Seed to Seed Quality
       
  What is the importance of clean paddy rice?  
  Identify the importance of clean paddy rice and describe two cleaning methods: winnowing and mechanical.  
     
Why is clean paddy rice important?
 

Threshed grain contains all kinds of dockage (impurities), which should be removed as soon as possible after harvesting and certainly before storage. Clean grain:

  • has a higher value than grain that is contaminated with straws, chaff, weed seeds, soil, rubbish, and other non-grain materials
  • improves the storability of grain
  • reduces price penalties at the time of selling
  • improves milling output and quality.
 
Cleaning grain by winnowing
  Winnowing is a simple traditional cleaning method that uses wind or a fan to remove light foreign matter from the grain. Mechanical winnowers that use a fan and several superimposed reciprocating sieves or screens are now used in many countries. These can be manually powered or motorized and have capacities from 100kg to 3 tons per hour.  
   
Winnowing is an important technique for cleaning grain at the farm level. If there is not enough wind, simple electric air fans can be used to separate lighter materials from the grain.
Cleaning grain mechanically
 

Where combine harvesters are used, there is a trend towards using large capacity centralized seed cleaners. These are normally equipped with a series of vibrating sieves and are capable of 10-30 tons per hour.

  
   
A mechanical seed cleaner, capable of cleaning 10-30 tons per hour.
Next lesson
   Now that the paddy rice is clean and free of dockage (impurities), it is ready for drying. In the next lesson, you will examine two drying methods and discover the optimal moisture content that paddy rice should have before it is dried.