Rice harvesting

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Rice harvesting
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When to harvest

• Harvest at the right time is important because
• maximize grain yield, and
• minimize grain damage and quality deterioration
• maintains the germination potential of rice seed

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Harvesting

• too early
• Harvesting rice earlier will result in a larger
  percentage of unfilled or immature grains, which
  results in lower yield and grain quality. Lower
  grain quality may lead to higher grain breakage
  during milling. If the grain has a moisture
  content gt 25 , it is more difficult to remove
  the grains from the panicle and some damage may
  occur during machine threshing.

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Harvesting

• too late
• beyond optimum maturity can lead to a rapid
  reduction in moisture content to lt20, which is
  too dry for mechanical harvest.
• This can lead to high shattering losses.
• Grains that dry during the day might absorb
  moisture during night or during rainfall
  resulting in cracks, which reduces the milling
  yield. In addition, grains become more brittle
  and therefore break easier in the thresher.

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The right harvesting time

• As a guideline, harvest can be based on
• 1. Measuring moisture content (M.C.)
• Measuring MC is  the most accurate
• method. For harvesting the grain moisture
  content ideally is between 20-25 (wet basis). 
  Grains should be firm but not brittle when
  squeezed between the teeth.

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harvesting time cont

• 2. Ripe grains per panicle
• The crop should be cut when 80-85 of the grains
  are straw colored.

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harvesting time cont

• 3. Number of days after sowing
• Generally the ideal harvest time lies between
• Late variety 130-136 days after sowing ,
  Medium variety 113- 125 days, and
• Early maturing varieties 110 days

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harvesting time cont

• 4. Number of days after heading
• Generally the ideal harvest time lies between
• In dry season harvest, an optimum time of
  harvest is 28 to 35 days after heading.
• In wet season harvest, optimum time is 32 to
  38 days after heading. 

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Harvesting operations

• Cutting
• Hauling
• Trashing
• Cleaning

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Harvesting systems

• 1. Manual system using manually operated tools

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Harvesting systems

• 2. Manual harvesting followed by machine
  threshing

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Harvesting systems

• 3. Mechanized cutting followed by machine
  threshing

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Harvesting systems

• 5. Combine harvesting

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Drying rice
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Rice dryingwhy drying rice grains ?
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Any questions
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The rice grain quality

• Components of grain quality
• Moisture content.
• Purity dockage and varietal.
• Cracked grains
• Immature grains
• Damaged grains
• Discolored/fermented grains

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Grain moisture content
Paddy is at its optimum milling potential at
moisture content of 14 wet weight basis
Rainfed lowland 25
Irrigated 55
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Purity

• Dockage.
• refers to materials other than paddy and
  includes chaff, stones, weed seeds, soil, rice
  straw, stalks, etc

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Puritycont

• 2. Varietal
• A mixture of varieties causes difficulties at
  milling, thus lower grade of milled rice.

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Cracked, immature and damaged grains

• Cracked.
• Overexposure of mature paddy to fluctuating
  temperature and moisture conditions leads to
  development of fissures and cracks in individual
  kernel.  Cracks in the kernel are the most
  important factor contributing to rice breakage
  during milling.

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Cracked, immature and damaged grains

• 2. Immature
• Affect yield and quality.
• The optimal stage to harvest grain is at about
  20-24 grain moisture or about 30 days after
  flowering

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..cont

• 3. Damaged
• development of off-odours and changes in
  physical appearance. These types of damage are
  caused from water, insects, and heat exposure.

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Discoloration/fermented grains

• over-exposure of paddy to wet environmental
  conditions before it is dried. This results in a
  combination of microbiological and chemical
  activity that overheats the grain

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Any questions
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Rice storage
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Tips on storage

• Safe storage of rice for longer periods is
  possible if three conditions are met
• Grain is maintained at moisture levels of lt13 or
  less
• Grain is protected from insects, rodents and
  birds
• Grain is protected from re-wetting by rain or
  imbibing moisture from the surrounding air.

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Seed moisture during storage

• Seed is hygroscopic .
• If seed moisture gt13 problem with insect and
  fungi damage in storage.
• Therefore, moisture of 9-12 must be maintained.
• For very long storage, very low moisture lt8 ,
  hermetic storage is practice, in air tight
  bottle.

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Thank you