New Soil Horizons Formed by Anthoropogenic Activities Nouveaux Horizons De Sols Résultant De L’Activité Anthropique
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Scientific registration no : 1430 Symposium no : 16 Presentation : poster New Soil Horizons Formed by Anthoropogenic Activities Nouveaux horizons de sols résultant de l’activité anthropique GONG Zitong , ZHANG Ganlin, LUO Guobao Institute of Soil Science , Academia Sinica , Nanjing 210008, China Soil horizons, the results of soil genetic process, have their specific formation and physico- chemical characteristics. Soil scientists have got great achievements in the study of the soil horizons formed under the natural conditions, but they have done less in the horizons formed by anthropogenic activities, which, however, make more and more important and extensive effects on soil formation. Owing to the long history of agricultural production for more than 5 000 years in China, soil development is intensively and extensively influenced by human activities . Consequently , it will consummate soil science and promote soil amelioration and agriculture development to study on anthropogenic processes and horizons in China . 1. The records of agriculture and soil science in ancient China 1.1 Long history of agriculture The relics of the Yangshao Culture and the Hemudu Culture in the New Stone Age were respectively discovered in the Banpo Village, Xi'an, located in the reaches of the Yellow River and in many places in the delta of the Yangtze River ,which both are the Chinese Culture cradles. The carbonized grains in those relics can date back to 5600-6080 years and 6890-7040 years ago, separately. In 1988, a great quantity of pottery of the New Stone Age, unearthed in the middle reaches of the Yangtze River, may be traced backed to 8200-9100 years ago . All mentioned above demonstrate that as early as the New Stone Age, our ancestors had already cultivated cereal crops. Afterwards, the farming activities gradually spread nationwide with the propagation of Chinese Culture . 1.2 Agriculture in ancient China In the period of the Spring and Autumn Period and the Waring Period (770 - 221 BC) , some famous water projects were built such as the Zhengguo Channel , Ximen Bao Channel, Dujiang Weir and Ling Channel, of which most today still play an important role in agricultural production . During the Han Dynasty (206 BC- 8 AD), people invented the technology of breeding and 1 transplanting rice seedling and planting vegetables in green house . Since then , the cultivation in the Yellow River Valley developed by degrees toward the traditional agriculture with ploughing , harrowing and hoeing as the main cultivated measures , applying huge amounts of farmyard manure ,conserving soil and water loss , planting green-manure crops , carrying out the rotation system and combining land use with land maintenance . Besides , ancient people also created terrace to take full advantage of moutainous land . In the aridic region , our ancestors built the Kanerjing wells for the development of irrigated agriculture . Ancient people also proposed to plant green manure , improve cultivated measures and renew soil fertility , which greatly push the agriculture forward . 1.3 The earliest records of knowledge of the soils 1.3.1 the earliest interpretation of Chinese character " (soil)" Xushen (58-147 AD), pointed out that ' the soil is something of the land bearing living things' . In the Chinese character " ÍÁ", the upper horizontal stroke " " refers to the topsoil, the lower horizontal stroke " Ò»" to the subsoil, and vertical stroke " l " to both above-ground and underground parts of plants (Fig. 1). It illustrates that the soil nurtures and supports plant growth, revealing the close relationship between the soil and plant, and shares the same meaning with the soil definition in modern pedology, which may be regarded as the earliest scientific interpretation of soil . Fogure 1 1.3.2 The earliest soil classification In Yu Gong , published 2,500 years ago , the soil fertility, soil colour, soil texture, soil moisture regime and vegetation were used as the criteria of soil classification. Also , the soil map was made according to the classification (Fig. 2). 2 Figure 2 1.3.3 The earliest soil exhibition Chinese emperor in almost every dynasty always established 'the land and grains altar' in order to show their worship to the Land God and Grain God for a good harvest and the security of the country . The altar was at first established in the Zhou Dynasty (1000 -771 BC ).The altar established in 1421 of the Ming Dynasty has been preserved till now at Zhongshan Park, Beijing . In which , the area of the highest layer is 15.8 m2 , paved with five types of soils with different colours: the soil in the east is blue ; south red; west white; north black; and centre yellow. It is consistent with the general soil distribution of the country: in the east of the country, most soils in colour are blue because of gleization; in the south, dominant soils are Ferralsols, in red; northwest, Aridisols and saline soils, in white; centre, Cambisol in the Loess Plateau, in yellow. Therefore, this is the preliminary, but scientific knowledge of the soil classification and distribution in the country, and is also the earliest soil exhibition(Fig.3). 3 Figure 3 2. The forming processes of Anthrosols With the population increasing , the agriculture developed from the river terrace and vast plains to the mountainous area, marsh and saline beaches ; and from the humid and semi-humid regions to the arid and semi-arid regions. Owing to the change of the natural conditions, soils have been ameliorated and cultivated gradually and persistently, resulting in the occurrence of a series of processes forming Anthrosols , which are mainly hydragric process, irragric process, cumulic process and fimic process, etc.. 2.1 The hydragric process Rice plantation needs levelling fields, of which the 'Terraced Fields' was made in the hilly and mountainous regions to prevent the loss of water and soil, and it can reach to the plateau with an elevation of 2,000 metres; 'Polder Fields' was formed in the lake and marsh area as a result of the establishment of dams to prevent the flood; 'Beach Fields' was constructed in the sea beaches to prevent seawater from invasion. Afterwards, people carried out farming and fertilization in these man-made paddy fields. The creation of the paddy fields reshaped the terrain and disturbed the soils. With the alternation of redox caused by the submerging, the accumulation and leaching features of the soil materials have been changed , as a result, Hydragric Anthrosols were formed. This process even started from thousands of years ago. At present, the area of the Hydragric Anthrosols is about 25-30 million hectares. 2.2 The irragric process 4 In the arid area, there is no agriculture without irrigation. However, a large amount of soil materials are silted with the irrigation water which called as an irragric process. When the amount of annual irrigation reaches about 1000 mm, the depth of silting materials can deposit to 0.3-0.5 cm each year. Year after year, a new horizon has been formed, whose material constituents, fertility and moisture regime are different from that of the original soils. In the Hetian region, Xinjiang, along ancient 'the Silk Road', irragric horizons in Anthrosols are several metres deep. Organic carbon of the irragric horizon at the depth of 5 meter dates from 1870 years ago . The irrigation history in Ningxia and Hetao region, inner Mongolia, exceeds 2000 years. The soils are extensively distributed in the arid region, the current total area is more than 1.5 million hectares. 2.3 The cumulic process It is an important process of Anthrosols-forming and can be classified into two types: one is earth-cumulic; and the other is mud-cumulic. The former is mainly distributed in the Loess Plateau of the Yellow River Valley, where the application of earth-mixed manure not only brings the nutrients into soils, but also thickens the original soils constantly, resulting in the old cultivated horizon on the ancient cultivated horizon and the new cultivated horizon on the old cultivated horizon, like stairs, which is named as Earth-cumulic Anthrosols. The latter is usually distributed in the Zhujiang River Delta and the Yangtze River Delta. Low-lying marshes, such as the Zhujiang Delta, are originally waterlogging. In order to make full use of the natural resource , people dug the lower area of the marshes and use the earth they had got to pile up on the higher area nearby. The lower part became fish pond ; and the upper part became mulberry fields, where the soil was once piled up about one metre above the water, and a few amount of the pond muds was added each year. This special Mud-cumulic Anthrosol is often used as mulberry fields. The leaves feed silkworms , the silkworm excrements feed fish, and the fish excrements fertilize the mulberry fields, forming a beneficial cycle . The soils formed by the process have the hydromorphic features, with snails and shells and rusty spots and streaks in the profile. The Earth-cumulic Anthrosols in Shaanxi Province can root from about 2800 years ago . The Mud-cumulic Anthrosols in the Zhujiang River Delta can root back to the Han Dynasty, more than 2 000 years ago. The area of the two kinds of soils adds up to 1.5 million hectares at present. 2.4 The fimic process Long-term application of the life garbage produced by human and organic manure into soils results in the accumulation and immigration of large amounts of P. Available P content in those phosphate-rich soils is even higher than that in guano . The soils are principally distributed around cities, including ancient cities, such as Zhibo, Shandong Province, with the age of 3 000 years. But more are modern cities with a long history.