Division of index areas of agricultural land grading factors

Index area refers to the applicable area of the evaluation index system composed of grading factor indexes for calculating the natural quality of agricultural land. According to the Regulations on Agricultural Land Classification and the Technical Briefing of Agricultural Land Classification and Evaluation Project (Phase III), the provinces (autonomous regions and municipalities) that carry out agricultural land classification must divide index areas, and the recommended classification factors, weights and the relationship table of "designated crops-classification factors-natural quality scores" of each index area shall be determined by the province. According to the requirements of "Regulations" and "Technical Brief", agricultural land classification in Guangxi Zhuang Autonomous Region must be divided into autonomous region-level factor index areas.

(A) the division of agricultural land classification factor index area

1. The division principle of secondary index areas in Guangxi Zhuang Autonomous Region

(1) index area refers to the sub-factors and their combinations that determine the natural quality of agricultural land in the whole working area. It is divided 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 a set of index system of agricultural land grading factors after scientific analysis and demonstration 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 factor of index area selection.

(3) The division of high-grade areas (first-grade areas) is connected with the national division system, and the low-grade areas (second-grade areas) are divided according to the differences of agricultural ecological types, land types and soil types, production and utilization and regional farming system characteristics in different parts of the autonomous region.

(4) Maintain the integrity of county-level administrative regions.

2. The basis and method for the division of secondary index areas in Guangxi Zhuang Autonomous Region.

1) division basis

Guangxi Zhuang Autonomous Region is located in Eurasia, facing the southeast edge of tropical ocean. Affected by the intense solar radiation in winter and summer and the sea-land monsoon circulation, it belongs to 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

According to the climate and soil zonation, the special zoning and agricultural zoning of soil improvement and utilization 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, belonging to subtropical climate. The mountains are mostly granite, sand shale and limestone, and the 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, cold and humid landform, great vertical climate difference and large temperature difference between day and night. The mountains are northwest-southeast, with continuous mountains, undulating peaks, high mountains and 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 little 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 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 in the arc mountain range of Guangxi Zhuang Autonomous Region, surrounded by mountains, and the western part of the basin is a karst mountain area. Terraces and plains are the main agricultural production land in the region, with great production potential, poor soil and water, and uneven rainfall distribution, but groundwater resources are rich, accounting for about 1/3 of Guangxi Zhuang Autonomous Region. Paddy soil is distributed along Rongjiang River, Longjiang River, Hongshui River, Liujiang River and Qianjiang River, while dry land is mainly distributed in karst canyons, basins and depressions.

(4) The low plain area in southern Guangxi is located in the south of Guangxi Zhuang Autonomous Region, south of the Tropic of Cancer. The land type is mainly hilly and flat land, which has a vast territory, abundant sunshine, high temperature, sufficient heat and abundant rain. It belongs to the tropical climate of South Asia, and its parent rocks and materials are granite, sand shale, purple rock, limestone, Quaternary red soil and river alluvium, 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 for cash crops such as grain, sugar cane and fruit in Guangxi Zhuang Autonomous Region.

(5) Youjiang River Basin 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 area has the effect of foehn, which is a famous high temperature area and low rainfall area in Guangxi Zhuang Autonomous Region. The annual average rainfall is1100 ~1374 mm, among which Tian Yang Valley is one of the three major arid areas in Guangxi Zhuang Autonomous Region. There are many mountains and less cultivated land, but the cultivated land is mostly distributed in low-lying areas, with deep soil layer, loose texture, fertility and rich light and heat resources. Therefore, the alluvial plain of Youjiang Valley is also one of the important rice and sugarcane production bases in the autonomous region.

(6) The karst mountainous area in western Guangxi is located in the west of Guangxi Zhuang Autonomous Region, with various landform types, mainly karst peak-cluster depressions and peak-forest canyons, 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 drought in spring and autumn, 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 south coast of 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. Agricultural land is mainly distributed on both sides of rivers, plains, terraces and hilly valleys.

2) division

Delphi method was used to divide the index areas of agricultural land classification factors in Guangxi Zhuang Autonomous Region. The expert consultation and guidance group of agricultural land grading and evaluation in Guangxi Zhuang Autonomous Region has been divided into two levels after many expert meetings.

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 districts is to maintain the integrity of county-level administrative districts on the basis of the division of primary districts. According to the differences of agricultural natural conditions (geology, landform, climate, hydrology, soil and vegetation), land resources and farming system characteristics, combined with soil zoning, agricultural comprehensive zoning and agro-ecological types, the zoning 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 characteristics of coastal agriculture affected by marine hot and humid climate.

3. The division result of secondary index area

According to the dominant factors and regional differentiation characteristics, the index area of agricultural land classification factors in Guangxi Zhuang Autonomous Region is subdivided into seven secondary areas, among which Nanling hilly area is subdivided into three secondary areas: hilly area in northeast Guangxi (IV3-I), mountainous area in northwest Guangxi (IV3-II) and karst plain area in central Guangxi (IV3-II). The low plain area in South China is further subdivided into three secondary areas, namely, the low plain area in southern Guangxi (V 1-I), Yanrong Mountain area in western Guangxi (V 1-II) and Youjiang Valley area (V 1-III). The coastal area of southern Guangxi (V2 area 1) belongs to the hilly area of Xishuangbanna, the southern coastal area of China. See Table 3-5 and Figure 3-4 for the specific division results.

Table 3-5 Land Classification Factor Index Zoning Scheme Table

Note: Counties (cities, districts) in the table are the administrative divisions of Guangxi Zhuang Autonomous Region in 2005.

Figure 3-4 Schematic diagram of distribution of agricultural land classification index areas in western Guangxi Zhuang Autonomous Region

4. The main agricultural characteristics of the secondary index area

1) IV3-I hilly area in northeast Guangxi.

Including 2 1 county (district) 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℃ ~ 2 1.2℃, which is cold in winter and frosts every year. The average frost days are 5 ~ 10 days, the extreme maximum temperature is 40.4℃, and the extreme minimum temperature is -6.6℃. The 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 mountain area in northwest Guangxi.

The regional scope includes Ziyuan County, Longsheng Autonomous County and other 15 counties. Regional agricultural production conditions are poor, with mountainous areas and less flat land, large area suitable for forest and grazing, and less cultivated land. Paddy fields are located in narrow valleys or small basins between mountains, and are the best agricultural land in this area. Dry land is mostly located on the slopes of higher hills. It belongs to subtropical mountain climate, with cold and humid terrain, large vertical difference of mountain climate and large temperature difference between day and night. Annual average temperature 16.5℃ ~ 20.6℃, extreme maximum temperature 40.7℃, extreme minimum temperature -8.4℃, accumulated temperature ≥ 10℃ ~ 7 10. 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 rice.

3) Iv3-III dissolved plain in central Guangxi.

Located on the north side of the Tropic of Cancer, this area is a basin in the arc-shaped mountains of 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 has a subtropical monsoon climate with good light and heat conditions. Annual average temperature19.0℃ ~ 210.5℃, extreme maximum temperature 40. 1℃, extreme minimum temperature -4.0℃, accumulated temperature ≥ 10℃6047.6℃~ 73265438+ surface water in karst area. 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 canyons, 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) V 1-I low plain area in southern Guangxi.

Including 28 counties (cities, districts) such as Nanning and Wuming. 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 land, which has a vast territory, abundant sunshine, high temperature, sufficient heat and abundant rain. It belongs to the tropical climate of South Asia, with an annual average temperature of 20.9℃ ~ 22.5℃, an extreme maximum temperature of 42.0℃, an extreme minimum temperature of -3.0℃ and 6967.4℃ ~ 8044. 1℃ ≥ 10℃ accumulated temperature and an annual average rainfall of1. Agricultural land is mainly distributed in river alluvial plains and hilly basins, with fertile soil and rich products. It is an important agricultural area of grain, sugar cane, fruit and other cash crops in Guangxi Zhuang Autonomous Region. Paddy field farming system is mainly "rice-rice-green manure" or "rice-rice-vegetable" (multiple crops); The main crops planted in dry land are sugarcane, corn, peanuts, potatoes and vegetables.

5) V 1-II karst mountain area in western Guangxi.

Including 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. The annual average temperature is 18.9℃ ~ 2 1.6℃, the extreme maximum temperature is 40. 1℃, the extreme minimum temperature is -4.4℃, and the cumulative temperature is ≥ 10℃ and 665438. 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. Lack of water, 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) V 1-III Youjiang valley

Including Youjiang District, Tianyang County and Tiandong County, this area belongs to the south subtropical monsoon climate zone, with excellent light and heat conditions, with an annual average temperature of 2 1.9℃~ 22.0℃, an extreme maximum temperature of 42.5℃, an extreme minimum temperature of-1.2℃ and ≥ 10℃. The valley of Sanxian County (district) has the foehn effect, which is a famous high temperature area and low rainfall area in Guangxi Zhuang Autonomous Region, with an average annual rainfall of1100 ~1374 mm, among which Tian Yang Valley is one of the three major drought areas in Guangxi Zhuang Autonomous Region. The parent rocks are limestone, sand shale, Quaternary laterite, river alluvial deposit, 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 in Youjiang Valley is also one of the important rice and sugarcane bases in Guangxi Zhuang Autonomous Region. The 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

Including Qinzhou City, Fangchenggang City, Beihai City, Hepu County and dongxing city City. The area faces the Beibu Gulf and belongs to the tropical climate of South Asia. The annual average temperature is 2 1.9℃ ~ 22.8℃, the extreme maximum temperature is 38.4℃, the extreme minimum temperature is -0.8℃, the accumulated temperature is ≥10℃ 7702.4℃ ~ 8218.4℃, and the annual average rainfall is 65438. 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. Agricultural land is mainly distributed on both sides of rivers, plains, terraces and hilly valleys. The paddy field farming system is mainly "rice-rice" or "rice-rice-winter vegetables"; The main crops planted in dry land are sugarcane, peanuts, potatoes and vegetables.

(2) Division of sub-regions of standard farming system

Maturity refers to the number of seasons for planting crops in the same field in a year. Farming system refers to all farmland technical measures adopted in agricultural production to achieve sustained high yield, mainly including planting system, soil farming system, fertilization and weed control system, which is the general name of crop planting system and related technical measures. The standard farming system refers to the farming method which is (or will be) widely adopted under the local current social and economic level, production conditions and technical level, is beneficial to production or maximizes the production potential of local land, and still has great development prospects in the future, does not cause ecological damage, and can meet social needs. The standard farming system here mainly refers to the planting system. Crop planting system is the center of farming system, which mainly determines crop planting structure and layout according to crop ecological adaptability and production conditions. Crop planting time is multiple cropping and leisure, and crop planting methods are intercropping, interplanting and single cropping, continuous cropping and rotation. The criteria for evaluating the farming system are as follows: ① Make full use of natural resources such as water, soil, light and heat to improve the utilization rate of light energy. (2) Combining land use with land cultivation, making full use of land and improving land output rate; At the same time, the soil structure has been improved and the soil fertility has been continuously improved. (3) High economic benefit, high and stable yield of crops in a large area, low input and high output. (4) Reasonable crop distribution promotes the virtuous cycle of farmland ecosystem. The establishment of farming system depends on natural resources, socio-economic conditions and scientific and technological level, and gradually evolves with the improvement of socio-economic and scientific and technological level. Therefore, the secondary index areas of the standard system of the autonomous region should be divided according to the natural and socio-economic conditions of agriculture in the autonomous region. The specific division basis and results are as follows.

1. Basis for the division of secondary areas of standard farming system

(1) According to the natural conditions of agriculture (landform characteristics, climate conditions, hydrological conditions, water resources, animal and plant resources) and socio-economic conditions, combined with the characteristics of soil zoning and comprehensive agricultural zoning, the agricultural ecological types are complex, the land types and soil types are obviously different, and regional production and utilization are outstanding.

(2) According to the Regulations on Agricultural Land Classification, Guangxi Zhuang Autonomous Region is divided into three first-class areas, namely IV3 Nanling hilly area, V 1 South China low plain area and V2 Xishuangbanna low hilly area along the coast of South China. The agricultural land farming system zoning in Guangxi Zhuang Autonomous Region is further subdivided on the basis of the national first-class farming system zoning, combined with the agricultural land grading factor index control area and the agricultural farming system zoning in the whole region.

2. The results of the division of the secondary area of the standard farming system

The secondary area of agricultural land grading standard farming system in autonomous region is consistent with the secondary area of agricultural land grading factor index, and it is also subdivided into the same seven secondary index areas in autonomous region.

3. Determination of standard farming system in secondary areas

Guangxi Zhuang Autonomous Region has many mountains, less flat land, diverse topography and rich water and heat resources, forming a complex agricultural production model. Most agro-ecological areas can be harvested twice or even more a year, and some can only be harvested once a year. For example, it is located in the southern subtropical low plain of southern Guangxi, which is the main agricultural area of cash crops such as grain, sugarcane and fruit in Guangxi Zhuang Autonomous Region, with fertile soil and rich products. The farming system in each district is mainly "rice-rice-green manure". However, in the cold and humid climate zone in the middle subtropical zone bordering Yunnan-Guizhou Plateau in northwest Guangxi, the farming system is mainly "corn-middle rice" or "middle rice-ratooning rice". Rice and corn are the main food crops in Guangxi Zhuang Autonomous Region, sugarcane is the main cash crop in the autonomous region, and Guangxi Zhuang Autonomous Region is one of the main sucrose production bases in China. Rice, corn and sugarcane are the main crops and traditional crops in Guangxi Zhuang Autonomous Region. After a long-term production process, they have a good consistency with the natural characteristics of land in Guangxi Zhuang Autonomous Region, which can properly reflect the main characteristics of agricultural planting and production in Guangxi Zhuang Autonomous Region, reflect the quality attributes of agricultural land in this region, and highlight the superior climatic conditions of Guangxi Zhuang Autonomous Region and its characteristics as the main grain and sugar production base in China. According to these characteristics and the actual farming system and crop composition in Guangxi Zhuang Autonomous Region, three farming systems, namely "early rice-late rice", "early corn-late corn" and "one-season sugarcane", were determined as standard farming systems.

The farming system in each secondary area is as follows: ① The standard farming system in hilly and mountainous area of northeast Guangxi (IV3-I) is two crops a year, namely "rice-rice" or sugarcane or corn; ② The standard farming system in the mountainous area of northwest Guangxi (IV3-II) is one cropping a year to two cropping a year, with medium rice or "medium rice-corn"; (3) The standard farming system in karst plain area of central Guangxi (IV5-III) is "rice-rice" or "corn-late rice" or sugarcane; ④ The standard farming system in the low plain area of southern Guangxi (V 1-I) is "two crops a year to three crops a year, rice-rice-green manure" or sugarcane; ⑤ The standard farming system in Yanrongshan area (V 1-II) in western Guangxi is two crops a year to three crops a year, namely "early corn-late rice" or "rice-rice" or sugarcane; ⑥ The standard farming system in Youjiang River Basin (V 1-III) is two crops a year, namely "rice-rice" or sugarcane; ⑦ The standard farming system in the coastal area of southern Guangxi (V2-I) is two crops a year, namely "rice-rice" or sugarcane.

4. Determination of reference crops and designated crops

1) benchmark crops and designated crops

The benchmark crop is the conversion benchmark of theoretical standard grain, which refers to the common major grain crops in China, such as wheat, corn and rice. According to the different growing seasons in different regions, it can be further divided into seven food crops: spring wheat, winter wheat, spring corn, summer corn, one-season rice, early rice and late rice.

Designated crops refer to the crops involved in the standard farming system in the farming areas within their respective administrative areas.

2) Determination of reference crops and designated crops

The determination of designated crops in each factor index area should, in principle, highlight the agricultural production habits in this index area. The crops involved in the division of seven standard farming systems are rice, which is the main food crop; The crops involved in the other six standard farming systems are sugarcane besides rice; The crops involved in the two standard farming system zoning in the mountainous area of northwest Guangxi and hilly area of northeast Guangxi are not only rice and sugarcane, but also corn. Referring to the standard farming system and crop composition of China in Appendix B.2 of the Rules for Agricultural Land Classification, and combining with the comprehensive agricultural division, agricultural production and agricultural ecological characteristics of various regions in Guangxi Zhuang Autonomous Region, three crops, namely rice, corn and sugarcane, were determined as the designated crops for agricultural land classification in Guangxi Zhuang Autonomous Region, among which rice was the reference crop.

See Table 3-6 for the standard farming system, benchmark crops and designated crops in each index area of agricultural land classification.

Table 3-6 Statistical Table of Standard Farming System, Reference Crops and Designated Crops in each index area of agricultural land classification in Guangxi Zhuang Autonomous Region

Note: Sugarcane is harvested once a year in the table.