Table 2- 1 Unearthed place and time of ancient cultivated rice in South China
Yuchan Rock in Daoxian County (photo 2-1):19931kloc-0/Hunan Archaeological Institute excavated for the first time, and found ancient cultivated rice and primitive pottery pieces; 1995 10 Hunan Provincial Institute of Archaeology organized this re-excavation in combination with agriculture, environment and other disciplines, and found ancient cultivated rice, rice and primitive pottery pieces. Four samples were tested in Peking University 14C laboratory, and the data was12320 ~14810 years ago. Rice was identified by Professor Zhang of China Agricultural University as "the most primitive ancient cultivated rice with comprehensive characteristics of wild rice, ginseng and japonica rice, which evolved from ordinary wild rice to cultivated rice in the early stage". At the same time, the electron microscope analysis of sediment soil samples shows that "rice silicate has bimodal papillae and fan-shaped morphological characteristics"; 199565438+February was named "Top Ten Archaeological Discoveries in China"; In March, 200 1 year, it was listed as one of the major archaeological discoveries in China 100 in the 20th century. 200 1 the State Council was approved as the fifth batch of national key cultural relics protection units; In June 2004, the Sino-American joint archaeological team conducted another archaeological excavation. The team consists of more than 65,438 professors, researchers and doctoral supervisors from China, the United States and Israel, including many world-renowned archaeologists and agricultural archaeologists. The team leader in China is a professor, the team leader in the United States is Professor Orff, and the team leader in field archaeology is researcher Yuan, an effective deputy. After a month's excavation, seven primitive rice grains were found in the accumulated soil. The discovery of artificially cultivated rice in Yuchanyan, Daoxian County, proves that Hunan Province is the earliest agricultural producing area in the world, indicating that soil was the first to be recognized and utilized. In addition, Chengtoushan site (photos 2-5 and 2-6), the "first city in China" in Lixian County, found that more than 600 square meters (excavated area) extended from south to north, with three-year-old paddy fields arranged in parallel, and the ridges were more than 30 meters long, and there were also preliminary irrigation systems such as artificial digging ponds and ditches. According to the determination of 14C and thermoluminescence, the lower layer was 6600 ~ 6000 years ago and the upper layer was 6300 ~ 6200 years ago. This is the oldest rice field found at home and abroad, so it also shows that Hunan is the earliest place to use soil.
Our country's understanding of soil was first seen in Shang Shu written by Yugong in Xia Dynasty (about 4 100 years ago), which summarized some characteristics, geographical distribution and fertility grade of soil in Kyushu. This is also the earliest monograph on soil science in the world, and it is a great pioneering work in the development of ancient soil science in the world. Since then, Zhou Li, Guanzi, Lv Chunqiu, Baihutong, Fan Sheng Zhi Shu, Qi Yaomin Shu, and Nong Zheng Quan Shu have all discussed about soil. However, the formation and development of pedology as an independent discipline was after18th century, and several representative soil-forming theories and viewpoints are briefly described as follows.
1. Agricultural geological soil theory
Agro-pedology focuses on the ability of soil to supply plant nutrients, and regards soil as the medium of chemical and biochemical reactions. They seldom know that soil is a part of the geographical landscape, so it is inevitable to come to some one-sided conclusions. After the weakness of the viewpoint of agrochemical soil science was exposed, by the first half of the 9th century, German geologists F.A. Flo, F.V. Richthofen and E. Raman studied soil with geological viewpoint and formed the viewpoint of agrogeological soil science. They regard the process of soil formation as the weathering process of rocks, and think that soil is the loose layer on the surface formed by rock weathering, that is, the product of rock weathering. The type of soil depends on the weathering type of rock, and it is considered that soil is a constantly changing and broken rock.
The viewpoints of agricultural geology and pedology reveal the importance of weathering in the process of soil formation, but they only emphasize the relationship between soil, rock and parent material, but confuse the essential differences between soil, rock and parent material, treating weathering process as soil-forming process and weathering products as soil. Even so, the viewpoint of agricultural geology and pedology has played a positive role in the development history of pedology, opening up a new field of studying soil from mineralogy and deepening the study of basic "skeleton" minerals in soil.
2. Theory of soil-forming factors
Figure 2- 1 Yuchanyan Ancient Cultural Site in Daoxian County
Figure 2-2 Yuchanyan in Daoxian County is listed as a national key cultural relic protection.
Figure 2-3 Excavation Site of Yuchanyan Ancient Cultivated Rice in Daoxian County
Fig. 2-4 Five kinds of carbonized cultivated rice in Yuchanyan, Daoxian County.
Figure 2-5 Chengtoushan Site in Lixian County
Figure 2-6 Profile of Chengtoushan Site in Lixian County
65438+ In 1970s and 1980s, Russian scholar Dokuchayev (ввдокучаев, 1846 ~ 1902). This view holds that the soil-forming process is driven by the weathering process of rocks. In his famous work "Russian chernozem" published in 1883, he believed that soil has its own history of occurrence and development and is an independent historical natural body. The factors affecting the occurrence and development of soil can be summarized as five factors: parent material, climate, biology, topography and land age, and the theory of 50% soil factor is put forward. It is pointed out that the distribution of soil on the earth has zonality law, and the theory of soil zonality is established. Dokuchaev's theory of soil forming factors and soil zonality has been accepted and developed by many soil scientists. More importantly:
1)1895 h.m. sibirtsev divides soil-forming factors into two categories: dominant factors and auxiliary factors. According to the dominant factors, the geographical distribution law is deepened into the concept of soil zonality, and certain soil types are related to certain climatic vegetation or geographical areas. His concept of soil zonality had a wide influence on soil science in the future, such as the soil classification system promulgated by USDA 1938 and the classification system used by China from 1950s to the second national soil survey, all of which originated from the theory of soil zonality.
2) B.P. Williams put forward the unified theory of soil formation. This theory emphasizes the leading role of biological factors in soil formation and the great influence of human production activities on soil. It is considered that the influence of various soil-forming factors on soil formation cannot be generalized. In other words, various soil types are formed under different combinations of soil-forming factors, one of which is the main factor, that is, the leading factor, and other factors (auxiliary factors) are also the leading factors. Obviously, biology is the dominant factor.
3) 1948 H. Jenny thinks that the dominant factors of soil-forming factors are not the same everywhere, but different regions and types of soil-forming factors can be different, that is, with the change of conditions, the dominant factors can become auxiliary factors, and an auxiliary factor can become dominant factors.
4) In 1973, Kovda put forward the influence of deep earth factors on soil formation. The deep earth factors include volcanic eruption, earthquake, neotectonic movement, deep groundwater and geochemical enrichment. The role of deep factors in the earth reveals the interdependence between the surface layer and the interior of the earth in soil formation. Therefore, it is an important development and supplement to the theory of soil-forming factors. In addition, with the progress of science and the development of productivity, human production activities have more and more influence on the direction of soil formation process, soil fertility and soil properties, and become the leading factor of some artificial soil formation; At the same time, due to improper reclamation and utilization of soil by human beings, soil erosion, soil pollution and soil degradation will be caused, which will become the main factor to destroy soil.
The development relationship of each soil-forming theory is shown in Figure 2- 1.
Figure 2- 1 soil-forming theory and its development network diagram