(Chongqing Institute of Land Survey and Planning, Chongqing, 400020)
According to the principle that the comprehensive grain production capacity will not be reduced, the quantity and quality of supplementary cultivated land will be converted into grades to achieve the balance between the quantity and quality of cultivated land. Based on the results of agricultural land classification in Chongqing, guided by the theory of agricultural land classification, this study completed the formulation of the quantity and quality of supplementary cultivated land in Chongqing through field investigation and statistical analysis of data, and using the mathematical model of equal standard grain yield. The research shows that agricultural land utilization can better reflect the differences of different quality agricultural land and its grain production capacity, and the grading of agricultural land utilization is more in line with the strategic significance of ensuring food security. The conversion coefficient between the highest grade and the lowest grade of agricultural land in Chongqing is 2.92, which accords with the actual situation in Chongqing.
Keywords: classification of agricultural land; Standard grain yield; Conversion coefficient; Chongqing
The quantity and quality of supplementary cultivated land are converted by grades, which is based on the principle that the comprehensive agricultural production capacity will not be reduced, and the quantity and quality of supplementary cultivated land are linked with the grade of occupied cultivated land by using the results and methods of grading conversion of agricultural land, so as to realize the balance between quantity and quality of cultivated land. Considering the requirements of ecological construction and environmental protection in China, as well as the limited reserve resources of cultivated land, we should base ourselves on improving the level of supplementary cultivated land to achieve the level of occupying cultivated land, and realize "occupying one and supplementing one". It is not advisable to advocate increasing the number of supplementary cultivated land to offset the quality, that is, "supplementing less with more"; At the present stage, in order to ensure that the quantity of cultivated land determined in the overall land use planning is not reduced, it is not allowed to reduce the quantity of supplementary cultivated land on the grounds of supplementing high-grade cultivated land, that is, "quality against quantity". The quantity and quality of supplementary cultivated land should be transformed according to the grade, and the grade of supplementary cultivated land should be improved on the basis of "taking one to make up one"; Affected by natural conditions and other factors, the level of supplementary cultivated land can not reach the level of occupied cultivated land, and the area of supplementary cultivated land must be converted according to the level.
Overview of Chongqing 1
Chongqing is located in the southwest of China and in the east of Sichuan Basin (e10517 ′ ~11′, N2810 ′ ~ 3213. Chongqing is the economic center in the upper reaches of the Yangtze River and the transportation hub in the southwest. It borders Hubei Province and Hunan Province in the east, Guizhou Province in the south, Sichuan Province in the northwest and Shaanxi Province in the north. City * * * governs 15 districts, 4 county-level cities and 2 1 county, with a total area of 82,400km2. Since 1997, Chongqing's social economy has developed rapidly. By the end of 2004, the city's GDP reached 266.539 billion yuan, an increase of 12.2% over 2003, and the absolute number was 2.3 times that of 1997. Chongqing belongs to the subtropical humid monsoon climate zone, with the characteristics of hot summer and warm winter, light and heat in the same season, long frost-free period, abundant rainfall and humid and cloudy. Annual average temperature 18.9℃, annual total rainfall1025.0mm; The terrain in the area fluctuates greatly, with an average elevation of 400m and a relative height difference of more than 2800m m. The karst landforms in the territory are widely distributed, with beautiful scenery and developed tourism.
According to the survey data of land change in 2004, the city's agricultural land is104160300mu, accounting for 844 1% of the total land area, of which the cultivated land area is 3431.1300mu, accounting for 27.80% of the total land area. Woodland is 48,769110,000 mu, accounting for 39.53% of the total land area; The garden area is 33 1.42 million mu, accounting for 2.69% of the total land area; Grassland is 3,570,800 mu, accounting for 2.89% of the total land area; Other agricultural land is 14 195000 mu, accounting for 0.50% of the total land area. Agricultural arable land is highly developed, and agriculture, forestry, animal husbandry and by-products are fully developed. It is an important grain producing area and commercial pork production base in China.
2. Study the technical route by grade transformation.
Using the standard grain yield utilization index to calculate the grade conversion coefficient can better reflect the difference of grain production capacity of different quality agricultural land. Because the standard grain yield reflects the comprehensive grain production capacity of agricultural land, the utilization index is the grain production capacity of different utilization modes and levels under the optimal economic conditions. Therefore, the standard grain yield utilization index is more in line with the purpose of transforming the quantity and quality of supplementary cultivated land into grades and the strategic significance of ensuring food security. The specific research technical route and method are as follows (Figure 1).
(1) Divide secondary districts, select typical counties to divide Chongqing into four secondary districts, and select a typical county for each secondary district according to the principle of similar natural, social and economic conditions;
(2) Under the guidance of agricultural land classification regulations, the agricultural land in four typical counties was classified, and the utilization classification of different plots (classification units) was determined;
(3) Calculate the standard grain output. Taking the standard grain yield coefficient (β) used in agricultural land classification as the conversion coefficient, the standard grain yield of four typical counties was calculated.
(4) Establish the corresponding relationship between agricultural land utilization index, utilization index and grain production capacity;
(5) Formulating the conversion coefficient table of standard grain yield-utilization ratio.
Figure 1 technical route of grade conversion research
3 Research process and methods
3. 1 Select a typical county
Agricultural land classification in Chongqing is divided into four secondary areas, which initially achieves the balance of the city's classification results, and the city's classification is 12 use. Based on the comprehensive analysis of geology, geomorphology, climate and hydrology, and soil vegetation in Chongqing, the related indexes and parameters of agricultural land classification in Chongqing were analyzed and studied, and combined with expert consultation, typical counties were selected in four secondary districts: Dazu County, liangping county City and Chongqing City. Because the research results of agricultural land classification in the four pilot counties are comparable, in order to test whether the agricultural land classification system established on the basis of the pilot counties is suitable for non-pilot counties, among the selected typical counties, except Dazu County, the other three typical counties are non-pilot counties for agricultural land classification (Figure 2).
Fig. 2 Schematic diagram of location distribution of typical counties in Chongqing after equivalent conversion.
3.2 Selection of survey sample points
When selecting the sample points of field investigation in four typical counties, different index areas and different altitudes are selected to represent villages. Including villages with different soil types; Considering villages with different distances from the city; Covering villages with the highest and lowest natural quality index and utilization index, as well as different natural grades and utilization grades. According to the results of agricultural land classification in four counties, the natural attribute data, utilization coefficient data, natural quality index, utilization index and utilization classification data of typical village classification maps are extracted.
3.3 Division of Utilization, etc
The utilization index of agricultural land classification results in four typical counties was summarized and divided into 12 grades according to the score interval of 100. The utilization level of Dazu County ranges from 1 to 12. The largest area distribution is 7, followed by 6. The utilization grade of liangping county is 3 ~ 12, etc. And the largest regional distribution is 8, followed by 9. The utilization grade of Pengshui County is distributed in 1 ~ 1 1 etc. The largest area distribution is 5, followed by 4, and so on. The utilization grade of Wuxi county is distributed in 1 ~ 12, etc. The largest area distribution is 4, followed by 5.
3.4 Regression analysis of standard grain yield utilization index
Through the conversion of β coefficient, the different crop yields obtained from the investigation are converted into crop yields consistent with the standard farming system adopted in agricultural land classification. Then it is converted into the standard grain yield of rice as the benchmark crop. According to the field survey data, each survey sample point corresponds to a utilization index and a standard grain yield, and a linear regression analysis between the standard grain yield and the utilization index of the survey sample point is established. The analysis is shown in Figure 3.
Equal exponential regression analysis of standard grain production and utilization in typical counties.
Because the number of survey points in each typical county in this grade conversion study accounts for more than 5% of the map points of each typical county classification unit; In terms of spatial distribution, it covers different topography, landforms, different natural grades and utilization grades. Therefore, the regression analysis established by the standard grain yield and utilization index of these measuring points is suitable for their respective typical counties; In the classification of agricultural land, the same classification parameters are used in the same secondary area, and the regression equations established according to the survey samples of four typical counties are suitable for their respective secondary areas.
Because the agricultural land classification index in Chongqing is based on the comparability between four typical counties, namely four secondary districts, under the control of the standard sample plots in the whole city, the linear equation obtained by regression analysis has universal applicability in the whole city, which is the conversion formula of Chongqing standard grain yield-utilization index:
y=6.68 x-875.43
Where y is the standard grain yield in kg/hm2, which is the utilization index.
3.5 Using the corresponding relationship of grain yield of equal standard
By classifying the field survey samples one by one, the corresponding relationship between the utilization grade of the survey samples in four typical counties and the standard grain output is calculated. The average utilization index of each utilization grade is calculated by the area weighted average method of all field survey samples included in the utilization grade, and the standard grain yield is calculated by substituting the average utilization index into the regression equation. See table 1 for the calculation results.
Table 1 the corresponding relationship between agricultural land classification and standard grain output in survey sample points.
4. Make the conversion coefficient table.
Transforming the quantity and quality of supplementary cultivated land into grades is a necessary means to effectively solve the current quality problem of supplementary cultivated land and ensure that the quantity and quality of supplementary cultivated land are equivalent to those of occupied cultivated land; It is an important measure to strictly protect cultivated land, especially basic farmland, improve the comprehensive agricultural production capacity and realize the national food security strategy. Therefore, in the study of the quantity and quality of supplementary cultivated land by grade conversion, the conversion must be based on the comprehensive grain production capacity, that is, the grade conversion coefficient is calculated according to the standard grain output corresponding to each utilization grade, and the grade conversion coefficient is calculated according to the following formula:
Kij=Qi/ Qj
Where: I and J are the serial numbers of agricultural land conversion grades, where I is higher than J; Kij is the conversion coefficient from bit I to bit J; Qi and Qj are the standard grain yields at I and J, and this yield is obtained by bringing the corresponding grades into the regression equation Y = 6.68X-875.43 with equal index.
According to the calculation method of the above conversion factors, the conversion factors of all levels in Chongqing are shown in Table 2.
Table 2 Chongqing conversion coefficient table by grade
By consulting experts from Chongqing Agriculture Bureau and analyzing statistical data, based on the general farming level, the highest yield in Chongqing is about 750 kg/mu, and the lowest yield is about 250 kg/mu, so the maximum conversion coefficient calculated simply is close to 3, so the maximum grade conversion coefficient obtained by this project is reasonable and accords with the actual situation in Chongqing.
5 Conclusion and discussion
Converting the quantity and quality of supplementary cultivated land by grades means linking the quantity and quality of supplementary cultivated land with the grade of occupied cultivated land, and using the results and methods of agricultural land classification to convert it, so as to realize the "one-to-one" of the quantity and quality of cultivated land. Through this study, we can draw the following conclusions:
(1) The utilization of agricultural land can reflect the difference of agricultural land with different quality and its grain production capacity, and the strategic significance of converting agricultural land utilization into grades is consistent with ensuring food security.
(2) The conversion coefficient between the highest grade and the lowest grade of agricultural land in Chongqing is 2.92, which is suitable for the actual situation in Chongqing.
(3) The conversion of agricultural land in Chongqing is based on the grain production capacity of 50kg, which is highly operable.
(4) Through this study, it provides a strong technical basis for Chongqing to implement strict land management, land development and consolidation and basic farmland protection.
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