Seed :: Cereals & Millets :: Rice ( Varities )

QUALITY SEED PRODUCTION IN RICE VARIETIES

What is quality seed?

Quality seed should be genetically pure, free from weed seeds, seeds of other crops and varieties, inert matter and pest and diseases and possess high germination and vigour thereby leading to better crop performance and higher yield.

Introduction

Rice is a staple food in several Asian Countries. Often, we use the grains harvested in the previous season as seed for sowing. We are not aware of whether seeds saved from our own produce are good quality or not. Usage of seeds saved from our own produce for several generations may cause changes in varietal characteristics of seed resulting in reduced crop yield. Moreover, farmers are many times required to get seed materials at high cost from outside source and the quality of such seeds are not fully known. The situation surely requires to be changed.

Attention

Mr. Attiannan, a progressive farmer of Thookanayakkanpalayam of Erode District (TN) is very well known for high productivity of rice in his field. The basic reason for his success is the use of quality seeds.

 

Rice seed production field

Land requirement

What are volunteer plants?

Volunteers are plants that grow in the field from the seeds found in the soil. These seeds should have been fallen from previous season crop. Since they grow without sowing or they volunteer to grow by themselves, hence the name volunteer.

The selected land should not have been cultivated with same variety in the previous season and the land should be free from volunteer plants. 

Isolation distance      

Rice is mainly a self pollinated crop. For pure seed production, the seed fields must be isolated at least by 3 meters from rice fields of other varieties.

Season

Varieties

Suitable season

Short duration(105-110 days)

November-December

Medium duration(110-125 days)

November

Long duration(125-145 days)

August

Seed rate

Short duration                           -           60 kg/ha
Medium duration                       -           40 kg/ha
Long duration                            -           30 kg/ha

How to produce elite seedlings?

Healthy and vigorous seedlings are the bases for better crop growth and yield. Vigorous seedlings produced in the nursery will be able to withstand pest attack in the main field.

Benefit of seed selection

Quality seeds are required to get vigorous seedlings. The seeds which are stored for more than a year should not be used for sowing as the germination capacity and vigour of such seeds are reduced. Also seeds with black spots should be removed to avoid seed borne diseases.

Upgradation of seed quality using salt solution

The density of stored seed diminishes during storage period, place, environment and pest and diseases. Aged seeds like used battery cells will loose vigour in due course of time. Using salt solution, good quality, denser and vigorous seeds can be separated.

How to prepare salt solution?

 Ten litre of water is taken in a plastic bucket of 15 litre capacity and a good quality fresh egg is dropped in the water and the egg sinks in water and reaches the bottom. The commercial grade common salt is added little by little and dissolved in water. As the density of salt solution increases, the egg raise up. The addition of salt (Sodium chloride) is stopped when the surface of the egg to the size of a 25paise coin is visible above the solution. Now the density of water is suitable for separation of quality seeds. To this salt solution add 10kg of seeds.
           
The seeds with low density float on the surface of the solution, whereas the seeds with high density sink in the solution. The seeds floating on the surface of the solution are removed. The seeds sunk in the solution are washed for 2-3 times in water and then used. Similarly another 10 kg of seeds are separated based on the density. By this method, 20kg of seeds required for one acre can be upgraded. Dense and quality seeds result in vigorous seedlings. 

 

            

Preparation of Salt Solution


            

Seed treatment

Seeds treated with a fungicide like bavistin or captan @ 2g/kg and kept overnight before sowing in the nursery.

How to select a nursery area?

Good management of the nursery will result in vigorous seedlings and also in controlling the occurrence of offtypes in the seed crop. The land on which rice nursery or rice crop was not grown in the previous season should be selected to prevent offtypes. If the previous crop was rice, then the nursery plot should be flooded with water to trigger germination of buried seeds and such germinated seedlings can be destroyed by ploughing the field after one week. Fertile soil with adequate drainage is essential for good nursery.

Nursery sowing

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For sowing 50 kg of seeds required for one ha, a nursery area of 800 m2 is required. The soil of nursery should be well pulverized by 2-4 ploughings and during last ploughing one tonne of farm yard manure should be applied. Nursery beds of 40m2 area are prepared.

Seeds are pre-germinated before sowing. For pregermination, the seeds are soaked in water for 12 hours and soaked seeds are loosely packed in gunny bag and then placed in darkness for 24 hours for sprouting. During the pregermination process, radicles would have protruded out of the seeds.

Attention

The water used for soaking should be pure. Already used water should not be used for soaking to avoid the spread of diseases through seeds.

Incidence of pests in the nursery and their control

The most common pest in the nursery is thrips. The symptom of this pest incidence is shrinkage of leaf tips. To control this, spraying of rogor at 2 ml/ litre of water is recommended. During winter sowing (Sep-Oct), blast disease is common in the nursery. Application of DAP to the nursery will help in the escape of the seedlings from the attack of this disease.

Fertilizer requirement for nursery

Application of Diammonium phosphate (DAP) @ 2 kg / 40m2 of nursery will help in the vigorous growth of seedlings. Incase of DAP is not available, urea 15 kg and super phosphate 30 kg may also applied 40m2  of nursery. If the roots of the seedlings are not cut while pulling out of the seedlings then the establishment of the seedlings in the field becomes easy.

Age of seedlings

Age of seedlings plays an important role in the growth of crop. A too young or too old seedling leads to reduction of yield. Based on the duration of the varieties, the age of seedlings suitable for transplantation varies.

Varieties

Age of seedlings

Short duration

13-22 days

Medium duration

25-30 days

Long duration

35-40 days

Preparation of main field for transplanting

Spread 25 tonnes of FYM on the field which selected for seed production. Then the field is irrigated and the land is ploughed 2 or 3 times and puddled. Before last puddling, urea, super phosphate and MOP are applied basally as per the following table:

Basal application of fertilizers in different varieties

Varieties

Urea(Kg)

Super phosphate(kg)

MOP (Kg)

Short duration

50

125

20

Medium duration

50

125

30

Long duration

50

125

40

For Zn deficient fields, basal application of zinc sulphate @ 30 kg ha-1 is recommended. After last Ploughing, the fields are well levelled.

Importance of field levelling

The field should be levelled properly to ensure uniform water spread for uniform growth and flowering resulting in higher yield.

Transplanting

Seedlings from well maintained nursery can be used for transplantation. To maintain required number of plants in the field, suitable spacing should be followed depending upon the varieties.

Spacing for different rice varieties

Varieties

Spacing(cm)

Short duration

20×10

Medium duration

20×15

Long duration

20×20

In the main field, after each 8 feet, a gap of one foot is to be left which is required for easy rouging. This is called rouging space. During transplantation, water level upto a height of 2 cm should be maintained.

Water management

Water level upto a height of 2 cm should be maintained for a period of one week after transplantation. On 30th day, water should be drained off completely for one or two days. This enables aeration in soil and increases root growth. During tillering stage a water level of 5 cm should be maintained. During booting, flowering and milking stages, water stress should be avoided. During maturity stage, 15 days before harvest, water is drained off completely from the field.

Weed control

Control of weeds from the earlier stage of the crop is essential. Within three days after transplantation, herbicide butachlor@ 2.5 lit ha-1 mixed with 20 kg sand should be applied to the field. . Use of rotary weeder from 15 DAT at 10 days interval. It saves labour for weeding, aerates the soil and root zone, prolongs the root activity, and improves the seed filling though efficient translocation. After 30-35 days, a hand weeding is essential. The objectionable weed found in rice is wild rice, Oryza sativa var fauta.

Wild rice

Objectionable weed plant     
               

Objectionable weed plant whose seed is difficult to separate once mixed with crop seed and which is poisonous or injurious or has a smothering effect on the main crop. It is difficult to eradicate once established, has a high multiplication ratio thus making its spread quick and serves as an alternate host for crop diseases and pests.

Fertilizer application

Since the seed crop requires more fertilizers than the grain crop, top dressing of nutrients is essential. After first weeding and during flowering stage, urea is applied and during milky stage, muriate of potash is applied. The dosage of fertilizer depends upon the duration of the crop.

Top dressing of fertilizers to different varieties of rice

Varieties

Urea (Kg)

MOP(Kg)

Short duration

25

25

20

Medium duration

25

25

30

Long duration

25

25

40

Rouging

Normally in rice fields, non-uniform height and differences in flowering among plant population is observed. The crop of the same variety cannot show such variations and so this shows the contamination of the seed field with some other varieties which affect the genetic purity of the seed crop. Also, certain weeds grow along with the crop seeds. Similarly some field fungi cause seed infection in the field itself.
            The off-type plants, weeds and diseased plants should be rogued out at appropriate stage preferably before flowering. By this, genetic purity of the seeds can be maintained

Stage of crop

Rogues to be removed

Before flowering

Very tall or short plants, early flowering plants.

Flowering stage

Late flowering plants, chaffy grains

Pre-harvest stage

Awned grains

Harvest stage

Based on seed size, shape and colour

Foliar application

For production of bold and highly vigorous seeds, foliar nutrition plays a major role. Spraying 2 per cent DAP results in higher seed yield with good quality. Depending upon the duration of the crop, the stage for DAP spray also varies.

Stages for foliar application of DAP in rice varieties of different duration

Varieties

Days for DAP spray(from sowing)

First spray

Second spray

Short duration

60 days

80 days

Medium duration

80 days

100 days

Long duration

100 days

120 days

Appropriate stage for harvesting

Harvesting of seed crop at correct stage is essential. Otherwise, seed yield will be greatly reduced. If the seeds are harvested at premature stage, the seeds get shrunk (during drying), thereby reducing the germination capacity. Delayed harvest results in discoloration of seeds besides inviting pest and disease incidence.
During maturity stage, 90 per cent of seeds would have acquired straw colour and seed moisture content will be 17-20 per cent.

Harvesting Stage of Rice

Seed quality maintenance

During threshing care should be taken to avoid mechanical injuries on seeds. If threshing is done by beating the ear heads on stones or iron blocs, there are more chances for seed injuries. So threshing should be done on wooden blocs. Mechanical threshers after adjustment can also be used for threshing purpose.

Threshing without mechanical injuries

The seed moisture content should be 15 to 18 per cent during threshing. If the seed moisture content is more or less than this level, the chances of mechanical injuries are more. These invisible injuries will reduce seed viability and increase disease incidence on the seeds.

Seed drying

Threshed seeds should be dried immediately in a systematic manner. Otherwise deterioration due to high respiration rate may occur. If the seeds are heaped without drying, temperature of the seeds may increase. Optimum time for drying the seeds under sun is 8.00 am to 12.00 noon and 3.00p.m. to 5.00p.m. Drying of seeds during 12.00 noon to 3.00p.m. Should be avoided as the incidence of UV rays from the sun is more besides temperature being high during this time.

Seed drying in Rice

Attention

Continuous drying of seeds from morning to evening under sun should be avoided. The seeds should be spread evenly every day after sun drying allowing free aeration otherwise, heating will occur resulting in lowering of seed quality.

Size grading

Seeds are graded to remove immature, broken, chaffy seeds, other crop seeds, stones, soil particles and dust. Based on the size, shape, dimension and density, seeds can be processed. Rice seeds can be classified as long slender, slender, medium slender and bold. For each category specific sieves are used during processing.

Optimum sieve size for seed processing

Varieties

Sieve size (Oblong aperture)

Long slender(Ponni, white ponni)

1/16×3/4"

Slender(IR 50, ADT 39)

1/15 ×3/4"

Medium slender(IR 20, CO 43)

1/14×3/4"

Bold (ADT 36, 37, 38, TKM 9, ponmani)

1/13×3/4"

Points to be noted during seed processing

Like grains, rice seeds can not be stored immediately after threshing. Proper drying is essential before storage to maintain viability. Seed driers, seed cleaners and seed treaters should be cleaned properly when used for different varieties to avoid varietal admixtures which cause genetic contamination.

Moisture content

Amount of moisture in the seeds is probably the most important factor influencing seed viability during storage. Seeds stored with high moisture content lose their germination capacity quickly. For short term storage, rice seeds with 13 per cent moisture can be stored in cloth bags or gunny bags. For long term storage, the seed moisture content is to be reduced to 9 per cent and stored in moisture vapour proof polythene bags.

Seed treatment

Before storage, seeds are treated with 4g/kg of captan or thiram. The seeds can also be treated with halogen mixture @ 5g/kg, which is non-toxic. You can prepare the halogen mixture yourself by mixing calcium oxychloride (Bleaching powder) with calcium carbonate at 1:1 ratio, pack in an air tight container and leave for one week. After one week, the halogen mixture is ready for seed treatment.

Seed storage

Storage of seeds till next sowing season deserves equal attention and care which was given during seed crop management.

Seed storage containers

Seeds are hygroscopic in nature and absorb moisture from the atmosphere under ambient storage. Hence, in the coastal and deltoic regions where the relative humidity in the atmosphere remains high, moisture vapour proof containers like 700 gauge polythene bags  have to be used. If seeds are stored in gowdown, up to 6 or 7 bags can be placed one above the other. If excess bags are placed, seeds in lower bags may lose their germination capacity due to the pressure excerted by the weigh of more number of bags above them. Direct contact of the bags with floor should be avoided. The bags should be placed on wooden pallets.

 

Seed dormancy

Seeds of some rice varieties possess dormancy so that they do not germinate, if sown immediately after harvest.

What is dormancy?

Condition by which a viable seed is not able to germinate even under favorable conditions of soil, moisture, light and temperature is called dormancy.

Normally, seed dormancy dissipates during dry storage of 30 to 45 days in the present day cultivated varieties. By the time, harvesting, threshing, cleaning and drying are completed, dormancy would have disappeared.  
If an unforeseen contingency of sowing fresh seeds immediately after harvest arises, mix 240 ml of nitric acid in 45 litres of water and 20 kg of seeds required for one acre is soaked in this solution for 12 hours and the seeds are washed 3-4 times in water and then used for sowing. Alternatively, seeds may be dried under sun for two or three days before sowing. This exposure to heat eliminates the dormancy.

Seed certification

Seed certification guarantees the quality of seed as it ensures that the certified seed has the genetic, physical, physiological and seed health qualities.  Genetic purity means that the seed gives rise to a plant which conforms to the varietal characteristics of the variety. The physical purity means that the seed is free from stones, broken seeds, straw bits and leaf bits etc. Physiological quality is measured by germination and seed health envisages freedom from pest and diseases.

Seed certification is being done in many stages. It starts from verifying whether seeds were obtained from authenticated source, verification of isolation distance and inspection during plant growth, flowering, harvesting, processing and bagging. Also seed samples are drawn form the seed lot and sent to seed testing lab to test whether the seeds are possessing required physical purity and germination. Then certification tag is issued. Colour of the tag is blue for certified seeds.

Only those seeds harvested from fields having prescribed field standards and possessing required seed standards are certified by the Certification Agency. Seeds thus certified are offered for sales. For further details nearer seed certification office may be contacted.

Seed certification standards

Field standards

 

Rogue / off-type (Maximum)

0.2 per cent

Weed (Maximum) Red rice varieties

0.02 per cent

Seed standards

 

1. Pure seed (Maximum)

98 per cent

2. Inert matter (Maximum)

2 per cent

3. Seeds without husk (Maximum)

2 per cent

4. Other crop seeds (Maximum)

20 / kg

5. Other variety seeds (Maximum)

20 / kg

6. Objectionable weed seeds (Maximum)

5 / kg

7. Weed seeds ( Maximum)

20 / kg

8. Germination per cent (Minimum)

80 per cent

9. Moisture content (Maximum)

 

Moisture pervious containers

13 per cent

Moisture impervious containers

8 per cent