Rainfall excess during the last harvest in the main productive areas of the country compromised most of the soybean seeds to be used in future plantings. A wide spectrum seed treatment can turn into the best ally to recover health, vigor and germination power: Keys to choosing the best product.
After the very delayed soybean harvest caused by the excess humidity and the constant rainfalls which were suffered by the main productive areas of the country, the quality of the soybean seed was highly affected. The situation brought uncertainty. Will the available seeds be able to cover the planting surfaces in the coming season? What is true is that very marked differences can be established at the time of evaluating the quality of the seeds which will soon be used for planting, this makes it essential to establish different ways of management, so as not to affect the results of the season’s planting.
On the one hand, there are high quality seeds: All the soybean seeds that were harvested before the bad weather in optimal environmental conditions. It can be drawn from the analysis that they have a germination power (GP) of between 90 and 95%, together with vigor and good health. For this case, from Rizobacter’s technical service, it is recommended to, “Get the most out of quality by adjusting the planting density. The best is to protect the seed to the maximum extent, with seed treatments which have excellent control, especially against pathogens present in our soils”.
The case of the seed which was harvested after the bad weather is different; This affected 60% of the seeds available for this season’s planting. Although each plot has its own particular situation, it is being clearly observed by different labs and quality tests that the seed has a regular to bad quality. From these tests, GP values which range from 25 to 80% can be found. In these cases, the strategy to follow with seed treatments will be essential not only due to the fall of the germination power but also the high presence of pathogenic fungus, the effect on vigor and the mechanical damage caused by bad conditions at the last harvest. It has been observed that healing can reach more than 20 GP points in highly-infected samples.
Specialists in seed therapics from Rizobacter’s technical service, set out a guide for good treatment before worry and alert set in among farmers.
For the rescue of germination power
The quality parameter most affected by the bad weather is the germination power. Low values are explained, in most of the cases, by the high presence of seed pathogenic fungi such as fusarium and phomopsis, with infection percentages much higher than in other years.
Although these pathogens drastically affect the GP, it is also known that seed treatments can control their action, especially those which combine different fungicide active ingredients, that can disinfect seeds to the maximum.
For effective control, Rizobacter recommends for these cases the application of MAXIM EVOLUTION, a seed treatment which has three state-of-the-art active ingredients in its formulation. FLUDIOXONIL, TIABENDAZOLE and METALAXYL-M.
Figure 1: Highly infected seeds – GP Control not cured: 42% – GP cured with Maxim Evolution: 88%
Vigor is another quality parameter compromised in soybean seeds. It needs special care because it it responsible for defining germination in the field when conditions are not optimal. In order to determine it a test different from the traditional GP, which is normally done in the lab, has to be carried out (for example, accelerated aging or cold test).
There is no doubt the tests show that in this planting season the vigor will be affected by the stress suffered by the seed from the physiologic maturity until the harvest, with high humidity percentages, high temperatures and the subsequent storage.
For these cases, the selection of a specific seed treatment makes a big difference. When the seed is taken to the field and germination is delayed, it is advisable to maximize the protection with molecules appropriate to the control of soil pathogens. Rizobacter proposes the application of Maxim Evolution since the combination of three fungicides offers superiority of control over rhizoctonia (FLUDIOXONIL), oomycetes such as Pythium and Phytophthora (METALAXYL-M) and fusarium spp (TIABENDAZOLE).
Figure 2: Emergence differences in favor of Maxim Evolution in highly infected seeds and with low vigor (more speed and uniformity than a conventional seed treatment such as Tiram plus carbedazim).
Covering the mechanical damage
This year, the harvest was carried out with humidity percentages higher than normal, which caused, in most cases, high mechanical damage due to dents on the seeds. This situation is worrying and also requires a special mode of treatment.
The level of damage is determined by the time of choosing the fungicide active ingredients which are present in the seed treatments, as well as the time for carrying out the treatment.
For seeds with high mechanical damage, Rizobacter’s technical service recommends not curing in advance and using fungicide molecules with formulations which are environmentally-friendly to minimize or avoid possible phytotoxicity problems. In this sense, it is necessary to clarify that there are differences between fungicidal seed treatments given by the formulation and the active ingredients, and that although there isn’t a recipe to apply, in general terms, the mixtures with Tiram + carbendazim tend to be more aggressive towards the seeds.
Another important point to consider when choosing a seed treatment, is that the seed with alterations to its teguments, cotyledons and embryo, is a substratum very accessible to soil microorganisms, which take advantage of the injures or lesions to produce the death of seeds and seedlings during the planting-emergence stage. The process is known as damping off, caused by the action of Rhizoctonia solani, Pythium spp, Phytophthora sojae, Macrophomina phaseolina and Fusarium spp. This is why it is necessary to use combinations of molecules which ensure an effective control of these microorganisms.
“It has been proven that any unforeseen weather events can come up and throw out all the plans. The only certain thing is that one never knows how much time the seed will be under the soil and that’s why it is very important to have it protected with a good therapic”, remarks Gabriel Mina, responsible for seed therapics at Rizobacter.
- Analyze the quality of each seed and determine the management plan for each plot based on that. Recommended tests: Germination Power, accelerated aging or cold test and if possible, pathology tests. All the analyses must be carried out on both cured and uncured seeds.
- Quantify the mechanical damage to the seed.
- In seeds with high mechanical damage (more than 10%) and high humidity (maximum 13.5%) it is NOT advisable to carry out the curing in advance.
- The plot of seeds selected as such must be classified and cleaned urgently to prevent it from deteriorating during the storage stage (all inert material which is a source for humidity must be eliminated).
Seeds which are highly infected and have low vigor must be protected to a maximum extent with fungicidal molecules which have different sites of action and are effective (MAXIM EVOLUTION).