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 redacao@seednews.inf.br


    I’m working as a consultant to a group of farmers that grow maize and I need to tell them the total amount of seed they need to purchase; please inform the weight in kilograms of a corn seed bag. 

    The law in Brazil is that seeds maize need to be traded on the basis of weight, however, specifically for maize, the bags have to carry 60,000 seeds with a weight ranging from 15 kg to 24 kg, according to seed size. Up to a few years ago, each maize seed used to bag average a weight of 20 kg.


    I’ve heard that to succeed on seed production of the tropical forage Brachiaria brizantha, seed maturation must occur under dry weather, being that Brazil has several regions with such climate. I also know that along the maturation period, the seed shattering is high and seeds remain on the soil surface until harvested, but since they’re dormant their physiological deterioration is minimum. What I’d like to know is what would the outcome would be if rains while the shattered seed is still on the ground? 

    Your comments are appropriate, since Brachiaria seeds show normally high physiological quality when harvested mature and in a dormant state. However, seed dormancy, as any biological process, doesn’t occur in all shattered seeds as there’s always a range of values for any biological event in Nature. This being said, if precipitation were to occur during the dry season with shattered seed still on the ground, non-dormant seeds will most likely germinate, thus rendering them useless.


    Seed testing for physical and physiological quality follows a standardized protocol which ensures that purity and germination tests, carried out in one country can be easily replicated in another, providing practically the same results. This is possible due to the rules for seed testing and quality control systems and at this time I’d appreciate your comments on the different ways a germination test can be carried out.

    Seed testing follows procedures that have been for a long time established and standardized, which facilitates that results from the same seed lot by different laboratories be approximately identical. As for germination tests specifically, there are over 20 different ways to carry it out, involving variables such as temperature, substrates, humidity, dormancy overcoming procedures, light and counting, among others. The different alternatives for each variable make it possible for seed labs from a specific region to employ those most easily available, as long as they don’t affect the test results.


    Could you please explain why companies marketing maize seed do not print on the bags what kind of hybrid, single, double or triple-cross?

    This is basically the result of perception. At first sight a double-cross hybrid looks better than a single-cross hybrid; however, the latter out-yields the former. Following this, seed companies print on bags that single-cross hybrids are recommended for growers employing high technology resources, meaning that it bears a higher performance potential.


    Considering that the dynamic cooling of soybean seeds to 15°C at the bagging time what would the maintenance temperature and vigor of the same soybean seed mass be if it were packed in big bags, when compared to conventional warehouse storage?     Seeds are not the best thermal conductors, so that in the event of being cooled they’re likely to remain in that state for several months, especially if they’re stored in large-sized bags with capacity for 1,000 kg. Research results have shown that after a 2-month storage period, the equilibrium between ambient humidity and the seeds refers to the first 2 cm from the bag surface. As for vigor, this will most likely remain unchanged for up to six months, if storage temperature doesn’t exceed 15°C.




    Soybean seeds are graded in Brazil according to their width, ranging from 5.0 mm to 7.0 mm; according to this, how could I choose the best option of disks for my sower if the average seed width is 6.0 mm?

    The implication of seeds with average width of 6.0 mm is that they will not pass through a 6-mm sieve with round holes, so that the average hole size for the sower disks should be at least 7.0 mm, since not all seeds are equal and size will likely range from 6.0 mm to 7.0 mm. While both seed sizes will pass through this sieve, it should be reminded that small seeds can pass this sieve grading but the opposite, large seeds passing through a smaller sieve grade is not possible, unless the latter is damaged.

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