1. Basic concepts

Agricultural geology is an interdisciplinary subject combining earth science and agricultural science. Zhou Guohua et al. (2007) put forward that agricultural geology is an applied discipline driven by agricultural production and its development demand, which applies the theory and knowledge of earth science to agricultural production and agricultural development. Its essence is to regard environmental factors such as rocks, soil, water, biology and human production activities as an interactive and interactive organic whole, and to study the development and evolution law, interaction and coupling relationship of various elements in the system, with the aim of solving the imbalance of agricultural ecosystem and specific problems in agricultural (planting, forestry, animal husbandry and fishery) production. With the rapid development of agricultural geology, the concept and research content of agricultural geology are constantly expanding, and the connotation of agricultural geology is different in different periods.

1988 used the term "ecological geochemistry" for the first time. In 2004, domestic eco-geochemical terms were clearly put forward, and combined with ecological viewpoints and methods, the concept of eco-geochemistry was put forward, which was more in line with the reality of China. Eco-geochemistry is a science that studies the relationship between element geochemical distribution, distribution state and ecological environment by using multi-objective regional geochemical survey method and earth system evaluation technical route. On this basis, Yang et al. made the concept of ecological geochemistry more concrete, and thought that ecological geochemistry is a science that studies the geochemical distribution, distribution characteristics and migration and transformation laws of chemical elements and their compounds in the ecosystem, and evaluates and predicts their ecological effects, which is the product of the combination of ecology and geochemistry. At present, it mainly includes two aspects or two levels of work: multi-objective regional geochemical survey and regional eco-geochemical evaluation.

Agricultural geological survey and evaluation is one of the important contents of multi-objective regional geochemical survey and evaluation. Geochemical investigation was originally a problem in geosciences, but when a large number of heavy metal elements were absorbed by grain, vegetables, aquatic products and so on. It affects the agricultural soil, the safety of agricultural products and the establishment of green bases, which has become an agricultural problem. Therefore, in recent years, China's multi-objective regional geochemical survey and evaluation work mainly focuses on agricultural geological survey and evaluation.

2. Main research contents

The development of large-scale agriculture (agriculture, forestry, animal husbandry and fishery) is seriously restricted by natural production factors such as light, heat, water, soil, gas and fertilizer, and geological environment conditions such as structure, strata, rocks and topography are important factors that determine or affect the agricultural ecological environment. Agricultural geological survey is to find out the spatial distribution and differentiation characteristics of geological and geochemical characteristics, grasp the relationship and influence mode between geological background and agricultural ecological environment elements, and serve the scientific and rational utilization of agricultural natural resources such as land and agricultural production development planning.

Most scholars believe that agricultural geology is a branch of geology, and its research field involves the causes and characteristics of soil, the types and storage of mineral fertilizers, the behavior and characteristics of groundwater, etc., but it is far beyond this scope in the actual research and application process. From the research history of agricultural geology, agricultural geological background, soil geochemistry, hydrogeology, water environmental chemistry and agricultural ecological environment are the central tasks of agricultural geology research.

In recent years, ecological geochemical investigation has become the main task and core research content of agricultural geological investigation in China, which has made agricultural geology develop into a discipline theory based on geology, geochemistry, pedology, plant nutrition, ecology, endemic diseases, bioengineering, environmental engineering and information technology, with geological background and ecological geochemical research as the core. Comprehensive application of regional geochemical survey methods, modern analysis and testing technology, computer, remote sensing, geographic information system and other technical means, on the basis of systematic investigation and comprehensive research, through agricultural geological environment evaluation and decision-making planning, directly guide agricultural production such as agricultural planting structure adjustment, safe agricultural product production, soil improvement and balanced fertilization, and serve the sustainable use and protection of land resources, agricultural industrial structure adjustment and optimization, guarantee and improve the output, quality and edible safety of agricultural products, and enhance national or regional digital construction. Focusing on the above objectives, the agricultural geological survey in recent years mainly focuses on the following three aspects.

1) Agricultural geological background investigation is the basic content of agricultural geological research. Agricultural geological background refers to the synthesis of various geological components (characteristics) and related geological functions that have certain influence or function on agricultural production and development in a certain area, involving all geological characteristics and problems related to agricultural production and scientific research and development. For example, the composition and characteristics of soil-forming parent rock, the source and nature of soil-forming parent rock, regional geological body and structural characteristics, geochemical specificity, groundwater occurrence and hydrogeological characteristics, landform development, surface geological function and so on. , which is the basic factor to determine the suitability of crop planting.

2) Multi-objective regional geochemical survey is a basic work, which systematically collects representative soil geochemical samples and water geochemical samples, uses large precision instruments to determine dozens of inorganic and organic geochemical indicators in the samples, compiles relevant geochemical maps, finds out the geochemical distribution and distribution characteristics of elements, and verifies the geochemical anomalies of important elements found, thus providing basic information for resources, environment, agriculture, ecology and other fields.

3) Trace the source and genetic characteristics of abnormal elements and organic pollutants according to the distribution characteristics and element anomalies of elements and compounds in large river basins or economic zones obtained from regional geochemical surveys; Find out the migration path, total input and output and speed of abnormal elements and organic pollutants; Study the geochemical cycle of elements between soil and plants and the content and occurrence of elements that restrict crop growth and quality; Risk prediction and hazard trend warning of abnormal elements and organic pollutants; Suggestions on the management, restoration and monitoring of polluted ecosystems are put forward.

Second, the research status and progress at home and abroad

Geology and agronomy are two ancient disciplines, each with its own connotation and development track. With the deepening of research and the development of disciplines, soil, as the same research object of the two disciplines, has built a bridge for the integration of geology and agriculture. With the rapid growth of the global population, problems such as insufficient food, massive consumption of resources and environmental degradation have become increasingly prominent. Geologists from all over the world have made various explorations, which also promoted the emergence and development of agricultural geology.

1. Research progress of agricultural geology abroad

The term "agricultural geology" was first put forward by German scholars F.A.Fellow and F.V.Richthofen in the middle of19th century. There is no clear definition, but it is only used to explain the relationship between rock weathering and soil formation. At the beginning of the 20th century, international geologists paid extensive attention to agricultural geological research and held many international conferences in Europe. During the period of 1907, the Institute of Geology of the Royal Hungarian Academy of Sciences established the first institution engaged in agricultural geology research in the world-the Agricultural Geology Department, which focused on soil geological investigation, mapping and soil genesis and classification.

In the first 50 years of the 20th century, British and American geologists wrote books to teach agricultural geology, such as Agricultural Geology 19 16 published by R.H.Rastll, Cambridge University, UK, and Agricultural Geology 1946 published by F.V.Emeison, Louisiana State University, USA. The original intention of these two books is to introduce geological knowledge such as rocks, minerals and structures to people engaged in agricultural research. All these show that agricultural geology at that time mainly infiltrated geological knowledge and understanding into soil research or directly served agriculture.

In the 1920s, American geographer H.H Barros clearly pointed out that geography is human ecology, which promoted the study of the relationship between man and land. In 1930s, K.Troll first put forward the term "geo-ecology". Now, this concept is generally understood as a science to study the geosphere as a part of the environmental system and the material basis of the biosphere and the changes of natural and human activities inside it. Russia (Soviet Union) systematically carried out a regional eco-geological survey and completed a1:5 million 14 eco-geological map. Since 1950s, with the increasingly prominent contradiction among population, resources and environment in the world, environmental geology (Betzf, 1962) has gradually emerged, and quite a few agricultural geological problems have been brought into the category of environmental geology. In the early 1960s, British geochemists headed by J.Webb made a systematic geochemical survey of river sediments in Northern Ireland, England and Wales, compiled maps of major elements and some trace elements, and analyzed their impacts on human beings, animals and plants. From1969 to1971year, the United States conducted a geochemical survey in Missouri, with the aim of providing basic data for epidemiologists to study the relationship between geochemical environment and human health. Until 1972, in order to unify the subject concept, the US Geological Survey interpreted agricultural geology as applied geology, and explored the causes and components of the distribution and characteristics of soil, fertilizer minerals and groundwater, which belonged to the category of applied geology. At present, agricultural geology is usually interpreted as "geology serves agriculture" abroad.

In the early 1970s, the Soviet Union made some useful explorations on the theory, method and application of ecological geochemistry in the Institute of Mineralogy, Geochemistry and Rare Element Crystallization. A large-scale agricultural geochemical survey was carried out in the northwest of China, which provided reliable data for improving agricultural soil, improving soil fertility, increasing crop yield and protecting the environment. Since 1990s, with the rapid development of rapid and accurate instrumental analysis methods and "3S" technology, the application fields of exploration geochemistry have been expanding all over the world. Russia and other countries have carried out the investigation and evaluation of regional geochemical environment, which integrates ecological environment evaluation, rational land use and metallogenic prediction. The United States, Canada, Japan, Germany, Italy, Finland, Belgium, Sweden, India, Poland, Czech Republic, Lithuania, Vietnam, Indonesia, South Korea, Romania, Sumatra, Kenya and Bolivia have also carried out extensive regional geochemical environmental investigations and studies according to their different problems.

2. Research progress of agricultural geology in China.

China's agricultural geological thought has a long history, and he had a deep understanding of the unity of biology and environment in ancient times. As early as the Zhou Dynasty, there was a saying in Flower King Gong Ji: "Those born in Huainan are oranges, and those born in Huaibei are oranges. Leaves are similar to disciples, but they taste different. Why? It can be seen that as early as 2500 years ago, the people of China realized the ecological relationship between fruit trees and soil; Wang's "Qunfangpu" (162 1) records that "the land is not too high, the soil and fertilizer are the best, the weeds are too much, and the soil is loose", which is the simplest understanding of the relationship between agriculture and geological environment by our ancient ancestors. The research on the relationship between crops and environment as a discipline has only a hundred years history, which is later agricultural geology.

The combination of geology and agriculture in China also started from the study of pedology and the investigation of some agricultural minerals under the guidance of geology. With the rapid development of agricultural geology, the concept, meaning and research content of agricultural geology are constantly expanding, and the connotation of agricultural geology is different in different periods. Before the founding of New China, the geological service for agriculture mainly focused on the geological problems encountered in agricultural management and agronomy. For example, through research, dozens of non-traditional agricultural mineral rocks, especially mineral fertilizers such as phosphorus, potassium and sulfur minerals, are widely used in various fields of agricultural production, and can be used as soil improvers, feed additives, fertilizers, compound fertilizers, drying and deodorizing of animal husbandry and fishing grounds, pesticide carriers, fish pond purifiers, etc. Since 1950s, China's agricultural geological work has made great progress, which can be divided into four stages.

The first stage: from 1950s to 1970s, agricultural geological work mainly focused on traditional fields such as regional geology, regional hydrogeology, pesticides, fertilizers and mineral exploration. At the beginning of the founding of New China, the food problem has always been a big problem that troubled the national security and survival. Under the guidance of the idea of "no gains from water, but less gains from fertilizer", the geological department has carried out the investigation and exploration of potash mines and phosphate mines, and carried out the exploration of farmland water supply, soil erosion and salinization improvement in semi-arid and arid areas in northern China. In the 1960s and 1970s, the hydrogeological exploration of farmland water supply was completed at a cost of1:50,000 yuan and1:004,000 yuan, totaling about 130× 104 km2.

The second stage: in the 1980s, the agricultural geological background research with strata, rocks, landforms and other background conditions as the research object, discussed the advantages and disadvantages of specialty crops under different geological backgrounds and their relationship with some elements, and realized that geological background conditions were an important factor affecting agricultural production. During this period, the Ministry of Geology and Mineral Resources or the local government deployed and carried out agricultural geological work focusing on agricultural geological background and research on famous products, as well as exploration and development of new mineral fertilizers and mineral feeds. There are mainly Shandong Feicheng Peach, pingyin rose, Shandong Tobacco, Taishan (Northeast Foot) Chestnut, Sichuan Citrus, Fuling Mustard, Hebei Cangzhou Jinsixiaozao, Guangxi Litchi, Liuzhou Sugarcane and Nanning Banana. The project has achieved rich results, accumulated a lot of data and information, summed up many theoretical understandings, and used these data and laws to discover or discover many new advantageous areas of agriculture and forestry, expanded planting and greatly promoted local economy. From 65438 to 0988, the Ministry of Geology and Mineral Resources reported to the State Council the work of developing geology to serve agriculture, which set off the first climax of agricultural geology. After 1980s, China's1:200,000 regional geochemical data began to be applied to the field of environmental geochemistry. The corresponding relationship between the contents of zinc, copper, cobalt, molybdenum and boron and crop yield in different regions was studied, the reasons of biological growth defects and low yield were found, and the normal, excessive or insufficient growth thresholds of some local elements and corresponding crops were summarized and put forward. Similar research provides a basic basis for the preparation and field application of micro-fertilizer and effectively promotes the transformation of local low-and medium-yield fields and grasslands.

The third stage: in the 1990s, eco-agricultural geology became a research hotspot; In recent 10 years, the introduction of ecological geochemistry has made agricultural geological work enter a brand-new historical period of rapid development. In 1990s, "agricultural geology" evolved into "agricultural ecological geology". "Agro-ecological Geology" is no longer the concept of early "agricultural geology", but has formed the embryonic form of a marginal discipline. 1992 geological society of china has established a professional committee of agricultural geology. The professional committee of agricultural geology introduced the latest achievements of agricultural eco-geology research in China to the 30th International Geological Congress, which attracted the attention of international colleagues. During the Ninth Five-Year Plan period, the Ministry of Geology and Mineral Resources added1:50,000 pilot eco-geological surveys and1:50,000 pilot agricultural eco-geological surveys in Linzi and Qingzhou, Shandong Province, and1:50,000 pilot regional and agricultural eco-geological surveys in Liu Chang and Longhua, Hebei Province.

The fourth stage: 2 1 century is the peak stage of agricultural geological development. 1999-2002, the pilot work of multi-objective regional geochemical mapping was carried out in the Pearl River Delta, Jianghan Plain and Chengdu Plain, and a series of important discoveries were made. Based on the previous experience of multi-objective regional geochemical survey, since 200 1, China has carried out multi-objective regional geochemical survey in nearly 20 provinces and regions in the central and eastern regions, with the main contents of building modern agriculture, promoting the adjustment of agricultural economic structure and improving the quality and safety system of agricultural products. On this basis, the Yangtze River Basin, the Yellow River Basin, the coastal economic belt and the Northeast Economic Zone are studied emphatically.

Generally speaking, the past 30 years have been the heyday of agricultural geology research in China, with endless theoretical viewpoints, rapid development of methods and technologies and fruitful practical application results. In 1980s, Li (1986) put forward in "Introduction to Agricultural Geological Background System" that "agricultural geological background is a special synthesis of closely related geological bodies and geological forces such as agriculture, forestry, animal husbandry, sideline production and fishery". Feng Qunyao (199 1) put forward in "Great Agricultural Geology" that "Great Agricultural Geology is a frontier discipline that studies related issues of great agriculture based on geological theory and combined with relevant theories of agriculture and forestry". Both of them emphasize the relationship between agricultural geological background, mineral rocks and their geochemical components and agriculture. By the end of the 20th century, Cheng Guanwen (1996) put forward in "On Agricultural Environmental Geology and Its Research Contents" that "agricultural environmental geology is to study the changing law of agricultural geological environment and the activation, migration and transformation of materials and energy in the environment under the action of natural factors and human factors, as well as the biological effects accompanying this changing law. Through the action of human beings and the application of modern science and technology, agricultural geological environment flows in time and space. Zhang Zonghu (1997) put forward that "agroecological geology is a subject that studies the structure, function and interaction of the whole system of human-agricultural production-geological environment". Both of them extend the research scope of agricultural geology to the field of ecological environment, greatly expanding the application prospect and social function of agricultural geology.

Third, the development trend of agricultural geological work

Up to now, agricultural geology has gone through the development history of 100 years. Agricultural geology is to solve the problem of agricultural development from the objective natural factors that restrict agricultural production. At present, the research on agricultural geological background and agricultural geological environment, soil chemical pollution and prevention, soil geochemistry, trace nutrients in agriculture, soil zoning and so on is focused. With the development of information technology and the improvement of ecological environment requirements, agrogeological research needs to closely combine lithosphere, atmosphere, hydrosphere, biosphere and social sphere. The main research contents of agricultural geological science have been extended to land resources utilization and management, agricultural production activities, agricultural product quality and food safety, ecological environment protection, regional economic planning, prevention and control of endemic diseases and geological disasters, sustainable development and many other fields, which embodies broad development prospects. In recent years, the research and development trends related to agricultural geology can be summarized as follows.

1. Multi-sector cooperation has become the development trend of agricultural geology.

For a long time, geochemistry, environmental chemistry, soil chemistry, plant nutrition, environmental biology, toxicology, pollution ecology, environmental medicine and other disciplines have done a lot of basic research on a series of problems such as the occurrence form, activation and migration, transformation cycle, biological absorption and accumulation mechanism and biological effect of toxic and harmful substances in the agricultural ecological environment, and have obtained a lot of theoretical research results and established a theoretical method system, which provides a basic theoretical basis for the comprehensive evaluation of the agricultural ecological environment. Agricultural geology is not only one of the best directions to broaden the research and service fields of geology and mineral resources system, but also a new way for agricultural departments to deepen and accelerate agricultural development by combining geological knowledge. Therefore, it is the only way for scientific and technological personnel from different industries to cooperate together.

2. Systematically study the relationship between characteristic crops and ecological conditions.

Agricultural geological background is one of the ecological basic conditions for the formation of crop characteristic quality. In actual production and scientific research, it is necessary to obtain enough agricultural geological background data, systematically and completely study the relationship between the quality of characteristic crops and ecological conditions, and find out the key geological background factors, so as to guide agricultural production more accurately and promote the development of related disciplines. In order to better study the position and function of agricultural geological background in crop production, the author thinks that the following aspects should be emphasized in the future research of agricultural geological background: first, extensive investigation of agricultural geological background should be carried out to study the relationship between characteristic agricultural products and agricultural geological background factors, and the reasons for the difference of crop quality in different agricultural geological background areas should be revealed; Secondly, on the basis of extensive investigation of agricultural geological background, the element geochemical characteristics and soil suitability of dominant agricultural producing areas and general agricultural producing areas are compared and analyzed; Finally, with the deepening of agricultural geological background investigation and research, we should give full play to the role of 3S(GIS, GPS, RS) technology in agricultural geological background investigation and research, avoid the waste of manpower, financial resources and time, reduce the difficulty of data synthesis and extraction, and improve the accuracy of survey data.

3. Agricultural environmental protection has become a major concern of all countries in the world.

The impact and harm of industrialization on the living environment of human beings have long attracted the attention of governments and scientists all over the world. The research on industrial pollution has been relatively mature, and many countries and governments have promulgated laws to stop the arbitrary discharge of harmful industrial pollutants, so that industrial pollution can be effectively controlled to a certain extent. In contrast, the negative impact of industrial modernization on the agricultural environment did not arouse people's vigilance until the second half of the 20th century. The discharge of industrial "three wastes" and urban domestic pollutants, as well as the extensive use of pesticides, fertilizers and other chemicals in agricultural production are one of the main reasons for the deterioration of agricultural ecological (geological) environment and the decline of agricultural products quality. At present, the construction of agricultural geological (ecological) environment and agricultural product safety system has been paid more and more attention by governments all over the world. Many countries, especially the United States, Britain, France, Germany, Japan and other western developed countries, have invested a lot of manpower and material resources, conducted a series of basic and applied research on the behaviors and effects of heavy metals, nitrates, pesticides and persistent organic pollutants (POPs) in the agricultural ecological environment, established specialized institutions, and formulated corresponding laws and regulations to strictly limit the scope and quantity of chemicals used in agricultural production. At the same time, vigorously develop organic agriculture and take the road of sustainable agricultural development. On the basis of a lot of basic and applied research, a large-scale real-time monitoring of agricultural ecological environment has been implemented; Precise and programmed production process control technology and real-time monitoring of product quality; Some developing countries, such as India, have gradually realized the negative impact of agricultural eco-environmental pollution on agricultural sustainable development, actively carried out relevant work, and stepped up the formulation of policies and technical measures to protect and improve agricultural eco-environment (geology) and prevent agricultural product pollution, so as to adapt to the trend of economic globalization and the process of international agricultural product integration.

Due to the restriction of economic and technological development, the research on agricultural eco-geological environment in China started late. Since 1980s, China has taken it as an important subject of applied basic research, investigated the agricultural eco-environmental pollution in more than 20 provinces, autonomous regions and municipalities directly under the Central Government, and carried out some research work in the aspects of soil geochemical background value, agricultural eco-geological environmental effects of pollutants, and agricultural zoning layout. The effects and action laws of organochlorine pesticides on agricultural ecosystem, and the harm, migration and transformation mechanism of heavy metals such as cadmium and mercury and inorganic and organic pollutants on agricultural ecosystem were also studied. During the Tenth Five-Year Plan period, in view of the current situation of strengthening the safety management of agricultural products and the urgent need to adapt to China's accession to the WTO, China is actively studying key technologies such as the protection and prevention of agricultural ecological environment and the control of agricultural products' safe production process. For the first time in China, the research on ecological agriculture and food safety technology was included in the "Tenth Five-Year Plan" major scientific and technological projects, and national standards such as "Water Quality Standard for Irrigation in Farmland" were studied and formulated. The safety of China's agricultural products (food) will be included in the Outline of China's Food and Nutrition Development (200 1 ~ 20 10), and scientific and technological research will be carried out with agricultural ecological environment safety and food safety as the main line.

4. The basic and applied research of agricultural geology has been deepened.

Some western developed countries, such as the United States and Britain, have carried out a series of in-depth and extensive studies on the pollution status, occurrence law, migration and enrichment process, recycling mechanism, quality and safety control strategies and treatment approaches of heavy metals, nitrates and organochlorine pesticides in agricultural ecological environment and agricultural products since the 1960s.

The pollution of agricultural production process to the environment is mainly non-point source pollution, because it involves a wide range, complicated process and mechanism, and the research in this area is relatively backward. The migration and enrichment of heavy metals in soil and plants, nitrogen and phosphorus levels and potential non-point source pollution, organic chlorine pollution and the application of information technology in the investigation and evaluation of agricultural non-point source pollution have been deeply studied abroad, but the related research is basically concentrated in areas with developed animal husbandry, and the soil studied is basically dry land, but the research on wetland soil and paddy soil is still insufficient.

In the development of agricultural information system, information expressway in developed countries is rapidly extending to rural areas and agriculture. Using the integrated advantages of computer technology, geographic information technology and network technology, the application of agricultural non-point source pollution information system, pig management system, new varieties of famous fruit trees, agricultural information management system and expert formula system of livestock and poultry feed has been quite mature. Especially, the developed countries represented by the United States, Japan and Western Europe have entered the era of agricultural informatization after completing agricultural industrialization and mechanization, and established three internationally famous agricultural databases, namely AGRIS, CABI and AGRICOLA, and the national food safety database. Satellite data transmission system has been widely used by agricultural producers, greatly improving agricultural productivity.

5. The research on methods and techniques of agricultural geological evaluation is in the ascendant.

For a long time, geology, agriculture, water conservancy, environmental protection, meteorology and other departments have formed investigation and research methods of rocks, soil, water, gas, biology and other media from different professional angles, and formulated corresponding norms and regulations. However, most of these investigations and research work are carried out from the perspective of departments and disciplines. The media elements of investigation and study are relatively single, and there are few analysis and test indicators. Many methods and techniques are mainly suitable for local and special research objectives. Different from the traditional single-discipline research, laboratory test and local investigation and evaluation, the investigation of agricultural geological environment is a complex system engineering, including regional and local multi-scale and multi-media water and soil organisms, which combines investigation with research and gives consideration to both foundation and application. Natural resources such as geotechnical geological background, climate, vegetation, biological and topographic conditions, environmental conditions and their quality are the basic factors affecting agricultural production; It needs to be supported by scientific, operable and practical evaluation methods and technical systems. Therefore, in recent years, the evaluation method model of environmental quality and pollution degree, especially the comprehensive evaluation system from the perspective of ecosystem, including evaluation framework, index system, standard basis and method model, has become the research focus of eco-environmental science.