Which regions of China have red soil and yellow soil distributed, and what crops are suitable for planting there?
Red soil and yellow soil are two different types of soil. Red soil, yellow soil and lateritic soil can be collectively called ferralsols. Below we will look at which regions of China red soil and yellow soil are respectively distributed in, and what crops they are suitable for planting.
1. The distribution regions of red soil and suitable crops for planting
Red soil is soil developed under tropical and subtropical rainforest, monsoon forest or evergreen broad-leaved forest vegetation. Its main characteristics are a lack of alkali metals and alkaline earth metals and a richness in iron and aluminum oxides, appearing acidic red. Red soil is the product of the interaction between biological enrichment and the desilication and ferralitization weathering process that occur in the middle subtropical zone under hot and humid climate conditions with evergreen broad-leaved forest vegetation.
In China, red soil is mainly distributed in the low mountain and hilly areas south of the Yangtze River, including: most of Jiangxi and Hunan provinces, southern Yunnan, the southeastern part of Hubei, northern Guangdong and Fujian, and parts of Guizhou, Sichuan, Zhejiang, Anhui and Jiangsu, as well as southern Tibet. Red soil shows an acidic to strongly acidic reaction. Hilly red soil generally has insufficient supply of nitrogen, phosphorus and potassium, low content of available calcium and magnesium, and is also very poor in boron and molybdenum. It often produces the "mosaic" phenomenon in citrus due to a lack of the trace element zinc. Red soil is the northernmost and most widely distributed soil type within China's ferralsol order, with a total area of 56.9 million hm2, mostly in the vast low mountain and hilly areas of the middle subtropical zone between 25° and 31° north latitude.
The average annual temperature of China's red soil region is 15-25°C, the accumulated temperature of ≧10°C is 4500-9500°C, the average temperature of the coldest month is 2-15°C, and the average temperature of the hottest month is 28-38°C; the annual rainfall is 1200-2500 mm; winters are warm and dry, summers are hot and humid, and the dry and wet seasons are distinct.
From a global perspective, red soil is mainly distributed in the low-latitude regions of Africa, Asia, Oceania and South America and North America, roughly limited by 30° north and south latitude, and is commonly found in tropical rainforest areas. Europe, especially the eastern Mediterranean coast and the Balkan Peninsula region, also has soils similar to red soil. In East Asia, from the Yangtze River coast in the north, south to the South China Sea islands and the Malay Archipelago, east to Taiwan, and west to the Yunnan-Guizhou Plateau and the Hengduan Mountains, this range is an important distribution zone of red soil. The red soil region has abundant rainfall and concentrated rainfall; sometimes a single rainfall event can reach more than 200-300 mm, and when ground cover is poor, rainstorms cause severe soil erosion.
Red soil is generally suitable for planting rice, tea, silk and sugarcane, and mountain areas are also suitable for planting economic forest trees such as Chinese fir, tung tree, citrus, moso bamboo and palm. In addition, red soil is also a good soil for planting citrus.
The strong acidity of red soil and its heavy, sticky texture are unfavorable factors in the use of red soil. Soil fertility can be improved through measures such as applying more organic fertilizer, applying an appropriate amount of lime and supplementing phosphate fertilizer, and preventing red soil erosion. In view of the very low organic matter content of red soil, green manure crops can be planted to increase the organic matter content and nitrogen fertility of red soil. Red soil is generally deficient in available phosphorus, so increasing phosphate fertilizer application and improving its utilization rate is an important agricultural measure for increasing yield. Applying lime to red soil generally achieves good results.
2. The distribution regions of yellow soil and suitable crops for planting
Yellow soil is soil developed under subtropical humid mountain or plateau evergreen broad-leaved forests. Its main characteristics are: acidic, with the soil layer often remaining moist, and it appears yellow because the subsoil contains large amounts of hydrated iron oxide (goethite), hence the name.
Yellow soil is concentrated between 23.5° and 30° north and south latitude. It is distributed in central Africa, narrow strips of South America and North America and the southern part of North America, Southeast Asia, South Asia, and mountainous areas such as northern Australia.
In China, yellow soil is mainly distributed in Sichuan and Guizhou provinces, as well as Yunnan, Fujian, Guangxi, Guangdong, Hunan, Hubei, Zhejiang, Anhui, Taiwan and other places, and is one of the main soil types in the mountainous areas of southern China. Its vertical distribution pattern is obvious. In the vertical zone spectrum of each mountain area, the lower part of yellow soil is generally red soil, while the upper part is mostly yellow-brown soil. The yellow soil zone spectrum is also closely related to regional water and moisture conditions. Under humid conditions, the vertical belt of yellow soil is relatively wide, sometimes up to 1000 m; there are also many types, often with more than two yellow soil subgroups appearing. The lower limit of vertical distribution varies greatly, from about 500 m at the lowest to 1800 m at the highest. With different lower limits, the upper limit of the vertical distribution of yellow soil also changes, generally between 800 and 1600 m, while in the Yunnan Plateau mountains it is above 2200-2600 m.
Yellow soil is an important soil resource in Chongqing, with an area of 2371750.39 hm2, accounting for 28.78% of the total land area. It is mainly distributed in low mountain, middle mountain and hilly areas with an altitude of <1500 m and on the second, third, fourth and fifth terraces along the Yangtze River and its tributaries. Among these, the distribution area at an altitude of 400 m-1200 m is the largest, accounting for 75.22% of the total yellow soil area.
Yellow soil is the main land for dry grain and multiple economic crops in the mountainous areas of Chongqing, and is also a forestry base. The main crops are corn, wheat, sweet potato, potato and various vegetables, as well as tea. The natural forest vegetation is evergreen broad-leaved and coniferous mixed forest, and the secondary forest vegetation is mainly arboreal forests such as masson pine, pine and camphor, as well as a wide variety of bamboo forests, shrubs and herbaceous plants, with many medicinal materials growing epiphytically under the forest. Yellow soil has three major characteristics: too sticky, too sandy and too acidic. Cultivated soil has the common features of being lean, cold, wet and especially deficient in phosphorus, so planting corn and wheat on yellow soil often results in red seedling phenomenon. At present, the most important problem of yellow soil is vegetation destruction, with a relatively large proportion of cut-over land and sparse forest land, severe soil erosion, and mostly infertile soil properties. According to the developmental stage, yellow soil is divided into three subgroups: yellow soil, bleached yellow soil and yellow soil-like soil.
The use of yellow soil is best suited to diversified management. Surface gleyed yellow soil and podzolic yellow soil distributed in middle mountain ridges and watershed areas are not suitable for planting crops or economic forest trees because they are located in areas with high altitude, steep slopes and thin soil layers; in the primitive forest land where they occur, the main focus should be on forest protection and the collection and cultivation of medicinal plants. For yellow soil distributed in plateau and hilly areas, especially yellow soil developed from old red weathering crust or sandstone and shale, if the terrain slope is relatively small and the soil layer thickness is more than 1 m, agriculture and comprehensive agriculture-forestry use can be developed. Rice, corn and wheat can be planted on the lower gentle slopes and valleys of hills; fruit trees, tea and rapeseed and other economic crops and fuelwood forests can be developed on the middle and upper parts of hills. For cultivated yellow soil, in order to prevent soil erosion, it is advisable to carry out basic farmland construction centered on comprehensive management of mountains, water and fields, apply more organic fertilizer and plant green manure, and apply an appropriate amount of lime and phosphate fertilizer.
3. The difference between red soil and yellow soil
Compared with red soil, yellow soil has a lower average annual temperature and is more humid, so hydrated iron oxide and iron activation degree are higher (10%-25%), and the soil is yellow (2.5Y8/6) or orange-yellow (2.5Y7/8). Because the weathering degree of clay minerals is low, vermiculite is dominant, followed by kaolinite and hydromica, with more goethite and limonite. Its organic matter content is also relatively high (50gkg-1-100gkg-1).