How many seasons can rice be planted in a year?

Generally, the heat resource is ≥ 10℃, the place with accumulated temperature of 2000 ~ 4500℃ is suitable for planting single-season rice, the place with accumulated temperature of 4500 ~ 7000℃ is suitable for planting double-season rice, and 5300℃ is the safe limit for double-season rice, and the place with accumulated temperature above 7000℃ can plant three-season rice.

The country with the largest rice planting area in the world is India, with an area of nearly 50 million hectares and a total output of 65.438+50 billion tons. China's rice planting area is about 30 million hectares, ranking second in the world, but China's rice production ranks first in the world, with a total output of over 200 million tons.

The harvested rice grains are called rice and have shells. When milling rice, the husk is often removed together with the rice bran layer, and sometimes a thin layer of glucose and talcum powder is added to make the rice grains shiny. Rice with only the husk removed during rice milling is called brown rice, which is rich in starch and contains about 8% protein and a small amount of fat, including thiamine, nicotinic acid, riboflavin, iron and calcium.

Extended data

(A) the growth environment

1, the lowest temperature of seedling germination is 10 ~ 12℃, and the optimum temperature is 28 ~ 32℃. The average daily temperature at tillering stage is above 20℃, and the optimum temperature for ear differentiation is around 30℃. Low temperature prolonged the differentiation of branches and glumes. The optimum heading temperature is 25 ~ 35℃. The optimum flowering temperature is about 30℃, lower than 20℃ or higher than 40℃, and pollination is seriously affected.

2. The relative humidity is 50 ~ 90%. The key period of fruiting is from panicle differentiation to full filling stage; The population with balanced nutritional status and high photosynthetic efficiency is of great significance to improve seed setting rate and grain weight. A lot of water and mineral nutrients are needed at heading and fruiting stage; At the same time, it is necessary to enhance the root activity and prolong the functional period of stems and leaves. It takes about 500 ~ 800 kg of water to form 1 kg of rice.

(2) storage method

1, moisture control: too much moisture is easy to get hot and moldy, and it is not resistant to storage. Therefore, the safe moisture content of rice is the basis of safe storage. Before storage, it should be dried naturally, and the water content should reach the safety standard (14% or less). If the original moisture is too large, it should be dried in time.

2. Impurities removal: Rice usually contains barnyard grass, weeds, ears, leaves, chaff ash and other impurities as well as shriveled grains. These substances have high water content, strong hygroscopicity, many bacteria, high respiratory intensity and extremely unstable storage, all of which are unsafe factors. Therefore, the impurity content must be reduced below 0.5% before storage, which can greatly improve the storage stability.

3. Timely ventilation: New rice often breathes heavily, and the grain temperature is high or the moisture is high, so it should be ventilated in time, especially when it is cool in autumn and the temperature difference between inside and outside the grain pile is large. At this time, ventilation should be strengthened, and the grain pile should be deeply ploughed with damp heat to prevent mildew. Mechanical ventilation can be used if conditions permit.

4. Low-temperature sealing: make full use of the cold and dry weather in winter for ventilation, so that the grain temperature will drop below 10℃ and the moisture content will fall within the safety standard. Before it gets warmer in spring, summer should be covered.

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