This section is coordinated by professors from the Federal University of Pelotas/Brazil, with the aim of answering inquires sent by the readers. Send your questions to

    I’ve learned that the main factors that affect negatively seed storage are temperature and moisture, which are responsible for the process of seed deterioration. Would it be reasonable to assume that a seed storage unit equipped with temperature and moisture control mechanisms would be the best option?

    You are right. However, temperature and moisture control equipments are planned for situations in which seeds are static, i.e. bulk stored, and it takes a long time (months) to reach thermal or hygroscopic equilibrium, since air barely flows among the seeds, it is not able to withdraw excess temperature or moisture. This can be overcome by dynamic cooling of bulk stored seed, which can be achieved after a few hours of treatment due to its higher efficiency and uniformity. As for moisture, you can manage it through drying procedures.

    I read on a publication about seed drying that some dryers are able to perform at values over 1pp/hour. Could you explain the meaning of this index?

    There are several types of seed dryers, some which operate at low drying speed such as stationary dryers and those termed as of continuous flow, which dry seeds at a faster rate. Continuous flow driers are capable of reaching speeds above 1pp/hour, which means that a seed lot with 18% moisture will, after one hour of drying routine, yield 17% moisture or less.

    The soybean seed harvested this year shows high values for germination and vigor, but problems have arisen with their grading. Part of the small sieve seed did not pass through the larger size sieve. I’d like to know about the tolerance values for percentage values of small seeds within the larger ones and how can moisture influence seed grading, since at the time of bagging the moisture value was of 13% and today is close to 9%.

    Some small-sized soybean seeds remain within the larger ones when the grading process is done through flat sieves with round holes. Despite not being standardized, the quantity of small seeds, it is advisable not to be no more than 5%. These seeds will increase the number of doubles during seeding and as for the role of moisture on seed grading, as moisture loss goes down, soybean seed size will be reduced.

    I enjoyed the articles on seed vigor and productivity published in SEED News last edition. This kind of published information, together with the promotion of high quality seed, will increase the use of commercial seed by growers and seed dealers will be forced to stop compensating on seed lot weight for the loss of physiological quality. Regarding this last point, how would the use of vigor tests impact on the seed trade?

    Plants originated from high vigor seeds are more productive and the grower is fully aware of this benefit. Considering there are several vigor tests which have been standardized, we think that in the near future seeds from the main agricultural crops will be traded on a vigor basis.

    Please comment on how to proceed on forage seed cleaning, since we’re purchasing seed lots contaminated by different species and soil dirt, which end up infesting our seed crops with weeds and nematodes.

    The process of cleaning forage seeds or seeds from other species has been mastered a long time ago. What happens is that along the cleaning process, several good seeds inevitably go with the undesirable material, thus reducing the quantity of seeds to be traded. Unfortunately, there are still people that do not consider seed quality an issue, thus some regions in Brazil are known to offer forage seeds with high levels of impurity. Brazil exports brachiaria seed with over 99% of purity, which clearly indicates that there is technology available to market high quality forage seed from tropical forage grasses.   

    With the advancement of image and computational technology, what’s the status of online image libraries on weed seeds? It has become increasingly difficult to have available showcases on this matter.

    Several image banks are on the making and will soon be available. However, it will be important to check on who’s responsible for the site, be it a university, class entity, etc.



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