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 Enquiries SEED News - jan/feb 2007
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This section is coordinated by the professors from the Federal University of Pelotas-Brazil, with the objective of answering the inquiries sent by the readers.
Send your question to e-mail: silmar@seednews.inf.br
"Please comment the importance of the sampler when analyzing quality of a seed lot. I understand that this person is not the one who performs the quality tests."
A 20 tons wheat seed lot has more than 600 million seeds, and for determining its germination potential only 400 seeds are used (4 x 100). Such example illustrates the importance of taking a seeds sample that is able to represent the lot. For that, special techniques and equipment are used and the sampler is a trained and accredited person for taking that seed sample.
"I know that several products are currently propagated along with their seeds in order to increase their performance, such as hormones, fungicides, micronutrients, and others. I would like to know how these materials are added to the seeds, because some of them are, even, presented as powder."
Science has achieved significant advances in the past years and currently we have available several products and processes for increasing seed performance and productivity. In order to propagate such products so that they are stuck with the seeds and are well distributed, a coating with polymer application is used. For each instance there is a product or process more suitable and the industry is able to attend it.
"I have noticed in the last edition of SEED News that in Brazil soybeans seeds are graded by means of flat, round holed sieves. I would like you to comment it. I have understood that cylindrical, oblong holed sieves are more efficient."
As a matter of fact, soybeans seed in Brazil are graded into two or three sizes according to their width, and for that round holed sieves are used. If they were graded according to their thickness then oblong holed sieves should be used. As to the higher efficiency of the cylindrical sieve, it is right. However, for soybeans, which is oval shaped; flat sieves also perform a good job, especially if we use coverage in the first sieve so that seeds do not jump.
We frequently receive questions about the best variety or hybrid for a given place. In this way, we will comment something general about this question.
The performance of a hybrid or variety is a function of its genetical load and the environment in which it is cultivated. Some materials are more responsive than others; however, all of them respond to such factors. So, in order to know what the best material that fits the region is, we must look for information about the material in the moment it was registered for commercialization. All materials, to be commercialized, must present the Value for Cultivation and Usage (VCU), which is obtained by experimentation during two years in different places.
"I have heard that a lot of Brassicas seeds with over 90% germination was exported and, one month later, presented less than 30% germination. Experts have been called and it was determined that the cause of the drastic germination reduction was the secondary seed dormancy. Could you explain this?"
Seeds present dormancy for species protection; it is an ordinary process in weed seeds. Secondary dormancy manifests when conditions are adverse to the seed or when flowering is programmed for a dry or cold season. Examples of stresses causing secondary dormancy are light, in case of lettuce seeds, and high temperature, for some Brassicas, sorghum, and red rice seeds.
"I do cultivate millet for fodder and soil coverage. In the past harvest I had to replant the crop due to low stand, even though the germination of the seed lot was over 80% and the soil conditions were good. I assumed that seeds were of low vigor and, in this sense, I would like to know which vigor tests can be used for millet seeds?"
We agree that your seeds probably were poor in vigor. There are few studies about vigor tests for millet seeds; however, the accelerated aging test, in which it is possible to separate seed lots with different physiological quality, has been showing good results. Another test, considered as a universal one, is the field emergence test, which tends to simulate soil conditions at sowing time.
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