Why can Hainan’s rice be harvested three times a year?

1. Rice in Hainan can be harvested three times a year. The main reason is that Hainan Island has high heat, rice grows quickly and the cycle is short.

2. Hainan Island is located at the northern edge of the tropics and has a tropical monsoon climate. It has always been known as a "natural greenhouse". It has long summers and no winters, and the annual average temperature is 22~27℃, greater than or equal to 10℃. The accumulated temperature is 8200°C, and the temperature in the coldest January is still 17-24°C. The annual sunlight is 1750-2650 hours, the light rate is 50%-60%, the light temperature is sufficient, and the photosynthetic potential is high. Hainan Island has early spring, rapid temperature rise, large daily temperature difference, no frost all year round, and warm winters. Rice can be harvested three times and vegetables are available all year round. It is an ideal base for breeding in southern China.

3. Rice likes high temperature, high humidity, and short days. It has no strict requirements on soil, but paddy soil is the best. The minimum temperature for seedling germination is 10-12℃, and the optimum temperature is 28-32℃. The average daily temperature during the tillering stage is above 20℃, and the suitable temperature for panicle differentiation is around 30℃; low temperature prolongs the differentiation of branches, stems and spikelets. The suitable temperature for heading is 25-35℃. The optimum temperature for flowering is around 30°C. If it is lower than 20°C or higher than 40°C, pollination will be seriously affected.

The relative humidity is 50 to 90%. The period from panicle differentiation to peak grain filling is the critical period for fruiting; a population with balanced nutritional status and high light efficiency is of great significance to improving fruiting rate and grain weight. The heading and fruiting stage requires a large amount of water and mineral nutrients; at the same time, it is necessary to enhance root vitality and extend the functional period of stems and leaves. Approximately 500 to 800 kilograms of water are needed to form 1 kilogram of rice.

4. Rice planting divisions in my country;

Rice is a short-day crop that likes temperature and humidity. Main ecological factors affecting rice distribution and zoning:

① Heat resources are generally ≥10°C. Places with accumulated temperatures of 2000-4500°C are suitable for growing one-season rice, and places with 4500-7000°C are suitable for growing two-season rice. 5300℃ is the safe limit for double-cropping rice, and three-cropping rice can be grown in places above 7000℃;

②Moisture affects rice layout, which is reflected in the principle of "water determines rice";

③The number of sunshine hours affects the distribution and production capacity of rice varieties;

④The change in altitude affects the distribution of rice through temperature changes;

⑤Good rice soil should have a high It has the ability to retain water and fertilizer, and it should have a certain degree of permeability, with a pH close to neutral.

The country’s rice regions can be divided into 6 rice growing regions and 16 sub-regions.

(1) South China Rice Growing Area

Located south of Nanling, the southernmost part of China, including the southern parts of Fujian, Guangdong, Guangxi and Yunnan, as well as Taiwan Province, Hainan Province and the South China Sea. All of the island. Including 194 counties (cities) (not including Taiwan Province for the time being), the rice area accounts for 17.6% of the country's total.

1. Fujian, Guangdong, Guitai plains and hills double-cropping rice sub-region

Starting from Changle County in Fujian and Taiwan Province in the east, to Guangnan County in Yunnan in the west, and to Wuchuan County in Guangdong in the south , including 131 counties (cities) with an annual accumulated temperature of ≥10°C ranging from 6500 to 8000°C, and most places have no obvious winter characteristics. During the rice growth period, the sunshine hours are 1,200 to 1,500 hours, and the precipitation is 1,000 to 2,000 mm. The safe growth period of indica rice (the number of days between the period when the daily average temperature stably passes 10°C and the period when the temperature reaches ≥22°C, the same below) is 212 to 253 days; the safe growth period of japonica rice (the period when the daily average temperature stably passes ≥10°C to the period when it reaches ≥20°C) is 212 to 253 days; ℃The number of days between the final cash period, the same below) 235 to 273 days. Rice fields are mainly distributed in river plains and hilly valleys, which are suitable for double-cropping rice growth. Perennial double-cropping rice accounts for about 94% of the rice area. The rice fields implement a multi-year cropping system based on double-cropping rice, and the main varieties are indica rice. The main pests and diseases are rice blast and stem borer. In the future, we should give full play to the advantages of a long and safe growth period to avoid the hazards of typhoons and autumn rains; select stress-resistant, high-quality, and high-yielding varieties; advocate returning rice straw to fields and increase the application of potassium fertilizer; develop winter legumes, vegetable crops and double-cropping rice. Crop rotation.

2. Single-crop rice sub-region in the valley basin of southern Yunnan

The northern boundary starts from Malipo County in the east, passes through Maguan and Kaiyuan to Yingjiang County, and includes 41 counties in southern Yunnan ( city), with complex terrain and diverse climate. The southernmost low-thermal valley has close to tropical climate characteristics, with an annual accumulated temperature of ≥10°C of 5800-7000°C, sunshine hours of 1000-1300 hours during the growing season, and precipitation of 700-1600 mm. Safe growth period: more than 180 days for indica rice and more than 235 days for japonica rice. Rice fields are mainly distributed in river valleys, and the upper limit of planting height is 1,800 to 2,400 meters above sea level.

Most places only grow one season of rice a year, and bacterial blight and borer are the main pests and diseases. In the future, it is necessary to improve irrigation conditions, increase multiple cropping, improve soil, and change the habit of extensive tillage.

3. Double-cropping rice multi-ripening sub-region in the Qionglei Platform Plain

Including Hainan Province and Leizhou Peninsula, ***22 counties (cities). Annual accumulated temperature ≥10℃ 8000 ~9300℃, the rice growing season lasts 300 days, and in the south it can last 365 days. Three seasons of rice can be grown in a year. During the growing season, there are 1,400 to 1,800 hours of sunshine and 800 to 1,600 mm of precipitation. The safe growth period of indica rice is more than 253 days, and that of japonica rice is more than 273 days. Typhoons have the greatest impact and land productivity is low. Double-cropping rice accounts for 68% of the rice field area, and is mostly a three-cropping system, mainly indica rice. The main pests and diseases include rice blast, stem borer, etc. In the future, it is necessary to improve water and fertilizer conditions, increase multiple cropping, expand winter cropping, and maximize the potential for increasing production.

(2) Central China Rice Growing Region

It starts from the coast of the East China Sea in the east, reaches the western edge of the Chengdu Plain in the west, borders the Nanling Mountains in the south, and the Qinling Mountains and the Huaihe River in the north, including Su, Shanghai, All or most of the eight provinces (cities) of Zhejiang, Anhui, Jiangxi, Hunan, Hubei, and Sichuan, as well as southern Shaanxi Province and Xinyang area in Henan, are the largest rice-growing areas in China, accounting for 67% of the country's rice area.

1. Double single-crop rice sub-region in the middle and lower reaches of the Yangtze River plain

It is located north of the annual ≥5300 ℃ isoline, south of the Huaihe River, east of the mountains of western Hubei and the coast of the East China Sea. Including 235 counties (cities) in Jiangsu, Zhejiang, Anhui, Shanghai, Hunan, Henan and Hubei. The annual accumulated temperature is ≥10°C and ranges from 4500 to 5500°C. Most areas have more than enough to grow rice in one season but not enough in two. The safe growth period of japonica rice is 159 to 170 days, and that of japonica rice is 170 to 185 days. During the growing season, precipitation ranges from 700 to 1,300 mm and sunshine ranges from 1,300 to 1,500 hours. The low temperature and rainy weather in spring make early rice seedlings easy to rot and die, but in autumn the temperature and light conditions are good and the production level is high. Double-cropping rice still accounts for 2/5 to 2/3, and in some plains south of the Yangtze River, it accounts for more than 80%. Multiple planting of "early indica and late japonica" is generally implemented. Rice blast, rice thrips, etc. are the main pests and diseases. In the future, we need to plant double-cropping rice, expand hybrid rice, make efforts to plant ultra-high-yield crops, rationalize multiple cropping rotations, and fertilize the soil in multiple ways.

2. Single-crop rice and double-cropping sub-region in the Sichuan-Shaanxi Basin

Mainly composed of the Sichuan Basin and the Sichuan Plain in southern Shaanxi, it includes 194 areas in the five provinces of Sichuan, Shaanxi, Henan, Hubei and Gansu. County (city). The annual accumulated temperature is ≥10°C and is 4500-6000°C. The safe growth period of indica rice is 156-198 days and that of japonica rice is 166-203 days. The precipitation during the growing season is 800-1600 mm and the sunshine is 700-1000 hours. The spring temperature in the basin rises earlier than that in the two eastern subregions, and the autumn temperature drops faster. The spring drought hindered the expansion of double-cropping rice, which has dropped to less than 3%. It is the area with the most winter paddy fields in the country, accounting for 41% of the rice fields. Mainly indica rice, with a small amount of japonica rice distributed in mountainous areas. The main pests and diseases include rice blast and rice planthoppers. In the future, conditions must be created to expand double-cropping rice planting, increase water storage capacity in hilly areas, transform winter paddy fields, and expand green manure planting.

3. Southeast hilly plain double-cropping rice sub-region

South of the annual ≥10℃ accumulated temperature line of 5300℃, north of the Nanling Mountains, from the eastern slopes of the mountains in western Hunan and Hubei to the coast of the East China Sea , ***294 counties (cities). The annual accumulated temperature is ≥10℃ 5300-6500℃, the safe growth period of indica rice is 176-212 days, and that of japonica rice is 206-220 days. Double-cropping rice accounts for 66% of rice fields. During the growing season, precipitation ranges from 900 to 1,500 millimeters and sunshine lasts from 1,200 to 1,400 hours. The warm spring and summer are conducive to rice growth. However, the "Meiyu" is followed by drought, causing early rice to mature at high temperatures and late rice to be difficult to plant. Rice fields are mainly found in coastal plains and hilly valleys. The plains are mostly winter crops - double-cropping rice with three crops, while the hills are mostly winter fallow fields - double-cropping rice with two crops. Both are mainly indica rice, and double-cropping hybrid rice has been expanded. Rice blast and stem borer are the main pests and diseases. The rice yield per unit area is 15% lower than that of the other two subregions. In the future, areas with favorable conditions can develop double-cropping rice in the form of "late planting and late planting", develop low-hill red and yellow soils, and transform medium- and low-yield fields.

(3) Southwest rice cultivation area

Located in Yunnan, Guizhou and Qinghai-Tibet Plateau, there are 391 counties (cities). Rice area accounts for 8% of the country's total.

1. The odd and even-cropping rice subregion in the mountainous plateau of eastern Guizhou and western Hunan

Includes 94 counties (cities) in central and eastern Guizhou, western Hunan, southwestern Hubei, and southeastern Sichuan. The climate has four distinct seasons. Annual accumulated temperature ≥10℃ is 3500~5500℃. The safe growth period of indica rice is 158 to 178 days, and that of japonica rice is 178 to 184 days.

The growing season has 800 to 1100 hours of sunshine and 800 to 1400 mm of precipitation. Spring drought is often followed by latent drought in the north, which affects transplanting, heading and grain filling. Most of them are one-crop mid-rice or late-season rice, and mostly rape-rice is the main two-crop crop. Rice is distributed vertically, with japonica rice grown at high altitudes and indica rice grown at low altitudes. Rice blast and stem borer are the main pests and diseases. The food self-sufficiency rate is low, and 30 to 50% of counties are short of food and rely on external transfers. In the future, we still need to emphasize increasing rice production, which is the basis for poverty alleviation. The low-heat Sichuan Road Valley should actively develop double-cropping rice.

2. Dian-Sichuan Plateau Ridge Valley Single-crop Rice and Double-Crop Sub-region

Including 162 counties (cities) in central and northern Yunnan, southwestern Sichuan, northwestern Guangxi and central and western Guizhou. The area is dotted with large and small dams, with obvious vertical differences. The annual accumulated temperature is ≥10°C and is 3500-8000°C. The safe growth period of indica rice is 158-189 days and that of japonica rice is 178-187 days. The growing season has 1100 to 1500 hours of sunshine and 530 to 1000 mm of precipitation. The long dry season in winter and spring limits multiple planting of rice. The main crops are broad beans (wheat) and rice, with winter paddy fields accounting for more than 1/3 of the rice fields. The highest height of the rice fields is 2,710 meters above sea level, which is also the highest limit of rice fields in the world. Most are cold-resistant medium japonica or early medium japonica types. Rice blast, stem borer, etc. cause serious damage. In the future, double-cropping rice will be actively developed in valleys below 1,500 meters above sea level, and medium-indica rice, mainly hybrid rice, will be developed in valleys between 1,200 and 2,000 meters above sea level, as well as high-quality rice.

3. Single-crop rice sub-region in the alpine valleys of Qinghai-Tibet

The area suitable for growing rice is extremely small, and rice fields are distributed in limited low-altitude valleys, including mid-level, Deqin, and eastern Tibet in Yunnan. Seven counties, including Mangkang and Medog, have rice. Due to poor production conditions, the rice yield per unit area is low and unstable, but it has the potential to increase production.

The rice cultivation area in northern China’s rice regions is only 30 million acres year-round, accounting for about 6% of the country’s rice sown area. The following is only a general introduction.

(4) North China Rice Growing Area

It is located north of the Qinling Mountains and the Huaihe River, south of the Great Wall, and east of the Guanzhong Plain, including Beijing, Tianjin, Hebei, Shandong, Henan, and Shanxi. In parts of Shaanxi, Jiangsu and Anhui, there are 457 counties (cities). Rice area accounts for only 3% of the country.

This area has two sub-areas: 1. Mid-early maturing sub-area in the northern plains of North China; 2. Mid-late maturing sub-area in the hills of the Huanghuai Plain. ≥10℃ accumulated temperature 3500～4500℃. The safe growth period of rice is about 130 to 140 days. During the growth period, there are 1,200 to 1,600 hours of sunshine and 400 to 800 mm of precipitation. There are droughts in winter and spring, and heavy and concentrated rains in summer and autumn. In the Haihe and Beijing-Tianjin rice areas in the north, most of the crops are mid-season japonica rice, while in the Huang-Huai area, most are double-crop wheat and rice, mostly indica rice. Rice blast, stem borer, etc. cause serious damage. In the future, it is necessary to develop water-saving rice planting technology and implement comprehensive management of rice fields.

(5) Northeast single-crop rice cultivation area

It is located north of the Liaodong Peninsula and the Great Wall, east of the Greater Khingan Mountains, and northeastern Inner Mongolia, with 184 counties (banners, cities). Rice area accounts for only 3% of the country's total.

This area has two sub-areas: 1. Extra early-maturing sub-area in the Heiji Plain Valley; 2. Early-maturing sub-area in the Liaohe Coastal Plain. The accumulated temperature of ≥10℃ is less than 3500℃, and low-temperature chilling damage often occurs in northern areas. The safe growth period of rice is about 100 to 120 days. During the growth period, there are 1000 to 1300 hours of sunshine and 300 to 600 mm of precipitation. In recent years, rice has expanded rapidly, and the varieties are particularly early maturing or medium or late maturing and early japonica. Rice blast and rice leafminer are more harmful. In the future, it is necessary to speed up the construction of the Sanjiang Plain, continue to expand paddy fields, improve the new technology system for rice cultivation in cold areas, and promote water-saving rice planting technology.

(6) Northwest Dry Area

Located west of the Greater Hinggan Mountains, north of the Great Wall, Qilian Mountains and the Qinghai-Tibet Plateau, the Yinchuan Plain, the Hetao Plain, and the edges of the north and south basins of the Tianshan Mountains are the main rice areas. Rice area accounts for only 0.5% of the country's total.

This area has three sub-regions: 1. Early-maturing sub-region in the North Xinjiang Basin; 2. Medium-maturing sub-region in the South Xinjiang Basin; 3. Early-mature maturing sub-region on the Gansu-Ningxia Shanxi-Mongolia Plateau. ≥10℃ accumulated temperature 2000～5400℃. The safe growth period of rice is 100 to 120 days. During the growth period, there are 1,400 to 1,600 hours of sunshine and 30 to 350 mm of precipitation. Rice cultivation relies entirely on irrigation. It is basically an early- to medium-ripening drought-tolerant japonica rice that matures once a year and has a high yield. Rice blast and water fly maggots cause serious damage. Drought, sand and alkali are the three major obstacles. It is necessary to promote water-saving rice planting technology, increase the application of farm fertilizers, and transform low- and medium-yield fields.