China has a long history of planting rice and a vast region. It is one of the main rice producing countries in the world. China's annual rice planting area is about 35 million h ㎡, accounting for about 29% of the sown area of grain crops. The total output of rice is 192 million tons, accounting for 42% of the total grain output. Regardless of planting area and output, it ranks first in China's grain crops.
There have always been a large number of weeds in paddy fields in all rice growing areas in China. According to statistics, there are more than 200 kinds of weeds in paddy fields in China, of which about 40 kinds are common, seriously damaged and the most common weeds (10 ~ 20 kinds are distributed in various rice areas). According to the survey, the area of rice field grass damage above medium level (Level 2 ~ 5) in China is 15.467 million h ㎡, of which the area of serious damage (Level 4 ~ 5) is 3.8 million h ㎡, accounting for 46.8% and 11.5% of the rice planting area respectively, and the loss of grain is more than 20 billion kg. Among these main weeds, barnyardgrass has the largest occurrence and damage area, up to 14 million h ㎡. about 43% of the total area of paddy field, barnyardgrass not only caused the largest area of occurrence and damage, but also caused the most significant reduction of rice yield; The occurrence and damage area of heterotypic Cyperus, duckweed, Scirpus Scirpus, thousand gold and eye vegetables were the second.
China is a vast country with different climate, soil and farming conditions in different regions. The types and occurrence of weeds in paddy fields are different. The weed damage in paddy fields can be divided into five areas.
1. Tropical and subtropical 2 ~ 3 season xiucao damage area
Lingnan area, including Hainan, Yunnan, Fujian, Guangdong and Guangxi, has an annual average temperature of 20 ~ 25 ℃ and an annual rainfall of more than 1000mm. The main weed species include barnyardgrass, heterotypic sedge, jiejiecai, Shuilong, sharp valve flower, Qianjin, four leaf Ping, duck tongue grass, sunshine floating grass, grass dragon, etc.
2. 1 ~ 2 season rice straw damage area in subtropical zone of North Central China
It is mainly in the Yangtze River Basin in Central China, which is the main rice growing area in China. It includes Northern Fujian, southern Jiangxi and Hunan, Northern Jiangsu, Anhui, Hubei and Sichuan, and southern Henan and Shaanxi. The annual average temperature is 14 ~ 18 ℃, and the annual rainfall is about 1000mm. The weed damage area of paddy field in this area accounts for about 72%, of which the medium and above damage area accounts for 45.6%. The weeds with common occurrence and serious damage include barnyardgrass, heterotypic Cyperus, cow felt, water Cyperus, Scirpus triqueter, broken rice Cyperus, eye vegetables, duck tongue grass, arrowhead mushroom, arthrodendron, water amaranth, thousand gold, double ear paspalum, wild arrowhead mushroom, empty lotus seed grass, carp intestines, moshang, water chestnut, Lin and Ping, etc.
3. Single season rice straw damage area in warm temperate zone
It mainly refers to the Huanghuaihai River Basin south of the Great Wall, including the north of Jiangsu and Anhui, the central North of Henan, the north of Qinling Mountains in Shaanxi, the south of the great wall and the south of Liaoning. Most of them are rice wheat rotation areas. The annual average temperature is 10 ~ 14 ℃, and the annual rainfall is about 600mm. The damage area of weeds in paddy field accounts for about 91%, and the damage degree above medium accounts for 71.5%. Among them, barnyardgrass, heterotypic sedge, Scirpus Scirpus, cattle felt, wild arrowhead, water amaranth, carp intestines, eye vegetables and duck tongue grass are common and seriously damaged.
4. Temperate rice field grass damage area
It mainly refers to the three northeastern provinces to the north of the Great Wall, the northwest and the north of North China. The annual average temperature is 2 ~ 8 ℃, and the annual rainfall is 50 ~ 700mm. The area of rice in this area is small, and the occurrence of weeds is relatively light in the south. The main weeds are barnyardgrass, Scirpus Scirpus, eye vegetables, cow felt, special-shaped sedge, etc.
5. Grassland damage area of paddy field in Yunnan Guizhou Plateau
Including Yunnan, Guizhou and southwest Sichuan. The annual average temperature is 14 ~ 16 ℃, the annual rainfall is about 1000 mm, and the terrain is complex. The main weeds are barnyardgrass, heterotypic Cyperus, eye vegetables, duck tongue grass, Alisma orientalis, wild arrowhead, four leaf Ping, firerush,, cattle felt, Scirpus Scirpus, etc.