - fungicides + insecticides (metalaxil – M and fludioxonil and fipronil) using 3,5ml of the two products mixed with 100 ml of water, to treat 200 seeds, corresponding to 34,60g of seeds.

After the samples were treated with chemicals, the test was conducted normally, using Germitest paper, free from toxic, water-soluble chemicals, fungi and bacteria that could interfere with germination. The material has adequate water absorption and retention power and a pH index of 6,0 to 7,5. Its texture must be such that the roots develop over and not through its surface. The paper sheets were placed in plastic trays previously washed and sterilized with 70% alcohol and moistened with water. Then the seeds were distributed on the paper in four repetitions, with each repetition having 50 seeds.

The germination roll was composed of three sheets of paper, previously moistened, two at the bottom, where the seeds were deposited, and one or two sheets at the top, covering the seeds. 

The seeds were distributed on previously moistened sheets of paper and also covered with sheets of paper, folding the bottom part of the paper and the right side, approximately 3cm, so as not to harm the development of the roots of the seedlings close to the folds. . Then, the tied and identified rolls were placed in the germinator at a temperature of 25°C.

The roller must not be too tight, so as not to harm the normal development of the seedlings, which can be damaged, in addition to the risk of aeration restrictions and greater possibility of biological contamination of the test. Each group of rolls, representing a sample, was identified with the name of each treatment. During the test, which lasted 7 days, the room temperature was monitored daily.

The seed germination count was carried out from the installation of the test until its closure, which lasted 7 days. After seed germination, the vigor of each seedling was assessed. The length of the seedling hypocotyls was measured, after seven days, from the end of the plumular hook to the beginning of the main root, where the appearance of secondary roots was observed.

Table 1 shows the averages obtained in the germination tests for each replication, which were verified for each treatment. In individual treatments, 200 seeds were used, divided into 4 replications containing 50 seeds.

It is possible to observe that in treatment T0 (control) there was no change in the germination content, coinciding with the same germination value of the seed lot supplied by Embrapa, which is 95%.

In the T1 treatment, using only the fungicide (Metalaxil – Me Fludioxonil), 200 of the 196 seeds germinated, equivalent to 98%, with an increase in seed germination in relation to the control of 3%. The T2 treatment was carried out with a fungicide and insecticide combination (Metalaxil – M and Fludioxonil and Thiamethoxam). In this case it was observed that of the 200 seeds, 193 germinated, the same as 96,5%, and in relation to the control there was an increase in germination of 1,5%. The T3 treatment, carried out with the fungicide and insecticide combination (Metalaxil – M and Fludioxonil and Fipronil) of 200 seeds, germinated 195 seeds, that is, 97,5% and there was an increase in germination of 2,5% in relation to the control. According to Table 1, the treatments that had the highest percentage of germination were, T1 - Metalaxil – Me Fludioxonil and T3 - Metalaxil – M and Fludioxonil and Fipronil.

In results evidenced by Krohn et al. (2004), it was attributed that most of the time treated seeds perform better than the control. The efficiency of fungicides and insecticides in eradicating fungi, whether pathogenic or not, as well as the harmful effect on seed quality, has been proven by several researchers, who recommend treatment immediately before sowing.

Castro et al. (2008), in research, found similar results for the insecticide imidacloprid, in the treatment of soybean seeds. On the other hand, treatments with imidacloprid + thiodicarb, acephate and carbofuran showed lower germination percentages than the other treatments, indicating little negative effect on this variable.

As for the analysis of vigor through the hypocotyl, it was as follows; the seedling was measured from the base of the hypocotyl to the cotyledons. As shown in Table 2, of the 4 four treatments, the hypocotyl was more developed: T1 - Metalaxil – Me Fludioxonil. T2 - Metalaxil – M and Ffludioxonil and Thiamethoxan, in relation to the control. Graph 1 shows that treatments T1, T2 and T3 recorded a higher rate of germination and vigor of the seeds, also compared to the control.  

In the T1 treatment, using only the fungicide (Metalaxil – Me Fludioxonil, germination was 98% in relation to the control. The T2 treatment, was carried out with the fungicide + insecticide combination (Metalaxil – M and Fludioxonil and Thiamethoxam). In this case a germination percentage of 96,5% was observed in relation to the control (95%).

In treatment T3, carried out with the fungicide + insecticide combination (Metalaxil – M and Fludioxonil and Fipronil), the germination percentage was 97,5%. The treatments that had the highest percentage of germination in relation to the control were T1 - Metalaxil – Me Fludioxonil and T3 - Metalaxil – M and Fludioxonil and Fipronil.

Of the four treatments, including the control, those that achieved the greatest development of the hypocotyl were: T1 - Metalaxil – Me Fludioxonil. T2 - Metalaxil – M and Ffludioxonil and Thiamethoxam.

In this work, it was observed that seeds treated with fungicides + insecticides had a higher percentage of germination and hypocotyl development, compared to the control.       

Edvan Costa da Silva, Eric Leonardo Maciel dos Santos, Léo Vieira Leonel and Humberto Filipe Torres Reis, State University of Maranhão

Article published in issue 203 of Cultivar Grandes Culturas.