Development Control
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SH ORT COMMUNI CATIO N
Z. H. Cao . J. L. Ding . Z. Y. Hu . H. Knicker .
I. K gel-Knabner . L. Z. Yang . R. Yin .
X. G. Lin . Y. H. Dong
Ancient paddy soils from the Neolithic age in China s Yangtze
River Delta
Received: 4 February 2005 / Accepted: 6 January 2006 / Published online: 17 March 2006
# Springer-Verlag 2006
Introduction
Abstract Identifying prehistoric irrigated rice fields and
characterizing the beginning of paddy soil development are
important for a better understanding of human develop- Worldwide, scientists of various disciplines are interested
ment and agricultural history. In 2003, paddy soils and in the origin and spread of rice farming (Chang 1976;
irrigated rice fields buried at a depth of 100 130 cm were Greenland 1998; Higham 1984; Shao 1998). From the soil
excavated at Chuo-dun-shan in the Yangtze River Delta, science point of view, wetland rice cultivation is directly
close to Suzhou, China. The fields of sizes between 1.4 and related to the origin, formation, and development of paddy
16 m2 were surrounded with ridges that were connected to soils which are also classified as a man-made type of soil
ditches/ponds via outlets to control the water level within (De Datta 1981; FAO/UNESCO 1994; Gong 1994;
the fields. Many carbonized and partly carbonized rice Greenland 1998; Li 1992). During the end of the 1970s
grains with an age of 3,903 B.C.(measured 14C age 5,129 to the early 1980s at a site near Hemudu on the lower
45 a BP) were recovered. The surface layers of these buried reaches of the Yangtze River, Yuyao, China, large
paddy fields showed a high content of soil organic matter quantities of carbonized rice grains were recovered and
dated to 5,500 BC by 14C-dating (Tang 1994; Yan 1991).
and a considerable high density of rice opals. The latter
were identified to derive from Oryza spp. Solid-state 13C This site was previously thought to represent the earliest
nuclear magnetic resonance spectroscopy revealed aromat- place of true rice domestication (Chang 1976; De Datta
ic carbon (C) as the predominant organic C form in the 1981; Greenland 1998; Higham 1984; Shao 1998). Within
fossil surface layer. This is expected, if the major source the same soil layer, rice husks, stalks, and leaves were
represents burnt rice and straw. In summary, our data are in disclosed together with 76 pieces of spades made from
agreement with new evidences indicating that in China, animal bones with attached wooden handles (Chang 1976;
paddy soils and irrigated rice cultivation were initiated and Shao 1998). This discovery provided conclusive evidence
for early cultivation of Oryza sativa (rice) at this location
developed more than 6,000 years ago.
(Chang 1976; Greenland 1998; Shao 1998). However, a
clear assignment to irrigated rice fields has not been
obtained yet. In fact, up to now, it was not possible to
determine whether rain-fed or irrigated rice was cultivated
at the Hemudu site or any other place where carbonized
rice grains were found (Higham 1984; Yan 1991). On the
other hand, identification of prehistoric irrigated rice fields
allowing for characterizing paddy soil formation from its
beginning is important for a better understanding of the
Z. H. Cao . Z. Y. Hu . L. Z. Yang . R. Yin .
X. G. Lin . Y. H. Dong origin(s) and development of paddy soils, and also for
Institute of Soil Science, Chinese Academy of Sciences, obtaining insights into the long-term impact of human
Nanjing 210008, China agricultural activity on soil properties.
From 1992 to 1995, at a site near Cao-xie-shan, the first
J. L. Ding
excavation of ancient irrigated rice fields was conducted
Archaeology Department of Suzhou Museum,
jointly by Chinese and Japanese archaeologists (Fujiwara
Suzhou 215001, China
and Ding 1996). Unfortunately, soil scientists were not
H. Knicker . I. K gel-Knabner
involved in that excavation, and the site was refilled by a
Lehrstuhl f r Bodenkunde, Technische Universit t M nchen,
highway construction in 2000. To fill this gap, a further
85350 Freising-Weihenstephan, Germany
excavation site approximately 7 km northeast of that at
e-mail: *******@***.***.**
233
Cao-xie-shan was examined by combining archaeological the Holocene, with humid subtropical vegetation and an
approaches and analytical tools applied in modern soil average temperature of 1 to 2 C higher than at present.
science. It was hoped that this approach would supply new Remains of broad-leaved plants, aquatic plants, large
evidence for the existence of prehistoric paddy soils and animals such as deer, pigs, buffaloes, elephants, etc.,
irrigated rice culture in China. were identified here and at surrounding sites. The favorable
conditions with plenty of fresh water, a forest vegetation,
wild life and hillside plain represented an excellent place
Materials and methods for ancient humans to settle. It allowed for hunting, fishing,
and gathering as well as for initiating agriculture (Jiaxing
In November 2003, the sixth excavation of the Chuo-dun- Cultural Bureau 2004).
shan site (31 24 07 N, 120 50 41 E) in the Yangtze River Soil scientists from the Chinese Academy of Sciences
Delta was performed by archaeologists from the Suzhou involved in this excavation, described the examined soil
Museum according to the standard procedures of the profile according to the Soil Survey Manual (USDA 1993).
Archaeology Society of China. Together with the archaeologists, they identified irrigated
Chuo-dun-shan is located in the east of the Taihu Lake rice fields with methods provided by (Fujiwara and Ding
alluvial plain at 3 to 4 m above sea level. Its distance from 1996). The rice opal density (method 1) was analyzed
the Yangchen Lake is approximately 200 m, which is about microscopically using the method of (Zheng et al. 2003).
The 14C age (method 2) was determined with a liquid
150 km from the present coastline of the Eastern China Sea
and about 60 km south from the bank of the Yangtze River. scintillation counter and calculated by comparing the
radioactive intensity of a 14C standard, the background and
According to (Xu et al. 1996), at 10,000 until 5,000 a BP,
the sample (Skripkin and Kovaliukh 1998). The 14C half-
the climate at this location belonged to a warmer period of
Fig. 1 Archaeological map of prehistoric irrigated paddy fields in Chuo-dun-shan site
234
Table 1 Description of a buried prehistoric paddy soil profile and some properties analyzed
Corg (g kg 1) Rice opal
Buried layer (cm) Color pH (KCl) Texture Fe and Mn mottle Bio-materials
(no. g 1 soil) and others
100 116 10YR2/1 5.85 Heavy loam 22.31 105,159 ++ Grey silt coatings Rice grains and pot pieces
116 130 10YR4/1 5.90 Heavy loam 18.26 64,007 + Grey silt coating Humus and root residues
130 150 7.5YR4/1 5.86 Light clay 19.68 17,327 ++ Many mottle Root residues
150 160 10YR5/1 5.75 Light loam 17.20 19,678 + Some mottle
160 174 10YR5/1 5.71 Light clay 10.70 0 + Mottle
174 200 10YR4/6 5.35 Light clay 4.00 0
life was taken as 5,730 years. Soil sampling and analysis rice grains were larger than that of wild rice. Double breast
were conducted according to the Methods of Soil and peaks, the shallow valley in the surface as well as the round
Agrochemistry Analysis (Lu 2000). Solid-state 13C nuclear shape of the grain showed that the recovered fossil rice
magnetic resonance (NMR) spectroscopy (method 3) of grains differed from wild rice (Gu 1998; Thompson 1996)
and belonged to the type of Japonica rice. This is in
carbonized rice grains and demineralized soil (10% m/m
hydrofluoric acid) from one of these prehistoric irrigated agreement with the results from the first excavation at Cao-
rice fields was performed on a Bruker DSX 200. The cross xie-shan (Fujiwara and Ding 1996; Gu 1998) and the rice
polarization magic-angle spinning technique with a ramped opal analysis above. Depending on the duration of irrigated
1
H-pulse during a contact time of 1 ms was used. A rice domestication/cultivation, the paddy soils of these
spinning speed of 6.8 kHz and a pulse delay of 350 ms prehistoric irrigated rice fields had developed to a
were applied. cultivated horizon of a height between 20 and 50 cm
above the parent material.
Table 1 gives a description and some analytical data of a
Results buried prehistoric paddy soil profile in the field S27 at the
depth of 100 to 200 cm. Because no marine fish bones and
At a depth of 100 to 120 cm, in a layer assigned to the shells were observed throughout the whole profile, it was
Majiabang culture (4,000 BC), a settlement was discovered concluded that this area was far enough from the coast to
with house remains, wall foundations, post hole, and door have not been affected by ocean deposition at that period.
ways. The kitchen included a fire place, drinking wells, and Soil organic matter (SOM) concentration in the upper-
most horizon (100 116 cm) of the prehistoric rice field at
cooking utilities such as a rice cooker, backing pots, and
earthenware pots. Additionally, animal bones and ash pile S27 is comparable to the average SOM content of present-
as well as 29 tombs with five skeletons were excavated day rice soils in this region (Zhang et al. 2003), but is about
five times higher than in the parent material layer (160
(Jiaxing Culture Bureau 2004). Approximately 1 to 20 m
away from the settlement, a total of 46 prehistoric rice
fields containing fossil rice grains were revealed within an
area of 500 m2 (Fig. 1). The approximate size of the fields
ranged from 1.4 to 16 m2 with almost round, round-
rectangular, or irregular shapes. The surface layer was
marshy meadows with a soft dark grayish color. Each rice
field was surrounded with ridges (consisting of parent
material) in yellowish and white color. Outlets of the
ridges, most tentatively constructed to control the water
levels, connected the paddies and ditches and/or small
ponds for water diversion and/or drainage from the fields.
Rice opals were frequently detected in this prehistoric
rice fields. In most of them, the densities were >5,000 and
some even excited >10,000. In addition to rice, opal of
reeds, Cyperaceae spp millet, caltrop, etc. were also
detected in various quantities.
A large amount of carbonized rice grains was sieved out
from the surface soils of these prehistoric rice fields. For
instance, more than 200 fossil rice grains were found in
Fig. 2 Solid-state 13C NMR spectra of fossil rice grain (a) and soil
0.04 m3 soil sample taken from the field S27 (Fig. 1). Their organic matter (b) derived from the layer 100 116 cm of the
measured 14C age is 5,123 45 a BP, which corresponds to prehistoric irrigated rice field S27. The asterisks indicate the
an calibrated age of 5,907 a BP. Morphologically, the fossil spinning side bands
235
200 cm). 14C-dating of SOM from the uppermost horizon growing over a long period. This amount was largely
portrayed a measured 14C age of 5,450 147 a BP, corre- extended in the entire horizon of the excavated prehistoric
sponding to a calibrated age of 6,280 a BP, which is about paddy soil, demonstrating that here rice grew for an
300 years older than the measured 14C age of 5,123 45 a BP extended time period. Considering further the age
determined for the charred rice grains (calibrated age difference between the SOM and the fossilized rice grains
5,907 a BP) found in the same layer. of the prehistoric horizon, it may be concluded that here
Figure 2 depicts the solid-state 13C NMR spectrum of rice was cultivated already for more than 300 years before a
milled fossil rice grains screened out of the ancient rice large-scale lake flooding, possibly caused by the rise of the
field S27. It shows a strong signal at 125 ppm in the sea level in this region, resulted in new deposition, burying
chemical shift region assignable to olefins or aromatic C this site (Xu and Shen 1990).
compounds. As aromatic C is the predominant C form In addition to rice, the occurrence of opals of other plants
formed during biomass burning (Almendros et al. 1992; reveal that the weed control techniques were still on a low
Knicker et al. 1996), the spectrum implies that the fossil level. Indeed, for the ancient rice farmers the only available
rice grains were charred. This confirms their blackish color method to control the weed invasion was to use saturated or
and supports the assumption that these fossil rice grains irrigated soil condition that favored for rice and aquatic
were part of the ash remains that ancient farmers returned weeds but were unfavorable to the majority of upland
to the field or the ash pile where straw burned in the field. weeds.
The dominance of the aromatic signal is also visible in
the solid-state 13C NMR spectrum of the SOM from the
Conclusion
100- to 116-cm soil layer of the respective prehistoric
paddy field, unveiling charred material as the most
important organic matter constituent. The lack of higher Close to a formerly discovered prehistoric settlement, at
amounts of other C groups allows the conclusion that those Chuo-dun-shan in the Yangtze River Delta, Suzhou, China,
char-derived constituents persisted more efficiently than 46 buried prehistoric paddy fields, connected with ditches
the unburnt natural SOM. The resonance at 169 ppm in the and ponds or wells were revealed. Artifacts and grain
spectrum is typical for carboxyl C in benzoic acids and remains found therein support their origin from irrigated
indicates oxidation of the charred residues during the rice cultivation. The lack of higher amounts of evolved
prolonged time of burial. farm tools implies that here the irrigated rice culture and
paddy soil development was at an initial state. The solid-
state 13C NMR spectra of the fossil rice grains and the
Discussion SOM in the uppermost layer of the prehistoric irrigated rice
field assigns most of their C as derived from charred rice
The morphology and shape of the excavated rice soils residues having remained in the ash after post-harvest
indicated that a distinct irrigation system existed. This is burning. Together with the presence of opals of weeds, this
supports the hypothesis stating that to plow with fire and
supported by its close resemblance to the irrigation system
to weed with water represents an important aspect of early
disclosed at the Cao-xie-shan site, although the latter was
classified to belong to the Majabang culture (Fujiwara and irrigated rice cultivation in China (Gu 1998). According to
Ding 1996). Supposedly, these two sites had some this theory, the fields were plowed by post-harvest burning
relationship with respect to farming techniques applied of the rice straw residues in fall. During spring, to kill the
during the Neolithic period. Many broken earth pot pieces upland weeds, water was diverted from the ponds via
dating back to the Neolithic age of 6,000 BP were ditches into the fields where the rice seeds were directly
recovered from the newly excavated fields and neighboring sown.
ponds. Considering that no other artifacts or sophisticated
Acknowledgements We thank the NSFC for their grant No.
devices were found for carrying water, they were most
40335047 and the Sino-German Center (DFG-NSFC) for the support
tentatively used also for irrigation during drought periods
of international collaboration. Sincere thanks to Prof. H. L. Sun at the
when ditches had no water. With an average volume of Chinese Academy of Sciences, Beijing, China and Prof. Dr. B.
these pots of 4 l, it may have taken 0.7 h to irrigate the Sattelmacher at the Universit t Kiel, Germany for their supportive
largest rice field (16 m2) by hand. Although not very encouragement and academic advices. Greatly appreciated is the 14C
dating analysis by Dr. Y. H. Wu. Friends from the Kunshan Institute
efficient, this practice could have been, without doubt,
of Archeology and the Soil and Fertilizer Station of Suzhou are
helpful for securing food supply. Except a stone axe and a graciously thanked for their help with sampling.
stone knife, no other tools for rice cultivation were found.
Thus, at this time, irrigated rice cultivation was at an initial
stage. Most probably, the ancient farmers used their hands References
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