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 Enquiries SEED News - may/june 2006
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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
I have been noticing that there is always half-broken seeds among my soybean seeds and, as they do not germinate, I would like to know if it is difficult to separate them during conditioning?
The presence of half-broken soybean seeds in a lot is undesirable as a matter of fact, both because of their appearance and their effect on germination. Separing such undesirable material is easy, and it can be done by using screens with oblong perfurations or either spiral separators. The fact is that seeds, when transported to be packed or even when handled, can break in halves. So all broken seeds can be removed; however, as they will be handled later, some of them can brake, thus affecting the lot quality.
In some visits, during harvest time, I noticed that some seed producers are using the pH of seed exudate test. Could you comment how is the test performed, and on what is it based on?
The test, pH of seed exudate, is a rapid one, often used on soybean seeds during harvest time. In just 30 minutes it is possible to know the seed viability. Basically, the methodology consists in soaking the seeds in water in a special tray with individual compartments for 30 minutes, then dropping a sodium carbonate plus phenolphthalein solution. The principle bases on the fact that low quality seeds have a buffering feature on the soaking water, which is higher than the soaking water of high quality seeds. Carbonate will cause the pH of the high quality seed to increase, turning the solution into a pink coloring due to the action of phenolphthalein (pH indicator).
I was a technical meeting about maize crop, where one of the lecturers showed a beautiful maize cob saying that it was a signal that the crop productivity with that cob would certainly be higher than 10t/ha. Please explain how such number was achieved.
In order to calculate the productivity of a maize crop, the following points must be taken into consideration: plant population per hectare, number of cobs per plant - which in average is 1.3 - , number of seeds per cob and seed weight. All those production components can be determined directly from the crop, except for seed weight. However, a variation of 2.5 to 4.5 seeds per gram can be considered. So taking your beautiful cob with 510 seeds and weighing 3 seeds/gram we will achieve 170g/cob and, with a population of 50,000plants/ha, with an average 1.3 cobs/plant, we come to 65,000 cobs/ha. Making the calculations, we find 65,000 cobs/ha X 170g/cob = 11,050kg/ha or 11.05t/ha.
We have an intermittent drier that I would like to use for drying seeds. Should I worry about any special detail?
Intermittent driers are suitable for drying seeds and they have a high drying capacity over (usually) 1.2 percentual point of moisture per drying hour. The care that we must take with this kind of drier relates to the number of turns the seeds will give to finish the drying process. In order to control such inconvenience, an high temperature of the drying air must be used, and making sure that the seed temperature is not over 43°C toward the end of the drying process. Usually temperatures of the drying air from 60 to 70°C, are recommended.
I liked very much the central issue of the last SEED News edition. The activity given by three large vegetables companies was very clarifying. However, I would like to know why do they all need to import seeds in order to supply the Brazilian market.
As you could see in the news, each company's portfolio is greater than 300 materials involving vegetables, medicine, and flower seeds. Such number is said to be high, and taking into consideration that several species need special sunlight and temperature conditions to flower, a seed company needs to look for seeds in places very far from the production site of the material for consumption. Other consequence of the high number of materials is the need for partnerships with improvement programs in order to better assist customers.
Please be so kind to explain the importance of the genetical variability to obtain better varieties.
The importance lies on improvement programs because, in order to improve a given variety, there must be genetic variability, so that the breeder is allowed to transfer the best features from a material to another.
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