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 Enquiries SEED News - may/june 2008
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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
"It is a well known fact that to engage in the production of large volumes of quality seed, a drying system capable of extracting seed moisture at a rate above one percentage point per hour is essential.
I'd like to know which species are more susceptible to this kind of high drying rate."
To achieve high drying rate, the best combination is that of high air flow with low relative humidity (provided through heating of ambient air). The air flow is responsible for the transportation of the moisture surrounding the seed outside of the drying environment, whereas the low relative humidity of the air flow triggers the migration of water from the inner parts of the seed to its surface and the surrounding environment, through the process known as hygroscopic balance. If this migration is too fast, internal cracks may result in the seed structure, being rice and corn the most susceptible species to this kind of injury. When high temperatures are used to lower the air's relative humidity, soybean seeds are one of the most susceptible to injury during drying.
"I have come to notice that all corn seeds on the market are graded, as are the majority of soybean seeds. Could you explain briefly the purpose of seed grading?"
If we examine a corn we'll notice that it has quite a range of shapes and sizes; the seeds from the top and bottom of the ear are rounded whereas those from the middle are flat and with a different size. Thus, corn seeds are graded as rounded, flat, long, short, wide or narrow and its applicability can be tested at the time of sowing, through the establishment of the percentage value for double seeds and planting failures. The procedure for soybean seeds is essentially similar and these are graded through their width. The scope of seed grading is to aid the sowing process, since this is the first step to establish the yield potential.
"For those of us who were born into agriculture, we have been told by our grandfathers that seed is the most important input, and that its production and supply are essential to keep agriculture alive. Regarding this issue, we would appreciate a comment on the importance of the different laws on seeds and their impact on their availability to growers."
Of course we share the concept that the seed is the most important input, however, with technology innovations being released with a high frequency, other inputs have come to be of relevance, too. Meanwhile, the laws on seeds were the necessary tools to discipline the domestic and international trade, providing those eager to invest in this activity with the necessary safe environment to guarantee an adequate supply. Our perception is that, if priority were to be assigned, an adequate seed production and supply comes first and legislation on the subject would follow, as a reflection of the need to adequate its functioning.
"The handbook on seed germination rules contains a series of procedures to overcome seed dormancy for a wide range of species. I would like to know for which of our main crops it is not necessary for the seeds to be subjected to dormancy overcoming tests prior to their germination analysis."
Seed dormancy is a basic survival mechanism by which seed germination is spread over time, so that some of them will be able to germinate and eventually end up setting a new generation of seeds. Among the main agricultural crops, corn seeds do not express dormancy as the result of the trait having been suppressed by intensive genetic breeding. Thus, to preserve species, man has intervened storing seeds in germplasm banks.
"As a soybean grower, I'm literally being bombarded by various seed growers that offer me seed from a range of varieties completely unknown, but that according to them show interesting traits.
How could I possibly verify that all these advertised features are really carried by the seeds?"
The performance of any plant cultivar results from its genetic load plus the influence of the environment under which that plant develops. To assess these issues, before any new plant cultivar is released into the market, it must undergo evaluation trials at three different locations during two growing seasons, or in two locations for three consecutive growing seasons. After this period, and if successful results were achieved, the new cultivars can be appropriately registered and marketed. Since this information is available to all those interested in it, you can ask and search for it. Typically, the new cultivars are tested under various environments to minimize the risk of judgment based on biased information and to be able to cover a larger area, which will ultimately be the target for marketing the product. If for any reason the information on the cultivars' performance would be unavailable there's always he chance to attend to field days, in which it is possible to observe the different cultivar plots and collect printed information on them.
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