What are the reasons for the low germination rate of rice seeds and what measures can be taken to improve it?

First, the reasons that affect the low germination rate of rice seeds

1, high temperature and high humidity climate leads to pre-harvest germination.

Generally speaking, the higher the maturity, the higher the germination rate. Full seeds usually take 25 days from pollination to maturity. The lowest temperature of rice seed germination is10-15℃. The optimum temperature is 30-35℃. Because the seeds on the same plant or even the same ear bloom in different places on the plant, they mature first and then mature, and all fully mature seeds are easy to germinate because of their shallow dormancy. However, immature seeds are in deep dormancy and often difficult to germinate. Some varieties, especially those that are prone to lodging, are easy to germinate or germinate on the ear.

2. The seeds are harvested too early and too late.

The dormancy period of rice seeds is not obvious. Seeds harvested prematurely are not fully mature. In the case of insufficient dryness, you still have to breathe hard. The consumption of nutrients significantly decreased the germination rate. The seeds were harvested too late. On the one hand, if they encounter high temperature and high humidity climate in the field, the seeds are easy to germinate, which leads to the decline of germination rate. On the other hand, seeds with high moisture content will accelerate seed aging and reduce germination rate without timely precipitation. Moreover, the harvest is too late to miss the best drying period, and the drying period is prone to mildew. It will also affect the germination rate.

3. The seeds are harvested thinly and ploughed in time.

Breeding units have a large number of seeds. Due to the limitation of threshing floor, warehouse and other conditions, there is a lack of necessary drying equipment, seeds are not thinned when they are put into storage, and they are not turned over in time after harvest. At this time, the water content of seeds is generally high, which leads to steamed seeds and black and moldy husks. In addition, the germination rate of seeds will be seriously affected if they are exposed to the sun in the cement threshing floor at high temperature and are not ploughed in time.

4. Mechanical damage.

Some varieties have thin shells or cracked seeds when they are full, and these varieties are easy to shell into brown rice when they are harvested, shed and carefully processed. Due to the removal of the protective layer, these brown rice are generally difficult to germinate, and even if they can germinate, it is difficult to become seedlings (it is easy to rot in rice fields).

5. When the seeds are put into storage, the water content is high.

Due to lax control, the seeds were not dried or poorly preserved before storage. The moisture content of seeds during storage is obviously higher than the quality standard. At this time, the seeds breathe vigorously, on the one hand, they release water vapor. After the water vapor is released, it is absorbed by the seeds, making the seeds more moist; On the other hand, the heat of respiration is released and accumulated in the seed pile, which gradually increases the temperature of the seed and strengthens the respiration, leading to mildew, moth-eaten, fever, sweating and dew condensation in some parts of the seed. This is the main reason for the decline of germination rate.

6, the impact of pests and diseases.

If pests and diseases are seriously harmed, prevention measures are not timely, functional leaves or transport channels are damaged, and their corresponding functions are reduced or lost, it will lead to the loss of seed embryo development function, insufficient nutrition stored in endosperm, insufficient seed plumpness and low vitality, and even if it can germinate, it will be weak and sick, making it difficult to become a seedling.

Second, preventive measures to improve the germination rate of rice seeds

1, select excellent varieties and strictly control sowing date.

(1) Seed drying: In sunny weather, seeds can be dried for about 3 days. When drying seeds, the seeds should be spread very thin and turned regularly to achieve uniformity. When turning over, prevent chaff from breaking and prevent mixing caused by turning over several varieties at the same time.

(2) Seed selection: Before soaking seeds, select shriveled grains in water. When selecting seeds in clear water, you can only choose empty seeds, and you can't choose those that are not mature enough. Therefore, when selecting seeds, the ratio of water is as important as 1. 13 (the proportion of 6 kilograms of salt dissolved in 25 kilograms of water is about1.13), and all rice grains with poor maturity can be selected by selecting seeds in this salt water. However, it is especially reminded that the seeds must be washed twice with clean water after being selected with salt water, otherwise the seeds will not germinate.

(3) Seed soaking: This is the first stage of water absorption of rice seeds, and the water absorption must reach 25%-35% of the weight of the seeds to germinate smoothly. Try to soak the seeds in hemp bags to accelerate germination. When soaking seeds, the weight of rice seeds and water is generally prepared according to the ratio of 1: 1.2, and the soaking water should not exceed the seed 15 cm, so that the seeds can absorb enough water. The soaking time depends on the temperature of the soaking water. When the seed soaking temperature reaches 100% every day (if the seed soaking temperature is 15%, it should be soaked for 7 days), the seed soaking is basically completed, which can accelerate germination.

(4) Disinfection: In order to kill pathogenic bacteria attached to the surface of seeds and between glume and seed coat, seed soaking disinfection is an economical and effective measure to control diseases and insect pests. Therefore, disinfectants can be selected for disinfection according to germs and pests.

(5) Accelerating germination: Under the condition of low temperature in early spring in the north, the seeds that have been accelerated to germinate can take root quickly, emerge early and emerge orderly, which can improve the seedling rate and shorten the seedling stage. The standard of whether seeds germinate is as long as the chest is broken and the bud length is 0. 1 cm, which cannot exceed 0.5 cm. When the temperature is too high in the early stage of accelerated germination, some seeds lose their germination ability, which in turn affects other seeds. If the temperature is insufficient or uneven when rice seeds are heated, the germination will be uneven, so heating before germination is the most critical link of germination quality. The simplest heating method is to prepare water at about 60℃ in a large container, and then quickly pour in the soaked seeds and stir them. At this time, the water temperature is about 25℃ ~ 30℃, soak at this temperature for more than 3 hours, and then take it out directly to dry to accelerate germination. When the germination reaches about 80% in the process of accelerating germination, put the seeds in a cool place (to prevent direct sunlight or freezing injury), spread them out with a thickness of 10 cm, and cool them. During the cooling process, the remaining seeds will continue to germinate.

2. Control the amount of fertilizer per ear.

Applying more panicle fertilizer is beneficial to increase 1000-grain weight, make grains full and have high germination rate. However, for varieties that are easy to crack, it is necessary to properly control the amount of panicle fertilizer to prevent the chaff from cracking and shelling into brown rice during threshing, ploughing and selection.

3. Add drying equipment.

Add necessary drying equipment to prevent problems before they happen.

4. Harvest and dry in time.

The harvest of rice seeds should generally be in the late stage of yellow maturity. At this time, most leaves of the plant turn yellow, but only the upper part remains green, the seeds show the inherent color of the variety, the contents of the seeds are like wax, and the barnyard grass shell shows the inherent color of the original variety. At this time, the dry matter accumulation of rice reached the maximum. The moisture is the lowest. At the same time, we should pay attention to listening to the local weather forecast, harvesting in bad weather and drying in time.