Division of index areas of agricultural land grading factors
The index area refers to the applicable area of the evaluation index system consisting of the grading factor indexes for calculating the natural quality of agricultural land. According to the Regulation of Agricultural Land Classification and Technical Briefing of Agricultural Land Classification and Valuation Project (Phase III), the provinces (autonomous regions and municipalities) that carry out agricultural land classification must divide the index areas, and the recommended classification factors, weights and the relationship table of "designated crops-classification factors-natural quality scores" of each index area must be determined by the province. According to the requirements of regulations and technical briefing, agricultural land classification in Guangxi Zhuang Autonomous Region must be divided into autonomous region-level factor index areas.
(I) division of index area of agricultural land grading factors
1. Division principle of secondary index area in Guangxi Zhuang Autonomous Region
(1) Index area refers to the division of various grading factors and combination of grading factors that determine the natural quality of agricultural land in the whole work area according to the principle of dominant factors and regional differentiation, and is the smallest unit that is different from other index areas.
(2) In an index area, only one set of index system of agricultural land classification factors that has been scientifically analyzed and demonstrated is applicable. The number of grading factors should be controlled at 5 ~ 7. The selected grading factors have obvious influence on the quality difference of agricultural land, while the unselected grading factors have little or no obvious influence on the quality of agricultural land. The calculation of natural quality score of agricultural land only involves the grading factors selected in the index area.
(3) the division of high-level areas (first-level areas) is connected with the national zoning system, and the low-level areas (second-level areas) are divided according to the differences of agricultural ecological types, land types and soil types, production and utilization and the characteristics of regional farming systems in the whole autonomous region.
(4) Maintain the integrity of county-level administrative regions.
2. Basis and method for the division of the second-level index area of Guangxi Zhuang Autonomous Region
1) Basis for the division
Guangxi Zhuang Autonomous Region is located in Eurasia, facing the southeast edge of tropical ocean, and is affected by the intense solar radiation and the sea-land monsoon circulation in winter and summer, belonging to a tropical and subtropical monsoon climate zone, which can be divided into three climatic zones from north to south: central subtropical zone, southern subtropical zone and northern tropical zone. Affected by the climate zone, the winter in all parts of the autonomous region is warm, and the average daily temperature is <: Although the low temperature weather of ℃ occurs in northern Guangxi and some mountainous areas in Zhongshan, the days are few and the duration is short. The average annual total accumulated temperature with daily average temperature ≥℃ in the whole autonomous region is 59℃ ~ 83℃, and the accumulated temperature ≥1℃ is 49℃ ~ 83℃. The regional distribution characteristics of accumulated temperature are similar to the average annual temperature, which is high in the south and low in the north, and low in the plains and mountains. Among them, Ziyuan County, leye county County, Nandan County and Jinxiu Yao Autonomous County are the areas with low accumulated temperature in the whole autonomous region (total accumulated temperature <: 62℃), the coastal areas of Qinzhou City, the left and right river valleys and other areas have the highest accumulated temperature (total accumulated temperature >; 8℃）。 However, the accumulated temperature difference between ≥℃ and ≥1℃ tends to decrease gradually from north to south and from mountain area to plain area. Soil temperature and moisture are directly restricted by atmospheric temperature and precipitation, forming a dependency relationship between soil types and climate change in horizontal and vertical directions. From the perspective of the whole autonomous region, the climate-soil change slightly presents the corresponding relationship between north tropical-latosol, south subtropical-latosol and middle subtropical-red soil.
According to the climate and soil zonality, special soil improvement and utilization zoning and agricultural zoning in Guangxi Zhuang Autonomous Region have been formed.
(1) The hilly area in northeast Guangxi is composed of mountains and hills, and the terrain decreases from northwest to southeast, which belongs to subtropical climate. Most of the mountains are granite, sand shale and limestone, and agricultural land is mainly distributed on both sides of rivers, mountain basins and hilly valleys.
(2) The mountainous area in northwest Guangxi is located at the edge of Yunnan-Guizhou Plateau, with subtropical mountainous climate, alpine and humid landform, large vertical climate difference and large temperature difference between day and night. The mountain range runs northwest-southeast, with continuous mountains, undulating peaks, high mountains, deep valleys and little flat land. The mountainous areas are mostly sand shale and limestone, with high mountains and deep valleys, poor agricultural production conditions and less cultivated land. Paddy fields are distributed in narrow valleys or small mountain basins, and dry lands are mostly on the slopes of higher hills.
(3) The karst plain area in central Guangxi is located on the north side of the Tropic of Cancer, with subtropical monsoon climate and good light and heat conditions. It is a basin inside the arc mountains in Guangxi Zhuang Autonomous Region, surrounded by mountains, and the western part of the basin is karst mountains. The agricultural production land in the region is mainly platform and plain, with great production potential, poor soil and water shortage, and uneven rainfall distribution, but the groundwater resources are rich, accounting for about 1/3 of Guangxi Zhuang Autonomous Region. Paddy soil is distributed along the banks of Rongjiang River, Longjiang River, Hongshui River, Liujiang River and Qianjiang River, while dry land is mainly distributed in karst valleys, basins and depressions.
(4) The low plain area of southern Guangxi is located in the south of Guangxi Zhuang Autonomous Region, south of the Tropic of Cancer. The land types are mainly hills and plains, and the hills and plains are vast, with sufficient sunlight, high temperature, abundant heat and abundant rain. It belongs to the tropical climate of South Asia, and the parent rocks and materials are granite, sand shale, purple rock, limestone, Quaternary red soil and river alluvial material, and the soil types are mainly paddy soil, lateritic red soil and mountain red soil. Agricultural land is mainly distributed in river alluvial plains and hilly basins. These places have fertile soil and rich products, and are important agricultural areas of grain, sugar cane, fruit and other cash crops in Guangxi Zhuang Autonomous Region.
(5) Youjiang Valley belongs to the south subtropical monsoon climate zone, with superior light and heat conditions, but the climate is dry. Because it is located in the valley basin, the valley zone has the effect of foehn, which is a famous high temperature area in Guangxi Zhuang Autonomous Region and a low rainfall area, with an average annual rainfall of 11 ~ 1374 mm, among which Tian Yang Valley is one of the three major drought areas in Guangxi Zhuang Autonomous Region. There are many mountains and less cultivated land, but most of the cultivated land is distributed in low-lying areas, with deep soil, loose texture, fertility and abundant light and heat resources. Therefore, the alluvial plain along the Youjiang River Valley is also one of the important rice and sugarcane production bases in the autonomous region.
(6) The karst mountain area in western Guangxi is located in the western part of Guangxi Zhuang Autonomous Region, with various landform types, mainly karst peak-cluster depressions and peak-forest valleys, as well as low mountains, hills, basins, terraces and alluvial plains, which are rich in land resources. Napo, Jingxi and Debao areas have high terrain and belong to the edge of Yunnan Plateau. The climate has plateau characteristics, with cool summer and warm winter, short sunshine, large temperature difference between day and night, severe spring drought and autumn drought, water shortage, less surface water, large leakage, frequent droughts and floods, and more dry land than paddy fields. Agricultural land is mainly distributed in karst valleys, basins and depressions.
(7) The coastal area of southern Guangxi faces the Beibu Gulf, and belongs to the tropical climate of South Asia. The terrain is mainly coastal platform, and the soil is developed from parent rocks such as granite, sand shale and shallow sea sediments, including latosol, coastal saline soil, fluvo-aquic soil and paddy soil. The agricultural land is mainly distributed on the banks of rivers, plains, platforms and hilly valleys.
2) division method
The index area of agricultural land classification factors in Guangxi Zhuang Autonomous Region is divided by Delphi method, and it is divided into two levels after many meetings of experts from the Advisory and Guidance Group of Agricultural Land Classification and Valuation Experts in Guangxi Zhuang Autonomous Region.
among them, the division of the first-level area is connected with the national zoning system, and it is mainly divided into three first-level areas: Nanling hilly area, South China low plain area and Xishuangbanna low hilly area along the coast of South China.
the division of secondary areas is based on the division of primary areas, maintaining the integrity of county-level administrative areas. According to the differences of agricultural natural conditions (geology, landform, climate, hydrology, soil and vegetation), the characteristics of land resources and farming systems, the division is combined with soil zoning, agricultural comprehensive zoning and agricultural ecological types, which fully reflects the influence of Guangxi Zhuang Autonomous Region as a typical karst landform area in China on agricultural utilization and rural economy, and the coastal areas are affected by maritime damp heat.
3. The results of the division of secondary index areas
The division of agricultural land classification factor index areas in Guangxi Zhuang Autonomous Region has been repeatedly demonstrated by experts. According to the dominant factors and regional differentiation characteristics, the agricultural land classification factor index areas at the autonomous region level are subdivided into seven secondary areas on the basis of the division of three primary areas in China, among which the hilly areas in Nanling are subdivided into three secondary areas, namely, hilly areas in northeast Guangxi (IV3-I) and mountainous areas in northwest Guangxi (IV3-I). The low plain area in South China is subdivided into three secondary areas, namely, the low plain area in southern Guangxi (V1-I), the Yanrongshan area in western Guangxi (V1-II) and the Youjiang Valley area (V1-III). The coastal area of South Guangxi (V2-I) is divided under the hilly area of Xishuangbanna, a coastal area of South China. See Table 3-5 and Figure 3-4 for the specific division results.
table 3-5 division scheme of land use grading factor index area
note: the counties (cities, districts) in the table are the administrative divisions of Guangxi Zhuang autonomous region in 25.
Figure 3-4 Schematic Diagram of Distribution of Agricultural Land Grading Index Area in West Zhuang Autonomous Region
4. Main Agricultural Characteristics of Secondary Index Area
1) IV3-I Hilly Mountain Area in Northeast Guangxi
Including 21 counties (districts) such as quanzhou county and xing an. The area is composed of mountains and hills, and the terrain decreases from northwest to southeast, belonging to subtropical climate. The annual average temperature is 17.3℃ ~ 21.2℃, and it is cold in winter, with frost every year. The average number of frosty days is 5 ~ 1 days, the extreme maximum temperature is 4.4℃, the extreme minimum temperature is -6.6℃, and the accumulated temperature of ≥1℃ is 532.℃ ~ 7. Paddy field farming system is mainly "rice-rice" or "rice-rice-green manure"; The main crops in dry land are sugarcane, followed by peanuts, silkworm peas and jute.
2) iv3-ii mountainous area in northwest Guangxi
The regional scope includes 15 counties such as Ziyuan County and Longsheng Autonomous County. Regional agricultural production conditions are poor, with more mountains and less flat land, a large area suitable for forest and grazing, and less cultivated land. Paddy fields are distributed in narrow valleys or small basins between mountains, which is the best farming land in this area. Dry land is mostly on the slopes of higher hills. It belongs to subtropical mountainous climate, with alpine and humid landform, great vertical difference in mountainous climate and large temperature difference between day and night. The annual average temperature is 16.5℃ ~ 2.6℃, the extreme maximum temperature is 4.7℃, the extreme minimum temperature is -8.4℃, the accumulated temperature of ≥1℃ is 4997.℃ ~ 7177.4℃, and the annual average rainfall is 186 ~ 1777 mm. The paddy field farming system is mainly "rice-rice" or "middle rice-ratooning rice", and the dry land is mainly intercropped with beans or potatoes of middle corn.
3) iv3-iii karst plain area in central Guangxi
This area is located on the north side of the Tropic of Cancer, and it is a basin inside the arc mountain range in Guangxi Zhuang Autonomous Region, which is dominated by karst topography, most of which are wide karst basins or karst plains, and the soil-forming parent material is mainly limestone, followed by sand shale and siliceous rocks. Including 12 counties (cities, districts) such as Jinchengjiang District and Luocheng County. It belongs to subtropical monsoon climate, with good light and heat conditions. The annual average temperature is 19.℃ ~ 21.5℃, the extreme maximum temperature is 4.1℃, the extreme minimum temperature is -4.℃, the accumulated temperature ≥1℃ is 647.6℃ ~ 7321.2℃, the annual average rainfall is 1345 ~ 1726 mm, and the rainfall distribution is uneven, but the groundwater resources are abundant. Surface water leakage is serious in karst area, which is prone to drought and waterlogging. There are many dry lands and few paddy fields, and corn is the main food crop with low yield. Paddy soil is distributed along Rongjiang River, Longjiang River, Hongshui River, Liujiang River and Qianjiang River, which is the main agricultural area in this area. Dryland is mainly distributed in karst valleys, basins and depressions. The paddy field farming system is mainly "corn intercropping with beans and late rice" or "rice-rice", and the crops planted in dry land are mainly corn, sugarcane, beans and potatoes.
4) V1-I low plain area in southern Guangxi
includes 28 counties (cities, districts) such as Nanning City and Wuming County. This area is located in the south of Guangxi Zhuang Autonomous Region, south of the Tropic of Cancer. The land type is mainly hilly and flat, and the hilly and flat land is vast, with sufficient sunlight, high temperature, abundant heat and abundant rain. It belongs to the tropical climate of South Asia, with an annual average temperature of 2.9℃ ~ 22.5℃, an extreme maximum temperature of 42.℃, an extreme minimum temperature of -3.℃, an accumulated temperature of ≥1℃ of 6967.4℃ ~ 844.1℃, and an average annual rainfall of 1177 ~ 194 mm.. Agricultural land is mainly distributed in river alluvial plains and hilly basins, with fertile soil and rich products. It is an important agricultural area for grain, sugar cane, fruit and other cash crops in Guangxi Zhuang Autonomous Region. The paddy field farming system is mainly "rice-rice-green manure" or "rice-rice-vegetable" (more crops and more crops); The main crops planted in dry land are sugarcane, corn, peanuts, potatoes and vegetables.
5) v1-ii karst mountain area in western Guangxi
includes six counties: Pingguo, Daxin, Tiandeng, Debao, Jingxi and Napo. This area is located in the southwest of Guangxi Zhuang Autonomous Region, with various landform types and plateau climate. It is cool in summer and warm in winter, with an average annual temperature of 18.9℃ ~ 21.6℃, an extreme maximum temperature of 4.1℃, an extreme minimum temperature of -4.4℃, an accumulated temperature of ≥1℃ of 6127.2℃ ~ 7597.℃, and an average annual rainfall of 1327 ~ 1677 mm. Short sunshine and large temperature difference between day and night. Agricultural land is mainly distributed in karst valleys, basins and depressions. The soil-forming parent rock is mainly limestone, followed by sand shale and siliceous rock. Water shortage, less surface water, large leakage, frequent droughts and floods, more dry land than paddy field, paddy field farming system is mainly "corn-middle rice (or late rice)" or "rice-rice", and crops planted in dry land are mainly corn, sugarcane and beans.
6) V1-III Youjiang Valley
includes Youjiang District, Tianyang County and Tiandong County, which belongs to the south subtropical monsoon climate zone and has superior light and heat conditions, with an average annual temperature of 21.9℃ ~ 22.℃, an extreme maximum temperature of 42.5℃ and an extreme minimum temperature of -1.2℃ ≥ 1. The valley of three counties (districts) has the effect of foehn, which is a famous high-temperature area and low-rainfall area in Guangxi Zhuang Autonomous Region, with an average annual rainfall of 11 ~ 1374 mm, among which Tian Yang Valley is one of the three major arid areas in Guangxi Zhuang Autonomous Region. The parent rocks are limestone, sand shale, Quaternary red soil, river alluvial material, proluvial, etc. The soil is mainly lateritic red soil and limestone soil. Cultivated land is mostly distributed in low-lying areas, and the alluvial plain along the Youjiang River Valley is also one of the important rice and sugarcane bases in Guangxi Zhuang Autonomous Region. Paddy field farming system is mainly "rice-rice" or "rice-rice-vegetable"; The crops planted in dry land are mainly sugarcane, corn and beans.
7) v2-I coastal area in southern Guangxi
includes five counties (cities, districts): Qinzhou, Fangchenggang, Beihai, Hepu and dongxing city. The region faces the Beibu Gulf and belongs to the tropical climate of South Asia. The average annual temperature is 21.9℃ ~ 22.8℃, the extreme maximum temperature is 38.4℃, the extreme minimum temperature is -.8℃, the accumulated temperature ≥1℃ is 772.4℃ ~ 8218.4℃, and the average annual rainfall is 1455 ~ 2785 mm. The terrain is mainly coastal platform, and the soil is developed from granite, sand shale, shallow sea sediments and other parent rocks, including latosol, coastal saline soil, tidal soil and paddy soil. Agricultural land is mainly distributed on both sides of rivers, plains, platforms and hilly valleys. Paddy field farming system is mainly "rice-rice" or "rice-rice-winter"