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 Enquiries SEED News - sept/oct 2005
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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 quite appreciated the central issue of SEED News last edition about seed dormancy, but I would like to know if all seeds have the same type of dormancy.
Dormancy is a survival mechanism of every species; so, depending on the species, there are several types of dormancy, some physical and others physiological ones. The most common physical dormancy is tegument impermeability to water, which we know as hard seeds (common in soybeans, cotton, alfalfa, and clover), while physiological dormancy is caused usually by some inhibitor.
How can one overcome seed dormancy, since germination and emergence need to be maximized?
In cases of physical dormancy, the most common is submitting seeds to sulphuric acid (Brachiaria seeds) or sand paper (clover seeds) scarification. In the event of physiological dormancy, the most usual is submitting seeds to cold (Ryegrass seeds) or heat (rice seeds). It is important to notice that seed storage tends to overcome dormancy. Usually, from three to four months after harvest dormancy is gone.
I noticed that many wheat seeds on the top of the silo had germinated. I am sure the seeds have been stored with 13% moisture content. What should have happened that caused seeds to germinate?
According to your data, the silo has a 300 m3 capacity, which for wheat, with a volumetric weight of 0.78/m3, corresponds to 234 tons. It means that for this silo the seed load is high. In this instance, there is air movement in the seed mass, and in case this air mass is at hot temperature and meets a cold mass, it can cause condensation on silo's walls, mainly at the top. Such condensation will cause leakage, moistening the top seed layer in the silo, so triggering the germination process. In order to avoid condensation, seeds aeration must be done, standardizing temperature and cooling the seeds. Briefly, probably you have not aerated the seeds.
I have often read and heard that intermittent dryers or continuous flow ones with intermittent drying, have a capacity of drying three to four seed loads a day or removing from 1.5 to 2.0 moisture percentage points per hour. As I have a dryer like this with a rather lower performance, I would like to know what must be the problem?
Drying speed is mainly a function of air flow and air relative moisture. For that, dryers are provided with fans dimensioned for supplying a suitable air flow and, for a low relative moisture, the temperature of the drying air must be raised. The problem is likely to be the use of a low temperature of the drying air. For those types of dryers the air temperature can be raised, usually, up to 60 - 70oC because the seed will heat until maximum of 40oC. In case the problem is not air temperature, check for air strangle with the slowers the of flow.
We are being bombed with information on negotiations between seed producers and owners of patented events who charge a technological tax for the use of their inventions. I believe that the whole process can be justified, however I would like your remarks as to the coming future, in which there will be several events incorporated to one single variety?
Currently royalties are charged by varieties owners, worth around 5% the value of the seed, and the technological tax, is higher due to the benefits it promotes. Since there are few patented events, the technological tax is still superior to royalties, but with the massive incorporation of patented events to one single variety, technological tax reduction is the trend, once benefits are less than the cost. We must always take into consideration that things are not achieved as gifts. In case we want to enjoy the benefits, we must remember they will cost something. In case things are not like this, there will be a distortion of the system and everyone involved will lose.
I have many soybeans seed lots with a percentage of greenish seeds. Could you please let me know at what extent must I worry to such situation?
It is known that greenish seeds have a lower physiological quality mainly manifested by the low storage potential. This way, in case your seed lots have more than 10% of those seeds, you should consider discarding them.
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