Classification, Evaluation and Rational Utilization of Cultivated Land Reserve Resources in Shaanxi Province

The essence of agricultural production is the development and utilization of land resources by human beings. The supply of land is limited, and the development of production and the increase of population occupy a lot of cultivated land, which directly threatens the foundation of agricultural production. The shortage of cultivated land reserve resources is the basic national condition of our country, so the reclamation and utilization of cultivated land reserve resources is particularly important and urgent.

1 Classification of cultivated land reserve resources in Shaanxi Province

According to the detailed land survey data, 70% of China's arable land reserve resources are concentrated in the western region. The reserve area of cultivated land in Shaanxi Province is 884,526.5 mu, of which 727,828.0 mu, accounting for 82.28% of the reserve area of cultivated land in Shaanxi Province. The reclaimed land area is 156698.5 mu, accounting for 17.72% of the reserve area of cultivated land in the whole province (Figure 1).

The distribution of cultivated land reserve resources in various places (cities) is shown in the following figure (Figure 2, Figure 3 and Figure 4).

By collecting all kinds of data and using the information of detailed land survey, land change survey, natural resources scientific survey, soil survey, agricultural survey and population survey, the classified areas of cultivated land and arable land in cities of Shaanxi Province are basically found out and summarized (table 1).

2 Suitability evaluation of cultivated land reserve resources in Shaanxi Province

As a big agricultural province, the development of agriculture plays an important role in the economic development of Shaanxi Province. However, on the whole, the quantity and quality of cultivated land in Shaanxi Province are not high, and it is decreasing rapidly.

Through the investigation and suitability evaluation of cultivated land reserve resources in Shaanxi Province, we can find out the quantity, quality grade, distribution characteristics and structural pattern of all kinds of suitable unused land in Shaanxi Province, make land use types and methods conform to land suitability, scientifically and rationally allocate land, strictly control unproductive land, give full play to the potential of existing unused land, and realize the dynamic balance of land resources.

In addition to adhering to the basic principles of combining economic benefits, social benefits and ecological benefits, and combining long-term interests with current interests, evaluation must also adhere to specific principles such as combining comprehensiveness with dominance, combining scientificity with feasibility, combining qualitative with quantitative, and combining suitability with utilization.

The evaluation is based on the investigation of cultivated land reserve resources, and the evaluation unit is the secondary land map of land use status map. The classification of cultivated land reserve resources follows the unified national classification system (Table 1).

According to the suitability classification system put forward by FAO in the Outline of Land Suitability Evaluation, the suitability evaluation of reserve cultivated land resources in Shaanxi Province is divided into three grades: first-class cultivated land, second-class cultivated land and third-class cultivated land. Its evaluation basis includes: regional differences in land environment, land fertility level, diversity of agricultural types and comprehensiveness of land conditions, long-term stability factors and short-term variability factors of agricultural land quality, etc.

Figure 1 Classification of Cultivated Land and Reclaimed Land in Shaanxi Province

Figure 2 Proportion of cultivated land reserve resources in each city in the whole province

According to the requirements of "Technical Specification for Investigation and Evaluation of Land Resources in Western Development" for the evaluation index of cultivated land reserve resources, the evaluation index of cultivated land mainly includes: natural slope, soil thickness, soil texture, groundwater level, sand dune fluctuation, temperature condition and moisture condition. The evaluation indexes of reclaimed land include: ground slope, excavation subsidence depth, water accumulation depth, maintenance degree of soil cover source, groundwater level, accumulation amount, influence of accumulated harmful substances, effective soil layer thickness of accumulated ground, and degree of water supply guarantee for reclamation (irrigation).

Figure 3 Proportion of cultivated land in each city in the whole province

Figure 4 Proportion of Reclaimed Land in Cities in the Province

Table 1 Classified area of cultivated land reserve resources in Shaanxi Province Unit: mu

The suitability evaluation of cultivated land reserve resources in Shaanxi Province mainly adopts leading factors, determines the weight and standard score of each evaluation index through expert evaluation, and makes quantitative analysis.

See Table 2 for the suitability evaluation scores of reserve cultivated land in Shaanxi Province.

The evaluation results of cultivated land reserve resources in Shaanxi Province are shown in Table 3.

2. 1 Evaluation of Cultivated Land and Grassland (Ⅰ1)

The main limiting factors of grassland utilization are slope and soil texture. Therefore, engineering measures should be combined with biological measures in the development and utilization, and terraces and shelterbelts should be built to prevent soil erosion.

Table 2 Farmland Suitability Evaluation Score

Table 3 Evaluation Results of Cultivated Land Reserve Resources in Shaanxi Province Table Unit: mu

2.2 Evaluation of Cultivated Land Saline-alkali Land (Ⅰ 2)

Judging from the natural situation of saline-alkali land in Shaanxi Province, most saline-alkali land is suitable for planting crops after reclamation. Among the reserve resources of saline-alkali land, Weinan saline-alkali land has good environmental conditions, great production potential and good economic benefits, and is rated as second-class suitable agricultural land; Saline-alkali land in Yulin City has low temperature, low accumulated temperature, poor land environment, average economic benefit and fragile ecological environment, and is rated as the third-grade suitable agricultural land.

2.3 Evaluation of Reclaimable Marsh (Ⅰ 3)

This kind of land is low-lying and accumulates water all the year round. In the future, it should be developed and utilized in a planned way, such as developing aquatic crops, engaging in aquaculture, planting cotton and other crops by drainage, and rated as Class II suitable.

2.4 Evaluation of Reclaimable Reed Land (Ⅰ 4)

Reed land is low and flat, with mild and humid climate. After draining the accumulated water or lowering the groundwater level, it can be reclaimed as cultivated land, which is suitable for the growth of local crops. For example, reed land in Xianyang area is suitable for planting rice, wheat, corn and other crops after reclamation, with an yield of more than 500 kilograms per mu, which is suitable for cultivating third-class land.

2.5 Evaluation of Reclaimable Tidal Flat (Ⅰ 5)

The slope of beaches in the whole province is mostly 1 ~ 6, most beaches are relatively flat, and only a few beaches have steep slopes as high as 1 ~ 2 meters, which can be reclaimed as terraces according to the situation; The thickness of soil layer is mostly above 50 cm, but generally speaking, the soil layer is thin, and the thickness of individual beaches is gradually increasing, so the suitability of cultivated land is better; Gravel content in soil texture is mostly less than 15%, and gravel content in some beaches is less than 5%. The soil is sticky, with high temperature, strong adsorption capacity and good ploughability. The groundwater level is in good condition, mostly above 1 m, suitable for farming, and the groundwater quality is generally good or better, suitable for human and livestock drinking, farmland irrigation and industrial water use; There are basically no sand dunes in the beaches of the province, only steep ridges like ridges, which are small in height and will not affect reclamation; Because most of them are located in the warm temperate zone of Guanzhong, the temperature and accumulated temperature conditions can basically meet the requirements of crop growth; The tidal flat water conditions in the whole province are quite different, and the tidal flat distribution areas with good water conditions are suitable for the development of rice, aquatic crops and aquaculture. In areas with good water conditions, the tidal flat can be gradually improved into cultivated land through flood diversion or artificial land reclamation, and crops such as wheat, corn, cotton and rape can be planted.

2.6 Evaluation of Reclaimed Sandy Land (Ⅰ 6)

The sandy soil in the whole province is sandy, leaking water and fertilizer, low in organic matter and available nutrients, and lacking in trace elements, which is often affected by wind erosion, especially spring sowing crops. The improvement measures are leveling land, changing dry land into irrigated land, pulling soil and covering sand, improving soil texture, applying more organic fertilizers, increasing nitrogen and phosphorus fertilizers, and creating windbreak and sand-fixing forest belts and farmland shelterbelts.

To sum up, the sandy land in Guanzhong area, such as Weinan, has high accumulated temperature, much precipitation, good ecological environment and socio-economic conditions around the land, great development potential and remarkable economic benefits. It is an ideal cultivated land and is rated as a second-class suitable land. Yulin area has a large sandy land area, but the temperature is low, the ecological environment is fragile, the land productivity is low, the economic benefits are average, and the social and economic conditions are average. The comprehensive evaluation of land is grade III suitable land.

2.7 Evaluation of Reclaimed Wasteland (Ⅱ1)

Take the evaluation of Dimiao Township in Xunyi County as an example.

The accumulation of abandoned land in this area is the soil accumulation of abandoned homestead, the accumulation amount is less than 5m3/m2, and there are no harmful substances. The slope of the accumulation ground is 6 ~ 10 degree, and the thickness of the effective soil layer on the ground is greater than 1m, so the water source for reclamation is well guaranteed. In addition, the population in this area is relatively concentrated, the labor force is sufficient and the transportation is convenient. Therefore, the abandoned land in this area can be evaluated as suitable farmland.

2.8 Evaluation of Subsidence Land Reclamation (Ⅱ 2)

The main limiting factors of this land reclamation are slope and geological disasters, so it is necessary to strengthen soil and water conservation measures and engineering measures. This kind of land is rated as third-class cultivated land.

2.9 Assessment of Reclaimed Land Damaged by Natural Disasters (2.3)

Mainly concentrated in Shangluo area. Because of its flat terrain, close source of covering soil, superior other conditions and low cost of development and reclamation, it was rated as a second-class recoverable reserve resource.

3 Economic benefit evaluation of cultivated land reserve resources in Shaanxi Province

Using land productivity, land economic analysis and other indicators to evaluate land economy and classify land economy reasonably can effectively encourage and guide people to use land correctly, limit unreasonable land use and promote the transformation of land use in a more reasonable direction. According to the situation in China, a reasonable classification of land economy should encourage people to adopt advanced production methods, increase investment in land, and arouse the enthusiasm of operators to use land correctly.

In the specific evaluation, we should first determine the appropriate evaluation unit according to the evaluation purpose, the characteristics of the evaluation area and the available information. Commonly used dividing units are land units, natural plots or natural fields, administrative or production management units, etc. Secondly, investigate the crop species and rotation cycle contained in the main land use patterns in the local area, determine the area of various crops as the object of land economic evaluation, and determine the evaluation time range and data statistics year. Thirdly, the input-output data of different evaluation unit types and various current rotation methods for many years are investigated and calculated. There are three main methods: traditional fixed-point typical observation method, improved typical fixed-point measurement method and data statistical measurement method. Finally, select appropriate evaluation indicators (such as yield per mu, net income per mu, unit product cost), convert the above input-output data, and get the scores of all kinds of land according to the evaluation results of various indicators. According to the type structure and land use structure of land evaluation units in a region or an agricultural enterprise, the overall evaluation results of the region or agricultural enterprise are obtained by using the weighted average method.

The following mainly uses the gross profit analysis method to evaluate the land economy of typical plots:

3. 1 Evaluation of Reclaimed Land —— Taking the land reclamation and development of Zhong 'an Village, Xinxing Town, Sanyuan County as an example

Zhong 'an Village is located two kilometers from the north and south tablelands of Xinxing Town, with 795 people, with a total cultivated land area of 1647.4 mu, including 800 mu of irrigated land, 847.4 mu of dry land and 2007 mu of cultivated land per capita.

(1) The investment in the first phase of this land reclamation project is 560,000 yuan, and 560 mu of cultivated land has been reclaimed, with an investment of 1000 yuan per mu. After the completion of the first phase of the project, the yield per mu of wheat will reach 250 kg. According to the calculation of wheat per 500g 0.6 yuan, the output value per mu reaches 300 yuan, and the land productivity is 300 yuan/mu. In this way, the output value of three mu can repay the reclamation cost, and the economic benefit is considerable.

(2) The flood drainage canal is designed for the second phase project, and more than 70 mu of economic forest is planted along the canal. In addition, it is planned to build a new U-shaped channel of 3,500m, drill wells 1 entrance, 2 culverts, a set of deep-well power transmission and transformation 1 set, and build a new field road and village road of 3km. It is estimated that the investment in the second phase of the project will be 1600 yuan/mu, so that the total investment per mu of land will reach 2 900 yuan. After the second phase of the project is completed, the yield per mu will reach 500 kilograms of wheat, the output value per mu will be 600 yuan, and the land productivity will be 600 yuan/mu, which will improve the land productivity and bring more considerable economic benefits.

3.2 Other Cultivated Land —— Case of Sandy Land Reclamation in Dali County

The sand garden land in the south of Dali County is mainly concentrated in Bayu Township, Zhangjia Township and Guanchi Town, with an area of 17009.5 mu. These sand gardens are located in the first terrace of Weihe River, with rich light and heat, and the annual average temperature is 14℃. The precipitation is unevenly distributed, and there are plenty of water sources (mainly well irrigation), but the soil is loose and the fertility is low.

The renovation project of Sandy Garden in Dali County includes drilling wells, roads, power supply and sprinkler irrigation facilities, with an estimated investment of 4,000 yuan per mu. After the renovation project is completed, the land production capacity can reach two crops a year. In addition to planting peanuts, the annual output value is 500 ~ 600 yuan, and wheat and daylily can also be planted. The annual output value reaches 800 ~ 1000 yuan, and the land productivity reaches 800 ~ 1000 yuan/mu. The reclamation cost can be recovered from the output value within 4 ~ 5 years, and the economic benefit is considerable.

From the perspective of Shaanxi Province, the area of cultivated land resources in Shaanxi Province is 727,828 mu. The cultivated land is calculated as 4000 ~ 6000 yuan per mu, and the investment is 291.1.2 ~ 4366968,000 yuan. If the annual income per mu is 400 ~ 600 yuan, the investment can be recovered in at most 10 years, and the established standard farmland can continue to be used. The province's reclaimed land 156698.5 mu, with an investment of 35 million mu, can build high-standard farmland, with an annual income of more than 600 yuan per mu, and the investment can be recovered in five years. Comparatively speaking, the economic benefit of reclamation land development is good, so it is suggested to give priority to the arrangement and utilization of reclamation land.

4 Shaanxi Province, the rational use of arable land reserve resources

Under the principle of protecting the ecological environment, being economically feasible and adapting to local conditions, the development and utilization direction of reserve cultivated land resources and the measures for regulating and developing them should be different because of the obvious differences in land resources, ecological environment and socio-economic conditions in the three natural regions of Shaanxi Province.

4. 1 northern Shaanxi

The northern part of northern Shaanxi is a sandstorm area, and the southern part is a hilly and gully area, which is the most serious area of soil erosion in the province. The development of reserve cultivated land resources in northern Shaanxi should adhere to the principle of combining remediation with development on the premise of protecting the ecological environment. The main reserve farmland resources in northern Shaanxi are grassland, sandy land, tidal flat, saline-alkali land and natural disaster damaged land.

Yulin and Yan 'an have a large area of grassland, both of which are more than 654.38+ 10,000 mu. Because the grassland is mostly distributed in hills and hillsides, the ground slope is 6 ~ 25 degrees. Suitable for millet, corn, potato and other crops. Once a year, the yield per mu is 75 ~ 150kg. In order to develop this kind of land, engineering measures such as terraced fields can be taken, and at the same time, attention should be paid to the layout of soil and water conservation measures, and protective forest belts should be arranged by combining trees, irrigation and grass, and economic forest fruits should be planted beside ditches.

Sandy land is mainly distributed in Mu Us sandy land, so it should be developed carefully. For areas with good vegetation, we should choose flat land to develop rice and vegetable fields. Never destroy vegetation for development. To open up wasteland in sandy land, shelter forests should be planted first, and then flood irrigation or flat sand should be introduced.

Tall plants, such as corn and sunflower, can be planted in beach development. Pay attention to flood control measures, because the precipitation time in northern Shaanxi is concentrated and the frequency and intensity of heavy rain are high.

The development of saline-alkali land should be carried out after the technology is mature. At present, the per capita land area in northern Shaanxi is relatively large, reaching per capita 10 mu. As long as the unit output is increased, the food demand can be met. It is suggested to delay the development of saline-alkali land.

4.2 Guanzhong

Guanzhong area belongs to national and provincial reserve bases for cultivated land development, and the types of reserve cultivated land resources are complete. After land development, it can be harvested twice a year, with an output value of 500 ~ 1000 Jin of grain per mu and 500 ~ 1000 yuan per mu, which has obvious economic benefits. The unique land resources in Guanzhong are:

(1) Reclaimed wastes occupy land. The whole province11601.1mu, of which Guanzhong area 1 13343. 1 mu accounts for 92.2%. The abandoned and occupied land is mainly distributed in Xianyang city in Guanzhong area, with an area of 1074 14.6 mu, mainly distributed in Weibei tableland, mainly in ancient villages and brick kilns. After engineering transformation, it can become a stable and high-yield basic farmland. Increasing cultivated land, increasing grain output and increasing farmers' income have obvious economic, social and ecological benefits. It is suggested that it should be included in the reclamation planning, combined with the urban planning, and give priority to the development of small towns.

(2) sandy land. Shayuan cultivated land in Dali, Shaanxi 17 1 19.5 mu. In the 1990s, the state implemented the reclamation project of Pingsha in Dali, with an investment of 4,000 yuan/mu and complete water, electricity, roads and sprinkler irrigation facilities. Developed that year, it worked that year. The cost of land reclamation will be recovered within three years. After five years of planting, it can become high-quality farmland. It is suggested to do a good job in land use and development planning, attach importance to the construction of sand barrier forest network, increase the application of organic fertilizer, implement ecological agriculture and raise cattle with straw, so as to develop it into a base for wheat, peanuts, jujube, day lily and high-quality greenhouse vegetables.

(3) saline-alkali land. Weinan city has 30044.6 mu of saline-alkali land, which can be used to grow wheat, cotton and other crops after improvement. Take engineering measures and biological measures to control saline-alkali land. The Lvbotan land development and reclamation project implemented by Shaanxi Real Estate Development Service Corporation plans to develop 8,700 mu, add 6,600 mu of cultivated land, develop and control 2,700 mu of land in the first phase and build 2,000 mu of standard farmland, with a total investment of140,000 yuan. The cost per mu of cultivated land is 700 yuan, and the cost per mu of land development is 5 185 yuan grows wheat, rape and other crops. Saline-alkali land engineering development is an important way of land development.

4.3 Southern Shaanxi

The climate in southern Shaanxi is warm and humid, but the economy is poor and the transportation is inconvenient, which needs further development. This area has a large mountainous area, less arable land, low valley, abundant water resources and superior irrigation conditions, and rice and wheat are harvested twice a year. The slope of mountain hills is large, the soil layer is thin and the soil fertility is insufficient, so it is particularly important to maintain water and soil. The reserve resource area in Shangluo area is 1 14796.6 mu, and that in Ankang city is 4679.4 mu. The rational use of land in this area needs to do a good job in basic farmland construction, soil and water conservation and prevention of natural disasters.