In this section we try to answer the questions submitted by readers. Doubts about any subject cobered by SEED news or even other pertinent to agriculture, can be forwarded to redacao@seednews.inf.br


    In the process of producing soybeans seeds, what is the percentage of utilization as seed in relation to grain production?

    The fields for seed and grain production, in terms of quantity, are conducted in a similar way. However, in terms of quality, they are quite distinct, because the seed must be alive and strong, and be pure, which does not occur with the grain. Thus, processes are used to separate undesirable materials from the seed such as damaged seeds, immature seeds, deteriorated seeds, miscellaneous impurities and fields with varietal mixture. Normally, these separations reach 50% of the yield of a field, that is, considering a productivity of 3,000kg / ha, only 1,500kg are used as seeds.



    The seeds spend some time stored before being sown; so I would like to know what I should take into account in order for the seeds not to lose their physiological quality. Would it be the temperature and relative humidity?

    Actually, the seeds spend some time stored before being used, varying from a few months, as is the case of soybean, up to years, as is the case with vegetables. For soybeans to be stored for up to 6-8 months, temperature conditions between 15-20oC and seed moisture between 11-12% are recommended, while for vegetable seeds, which are stored in various environments (including supermarkets), moisture is reduced to 4-5% and should be placed in impermeable packaging to avoid hygroscopic equilibrium and increase moisture. The recommendation is to use as reference the temperature and seed moisture, instead of the air humidity, although there is a hygroscopic equilibrium, as this may take a long time to occur if the air does not pass through the seed (as is the case with seeds in a stack).



    Some seeds are being sold per unit and not by weight, which I consider to be a major advance, since the stand is defined by seeds per m2 and not by weight. In this sense, I would like to know how the number of seeds in a Big Bag with around five million seeds is determined?

    The determination is performed by sampling, where eight replicates of 100 seeds, whose average is multiplied by 10, are weighed. Thus, the weight of 1000 seeds is obtained, which in soybean varies from 120 to 200 grams. In this way, a Big Bag with five million seeds means that the weight of a thousand seeds was 200 grams.




    I am a sorghum seed producer in a tropical region. I plan the production so that the harvest coincides with the period of the year when there are no rains in the region. Even so, I’m having trouble getting high-quality seed in quantity. What can I do?

    Sorghum seeds, which are in a panicle, mature unevenly, and as drying is relatively slow, due to the difficulty of the air passing through the seeds, those that mature first tend to deteriorate, waiting for the others to dry. So, the recommendation is to harvest the seeds with 15-17% moisture content and pass them through the dryer. Seeds in a compact panicle are literally stored in an unfavorable microclimate.



    Following the technical recommendations, I projected to dry 60% of my soybean seed production, buying two dryers of the intermittent type. It happens that, even using an air temperature of 60oC, the drying speed of my dryer is 0.4 percentage points per hour, instead of 0.8 to 1.0 pp/h. Could you comment on that?

    In fact, intermittent dryers are designed to dry at around 1.0 pp / h, using low relative humidity (increasing air temperature) and high airflow. In your case, where the temperature used is within the recommended temperature, it seems that your problem is in the airflow  that is passing through the seed. So, check that the air is not strangled somewhere between the heater and the drying chamber. Often the problem happens at the entrance of cold air, where it mixes with the hot air coming out of the heater.

  

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