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. For example, the vegetable bases for the royal family in Beijing had been established 600 years ago; those in Hangzhou can date back to more than 1 000 years ago; and those in Urumqi has a history of more than 100 years. Therefore, Fimic Anthrosols are mostly found around the cities mentioned above.with the P-rich characteristic. The area of the soils in China is at least 0.7-1 million hectares. In addition, the anthroturbic process also has a positive influence on the formation of Anthrosols .

3. Diagnostic horizons of Anthrosols

5 Under the condition of submerging cultivation, with the alternation of redox and fertilization, anthraquic horizon sequence has been formed, which includes anthrostagnic epipedon and hydragric horizon; under the upland farming, with irrigation and fimic process through accumulation and vegetable plantation , irragric epipedon, cumulic epipedon and fimic epipedon have been formed.

3.1 Anthrostagnic epipedon The anthrostagnic epipedon is an anthropic surface horizon (including the cultivated horizon and the plowpan) formed under the condition of submerging cultivation

An anthrostagnic epipedon has all the following characteristics: (1)A thickness of 18 cm or more; and (2) In most years, when the soil temperature is more than 5 ¡æ , an anthrostagnic regime for at least three months per year ; and (3)In most years, when soil temperature is more than 5 ¡æ , in the upper part of the epipedon (the cultivated horizon) , puddling for at least half a month per year due to soil mixing by submerging cultivation ; and (4)Under a submerged condition, a colour value, moist, of 4 or less and a chroma, moist , of 2 or less and a hue of 7.5 YR or yellower showing GY, or B, or BG; and (5)More rusty spots and rusty streaks after drainage; and (6)In a dry condition after drainage, a ratio of the soil bulk density in the lower sub-horizon to that in the upper sub-horizon is 1.10 or more .

6 Figure 4 3.2 Irragric epipedon The irragric epipedon is an anthropic surface horizon formed by gradual deposition of suspended particles during long-term irrigation and the mixture of cultivation. An irragric epipedon meets the following requirements: (1)A thickness of 50 cm or more; and (2)A uniform colour, texture, structure, consistence, calcium carbonate content etc. in the whole epipedon; the textures of the adjacent sub-horizons are also located in the adjacent positions of triangular textural diagram stipulated by the United States Department of Agriculture (USDA); and (3)The weighted average of organic carbon is 4.5 g/kg or more within 50 cm of the soil surface, and gradually decreases with increasing depth, but at least 3 g/kg at the bottom of the horizon ; and (4)After soaking for an hour and screening through 0.2 mm wet sieve , shows dense flat half- rounded section of soil and silted micro-beddings under magnifer ; or has the micromorphology of anthropic disturbance: semi-rounded or rounded fine-textural blocks, inside which, sometimes, residual silted micro-beddings may be found; and (5)Has coal cinders, charcoals, brick or tile fragments and other artificial intrusive bodies throughout the horizon .

3.3 Cumulic epipedon The cumulic epipedon is an anthropic surface horizon formed by long-term intensive cultivation and frequent irrigation, application of large amounts of manure, soil materials rich in organic matter and pond muds etc (Fig 5 ). A Cumulic epipedon meets the following requirements: (1)A thickness of 50 cm or more; and (2)A fairly uniform colour, texture, structure, consistence etc. throughout the whole epipedon; the textures of the adjacent sub-horizons are located in the same or adjacent positions of the triangular texture table stipulated by USDA ;and (3)The weighted average of organic carbon is 4.5 g/kg or more within 50 cm of the soil surface ; and (4)The soil particle composition is similar to that in the original soil to which is adjacent , influenced by the sources of cumulic materials , and has one of the following characteristics: a.Has the characteristics of hydromorphic soils and half-hydromorphic soils: residual or recently- formed rusty spots , rusty streaks , gley spots, or additional aquatic animal residuals such as shells of conches and shellfish (mud-cumulic features); or b.Has some diagnostic horizons and characteristics similar to the adjacent automorphic soils (earth-cumulic features); and (5)Has coal cinders, charcoals, brick or tilt fragments, ceramics pieces and other artificial intrusive bodies .

7 Figure 5

3.4 Fimic epipedon The fimic epipedon is an anthropic surface horizon with high mellowing formed by long-term planting vegetables , applying large amounts of night soil, manure, and organic trash etc., and intensive cultivation and frequent irrigation . A fimic epipedon meets the following requirement: (1)A thickness of 25 cm or more (in which the upper part is highly-fimic sub-horizon and the lower part is transitional fimic sub-horizon ); and (2)The weighted average of organic carbon is 6 g/kg or more; and (3)The weighted average of extractable P contents ( by 0.5 mol/L NaHCO3 ) is 35 mg/kg or more (P2O5 is 80 mg/kg or more) ; and (4)Has large amounts of wormcasts , and wormholes with intervals of less than 10 cm , which occupy half or more of the total ; and (5)Has coal cinders, charcoals, brick or tilt fragments, ceramics pieces and other artificial intrusive bodies .

8 Figure 6 4. Key to Anthrosols

A. Anthrosols that have an anthrostagnic epipedon and a hydragric horizon . Hydragric Anthrosols B Other Anthrosols . Orthic Anthrosols

B.1 Orthic Anthrosols that have a fimic epipedon and a phos-agric horizon . Fimic Anthrosols B.2 Other Orthic Anthrosols that have an irragric epipedon . Irragric Anthrosols

B.3 Other Orthic Anthrosols that have a cumulic epipedon with hydromorphic characteristics , and have both of the following : a. Rusty spots and rusty streaks with a high chroma value in reduced materials with a low chroma ; and Relicts of aquatic animals, such as snails and shells . Mud-cumulic Anthrosols B.4 Other Orthic Anthrosols . Earth-cumulic Anthrosols

The classification of Anthrosols in Chinese Soil Taxonomy (1st propsosal ) , proposed in 1991 , has been adopted basically in World Reference Base for Soil Resources (WRB) (Draft) as its classification of Anthrosols in 1994 .

9 10 ACKNOWLEDGMENT This paper comes from the research project "Chinese Soil Taxonomy and Sustainable Soil Management", supported by Chinese Academy of Sciences and National Natural Science Foundation of China (grant No. 49131020).

REFERENCES

Chinese Soil Taxonomy Research Group ,1995 , Chinese Soil Taxonomy (Revised Proposal ) , Chinese Agricultural Science and Technology Press , Beijing , China Gong Zitong , 1986 , Origin , Evolution , and Classification of Paddy Soils in China , Advances in Soil Science , Vol. 5 , 179-200 Gong Zitong , 1994 , Formation and Classification of Anthrosols : China's Perspective . In : Transaction 15th World Congress of Soil Science , Acapulco , Vol. 6A , PP. 120-128 Gong Zitong et al. , 1997 , Extractable Phosphorus in Soils with a Fimic Epipedon , Geoderma 75,289-296 FAO/Unesco , 1988 , Soil Map of the World , Revised Legend , Rome ISSS/ISRIC/FAO , 1994 , World Reference Base for Soil Resources (Draft) , Wageningen/Rome Lin Putian , 1996 , Soil Classification and Land Utilization in Ancient China , Science Press , Beijing Soil Survey Staff , 1975 , Soil Taxonomy , U.S.Dep. Agriculture Handbook NO. 436 , Washington DC

Keywords: Anthrosols, anthropogenic diagnostic horizons, soil classification Mots clés : Anthroposol, horizons de diagnostic anthropiques, classification du sol

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