module 02 Harvesting
 lesson 07 Cleaning the grain
 obj 1 To identify the importance of cleaning and to describe different cleaning methods.
What is cleaning?
Clean the grain Cleaning is one of the last operations of the harvesting process. Cleaning grain means removing all the materials other than the grain. This could be sand, stones, straw, weeds and so on.

After cleaning, the grain is put in bags to get transported to the place of drying (bagging).
  Why is proper cleaning important?
Clean grain is worth more  Grain cleaning after harvest is important as it removes unwanted materials from the grain. Clean grain has a higher value than grain that is contaminated with straws, chaff, weed seeds, soil, rubbish, and other non-grain materials.

Grain cleaning will improve the ability of the grain to be safely stored, reduce unwanted materials (dockage) for milling, and improve milling output and quality.

Dirty grain can attract certain insects or fungus that might damage the grain.
Cleaning methods:
Winnowing: Lighter materials such as unfilled grains, chaff, weed seeds, and straw can be removed from the grain by using a blower, air fan, or by wind. Winnowing recovers only the heavier grains.

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Screening/Sifting: Smaller materials such as weed seeds, soil particles and stones can be removed by sieving the grain through a smaller sized screen (1.4mm or less sieve opening).

How to select seeds from the grain?
If your harvest, or part of the harvest, is to be used as seed, additional care must be taken during the cleaning process.
Inspect the seeds! Seed cleaning: Malformed, discolored, germinated, broken or moldy grains in seed lots can severely impact seed quality, viability and vigor. Visually inspect the seeds prior to storage and remove these grains from the seed lot.

Choose seed with the same size and shape!  Seed grading: For good seed processing, seed grains should have uniform size and weight. A variety of commercial equipment can be used to achieve uniformity in seed size and shape. These include gravity tables, rotary screens, indented cylinders, and length graders.
Keep seed pure! Seed lot purity: Maintain seed purity by preventing mixing with other varieties and contamination with other species.
Next lesson

In this lesson you learned how to clean the grain. In the next lesson you will learn about a machine that can do different harvesting operations in one go.



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