Paddy Seed Germination (Rice)
Paddy is an essential food crop for billions of people in India. Seed germination and seedling emergence are the most important phases of a Paddy crop cycle. The seed germination process is a key phase of the plant life cycle. Quality seed is important to increase production. It is essential to maintain the varietal purity of seed, and control the seed-borne disease for the production of high-quality seed. Therefore, the main objective of the Paddy seed production technique manual is to improve the knowledge of farmers about technical and management activities, including increment in the production of quality seed of Paddy. It is mainly considered to be a semi-aquatic annual grass and is grown in paddies in wetlands or under shallow water. Several new methods of propagating Paddy have been developed which allow Paddy to be cultivated in less conventional areas like drought-resistant varieties are grown in upland areas. In this article we also discuss the below topics about Paddy seed germination;
- How do you germinate Paddy seeds
- How much time take for Paddy seeds to germinate
- Germination of Paddy seeds
- Paddy seed germination test
- How to measure germination of seeds
- Germination percentage of Paddy
- Importance of seed germination
A Step-by-Step Guide to Paddy Seed Germination Process, Methods
Paddy is an important food crop in India. It can be grown on different soil varieties including silts, loams, and gravels, and can tolerate acidic as well as alkaline soils. Though, deep fertile clayey or loamy soils which can be easily puddled into the mud and develop cracks on drying are considered ideal for raising this crop. High-level loams and lighter soils best for quick maturing Paddy crop varieties. Also, black lava soil is useful for Paddy cultivation.
Type of Paddy Varieties
Various types of Paddy varieties are consumed in India are Basmati, White, Brown, Red, Jasmine, Parboiled, and Sticky Paddy. Of these, Basmati and White Paddy are most favored in the country. Paddy cultivated states for the Rabi in India are Assam, West Bengal, Odisha, Andhra Pradesh, and Tamil Nadu, etc.
Paddy Propagation Method
Generally, Paddy is propagated directly from the seed and then sown on seedbeds or used to grow transplants in a nursery bed. Seeds can be sown in the field by broadcasting or by mechanical drilling. Then, the main propagation methods are used for direct seeding Paddy in lowland areas are dry seedbeds, wet seedbeds, and dapog. Dry seedbeds are prepared close to a water source and each bed is about 1.5 m in width. The seeds are covered with a light layer of soil and then the bed is saturated with water until the seeds germinate. When the seedling reaches about 2 to 3 cm in height, shallow irrigation is used. Pre-germinated seeds are spread out on cement of wet soil and then covered with leaves or plastic sheeting. The cover is pushed down onto the seeds and then continuously watered. After 11 days, the mat is rolled up and transferred to the field. Seedling becomes ready for transplanting on the 12th day after seeding in the dapog method.
Methods of Paddy Cultivation
Below methods of Paddy cultivation are practiced in India;
1. Broadcasting method – In this method, seeds are sown broadcast by hand. This is practiced in those areas which are comparatively dry and less fertile. Also, it is the easiest method requiring minimum input but its yields are also minimum.
2. Drilling method – In this drilling method, ploughing of land and sowing of Paddy seeds is done by two persons. This method is mostly confined to peninsular India.
3. Transplantation method – The transplantation method is done in areas of fertile soil, abundant rainfall. Then, seeds are sown in the nursery, and seedlings are prepared. After 4 to 5 weeks the seedlings are uprooted and planted in the field which has already been prepared for the purpose. The entire process is done by hand. Therefore, it is a very difficult method and requires heavy inputs. But at the same time, it gives some of the highest crop yields.
4. Japanese method – Japanese method includes the use of high-yielding seed varieties, sowing the seeds in a raised nursery-bed, and transplanting the seedlings in rows to make weeding and fertilizing easy. Also, it involves the use of a heavy dose of fertilizers so that very high yields are obtained.
Importance of Good Quality Paddy Seed
- Quality Paddy seed gives more production when compared to a normal seed.
- Also, it leads to an increment in the production and income of farmers.
- Quality seed production can be easily traded in the market.
- Quality seed production can contribute to food security by increasing productivity.
Seed Quality and Selection for Paddy Germination Process
By using good quality seed increases the crop yields by approximately 5 to 20%. Though, vigorous growth in the early stages reduces weed problems and increases crop resistance to insect pests and diseases. Choosing a seed of a suitable Paddy variety that suits the environment and ensuring the seed chosen of that variety is of the highest possible quality is the necessary step in Paddy production.
Selection of seed – Paddy seed selection plays an important role in Paddy cultivation. The seeds selected must be of uniform size, age, and free of contaminants. They should have good germination capacity.
Separation of quality Paddy seed – For separating the quality seed, soak the seeds in water and then the unviable seeds will float on the surface of the water. Then, these seeds can be easily removed and the seeds that sink can be used for cultivation. By this process, damaged seeds are easily removed. Another method is to take some water in a vessel and then drop an egg in it. After that, keep adding salt slowly till the egg reaches the surface, and then wash the selected seeds in good water 2 to 3 times to remove the salt deposits. If this is not done, the seeds germination capacity will be affected.
Factors Affecting Seed Quality
Generally, seed quality is determined by several characteristics.
The genetic factors that can influence quality include;
- Genetic make-up
- Seed size
- Bulk density
The physical or environmental characteristics include;
- Injury during planting and establishment
- Growing conditions during seed development
- Nutrition of the mother plant
- Physical damage during production
- Moisture and temperature during storage
- Age or maturity of seed.
Also, temperature, nutrients, and other environmental factors affect seed development and influence seed quality.
High-quality Paddy seeds are the result of good production, this includes;
- Proper maintenance of genetic purity
- Good growing conditions
- Proper timing and methods of harvesting
- Appropriate processing during threshing, cleaning, and drying
- Appropriate seed storage and seed distribution systems.
Different Growth Stages of Paddy
The main growth stages of the Paddy plant are;
- Imbibition stage – 0 – 18 hours
- Activation stage – 18 – 72 hours
- Post germination growth stage – 72 hours → (at 20 ℃)
When the moisture content of the seed is about 30-40 % germination commences.
Lower than 8℃ and more than 45℃ no germination process
The Paddy plant growth is divided into three stages;
1. Vegetative (germination to panicle initiation);
2. Reproductive (panicle initiation to flowering); and
3. Ripening (flowering to mature grain)
Crop growth stages help to identify critical periods during the Paddy crop life cycle. Generally, they are separated into stages associated with vegetative or reproductive development. The vegetative phase occurs first and is associated with the 6 to 8 week period following planting. The reproductive phase follows and is associated with the formation, development, and maturation of the panicle and grain.
Germination and emergence are the first stages in the vegetative phase of the Paddy crop and then the plant population is determined. Normally, germination begins with the appearance of the young shoot and root through the seed coat at one end of the seed. As the shoot elongates and then reaches the surface of the soil, emergence occurs. Seed germination and emergence occur almost simultaneously when Paddy is planted on the soil surface.
Seedling growth follows emergence and is denoted by some leaves (1-leaf, 2-leaf, etc., stages). Normally, Paddy seedling stages are determined by the number of leaf blades that are fully developed. Though, the emerging leaf should not be counted. Seedling stages occur during the first 2 to 5 weeks after planting.
Why Use Quality Seed?
That among different factors responsible for good crop production, quality seed alone can contribute to 5 to 20% higher yield. So, a lot of importance has been given to the use of quality seed for achieving higher yield in Paddy. Generally, the benefits of using quality Paddy seed are given below;
- Genetic seed purity as per varietal features is obtained.
- Some off-type plants become less.
- The requirement of seed quantity remains within the prescribed seed rate because of the high seed germination percentage.
- Healthy seeds give rise to healthy seedlings which compete well with the weed or grasses.
- Less disease and insect incidence are marked.
- Crop stand becomes uniform that flowers and matures uniformly and also helps in higher yield.
Germination Stage for Paddy Cultivation
- Seed germination is the most important stage in a Paddy life cycle.
- Paddy seed germination is affected greatly by temperature levels. A temperature colder than the favorable range like 18–33°C retards the germination process.
- Cold temperatures slow down the diffusion procedure which causes disrupted imbibition and escape of solutes from the Paddy seeds.
- The temperature level for Paddy seed germination is considered to be about 30°C. The minimum temperature level of Paddy germination is 10°C. Soil temperature levels below 10°C can result in complete failure of germination. Temperature levels below 20°C decrease the speed and percentage of seed germination in Paddy, lower crop stands, and consequently reduce grain yield.
- Speed of the germination process is related to seedling vigor and it can be a significant determinant of good field performance.
- Seed germination occurs when the first shoots and roots start to emerge from the seed and the plant begins to grow.
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Germination Test for Paddy Seeds
What is a Germination Test?
The germination test determines the percentage of the seed that is alive in any seed lot. The germination speed changes based on selected varieties, seeds must absorb moisture within 2 days and produce a root and the first leaf within 4 days. The Paddy seed is considered to have germinated.
Paddy is an important food crop. Paddy seed germination can determine its seedling growth. In some cultivars, the mature seed can germinate in panicles (named as pre-harvest sprouting) encountering suitable climate conditions, which reduces seed yield and quality.
The germination test is mainly considered to measure the seed’s ability to produce normal seedlings. The methods of germination test of Paddy seed are given below;
- Firstly, tie a handful of seeds in a white cloth, and then soak it in water for 12 hours and keep it in a dark place for 24 hours.
- Check the germination percentage the next day.
- Keep the seeds in the center of the mat and then roll and tie it.
- Dip it in water for a minute and count the seeds that have germinated after 24 hours.
- After that, take a wet gunny bag, fold it, put the seeds in between the 2 layers, and keep the bag in the dark for a day.
- Check the germination the next day.
Germination test of seeds should be tested to identify the vigor and germination rate of seed, which helps to identify the health quality of seed, future growth of seedlings and amount of future yield, etc.
If the seed has good germination vigor, the higher number of seeds germinates; and the required amount can be harvested. Another method of germination test of Paddy seed is as followings;
- Firstly, dip the seeds for 24 hours in water before the germination test.
- Prepare the 2 cartoon boxes with plastic film inside them then put fine sand or sandy soil in them.
- Remove small stones or pebbles from the sand or sandy soil in each cartoon box.
- Plain the surface and then make rows not deeper than an inch in each cartoon box.
- After that, take about 200 seeds randomly from saltwater-treated seed.
- For this process, sow about 100 seeds in 10 rows (10 seeds for each row) in 1 carton box, and then sow the next 100 seeds similarly in the next carton box.
- Then, apply water to each germination test box every day for making the soil wet.
- Start counting seedlings 5 days after the sowing process, and keep recording.
- The seedlings number of 5 days after sowing gives the vigor rate, and 8 days after sowing gives the germination rate.
- The average germination rate from two test boxes must be at least 80%.
- Based on the germination test result, the amount of sowing seed can be decided to a nursery bed.
- The temperature condition must be 25-30ºC during the germination test.
Seed Rate and Seed Treatment in Paddy Cultivation
Seed rate explains the quantity of seed necessary for transplanting a fixed area. Transplanted Paddy with line transplanting is more suitable for quality Paddy seed production because it is easy to safeguard purity in the transplanting system. The plant to plant and line to line distance for different duration Paddy varieties, taking into account the optimum utilization of sunlight for yield.
For Paddy cultivation, use 20 to 25 kg seed per hectare of fine, 30 to 35 kg seed for medium, and 35 to 40 kg seed for coarse Paddy in the nursery to transplant it in one-hectare land.
Seed treatment mainly helps to improve germination potential, vigor, and resistance to pests and disease. The different methods of Paddy seed treatment are;
Soaking the Paddy seeds in water – For this process, tie the seeds in a small gunny bag and then soak it in water for 12 hours. Carefully remove the gunny bag from the water and cover it with a moist gunny bag. The following day, soak the Paddy seeds in water for 8 hours again. Remove the seeds from the water and sow them carefully. This process helps to improve the germination capacity of the seeds.
Hot water seed treatment
- Before seed sowing in a nursery bed, the Paddy seed must be made wet in normal water for 4 hours
- After that, the seed must be immersed in hot water of 60 ºC for 10 minutes or 58ºC for 15 minutes and put out from hot water.
- The Paddy seeds must be dried and treated with fungicide.
Using cow dung solution – Treating Paddy seeds in a cow dung solution enhances their germination. Take 1⁄2 kg of fresh cow dung and 2 liters of cow urine and dilute them with 5 liters of water. Then, soak 10 to 15 kg seeds first in water for 10 to 12 hours and then in the cow dung solution for 5 to 6 hours. Dry the Paddy seeds before sowing them.
Using goat dung solution – Treating 30-day old seeds for one day in a goat dung solution increases their germination process. By using cow’s urine solution mix about Dilute 500 ml of cow’s urine in 2.5 liters of water. After that, tie the Paddy seeds in small bags and soak them in the solution. Then, dry the seeds before sowing them.
Using sweet flag extract – Dissolve 1.25 kg of sweet flag rhizome powder in 6 liters of water. Dry the seeds in the shade before the sowing process. Spread the leaves of Salvadora persica at the bottom of a closely-knit bamboo basket, and then fills it with seed and pours about 10 to 12 liters of water over the basket. Cover the basket with the leaves and place a weight over it. Then, leave the seeds undisturbed for 24 hours. The seeds are then ready to be used for the sowing process. This helps in early and vigorous germination. Seed treatment by using Amrut Pani/Panchagavya/Cow Pat Pit Manure/Jeevamrut is also effective for Paddy crops. The efficiency needs to be evaluated.
Using bio-fertilizers – Biofertilizers like azospirillum/azotobacter/pseudomonas are first mixed in one liter of cooled Paddy gruel. Carefully spread the sprouted seeds on a clean floor, and then add the biofertilizer slurry and mix well. Dry the seeds in the shade for 30 minutes before seed sowing. Then, drying the seeds for half an hour in the bright sun before sowing improves germination rate and seedling vigor.
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Germination Percentage and Viability of Paddy Seeds
- The viability of a seed in the field is mainly determined by its germination potential, vigor, and moisture level.
- The rate of seed germination in Paddy crops is an indicator of vigor.
- The rapid seed germination process increases the chance that the seed will establish well in the field.
- Seed vigor refers to the seed’s level of activity and performance during seed germination and seedling emergence. The ability of the germinating seed to continue to grow and survive is very important in crop establishment.
- Seeds that are low in vigor produce weak seedlings that are susceptible to some environmental stresses. On the other hand, seeds that are high in vigor produce early and uniform stand and gives them a competitive advantage against stresses.
Germination percentage is defined as the proportion of the total number of seeds that are alive. Good seeds have more than an 80% germination rate.
Many seed varieties have a dormancy period immediately after harvest.
Compute the germination percentage using the following formula:
Germination % =number of seeds germinated/number of seeds on the tray ×100
At least 80 seeds have germinated to be considered “good seed” (80% germination).
Harvesting Process of Paddy
Generally, the Paddy crop is harvested after 25 to 35 days after flowering; i.e. for early varieties it is after 25 days and for late varieties, it is after 35 days. Otherwise, the crop becomes ready for harvesting when the grains become yellow and hard after getting dried.