Process of harvesting and preservation of cross-bred corn

   After harvesting, seed moisture content of corn as well as some other plant varieties is high, if they are not dried and processed timely, productivity, seed quality and activities in time preservation will be affected directly. Therefore, after harvesting, breeding corn should be dried, separated seeds, and dried again until the seed moisture content downs 10-12%, then they can be preserved.

Previously, farmers used to dry corn under natural sunlight. At present, however, because of large-scale production, corn will be sowed and they also ripen at the same time, furthermore, maybe in the harvest time, weather will be not appropriate to dry under natural sunlight. Therefore, drying corn by kiln with blower is more guarantee method. However, drying by kiln to reduce moisture content must conform to strict rules of temperature during process of drying. Because heat can crack seeds, kill embryos, and reduce seed quality or even damage whole breeding lot.

  1. Harvesting:

Requirements:

100% number of harvesting corns are correct description of seed, corns are not heated, waterproof; clean corn silk, clean husks, no long rat tail.

Harvesting:

– Harvest timely, when 80-90% husks turn to yellow (ripe completely), it is on not rainy days.
Peel husks cleanly, pluck silks cleanly.
After harvesting, don’t pull into the pile or store in tight sacks overnight, because it is easier to make heating phenomenon, and damage the seeds.
Remove mixed corn, decay or rotten corn, or sprouting corn.
– After selecting carefully, corn are quickly transported to drying and processing facility; Transport to drying facility as quickly as possible.
Operation:
Mobilizing technical human resource getting experience in breeding corn to monitor harvest, pick corn, peel husks, pick and remove decay or rotten corn, sprouting corn and weigh correct seed. Pay local director a flat rate for quality.

  1. Drying corn:
    Requirements:
    – Dry corn as soon as harvesting
    – Drying temperate must conform to strict process.
    Drying:
    – Corn are arranged to bin as prescribed, specifically about 15-16 tons corn/bin
    – Make a fire in a kiln, startup drying kiln, set temperature and monitor its temperature.
    – Adjust the temperature of the kiln matching with set temperature, keep stably as prescribed, for example, seed moisture content at harvest are as follows:
    * Seed moisture content from 30-32%, set temperature at 38.5°C
    * Seed moisture content from 26-27% set temperature at 39.5°C.
    * Seed moisture content from 20-22% set temperature at 40.5°C.
    – Drying duration is about 60-70 hours depending on seed moisture content, stop running machine until seed moisture content from 18-20%

New trial process of Department of Seed Technology
Dry at temperate 39 – 42 – 43 – 44°C with wind flow 300 m3/h
1. Harvesting fresh corn at seed moisture content from 32-34%, then transport to drying bin.;
2. Adjusting blower of wind flow to 300m3/h, run blower in 1-5 hours depending on seed moisture content.
3. Adjusting temperature:
Set initial temperature at 39°C, then increase 0,5°C after each of 4 hours.
Keep temperature until reaching 44°C
Dry until reaching seed moisture content 17-19%, then stop heating and fan coolly in 1 hour.
Separate corn (use dedicated corn separating machine)
4. Separating seed:
Requirements:
– Seeds are not crushed, broken, chipped embryos.
– Clean corn cob
– Don’t mix motorized things.
Implementation:
– Prepare corn separating machine, check, and test running
– Put corn into funnel, and run machine
– Check degree of crushing, breaking of seed and chipping of embryo; cleanness of corn cob.
– Clean machine after seperating
5. Drying seed:
Requirements:
– Temperature have to appropriate to each period of seed moisture content, the highest temperature is 43°C
– Drying seed block don’t be sunk partially
– Thickness of drying seed block is correct as prescribed
– Stir drying seed block 2-3 times/day, especially those have just seperated.
Implementation:
– Seeds are transfered to bin by manual method or by transfering buckets, then spread out
*Temperate in period of drying seed prescribes as follows:
– Seed moisture content from 18-20%, set temperature at 41°C
– Seed moisture content from 15-16% set temperature at 42°C.
– Seed moisture content under 13% set temperature at 43°C. Maintain this temperature until seed moisture content reaches their standard.
– After drying seed, turn off kiln by stopping providing the heat or take compostibles out, continue to fan coolly 45 – 60 mins.
6. Selecting and classifying:
Requirements:
– Clean impurities (£ 1%)
– Classify unqualified seed breeding (small or big seeds, omitted corn cobs)
Implementation:
– Pour corns into pit of transferring buckets, moving up silos, start up the separating machine, adjust machines to run smoothly
– Check cleanliness by measuring the proportion of impurities.
7. Process seeds:
After separating, seeds will be poured into pit of transferring buckets, move to silos to mix chemicals (chemicals have been mixed with water), then needle will spray chemicals to seed block needing to mix.
Requirements:
Chemicals have to mix well, colour of seeds is fresh, seed moisture content after mixing increases about 0.8 – 1%.
We can dye chemicals then dry seeds again. Advantage of this method is: seed moisture content after mixing could be fixed.
8. Packaging:
Requirements:
– Weigh enough quantity as quantity in packing
– Stick tightly, print brand of producer in packing as possible.
– Avoid temperature of high-temperate tape.
Implementation:
– Put corns into packing, stick by machine or hands.
9. Preservation:
After have dyed chemicals, mixed pigments, packaged as quantity, seeds have moved to storage whose seed moisture content and temperate are low to preserve.

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