HARVESTING TECHNOLOGY

The crop should be harvested when the grains are fully mature and turn yellow or straw colour (varies according to the variety). Timely harvesting ensures good grain quality and consumer acceptance, since the grain is less likely to break when milled. Harvesting should be carried out when the moisture content of the grain is about 20– 25% and when about 80% of the panicles have about 80% of ripened spikelets. If delayed, grain may be lost due to damage by rats, birds, insects, shattering and lodging. The crop is generally cut by hand using sickles with a serrated edge. The plants should be cut quite close to the ground and left in the field for a few days to dry.Later on they should be collected in bundles and stacked for threshing.

Post Harvest Management

Drying

Direct drying under the sun leads to increased breakage of the grains during milling. Gradual drying in the shade is essential for better recovery in the mills. The moisture content should be reduced to 13–14 percent before milling.

Threshing

The most common methods of threshing are trampling by bullocks, rubbing with bare human feet (in hills) or lifting the bundles and striking them on a raised wooden platform. On big farms, pedal threshers or power driven stationary threshers are also in use. Threshing of rice is still a major problem on small farms.

Milling

The produce, after harvesting, is known as rough rice, paddy or grain. The rough rice is milled before it is consumed. With the husk or hull removed, the highly milled rice is white, translucent or opaque and is classified as head rice, broken, screenings or brewers' rice, according to the size of the kernels.

Storage

Proper storage of the produce is necessary. If rice is stored in a moist place, fungal attack will set in and this will lead to grain discolouration. Bad odour and bitter taste may also develop. To avoid such problems, controlled mechanical drying of paddy is useful. In advanced countries, mechanical devices and large-scale storage units are available and these facilities can be availed by farmers on custom-service basis. Such a system can be adopted in our country. Alternatively, economical and effective storage structures that are available now can be established at block or district levels.

Traditional storage techniques

The ambaram is a traditional seed storage structure that has been in use for more than a hundred years in several villages of Tamil Nadu. It is constructed in an open space and grain stored in it for more than a year. The straw of tall traditional paddy varieties like samba mosanam, kappakar, kullakar and vaigunda are used in making an ambaram.

The size of these structures is need-based. To set up an ambaram of eight tonnes capacity, soil is first heaped to a height of about one foot with a six feet diameter. A two-inch layer of straw is spread over this and old gunny bags spread over. Around this, three haystacks are laid, one above the other and tied intact. Two handfuls of long paddy straw are taken and tied vertically in two places. Likewise, the required amount of straw is taken and placed at the base. The paddy grain is poured into the structure to a height of about six feet. Above this, paddy straw is once again spread in a layer about 1.5 feet thick and is tied intact, again using paddy straw. The structure is finally covered using palm leaves.

Advantages

• The grain can be protected from cattle and rodents.
• The ambaram also offers protection from storage grain pests.
• Quality and viability of the seeds is maintained.
• The cost incurred on gunny bags is saved.
• The ambaram overcomes the constraints on space for storage in houses (since it is always constructed in the open space).

Storage pests

Rice weevil (Sitophilus oryzae)

Life cycle

Adults are reddish brown or black in colour. They have four light, reddish or yellowish spots on the elytra. The adult lays about 200 eggs inside the grain kernel. The eggs are oval, whitish and transparent. Tiny whitish grubs emerge from these eggs in 3–6 days. The grubs are yellowish brown headed. The larval stage lasts for about 19–34 days. They enter the pupation stage inside the grain. Pupal period lasts for 3–6 days. The insect can complete five generations in a single year.

Damage pattern

The larvae generally feed on the endosperm of the grain, reducing its weight and food value. They generally render the grains unfit for consumption. Moreover, the larvae also produce large quantities of powdery excreta. This generates an unpleasant odour in addition to contaminating the grain with dust particles.

Lesser grain borer (Rhizopertha dominica)

Life cycle

Adults are tiny, shiny, dark brown or black in colour. The wings are highly active. The head is bent under the thorax. Adult female lies about 300–500 eggs among the grains. The egg stage lasts for 5–11 days. The larvae that emerge from the eggs are white coloured and brown headed. The larval stage lasts for 24–50 days. They undergo pupation on the surface of the grain, which lasts for 7–8 days. The insect completes about 3–4 generations in a year.

Damage pattern

The larvae bore holes into the food grains and eat away the flour. Both larvae and adult feed voraciously and can cause serious damage.

Angoumois grain moth (Sitotroga cerealella)

Life cycle

Adults lay about 400 eggs on the surface of the grains. They lay eggs on the panicles and on the grains. The eggs are initially whitish and gradually turn reddish. The eggs are oval in shape. The larvae emerge from these eggs in about a week. The larval stage lasts for 7– 14 days. They enter into pupation when among the grains. The adults emerge from the pupa in 4–6 days. The adults are yellowish brown in colour with tiny sharp wings.

Damage pattern

The infestation begins at the field level. In the storage godowns, the pest attack is found on the upper surface of the grains. The larvae bore into the grain and remain inside until they turn into adults. As a result of the insect attack, the grains become powdery. Larval excreta can be found along with the grain and infested grains appear grouped.

Rice moth (Corcyra cephalonica)

Life cycle

The adults are greyish brown in colour. Their wings measure about 14–24 mm in length. The adults lay 90–200 white coloured eggs which last for 3–5 days. The larvae that emerge from these eggs are white in colour. The larvae group the grains with their excreta, remain inside them and feed on them. The larval and pupal stages last for 20–30 days and 8–10 days respectively. They turn into pupae when among the grains.

Damage pattern

The infested grains are found grouped.

Storage pest management

• While filling grain in storage bags, place 200 gm of salt for every 50 kg of grain. This helps to control moth and weevil infestation during storage.
  
• Place red chilies in storage bags (@10–15 fruits per every one quintal bag). The pests stay away due to the pungent odour.
  
• Mix turmeric powder with paddy to protect the grain from weevils.
  
• Mix leaves of Ipomoea carnea along with the grain to prevent common storage pests.
  
• Place about 1–2 garlic bulbs in 5–10 kg of rice in the bin for storage.

Pest management in storage godowns

• Storage godowns should be kept clean. Wastes and other unwanted materials in the godown area should be periodically removed.
  
• Cracks found on the floor, walls and roof should be sealed.
• The grain stored should not have more than 12% moisture content.
• Fumigating the storage room with frankincense powder helps to control the spread of disease causing pathogens.
  
• The gunny bags should be stacked with proper aeration between them so that they can be managed properly.
  
• If the grain is to be stored in the gunny bags for long periods, the bags should be dried first in the sun once every three months. This prevents pest attacks.
  
• When the grain is stored in gunny bags, they should not be kept directly on the floor but on wooden logs that are one foot above the ground level. By this method, the grains can be protected from getting moist and pest attack can be controlled.
  
• When the grains are stored in mud pots, the mouth of the pot should be sealed with neem leaf paste to prevent entry of pests.
  
• Pest attack during storage can be avoided by mixing the seed with neem oil. One kilo of paddy seeds should be mixed with 10 ml of neem oil and dried in the shade before it is stored.
  
• Gunny bags used for seed storage should be treated with 10% neem seed kernel extract before being used. (The extract should be used immediately after preparation.) They should be soaked in the extract for 15 minutes, then dried in the shade before they are used for storing grains. In case the gunny bags are new, they should be soaked for half an hour. If the gunny bags are with a close mesh and small pores, a thinner solution should be prepared. By using this method, grain can be protected from insects for about four months.
  
• In store rooms, along with the cow dung that is used for cleaning the mud floor, neem seed kernel extract or neem oil should be used directly (in the same concentration used for spraying purposes).
• The same could also be used for mud walls.
• If bamboo bins are used for storage, the bins can be painted with thick neem seed kernel extract. This prevents the pests from getting into the bin.
• The seeds and grains stored in the godowns can be protected from pests by placing the leaves of vitex, neem and pongam on the gunny bags and in different places of the godown.
• While filling the gunny bags, for every 20 kg of seeds, two handfuls of the powder of vitex, neem and pongam leaves should be spread. By using this method, grain can be protected from insects for more than a year.
• Storage godowns or rooms should have proper aeration.
• Adult moths can be controlled by fumigation with neem or vitex leaves.

Source : Centre for Indian Knowledge Systems, Chennai

Updated on : Dec 2014