Goodman-Elgar 2008a Terraces

8/7/2019 Goodman-Elgar 2008a Terraces

1/15

Evaluating soil resilience in long-term cultivation: a study of pre-Columbianterraces from the Paca Valley, Peru

Melissa Goodman-Elgar*

Department of Anthropology, Washington State University, College Hall, Pillman, WA 99164-4910, USA

a r t i c l e i n f o

Article history:

Received 14 February 2008

Received in revised form 31 May 2008

Accepted 4 June 2008

Keywords:

Agriculture

Andes

Geoarchaeology

Soil micromorphology

Resilience

Terraces

a b s t r a c t

This study evaluated the soil properties of pre-Hispanic stone-walled terraces by comparing soil quality

along terraced catenas in the Paca Valley, a tributary of the Mantaro Valley, Peru. Micromorphological

and bulk analyses of terrace soils revealed that despite terracing soil horizonation largely followed the

catena. Upland terraced fields had deeper A-horizons with higher biotic activity than uncultivated

controls, but less fine material and greater carbonate accumulation. Midslope fields were highly variable

in depth and soil properties reflecting considerable substrate and anthropogenic variations in this

growing zone. Silts and clay accumulated in valley bottom terraces where pedofeatures indicate an

ongoing downhill movement of fine material. The distribution of soil separates down Paca hillsides

demonstrates that terraces help moderate, rather than control, the erosion of key soil fractions required

for long-term agricultural productivity. This study illustrates how the loss of fine material is partly

mitigated by soil consolidation in dense topsoil peds, microaggregates and saprolite. These aggregates

are retained by terraces and contribute to deep soil profiles. Nevertheless, many fields show signs of

degradation, especially from insufficient organic matter amendment. In addition to farming itself, buried

soils and associated artefacts in valley bottom fields indicate mass soil movement, a likely result of

disruption caused by Inca road and terrace construction. The poor soil quality of many upland terraces

also confirms that stone-walled terraces were constructed on mediocre substrates for farming, indicating

a high labour investment for marginal agricultural returns in these areas. Overall, Paca Valley terracesimprove topsoil retention and promote deep soil profiles. However, these fields present quite varied

growing substrates. It is also apparent that over the last millennium, soil depletion from cultivation has

compromised soil quality through loss of fine material and organic matter. Shifts in farming practice

away from pre-Hispanic practices such as long-fallow and middening appear to exacerbate this trend.

2008 Elsevier Ltd. All rights reserved.

1. Introduction

Pre-Columbian Andean peoples developed an elaborate net-

work of stone-walled terrace systems to facilitate intensive agri-

culture in the mountainous uplands. These managed landscapes

emerged as growing populations intensified their landuse practices

and formalized their landholding systems. Early terrace systemswere established by at least 2000 B.C. (Denevan, 2001: p. 173) but

their development is poorly understood. In the central highlands,

agricultural intensification is found by the Early Horizon, 900200

B.C. (Burger, 1992; Hastorf, 1993a; Whitehead, 1999). Highland

terrace construction is associated with several Andean cultures

notably the Huarpa (Leoni, 2006), Wari (Branch et al., 2007; Wil-

liams, 2002) and the Inca (Branch et al., 2007; DAltroy, 2002;

Denevan, 2001; Treacy, 1994). The arrival of the Spanish generally

marks a hiatus in terrace construction until recent attempts to

renovate terrace technology.

This study addresses pre-Columbian terrace systems in a central

Andean valley in order to assess the role of stone-walled terraces in

soil conservation and their contribution to the long-term resilience

of farming systems. Soil quality underlies the long-term success of

agricultural strategies. In soil science, resilience concerns the ca-pacity of a soil to recover its functional andstructural integrity after

a disturbance (Seybold et al., 1999: p. 225). Soil resilience is

evaluated in terms of vulnerability to disturbance, the rate and the

degree of potential recovery after disturbance. Mountain soils are

particularly vulnerable to erosion disturbance. Agriculture presents

a profounddisturbance to soil systems and often leads to regressive

soil processes such as erosion and nutrient depletion (Park, 2006).

Even under traditional Andean farming regimes (Denevan, 2001),

the processes of hand tillage, weeding, cropping and harvest can

degrade soils. Maintenance of soil quality is a dynamic between

landuse management techniques and underlying natural condi-

tions including soil type, climate, and natural vegetation (Herrick,* Tel.: 1 509 335 4807; fax: 1 509 335 3999.

E-mail address: [email protected]

Contents lists available at ScienceDirect

Journal of Archaeological Science

j o u r n a l h o m e p a g e : h t t p : / / w w w . e l s e v i e r . c o m / l o c a t e / j a s

0305-4403/$ see front matter 2008 Elsevier Ltd. All rights reserved.doi:10.1016/j.jas.2008.06.003

Journal of Archaeological Science 35 (2008) 30723086
mailto:[email protected]://www.sciencedirect.com/science/journal/03054403http://www.elsevier.com/locate/jashttp://www.elsevier.com/locate/jashttp://www.sciencedirect.com/science/journal/03054403mailto:[email protected]


2/15

2000). Ideally, stable farming systems will balance soil and eco-

system resilience thresholds with farming technologies that mini-

mize disruption. Terraces are generally seen as a means to promote

the progressive soil conditions that promote soil deepening and

horizonation (e.g. FAO, 1989: pp. 2229), although terrace con-

struction is also disruptive (Park, 2006: Fig. 2).

This study aimed to evaluate the contribution of terraces to soil

resilience through an assessment of soils quality indicators, par-

ticularly plant nutrients and soil structure. Recent research into

Andean farming systems has focused on coastal agriculture (e.g.

Wilson et al., 2002; Huckleberry and Billman, 2003; Nordt et al.,

2004) and the Andean highlands are beginning to see renewed

interest (e.g. Branch et al., 2007). However, little research has been

directed at assessing the role of terraces within the context of

specific soil parameters. A case study was selected with pre-His-

panic terraces that are currently cultivated in order to address

features that contribute to long-term soil resilience. Most terraces

were currently cultivated. This study addressedthe contributions to

soil quality of both inherent soil properties and human land man-

agement techniques.

The movement of the fine fraction was a particular focus as silt

and clay are associated retention of crop nutrients (Caravaca et al.,

1999). The mobilization of fine particles by natural processes (e.g.freezethaw, extreme rainfall) and anthropogenic processes (e.g.

clearance, burning, cultivation) is most visible in thin section (see

Courty et al., 1989: pp.104137; FitzPatrick,1993: p.185). It has also

been suggested that ploughing may also help retain silt and clay in

the subsoil (e.g. Jongerius, 1983), particularly animal-drawn ard

tillage (Lewis, 1998).

Terrace soils frequently display deep profiles which are attrib-

utedto the stabilizationprovided by terrace walls (e.g. Keeley, 1985;

French and Whitelaw, 1999; Sandor, 1992). However, landuse and

substrate differences impact terrace soil development, even in

similar settings. For instance, although terrace soils in the US

Southwest had deeper A-horizons than uncultivated areas, they

were lighter in colour and lower in organic matter, phosphorus and

nitrogen suggesting landuse impacts (Sandor et al., 1986). In the

Grand Canyon, little difference was found between terrace and

uncultivated Mollisols but terraced Aridisols had elevated pH, car-

bonate and CEC values over uncultivated samples suggesting car-

bonate accumulation (Sullivan, 2000).

Research in Peru reveals dramatic substrate and anthropogenic

differences between terrace systems. Rainfed pre-Inca terraces in

the Cusichaca Valley, Peru were situated to take advantage of nat-

ural features (e.g. alluvial fans) with limited soil modification

whereas Inca terraces were elaborate constructions with heavily

modified terrace fills (Keeley,1985). In theColca Canyonabandoned

irrigated terrace soils varied between deep, poorly developed

stratified A-horizons and well-developed profiles with prominent

subsoil accumulations of clay, carbonate, and silica (Sandor, 1992;

Sandor and Eash, 1991). The underlying geology is Miocene an-

desite lava, tufa and volcanic breccia. Earthworms observed in the

Ap-horizon did not penetrate subsoils and buried soils were com-

mon. These terraces had high concentrations of organic carbon,

nitrogen, and especially phosphorus reflecting long-term fertiliza-

tion (Dick et al., 1994; Eash and Sandor, 1995; Sandor and Eash,

1995). Colca Canyon terraces are irrigated making the role of ter-

races difficult to isolate. This study controls for this by focusing on

rainfed terraces.

1.1. Case study

Investigations were conducted in a tributary of the Mantaro

Valley, the Paca Valley, in the central Peruvian Andes (Fig. 1). The

topography of the Paca Valley is ruggedwith alluvial fans, scree and

jagged cliff edges that attest to periodic mass movements. Steep,

irregular topography leads to strong down-cutting and alluvial

deposition along seasonal channels and streams. Terracing is

present on the more stable parts of the hillsides, primarily on

western valley walls.

The dominant parent material in the Mantaro Valley is calcar-

eous limestone. These deposits uplifted and deformed to create the

Fig. 1. The Paca Valley, Peru showing transect areas (Base image Google Earth).

M. Goodman-Elgar / Journal of Archaeological Science 35 (2008) 30723086 3073


3/15

WankayoJauja depression and subsequently formed Quaternary

fluvioglacial deposits (Megard and Philip, 1976; Megard, 1987). The

bulk of central Andean shortening concentrates in the Maranon

Thrust and Fold Belt from about 7 to 12300 trending NW through

the study area. In the Paca Valley, the western valley wall is a ridge

formed by uplift of Jurassic limestone (Pucara Group) (Megard and

Caldas, n.d. [1996], Paredes, 1970 [1994]). Chucllu and the Paca

ridge are separated by a low saddle of Pleistocene conglomerate

sands with subsurface drainage. The Paca ridge is bisected by sev-

eral deep, intermittent streams that drain to Lake Paca. The valley

floor is tilted upward towards the north and contains Recent

Quaternary fluvioglacial terraces (Paredes, 1994). Lake Paca was

formed either by a karst solution depression in the limestone

(Hansen et al., 1994) or as an oxbow lake from the main Mantaro

River to the south (Wright et al., 1989: p. 84). The lake drains by

underground streams. The eastern valley wall is primarily Pre-

cambrian metamorphic Maraizo-Huaytapallana gneiss. The north-

east section is calcareous limestone intercalated with sandstone,

claystone and sandy conglomerate lavas (Paredes, 1994), and agri-

culture concentrates in this area.

The Mantaro Valley has a semi-arid climate and recent annual

rainfall averaged 730 mm/year, with 92% falling between Septem-

ber andApril (Silva et al., 2007). Rains originate over the Amazon tothe east and rainshadow effects leave eastern valley walls drier

than their western counterparts. Wind, elevation and good drain-

age contribute to rapid drying out after rainfall and pronounced

wetdry effects. Frost is frequent in the dry season, averaging 150

days annually (Schwerdtfeger, 1976a,b). Strong El Nino-Southern

Oscillation (ENSO) effects result in dramatic inter-annual climate

variation making both drought and floods relatively frequent

(Vuille et al., 2000). Native vegetation in uncultivated land includes

a vast array of annuals, several perennial cacti (e.g. Opuntia), and

rare shrubs and trees (Hastorf, 1993a).

The primary indigenous food crops of the Paca Valley include

tubers, beans, quinoa and Andean maize (Hastorf,1993a). The many

varieties of Andean tubers prefer organic-rich, well-drained soils

and have variable rooting depths. For instance, ulluco (Ullucustuberosus Loz.) produces many tubers which can be up to 15 cm

long (NRC, 1989: p. 112). The nitrogen-fixing lupine tarwi (Lupinus

mutabilis Sweet) tolerates poor soils and drought and is supported

by a short tap root (NRC, 1989: pp. 188189). Quinoa (Chenopodium

quinoa Willd.) is supported by a tap root with dense rootlets (20

25 cm) andalso tolerates poor soilsand drought (NRC,1989: p.159).

Andean maize (Zea mays L.) is adapted to a wider range of soils and

is more cold tolerant than other varieties (Brandolini et al., 2000).

However, local farmers report that maize is the most water and

nutrient demanding of the common indigenous crops. Maize forms

elaborate root systems first developing a single primary root with

seminal roots followed by shoot-born roots as the plant develops

(Hochholdinger et al., 2004). Most roots are found to 50 cmbs

(Amos and Walters, 2006). Crop limits make planting rotations andfallow periods vary with elevation and these present characteristic

growing zones (Hastorf, 1993a). However, climate variations in

prehistory impacted the area available to specific crops, particularly

maize (Seltzer and Hastorf, 1990).

Andean paleoclimate reconstructions are limited by the wide

distribution of studies, few absolute dates and lack of consensus

between ice cores, glacial moraines and pollen cores. Glacial mo-

raines on Mt. Huaytapallana, which overlooks the central Mantaro

Valley, indicate warm conditions after deglaciation except for two

colder periods around A.D. 710 and A.D. 1350 but moraines have

coarse resolution (Seltzer, 1991). Pollen from Lake Paca indicates

cooling with a ChenopodiaceaeAmaranthaceae increase and Aliso

decline followed by a warming trend but this study had only

a single basal date (5305

90 SI-7001) (Hansen et al., 1994). Icecores on Mt. Quelccaya and Mt. Huascaran have very high

resolution and show a series of dry periods or dust events between

A.D. 540980 with wet periods A.D. 602635 and A.D. 7601050

(see Thompson et al., 2000). However, these cores are well above

agricultural lands and far from the study area. Despite low reso-

lution palaeoclimatic data, the absence of irrigation features in the

study area indicates sufficient rainfall for agriculture at the time of

terrace construction. Pre-Columbian climate fluctuations impacted

the land area available to differentcrops, particularly maize (Seltzer

and Hastorf, 1990). However, cold and drought resistant crops such

as tarwi and quinoa could have been cultivated during all major

occupation periods. The range of conditions indicated by climate

reconstructions would subject Paca soils to frequent wetdry and

freezethaw cycles.

The Mantaro Valley is an important agricultural centre but has

no established soil sequence. Saleva et al. (1954) identify a Paca soil

series adjacent to Lake Paca without scientific analyses. In the

southern Mantaro Valley, fallow fields on limestone had neutral pH

in the topsoil with relatively high K, total nitrogen and available

phosphorus but low organic matter (Alegre et al., 1990). The Quil-

casWankayo area of the southern Mantaro Valley has soils similar

to the Paca region comprising moderately deep brown-grey gravely

loams, shallow dark brown sandy loams and erodible deep reddish

brown (clay) loams on limestone, claystone and sandstone (Kauff-man and Ramos, 1998).

1.2. Cultural setting

By 3000 B.C. incipient agriculturalists settled in the Paca Valley

in small, dispersed settlements (Rick, 1988). Settlement increased

during the Formative Period but population density remained low

(Hastorf et al., 1989: p. 87). During the Early Intermediate Period

(400 B.C.A.D. 500), the lakeside site of Pancan emerged and be-

came a long-lived centre (Borges, 1988). Chenopod, maize, legumes

and tubers were cultivated by early Pancan residents, possibly in

raised fields adjacent to the lake (Hastorf, 1993a: pp. 167176). The

Wanka emerged as a local cultural tradition in the Middle Horizon(A.D. 5001000) with five new communities in the Paca Valley

(Borges, 1988: p. 45). Subsistence shifted to camelid pastoralism

and valley bottom agriculture (Hastorf et al., 1989; Hastorf, 1990,

1993b). The terrace systems adjacent to these sites may be con-

temporaneous constructions but few diagnostic Wanka I artefacts

were recovered from fields (Goodman-Elgar, 2003). In the sub-

sequent Wanka II phase (A.D. 10001438), population increased

and shifted dramatically to concentrate in defensive upland set-

tlements in the Yanamarca Valley. Paca settlement appears reduced

to Pancan and two small hillside settlements (Hastorf, 1993a).

Yanamarca Valley farmers developed a small hydraulic network,

terraces, lynchets and ridged fields (Hastorf, 1990, 1993a). These

fields are now severely eroded and uncultivable. No irrigation

features were found in the Paca Valley suggesting rainfed agricul-ture throughout the occupied periods.

The Inca conquered the Mantaro Valley by 1450 A.D. and con-

structed a footpath along the western ridge of the Paca Valley

(DAltroy, 1992). The Inca restructured Wanka II communities to

areas of agricultural productivity and developed terraces in the

Paca uplands (Earle et al., 1987; Goodman-Elgar, 2003). Less than

a century later, the Spanish overthrew the Inca and established

their first colonial capital in Jauja (Fig. 1). The local population was

decimated by disease and relocated to the valley bottom. Upland

terraces may have been briefly abandoned but subsequently

returned to use as population began to recover through the 19th

century (Mallon, 1983). Residents reported that civil unrest in

1980s promotedlarge-scale out-migration. Regional population has

largely recovered and there are several agricultural communitieswithin the study area.

M. Goodman-Elgar / Journal of Archaeological Science 35 (2008) 307230863074


4/15

Changes in farming technology and landuse mirror these cul-

tural trajectories. The main pre-Hispanic agricultural implements

were the chaquitaclla (footplow) and rucana (hoe or mattock) made

of wood and stone (Donkin, 1970; Poma de Ayala, 1987 [1584

1615]). Stone hoes are widely distributed in Wanka sites ( Russell,

1988) and frequently encountered on the surface of Paca fields

(Goodman-Elgar, 2003). Animal traction was introduced by the

Spanish and prompted terrace modification to enable access for

animal teams (Morales, 1978). Upland fields are inaccessible to

traction and continue to be hand-tilled. Mechanized ploughing is

only used in a few valley bottom locations. Pre-Hispanic commu-

nities had substantial camelid herds and a ready source of dung

fertilizer (Sandefur, 2001). Camelid herding declined following

Spanish colonization and the introduction of European animals.

Contemporary farmers add a little organic matter through limited

sheep grazing, middening and burning.

Paca Valley terraces have stone-walled masonry constructed of

unmodified or very roughly cut fieldstone, which is commonly

double walled with gravel fill (Goodman-Elgar, 20 03). Walls gen-

erally have larger, rectangular stones at the base (to ca. 1 m long by

30 cm high) with smaller stones in upper courses (to ca. 25 cm by

25 cm). Wall height decreases with elevation and soil depth aver-

aging over 2 m at the footslope to under 1 m in the highest terraces.Field shape accommodates topography and drainages. Most are

rectangular valley side, sloping field terraces with small sections of

architecturally planned bench terraces at the footslope (Goodman-

Elgar, 2003; see Denevan, 2001: pp. 175180 for terrace forms).

Long walls are perpendicular to the slope. Many terraces are cur-

rently in poor condition with damaged or missing masonry.

2. Field and lab methods

Field investigations in 19951996 concentrated on the western

limestone ridge of the Paca Valley in three parallel eastwest

transects, a northsouth transect in a saddle between Cerro Ushnu

and Paca (Acolla), and two short transects in Chucllu (Fig. 1). Thewestern hillslope is almost entirely terraced whereas terracing on

the eastern slope starts at midslope and is discontinuous. Test

trenches were selected along transects that captured catena vari-

ations in elevation, growing conditions and field practices (Fig. 1,

Table 1). Triplicate parallel transects P1, P2 and P3 controlled for

spatial variation between fields in the same growing zone (Good-

man-Elgar, 2007). Trenches were excavated to the B/C horizon or

3 m and profiles were described for Munsell colour, texture,

structure and inclusions. A continuous column of parallel bulk and

block samples was collected from each pit. This collection was

subsampled and the results of 16 test pits from P1, P2, and P3

transects are presented here. P1 transect crossed the valley bottom

to account for both sides of the valley, whereas P2 and P3 are only

on the western side of the valley. Archaeological studies of agri-cultural fields are generally controlled by comparison to un-

cultivated contexts (e.g. Sullivan, 2000). However, in the Paca

Valley essentially all arable land was under cultivation. Only two

uncultivated profiles (N1and N2) were collected as controls from

unenclosed land at 35503650 masl between P1 and P2 transects

and no suitable controls were identified at lower elevations.

Analyses concentrated on thin sections in order to assess the

distribution of fine material. Bulk analyses were used to further

characterize soil types and define horizons. A subset of 109 thin

sections is summarized here. Thin sections were prepared by air

drying followed by resin impregnation under vacuum. Most slides

were mammoth (51 mm75 mm) hand-finished, thin sections

made at the McBurney Laboratory, University of Cambridge. The

remainder were large (27 mm46 mm) machine-finished thin

sections prepared by Spectrum Petrographics (Vancouver, WA,

USA). Thin sections were analyzed on Leica Wild and Leitz Laborlux

microscopes (Bullock et al., 1985; Courty et al., 1989; FitzPatrick,

1993) with digital image capture on Omninet Enterprise version 2.0

software (Buehler, Lake Bluff, IL, USA; Goodman-Elgar, 2003: Ap-

pendix J). Soils were characterized by microscopic analysis of soil

fabric and structure with an emphasis on primary and secondary

carbonates, silt and clay pedofeatures, and other indicators of soil

quality. The microstructure, birefringence-fabric (b-fabric), texture

and accumulation pedofeatures were used to assign soil fabrics.

A subset of parallel bulk samples was analyzed for texture, or-

ganic matter, carbonate, nitrogen, potassium and phosphorus

(Table 2). Bulk analyses were conducted at the Department of Ge-ography, University of Cambridge based on standard protocols

(MAFF, 1986; SSSA, 1996). Soils were air-dried and stored before

analysis, which may impact phosphate and nitrogen results (Hay-

nes and Swift, 1985). Samples were lightly ground and the 2 mm

fraction was used for all bulk analyses. Texture was determined by

dry sieving followed by dispersion in sodium pyrophosphate and

laser particle analysis (Malvern Mastersizer 200 0). Determinations

of pH and electrical conductivity (EC) were determined on elec-

trodes. Organic carbon and carbonate were determined by loss-

on-ignition. Essential plant nutrients nitrogen, potassium and

phosphorus (Soon, 1985; Elliott, 1996) were assayed on extracts in

Olsens solution.

Carbonized organic remains were collected from test pit exca-

vations for radiocarbon dating. However, high levels of bio-turbation, buried modern artefacts (plastic, metal) and a lack of

secure contexts under terrace walls conspired against a successful

application of radiocarbon dating and this effort was discontinued.

Terrace wall architecture and artefact distributionwere surveyed to

estimate the cultural contexts of Paca terraces (Goodman-Elgar,

2003). The cultural associations of Paca Valley fields are pre-

dominantly Late Intermediate Period to Inca.

3. Results

Seven profiles were investigated in P1 transect, four along the

western valley wall and three up the eastern wall (Table 3). Topsoils

were generally deep while subsoils varied widely but were gener-ally less developed on the eastern valley wall. Five profiles were

investigated in P2 transect andthese hadshallower topsoilsthan P2

and again variable subsoils. P3 transect is represented by seven

profiles and these profiles show the greatest variability in terms of

Table 1

Field characteristics of test trenches

Growing Zonea Slope position (masl) Depth (cm) Landuse Test trenches

Fertile Lowland Toeslope-valley 33803420 110310 Animal or mechanical till, maize, beans, dung, midden P1-2, P2-1, P3-1, P3-2

Intensive Hillside I Toeslope-midslope 34153510 4788 Hand or animal till, short-term fallow, grains, maize, beans,

tubers, rare surface treatment

P1-1, P1-3, P1-5, P2-2,

P2-3, P2-4, P3-3

Intensive Hil lsid e I I M id sl op e 3 49 5 356 0 10 0 173 Han d or u ntil led, tub ers or n o c rop, no sur fac e treatment N 2, P3-4 , P3-6

Extensive Hillside Midslope-Upland 35453595 2362 Hand or animal tilled, grain or tubers, P1-4, P1-6, P3-5

High Elevation Upland 36503675 25130 Hand till, potato or no crop, Some dung N1, P1-7, P2-5, P3-7

a Adapted from Hastorf (1993a).

http://-/?-http://-/?-


5/15

soil depth and horizonation. The boundaries between soil horizons

were gradual in the field with considerable evidence for root and

soil faunal bioturbation. Overall, profile position was not a good

indicator of soil depth except for lowest profiles. Buried artefacts,

charcoal and ash suggested buried soils in several low-elevation

fields (Table 3).

Control sample N1 was located on a natural uplift adjacent

a deep dry watercourse at 3650 masl. The surface was cemented

with sparse vegetation, predominantly lichen. The top 30 cm was

consolidated with fine material, a massive structure, very sparseroot, 30% subangular to subrounded pea gravel and Munsell colour

7.5 YR 3/4 (wet). An ice pick was required to excavate it. These

properties suggested an exposed Btk horizon after topsoil loss. This

soil continues to 50 cm but the structure is less compact and pea

gravel increases to 20%. From 50 to 65 cm, there was a shift to

a siltier, more friable soil with gravel 10%. Below 65 cm there is

a dramatic increase in crumbling subangular rock and saprolite

suggesting the B/C horizon.

N2 profile was situated at midslope between two deep drain-

ages in precipitous terrain at 3550 masl. The topsoil supported

sparse drought tolerant plants and large lichens. The topsoil from

0 to 20 cm was compact with low porosity, 20% subangular to

subrounded gravel, fine root, and wet Munsell colour 7.5 YR 4/4

(Fig. 2A). The dense, consolidated texture suggested an A/B-horizonwith the suggestion of topsoil loss. From 21 to 38 cm root and

porosity decreased to a massive structure. After 39 cm there was

a sharp transition to a cemented Bk with a drop in gravel to 5% and

wet Munsell colour 7.5 YR 4/6 (Fig. 2E).

P1-7 is in a comparable slope position and profile depth to N1

but is characterized by carbonate accumulation, which was also

found in several cultivated fields (P1-6, P2-4, P3-3, P2-1). Terraced

upland and midslope fields have significantly deeper topsoils than

the two controls. The controls also had higher clay and silt accu-

mulations in the subsoil, which are only found in lower elevation

positions in cultivated fields. P1-6, P2-4 and P3-5 are all compa-

rable in elevation to control sample N2 but were significantly

shallower and had less silt in the B-horizon. In the case of P1-6, the

subsoil was leached with significant carbonate.No uncultivated land was identified at lower elevations. The

depths and horizonation of excavated fields at these elevations

were highly varied. Topsoils were all adequate to support Andean

crops while subsoils varied widely. Eastern Paca Valley fields P1-2,

P1-2 and P1-4 had notably poorer, leached soils with poor profile

development.

3.1. Thin sections

Representative topsoil and subsoils thin sections from controls,

upland, midslope and toeslope fields are found in Fig. 2. The sur-

face soils of both natural profiles had subsoil properties making

them poor controls for cultivated topsoils. Topsoil fabrics also

follow the catena such that upland fields have little fine material(Fig. 3A, B) and many accumulated carbonate (Fig. 3B, C). Midslope

fields are highly variable but generally have loamy topsoils (Fig. 3E,

F) whereas silt and clay accumulate in lower elevation fields

(Fig. 3G, H).

Paca fields display dramatic differences in pedofeatures, par-

ticularly accumulations of clay, carbonate and silt as well as evi-

dence for soil fauna (Fig. 4). Clay in Paca soils was largely

encountered as coats, infillings or nodules (Fig. 4AC) with rare

domains of high clay integration into the groundmass (Fig. 3G, H).

Clay increased downslope where clay-rich subsoil pedofeatures

covered 10% or more of the thin section in P1-3 transects. Larger

clay accumulations have silt and sesquioxide laminations, which in

an extreme case numbered over 100. Surface rounding, sharp

boundaries with the groundmass, and random orientation of some

clay pedofeatures indicate movement as aggregates (Boggs, 2001:

pp. 7480; FitzPatrick, 1993: pp. 178182). These clay-rich horizons

display Vertisol features and low biological activity due to re-

stricted pore space. Compound infillings cemented domains in

several B-horizons (Fig. 4I).

Carbonates were common in cultivated upland topsoils and in

deep subsoils. Two mechanisms for carbonate accumulation were

observed in thin section: primary limestone weathering and sec-

ondary carbonate accumulation. Primary weathering of carbonate

rock was observed as carbonate pendants, porous internal struc-tures and crystals deformed by dissolution and transformation

(Fig. 4D; Bullock et al., 1985: pp. 5865, FitzPatrick, 1993: pp. 206

217). Inherited carbonate features include altered limestone and

inclusions such as shell. Saprolitic limestone was often riddled with

small pores filledwith clay whose limpidityand colour suggested in

situ formation from limestone dissolution (Fig. 4E, F; Carroll, 1970;

Atkinson and Smith, 1976). Secondary carbonates were found to

penetrate the parent material as carbonate infillings, hypocoats and

intercalations (Fig. 4GI; Bal, 1975a,b; Courty et al., 1989: pp. 169

179; Gile et al., 1965, 1966; Scoffin, 1987). Secondary carbonates

represented both the terminal phase of limestone alteration and

precipitation from carbonate saturated waters.

Fine fraction translocation was observed in silt and clay accu-

mulation in the groundmass and in pedofeatures. Silt pedofeatureswere identified in valley bottom Ap-horizons (Fig. 4J) and as dis-

crete subsoil horizons. Silt accumulation suggests downhill turbu-

lent water flow strong enough to dislodge and transport silt

particles (Nettleton et al., 1994). Both control samples have signif-

icant silt in the subsoils but not in nearby upland fields. Silt

pedofeatures were characteristic of P3 transect. Laminated silt

pedofeatures suggested periodic translocation of silt (Fig. 4K, L).

Bioturbation was identified in all cultivated contexts except

cemented B-horizons (e.g. Btk horizons) by features such as fresh

and mineral-replaced root, cylindrical channels, mite droppings,

partially sorted groundmass, crescentic and vermiform excrement

pedofeatures, biospheriods and preserved fauna (Fig. 4MO; e.g.

Bal,1975b; Becze-Deak et al., 1997; Bullock et al., 1985: pp.133137;

Courty et al., 1989: pp. 142146; FitzPatrick, 1993: pp. 133, 136142). Faunal bioturbation was much higher in cultivated than

control samples. Roots frequently extended well into the subsoil

where they are commonly carbonate- or sesquioxide-replaced.

3.2. Physical and chemical results

Bulk soil analyses aimed to substantiate and augment thin

section observations. Texture determination was intended to bridge

two- and three-dimensional differences in soil fraction represen-

tation (Bullock et al., 1985). Particle size analysis indicated a sandy

texture (Table 3, Table 4). In comparison to thin section observa-

tions, bulk texture determinations under-represented the fine

fraction beyond expected differences between two- and three-di-

mensional results. This indicates that the protocol followed heredid not effectively disperse aggregates to defluocculate clays

Table 2

Summary of bulk soil analyses

Analysis No. Method

Organic, inorganic carbon 95 Loss-on-ignition (LOI)

Electrical conductivity 47 Electrode, 1:1 aqueous slurry

Nitrogen-nitrate 66 Electrode, extract in Olsens solution

Phosphorus (total) 32 Spectrophotometry, extract in Olsens solution

pH 47 Electrode, 1:1 aqueous slurry

Potassi um 6 8 Flame p hotometry, extra ct i n n itra te solu ti onPartic le size (coar se) 8 9 Dr y sieve

Particle size (fine) 86 Malvern Laser Mastersizer, suspend in

sodium pyrophosphate



6/15


7/15


8/15

(van Wambeke, 1974; Gee and Bauder, 1996) demonstrating the

relative stability of aggregates.

Field determinations of topsoil pH ranged from 6.7 to 8.6 and

laboratory pH determinations ranged from 5.2 to 8.8, and averaged

7.9. Outliers clustered in the same profiles. Electrical conductivity

determinations ranged from 8 to 124 mS/cm, with slightly higher

average EC in the topsoil (62mS/cm) than the subsoil (55 mS/cm). To

test for ion release 18 parallel samples were suspended 3 h in

aqueous slurry and EC increased by an average of 9 mS/cm. Electrical

conductivity and pH do not covary with elevation or growing zone.

EC distribution is more variable than pH but low EC corresponds to

low pH (Fig. 5). Overall, the Paca soils are calcareous with a lowfree

ion concentration regardless of elevation.

The carbonate concentration ranged between 1.5 and 52.4%

making averages of limited use. The distribution of carbonate var-

ied widely both between profiles and within individual profiles.

Although the uncultivated N1 andN2 profiles and upland fields had

carbonate accumulations,the range was tighter in the controls than

in cultivated fields. Upland fields had significantly more carbonate

than lowland fields, especially in topsoil.

Paca soils had low to moderate organic matter (OM) with

a range of 2.57.1%. Topsoil OM averaged 5.4% and the B-horizon

averaged 4.6%. Valley bottom maize fields hadlower organic matterconcentrations than upland tuber potatoes fields. Again the range

of OM was narrower in uncultivated controls than in the cultivated

fields. The nutrient indicators nitrogen, phosphorus and potassium

did not covary tightly with OM, elevation or clay as observed in thin

section. Nitrogen concentrated in topsoil across all Paca transects as

seen in the elevated A-horizon average (487 mg/L) compared to the

B-horizon average (310 mg/L). However, there were also significant

fluctuations in nitrogen distribution between horizons within

profiles, particularly in P3 transect and N1. The cultivated fields had

a higher range, with a few highly fields having very high values.

The average concentration of potassium (K) was 307.25 mg/L

from a range of 61600 mg/L (where 600 mg/L was the maximum

detectable). Wide fluctuations within certain profiles demonstrate

K mobility. The lowest topsoil K was in fallowfield P3-7 (90.9 mg/L)which had a subsoil average of 386.37 mg/L. Conversely, fallow P3-

4 had 247.6 mg/L K in topsoil but the soil immediately underlying

had a K concentration of 92.6 mg/L.

A subset of samples was assayed for phosphorus-phosphate (P)

from P3 transect and the controls. The phosphorus range of 2.9

318.3 mg/L spans both high and low extremes of limits for agri-

culture (MAFF, 1986). The average of 63.3 mg/L is skewed by rare

high values. P concentrated in the valley bottom fields of P3 tran-

sect. Soil profile designations were determined by comparing thin

section analysis to bulk analyses results (Table 3; Douglas and

Thompson, 1985). Mass soil movementis suggested in N1 profileby

a pronounced lack of topsoil. Clay and silt accumulated densely

lower in the profile. N2 profile displayed weak topsoil development

also suggesting topsoil loss. Subsoils of both natural profiles hadlow porosity from concentrated infillings.

The parallel transects show comparable field conditions in the

uplands but increasingly variable soil properties moving down-

slope. In P1 transect, carbonate accumulated in the western up-

lands with little profile development. Clay accumulation is seen in

western midslope profile subsoils whereas valley bottom profiles

are well developed with significant subsoil accumulations and

relatively higher clay and silt throughout the profile. Dense Wanka

II artefact finds in P1-1 subsoil indicate a buried A-horizon and

suggest mass soil movement. The eastern fields had significant

depletion features not identified elsewhere.

The P2 uplands are characterized by carbonate accumulation

and little profile development but clay accumulation appears at

3550 masl. Midslope fields do not have significant silt or clay ac-cumulation in the subsoils and P2-2 is dominated by carbonates.P3-5

A

5YR3/4

Granular

Reticulateparallel

23

19

21

95.2

3

3.0

6

1.0

6

6.5

8

3.2

6

6.1

33

704.5

8

174.9

8

B

Granular

Reticulateparallel

13

17

18

94.9

5

2.9

3

1.3

2

6.4

7

3.4

2

1069.6

8

119.9

4

P3-6

A

C

5YR4/4

Vughyblocky

Stipple

parallel

23

18

45

93.8

8

3.2

2

1.9

3

5.1

5

3.2

5

5.2

35

1100.0

0

188.4

1

DF

7.5

YR4/6

Granular

Reticulateparallel23

14

29

94.4

3

3.1

7

1.6

2

3.9

0

2.63

6.6

28

242.4

1

342.5

7

P3-7

A

7.5

YR4/3

Granular

Mosaic

/crystallitic

13

21

18

95.5

3

2.2

1

1.1

9

5.5

1

18.3

3

8.2

80

422.9

8

90.8

5

B

7.5

YR4/4

Granular

Mosaic

/

crystal

litic/parallel

15

22

9

4.7

3

15.0

0

Ash

0

CD

7.5

YR4/4

Blockyspongy

crumb

Mosaic

parallel/

crystal

litic/parallel

5

20

10

95.6

5

2.1

6

0.8

2

4.7

8

5.8

2

8.2

55

335.4

2386.3

7

Not

es:B-fabricsseparatedbyaslash(/)arediscretefabricsasarenumbersinparenthesis.

Crystallinefeaturesincludeallsecondarycarbonatefeatures(i.e.

infilling,pendants,

hypocoats).

Gravel,sandandsiltpercentagesareestimatesofslideareasbasedonpointcountingdifferentdomainsacrosstheslide.



9/15

The valley bottom field P2-1 was significantly deeper than in P1transect and demonstrated carbonate accumulation in the subsoil

and buried Wanka II artefacts.

In P3, the uppermost field demonstrated topsoil carbonate ac-

cumulation but clay also accumulated in the subsoil. Below this

level the subsoils accumulate silt and clay. The depth of midslope

profiles is highly variable suggesting karst substrate undulations.

The basal sample of shallow profile P3-3 had abundant soil faunal

features suggestive of a buried A-horizon. The valley bottom pro-

files are well developed with considerable clay accumulation in the

subsoil. Clusters of artefacts in the subsoil of P3-1 also suggest

buried soil. Soil depth and horizonation in P2 and P3 undulated

along the catena and did not mirror slope position. These un-

dulations suggest substrate variations, such as limestone dissolu-

tion, and cannot be directly related to anthropogenic causes.

3.3. Discussion

These results suggest that both inherent and anthropogenic

processes contribute to the soil patterns in the Paca Valley. These

include mass soil movement and its stabilization, topsoil depletion,

clay and silt translocation, aggregate formation, bioturbation and

carbonate accumulation. The two uncultivated samples both show

evidence of topsoil loss whereas all terraces samples had com-

paratively deep A-horizons, confirming the stabilizing effects of

terraces. However, soil depth alone does not indicate fertility. Many

topsoils had low levels of OM and fine material suggesting poor

growing conditions and some were abandoned at the time of thisstudy.

The analyses performed here confirm that the terraced fieldsin the Paca Valley represent a mosaic of different growing envi-

ronments as noted elsewhere in the Andean highlands (Zim-

merer, 1999). The pH and EC data indicate that most soils are

alkaline and have moderate total nutrient status. Peaks in pH,

carbonate and EC covary suggesting that the majority of free

cations are calcium. The upper and lower pH of this range are

limiting to agriculture (Wild, 1993: p. 178). Paca pH is generally

higher than in the southern Mantaro Valley (range: 6.97.3;

Alegre et al., 1990) and considerably higher than in other Andean

regions suggesting important landuse and substrate influences

(e.g. Eash and Sandor, 1995; Pestalozzi, 2000; Sandor and Eash,

1995; Sarmiento, 2000). EC averages are low and compare well

with fallow soils in Bolivia (average 47.9 23.0 mS/cm; Pestalozzi,

2000).Carbonates in upland soils reflect proximity to exposed lime-

stone bedrock above the terraces, poor soil formation and poor

retention of fines. Clay and silts accumulate in subsoils from mid-

slope and increase moving down valley from P1 to P3 transect,

which suggests the ongoing translocation of fines in the valley

system. Comparison of control to cultivated upland fields suggests

loss of fine material suggesting anthropogenic influence from ter-

race walls, tillage and possibly amendment. However, the high silt

and clay concentrations in the controls indicate that the parent soil

had more silt and clay in the upper elevations than in cultivated

fields suggesting loss of fine material. Silt and clay pedofeatures in

low-elevation fields probably reflect natural fine particle trans-

location that has been augmented by agriculture. Laminated silt

pedofeatures suggest periodic disruption, which is likely from till-age and harvesting of tubers. This is further suggested by

Fig. 2. Thin sections of representative topsoil and subsoils from control, upland, midslope and toeslope fields. (A) Control profile topsoil (N2A), (B) upland field topsoil (P3-7A), (C)

midelevation field topsoil (P1-5A), (D) toeslope field topsoil (P2-1A), (E) control profile subsoil (N2G), (F) upslope field subsoil (P3-7D), (G) midslope subsoil (P1-5E), (H) toeslope

subsoil (P2-1I).



10/15

comparing cultivated upland tuber fields to the controls, which

indicates silt loss from cultivated fields.

Potential buried soils were identified in the field by buried ar-

tefacts andchanges in soil structure. Buriedsoil is suggested in P1-1

by concentrations of pre-Columbian ceramics, bone, ash and char-coal. Increased OM between 69 and 83 cm further suggests a buried

soil, although microstructure and pedofeatures indicate B-horizon

formation. Field finds for P1-2 include charcoal and ceramics and

soil chemistry revealed an increase in OM over the topsoil. In

contrast, artefacts in P2-1 and P3-1 are widely distributed through

the subsoils and soil data do not provide strong A-horizon evi-dence. Microstructure and b-fabric changes in P3-3 suggest

Fig. 3. Topsoil microfabrics. (A, B) Upland topsoil b-fabric with little fine material (P1-5A) (ppl, xpl), (C, D) upland carbonate topsoil b-fabric (P3-5A) (ppl, xpl), (E, F) midslope loamy

topsoil b-fabric (P2-3A) (ppl, xpl), (G, H) toeslope topsoil b-fabric (P1-1A) xpl, ppl.



11/15

Fig. 4. Characteristic pedofeatures. Clay features: (A) laminated silty clay topsoil infilling (P1-1A) (ppl), (B) laminated clay nodule with rounded edges (pseudosand) (P2-4C) (ppl),

(C) rounded clay nodules showing laminations in disturbed orientations (pseudosands) (P3-8E) (ppl). Primary carbonate weathering: (D) limestone dissolution and alteration

showing the incorporation of adjacent groundmass peds within thick calcite infillings (P3-1A) (xpl), (E, F) saprolitic rock with clay accumulation in pores (P1-1A) (ppl, xpl).

Secondary carbonate formation: (G) bladed calcite coat (N1A) (xpl), (H) Calcite hypocoat (P2-5B) (xpl), (I) complex infillings with carbonate over clay cementing peds (N1-Jb) (xpl).

Silt pedofeatures: (J) thin silty accumulations in upper subsoil (P2-1C) (ppl), (K, L) size sorted silt accumulations in lower subsoil (P2-1I) (ppl, ppl). Faunal bioturbation features: (M)

organic-enriched excrement pedofeaures (P3-5B) (ppl), (N) Biospheriod carbonate excrement pedofeature (P3-5B) (xpl), (O) partly sorted groundmass (P2-3D) (ppl).



12/15

a possible buried soil but this is not indicated by OM or artefacts.Overall, artefacts are stronglysuggestive of buried soils in the lower

elevations. Thin sections and geochemistry indicate preserved A-

horizon properties to support artefactual evidence in P1 transect

and suggest an additional buried soil at P3-3 which was not visible

in the field.

The concentration of OM and plant nutrients was relatively low

by international standards (i.e. MAFF, 1986; Landon, 1991). Low OM

suggests that cultivation losses are not counterbalanced by ade-

quate inputs leading to depletion. Nitrogen was variable but suffi-

cient in topsoil not to regularly limit agriculture. Potassium was

distributed more irregularly with evidence of poor retention.

Phosphorus distribution was highly irregular in the limited assays

performed here but may be limiting for agriculture in several

contexts (e.g. P2-2, P3-7). In deep profiles, cemented B-horizonsretain higher nutrient concentrations indicating a nutrient pool

below the root zone. In several instances peaks of nitrogen, po-

tassium or phosphorus in the absence of high OM suggest the in-

expert use of chemical fertilizers. This represents a shift from

traditional long-fallow practices. Elevation differences in nutrient

concentration may also reflect demands of different crops, maize in

the valleys and potatoes in the uplands.

Gradual horizon boundaries suggest colluviation and bio-

turbation. In contrast to the Colca Canyon where undisturbed

subsoils were common (Eash and Sandor, 1995; Sandor and Eash,

1995), in Paca bioturbation limits the depth of cemented horizons

by aerating soils, mixing sediment and digesting soil components.

This provides a mechanism for the exchange of nutrients in these

soils, which contributes to their vitality.

The effects of terraces on controlling fine fraction movement are

less clear from this study. Little clay was identifiedin high elevation

topsoils but increases downslope where subsoil accumulations are

also common suggesting decalcification followed by clay eluviation

(MacKeague, 1983). Silty laminations in subsoil infillings (Fig. 6)

may suggest tillage effects (see Macphail et al., 1990) but such as-

sociations can be problematic (Carter and Davidson, 1998) and

there are no experimental results for the Andes to support this. If

these do represent tillage pedofeatures, they may have been aug-

mented by animal traction over the last 500 years as footplows

generate large clods and minimal structural disruption (Schjel-

lerup, 1986). In contrast, in situ laminated clay pedofeatures in

valley bottom ploughzones indicate continuous translocation of

fine material downslope. The accumulation of clay in subsoil pro-vides a moisture retention mechanism in these rainfed fields

(Buytaert et al., 2002; Sandor et al.,1990: p. 74) and probably active

soil fauna.

Stable microaggregates (pseudosands) and saprolite protect

some fine material from erosion in the Paca Valley. Stable soil

aggregates may be bound by ferrous compounds (van Wambeke,

1974), salts (Aubert, 1983), clays and organic matter (Six et al.,

2000). Carbonates and clay were most visible in thin section.

Upland topsoil peds were generally smaller, denser and less ac-

commodated than peds at lower elevation probably as a result of

more frequent freezethaw cycles and low clay concentration. The

presence of microaggregates demonstrates that Paca soils have

a capacity to sequester nutrients, which promotes soil resilience.

Clay in saprolitic rock provides a continual source of cationbuffering as limestone weathers rapidly at high elevation pro-

ducing residual clay (Fig. 4H, I; Atkinson and Smith, 1976). Dense

peds, stable microaggregates and saprolite appear to act as nu-

trient sinks which are released slowly through weathering and

low-intensity ploughing. Microaggregate formation appears to be

multicausal from anthropogenic and natural practices and cannot

be directly attributed to terracing. However, terraces clearly sta-

bilize the aggregates themselves and prevent their downhill

movement.

Carbonate accumulation represents a limiting factor for agri-

cultural productivity in many Paca soils, which was often noted by

contemporary residents. Carbonate accumulationwas derived from

in situ limestone dissolution and pedogenic carbonate accumula-

tion. These carbonate sources were eventually drawn into the

parent material and diluted it to make carbonate soil.

4. Conclusions

This study focused on soil quality of rainfed pre-Hispanic ter-

races that arein activeuse to assessthe role of terracesin long-term

agriculture. Compared to uncultivated lands, Paca terraces stabilize

sands and aggregates which preserve topsoil and contribute to soil

resilience. Yet, buried artefacts and soils also show dramatic

changes to the Paca landscape. Buried Wanka II ceramics in valley

bottom positions indicate mass soil movement during the late pre-

Columbian periods. The most likely cause is the documented ex-

pansion of Inca agriculture and road building (DAltroy, 1992;

Goodman-Elgar, 2003). These buried soils demonstrate the detri-mental short-term impacts of terrace construction despite their

potential long-term contributions to soil resilience (Park, 2006).

The construction of footpaths has also been shown to augment

erosion in the Andes (e.g. Harden, 1993).

The low organic matter, moderate plant nutrients and little

available clay in upland fields compared to controls indicate that

they are poor agricultural substrates. Many showed no sign of re-

cent cultivation and appear abandoned. These fields are highly

vulnerable to degradation and clearly show the impacts of overuse.

Local farmers indicate that precipitated fallow times has been

shortened by several years, which limits the soils ability to recover

after cultivation. A dearth of OM in the uplands was also apparent

from this study. These terraces therefore appear situated on poor

agricultural substrates that require high maintenance to remainproductive. The juxtaposition of these terraces along an Inca road

Table 4

Bulk particle size fraction ranges

Sand Silt Clay

Fraction V. coarse (12000mm) Coarse (5001000mm) Medium (250500 mm) Fine (125250 mm) V. fine (63125mm) All (2 63 mm) All (


13/15

Fig. 6. Horizonation of Paca transects (elevation is scaled, the distance between sample points is not representative).



14/15

indicates that agricultural productivity was not necessarily the

driving force for their construction. Constructing these fields re-

quired high labour investment in difficult terrain for marginal ag-

ricultural returns. The Inka had access to labourers from conquered

territories and a grand surplus of goods enabling this kind of dis-

play (see DAltroy, 2002) and such practices may have formed part

of their territorial conquest strategy.

Midslope fields also show signs of overuse, particularly through

relatively low OM and plant nutrients. The erratic distribution of N,

K and P demonstrate that contemporary efforts to use chemical

fertilizers are not adequately compensating for nutrient losses

through overuse and erosion. Little organic fertilizer is currently

applied to fields resulting in a loss of soil quality and the potential

for progressive degradation. In pre-Hispanic times, soil depletion

was probably offset to a greater degree by grazing camelids on crop

stubble (Denevan, 2001: pp. 3536) and middening household

waste, which is suggested by artefact scatters within the Paca field

systems (Goodman-Elgar, 2003). The long-fallow and organic re-

placement practices typical of traditional Andean agriculture

combine to favour a dynamic of soil quality maintenance whereas

contemporary practices are pushing this soil system towards

depletion.

Inherent soil properties also contribute to soil resilience in thePaca Valley. These soils are prone to stable aggregate and saprolite

formation which sequesters nutrients in larger aggregates that re-

sist erosion. Terraces stabilize these aggregates and enhance topsoil

retention contributing to soil quality. However, these mechanisms

provide soil replenishment at a slow rate as nutrient release is

derived from slow aggregate weathering. Under contemporary

farming practices, this slow release cannot compensate for nutrient

losses through cultivation resulting in depletion of some fields.

Another inherent quality of importance for agriculture is the

presence of well-developed Bt horizons. Subsoil clay accumulation

contributes to water retention and contributes to plant and soil

fauna growth in this semi-arid environment.

Overall, both inherent soil conditions and terracing contribute

to the resilience of rainfed agriculture in the Paca Valley. The longfarming history in this region indicates that soils and farming

practices are relatively resilient. However, this resilience is fragile

and represents a balance between management and overuse. The

disused upland fields in the Paca Valley, and the larger abandoned

agricultural systems in the neighbouring Yanamarca Valley, attri-

bute to the long-term outcomes of mismanagement in the Andes.

Evidence for large-scale landscape disruption and construction on

poor substrates in Inca times also suggests that pre-Hispanic ter-

racing has a wide range of impacts, some of which may be un-

intentional. The role of terraces in soil stabilization provides an

important advantage to upland farming in the Andes but cannot

compensate for poor substrates and farming practices making even

terraced fields vulnerable to overuse.

Acknowledgements

Fieldwork was conducted under permissions from the Instituto

Nacional de Cultura, Peru. Andres Moya Castro and colleagues

provided field assistance. Dr. Charles A.I. French and Dr. Steve

Boreham provided technical support. Julie Boreham (McBurney

Laboratory, Cambridge) and Spectrum Petrographics (Vancouver,

WA) manufactured thin sections. Funding was provided in part by

the McBurney Laboratory, Jesus College Cambridge, British Feder-

ation of Women Graduates, University of Cambridge Board of

Graduate Studies, American Friends of Cambridge University and

the Anthony Wilkin Fund. Many thanks are offered to these in-

dividuals and institutions for their support. This paper benefitted

from the helpful comments of four anonymous reviewers.Remaining errors are the responsibility of the author.

References

Alegre, J.C., Felipe-Morales, C., La Torre, B., 1990. Soil erosion studies in Peru. J. SoilWater Conserv. MayJune, 417420.

Amos, B., Walters, D.T., 2006. Maize root biomass and net rhizodeposited carbon: ananalysis of the literature. Soil Sci. Soc. Am. J. 70, 14891503.

Atkinson, T., Smith, D., 1976. The erosion of limestone. In: Ford, T., Cullingford, C.(Eds.), The Science of Speleology. Academic Press, London, pp. 151177.

Aubert, G., 1983. Observacions sur les caracteristiques, la denominacion et la clas-sificacion des sols sales ou salsodiques. Pedologie 20 (1), 7378.

Bal, L., 1975a. Carbonate in soil: a theoretical consideration on and proposal for itsfabric analysis. 1. Crystic, calcic and fibrous plasma fabric. Nethe. J. Agric. Sci. 23,1835.

Bal, L., 1975b. Carbonate in Soil: a theoretical consideration on and proposal for itsfabric analysis. 2. Crystal tubes, intercalcary crystals, K fabric. Neth. J. Agric. Sci.23, 163176.

Becze-Deak, J., Langohr, R., Verrecchia, E.P., 1997. Small scale secondary CaCO3 ac-cumulations in selected sections of the European loess belt. Morphologicalforms and potential for paleoenvironmental reconstruction. Geoderma 76,221252.

Boggs Jr., S., 2001. Principles of Sedimentology and Stratigraphy, third ed. PrenticeHall, London.

Borges, K.C., 1988. Political Organization in the Upper Mantaro Valley During theMiddle Horizon. Masters of Arts thesis, Archaeology Program, UCLA.

Branch, N.P., Kemp, R.A., Silva, B., Meddens, F.M., Williams, A., Kendall, A., VivancoPomacanchari, C., 2007. Testing the sustainability and sensitivity to climaticchange of terrace agricultural systems in the Peruvian Andes: a pilot study. J.Archaeol. Sci. 34 (1), 19.

Brandolini, A., Landi, P., Monfredini, G., Tano, T., 2000. Variation among Andeanraces of maize for cold tolerance during heterotrophic and early autotrophicgrowth. Euphytica 111 (1), 3341.

Bullock, P., Federoff, N., Jongerius, A., Stoops, F., Tursina, T., Babel, U., 1985. Hand-book for Soil Thin Section Description. Waine Publications, Wolverhampton,England.

Burger, R., 1992. Chavn and the Origins of Andean Civilization. Thames & Hudson,New York.

Buytaert, W., Deckers, J., Dercon, G., de Bievre, B., Poesen, P., Govers, G., 2002. Im-pact of land use changes on the hydrological properties of volcanic ash soils inSouth Ecuador. Soil Use Manag. 18 (2), 94100.

Caravaca, F., Lax, A., Albaladejo, J., 1999. Organic matter, nutrient content and cationexchange in fine fractions from semiarid calcareous soils. Geoderma 93,161176.

Carroll, D., 1970. Rock Weathering. Plenum, London.Carter, S.P., Davidson, D.A., 1998. An evaluation of the contribution of soil micro-

morphology to the study of ancient arable agriculture. Geoarchaeology 13 (6),535547.

Courty, M.A., Goldberg, P., Macphail, R., 1989. Soils and Micromorphology in Ar-

chaeology. Cambridge University Press, New York.DAltroy, T.N., 2002. The Incas. Blackwell, Boston.DAltroy, T.N., 1992. Provincial Power in the Inka Empire. Smithsonian Institution,

Washington, D.C.Denevan, W.M., 2001. Cultivated Landscapes of Native Amazonia and the Andes.

Oxford University Press, New York.Dick, R.P., Sandor, J.A., Eash, N.S., 1994. Soil enzyme activities after 1500 years of

terrace agriculture in the Colca Valley, Peru. Agric. Ecosyst. Environ. 50,123131.

Donkin, R., 1970. Pre-Columbian field implements and their distribution in thehighlands of Middle and South America. Anthropos 65, 505529.

Douglas, L.A., Thompson, M.L. (Eds.), 1985. Soil Micromorphology and Soil Classi-fication. SSSA Special Publication, No. 15. SSSA, Madison, WI.

Earle, T., DAltroy, T., Hastorf, C., Scott, C., Costin, C., Russell, G., Sandefur, E., 1987.Archaeological field research in the Upper Mantaro Valley, Peru, 19821983:Investigations of Inka Expansion and Exchange. In: Institute of ArchaeologyMonograph, 28. UCLA, Los Angeles.

Eash, N.S., Sandor, J.A., 1995. Soil chronosequence and geomorphology in a semi-arid valley in the Andes of Southern Peru. Geoderma 65, 5979.

Elliott, E.T., 1996. Aggregate structure and carbon, nitrogen and phosphorus innative and cultivated soils. Soil Sci. Soc. Am. J. 50, 627633.

FAO, 1989. Sustainable Agricultural Production: Implications for International Ag-ricultural Research. FAO Research and Technology Paper 4. FAO, Rome.

FitzPatrick, E.A., 1993. Soil Microscopy and Micromorphology. Wiley, New York.French, C.A.I., Whitelaw, T.M., 1999. Soil erosion, agricultural terracing and site

formation processes at Markiani, Mamorgos, Greece: the micromorphologicalperspective. Geoarchaeology 14 (2), 151189.

Gee, G.W., Bauder, J.W., 1996. Particle size analysis. In: Methods of Soil Analysis Part3: Chemical Methods. SSSA Book Series, No. 3. Soil Science Society of America(SSSA), Madison, WI, pp. 383411.

Gile, L.H., Peterson, F.F., Grossman, R.B., 1966. Morphological and genetic sequenceof carbonate accumulation in desert soils. Soil Sci. 101, 347360.

Gile, L.H., Peterson, F.F., Grossman, R.B., 1965. The K horizon: a master soil horizonof carbonate accumulation. Soil Sci. 99, 7482.

Goodman-Elgar, M., 2007. Off-site archaeology: the study of agricultural fields. In:Pearsall, Deborah (Ed.), The Oxford Encyclopedia of Archaeology. Oxford Uni-versity Press, New York.

Goodman-Elgar, M., 2003. Anthropogenic Landscapes in the Andes: a Multidisci-plinary Approach to Pre-Columbian Agricultural Terraces and Their Sustainable



15/15

Use. Doctoral dissertation, Department of Archaeology, University ofCambridge.

Hansen, B.S., Seltzer, G., Wright Jr., H.E., 1994. Late Quaternary vegetational changein the central Peruvian Andes. Paleogeogr. Paleoclimatol. Paleoecol. 109,263285.

Harden, C.P., 1993. Land use, soil erosion, and reservoir sedimentation in an AndeanDrainage basin in Ecuador. Mt. Res. Dev. 13 (2), 177184.

Hastorf, C.A., 1993a. Agriculture and the Onset of Political Inequality Before the Inka.Cambridge University Press, New York.

Hastorf, C.A., 1993b. Pre-Hispanic political change and the role of maize in the

Central Andes of Peru. Am. Anthropol. 95 (1), 115138.Hastorf, C.A., 1990. The effect of the Inka State on Sausa agricultural production and

crop consumption. Am. Antiq. 55 (2), 262290.Hastorf, C.A., Earle, T., Wright Jr., H., Lecount, L., Russell, G., Sandefur, E., 1989.

Settlement archaeology in the Jauja Region of Peru: evidence from the EarlyIntermediate Period through the Late Intermediate Period: a report on the 1986Field Season. Andean Past 2, 81129.

Haynes, R.J., Swift, R.S., 1985. Effects of air drying on the adsorption and desorptionof phosphate and levels of extractable phosphate in a group of acid soils, NewZealand. Geoderma 35, 145157.

Herrick, J.E., 2000. Soil quality: an indicator of sustainable land management? Appl.Soil Ecol. 15, 7583.

Hochholdinger, F., Woll, K., Sauer, M., Dembinsky, D., 2004. Genetic dissection ofroot formation in maize (Zea mays) reveals root-type specific developmentalprogrammes. Ann. Bot. 93, 359368.

Huckleberry, G., Billman, B.R., 2003. Geoarchaeological insights gained from surfi-cial geologic mapping, middle Moche Valley, Peru. Geoarchaeology 18 (5),505521.

Jongerius, A., 1983. Micromorphology in agriculture. In: Bullock, P., Murphy, C.P.(Eds.), Soil Micromorphology. A B Academic Publishers, Berkharnsted, UK, pp.111138.

Kauffman, S., Ramos, M.V., 1998. A Farmer Assisted Soil Survey and Land Evaluationin the Peruvian Andes. A Case Study for the San Marcos (Cajamarca) and Quilcas(Huancayo) ILEIA Project Pilot Area. International Soil Reference and In-formation Centre (ISRIC), National Agricultural University (Peru), La Molina,Wageningen.

Keeley, H.C.M., 1985. Soils of prehispanic terrace systems in the Cusichaca Valley,Peru. In: Farrington, I.A. (Ed.), Prehistoric Intensive Agriculture in the Tropics.BAR International Series, 232 Oxbow, Oxford.

Landon, J., 1991. Booker Tropical Soil Manual: a Handbook for Soil Survey and Ag-ricultural Land Evaluation in the Tropics and Subtropics. Longman Scientific &Technical, New York.

Leoni, J.B., 2006. Ritual and Society in Early Intermediate Period Ayacucho: a Viewfrom the Site of Nawinpukyo. In: Isbell, W., Silverman, H. (Eds.), Andean Ar-chaeology III: North and South. Springer, New York, pp. 279306.

Lewis, H.A., 1998. The Characterisation and Interpretation of Ancient Tillage Prac-tices Through Soil Micromorphology: a Methodological Study. Doctoral dis-

sertation, Department of Archaeology, University of Cambridge.MacKeague, J.A., 1983. Clay skins and argillic horizons. In: Bullock, P., Murphy, C.P.(Eds.), Soil Micromorphology, Vol. 2. Soil Genesis. A B Academic Publishers,Berkhamstead, UK, pp. 367388.

Macphail, R.I., Courty, M.A., Gebhardt, A., 1990. Soil micromorphological evidence ofearly agriculture in north-west Europe. World Archaeol. 22 (1), 5369.

Mallon, F., 1983. The Defence of Community in Perus Central Highlands: PeasantStruggle and Capitalist Transition 18601940. Princeton University Press,Princeton, NJ.

Megard, F., 1987. Structure and evolution of the Peruvian Andes. In: Schaer, J.P.,Rodgers, J. (Eds.), The Anatomy of Mountain Ranges. Princeton University Press,Princeton, pp. 179210.

Megard, F., Caldas, Y., n.d.[1996]. Mapa Geologico del Cuadrangulo de la Oroya,Departimento de Junn [Peru]. Ministry of Energy and Mines, Institute of Ge-ology, Mines and Metallurgy, Lima.

Megard, F., Philip, H., 1976. Plio-Quaternary tectono-magmatic zonation and platetectonics in the Central Andes. Earth Planet. Sci. Lett. 33, 231238.

Ministry of Agriculture, Fisheries, and Food (MAFF)., 1986. The Analysis of Agri-cultural Materials: a Manual of Analytical Methods Used by the Agricultural

Development and Advisory Service, third ed. Her Majestys Stationery Office,London. Reference Book 427.

Morales, F.C., 1978.Efectos de diversos sistemas de cultivo con papa sobre el ren-dimiento, la fertilidad y erosion de suelo. Paper presented at the UNA-CIPConference, 1978.

National Research Council (NRC),1989. Lost Crops of the Incas: Little-known Plantsof the Andes with Promise for Worldwide Cultivation. National Academy Press,Washington, D.C.

Nettleton, W.D., Brasher, B.R., Baumer, O.W., Darmody, R.G., 1994. Silt flow in soils.In: Ringrose-Voase, A.J., Humpreys, G.S. (Eds.), Soil Micromorphology: Studiesin Management and Genesis. Proceedings of the IX International WorkingMeeting on Soil Micromorphology. Elsevier, New York, pp. 361371.

Nordt, L., Hayashida, F., Hallmark, T., Crawford, C., 2004. Late prehistoric soil fertilityand agricultural production in northwest coastal Peru. Geoarchaeology 19 (1),2146.

Paredes, J., 1970. [1994]. Mapa Geologico del Cuadrangulo de Jauja, Departimento deJunn [Peru]. Ministry of Energy and Mines, Instititue of Geology, Mines andMetallurgy. Lima.

Paredes, J., 1994. Geologa del cuadrangulo de Jauja. In: Sanchez, A., Lipa, V. (Eds.),Instituto Geologico Minero y Melaturgico del Peru, No. 48 Lima.

Park, S.J., 2006. Resilience, land use, and soil management. In: Lal, R. (Ed.), Ency-clopedia of Soil Science. CRC Press, Boca Raton, FL, pp. 14981503.

Pestalozzi, H., 2000. Sectoral fallow systems and management of soil fertility: therationality of indigenous knowledge in the high Andes of Bolivia. Mt. Res. Dev.20 (1), 6471.

Poma de Ayala, F.G., 1987 [15841615]. El primer Nueva Cronica y Buen Gobierno,vol a, b, c. In: Murra, J.V., Odono, R., Uroste, J. (Eds.), Cronicas de America, No. 29.Historia 16 Madrid.

Rick, J., 1988. The character and context of highland preceramic society. In:Keatinge, R. (Ed.), Peruvian Prehistory: an Overview of Pre-Inca and Inca soci-

ety. Cambridge University Press, New York, pp. 340.Russell, G., 1988. The Impact of Inca Policy on the Domestic Economy of the Wanka,

Peru: Stone Tool Production and Use. PhD dissertation, Department of An-thropology, UCLA.

Saleva, V., Lewis, A., Wells, L., Preston, H., 1954. The Agricultural and EconomicDevelopment of the Mantaro Region of Peru. International Development Ser-vices, New York.

Sandefur, E.C., 2001. Animal husbandry and meat consumption. In: DAltroy, T.,Hastorf, C.A. (Eds.), Empire and Domestic Economy. Plenum Press, New York,pp. 179202.

Sandor, J.A., 1992. Long-term effect of prehispanic agriculture on soils: examplesfrom New Mexico and Peru. In: Holliday, V.T. (Ed.), Soils in Archaeology:Landscape Evolution and Human Occupation. Smithsonian Institution Press,Washington, D.C., pp. 217245.

Sandor, J.A., Eash, N.S., 1995. Ancient agricultural soils in the Andes of southernPeru. Soil. Sci. Soc. Am. J. 59, 170179.

Sandor, J.A., Eash, N.S., 1991. Significance of ancient agricultural soils for long-termagronomic studies and sustainable agriculture research. Agronomy Journal 83,2937.

Sandor, J.A., Gersper, P.L., Hawley, J.W., 1990. Prehistoric agricultural terraces andsoils in the Mimbres area, New Mexico. World Archaeology 22 (1), 7086.

Sandor, J.A., Gersper, P.L., Hawley, J.W., 1986. Soils at Prehistoric agricultural ter-racing sites in New Mexico 1: organic matter and bulk density changes. Soil. Sci.Soc. Am. J. 50, 173177.

Sarmiento, L., 2000. Water balance and soil loss under long fallow agriculture in theVenezuelan Andes. Mt. Res. Dev. 20 (3), 246253.

Schjellerup, I., 1986. Ploughing in Chuquibamba, Peru. Tools Tillage 3, 180189.Scoffin, T.P., 1987. An Introduction to Carbonate Sediments and Rocks. Blackie,

London.Schwerdtfeger, W., 1976a. Introduction. In: Schwerdtfeger, W. (Ed.), Climates of

Central and South America. Elsevier, Amsterdam, pp. 112.Schwerdtfeger, W., 1976b. Appendix II high thunderstorm frequency over the

subtropical Andes during the summer; cause and effects. In: Schwerdtfeger, W.(Ed.), Climates of Central and So uth America. Elsevier, Amsterdam, pp. 192195.

Seltzer, G.O., 1991. Glacial History and Climate Change in the PeruvianBolivianAndes. PhD dissertation, University of Minnesota, Minneapolis.

Seltzer, G.O., Hastorf, C.A., 1990. Climatic change and its effects on prehispanic

agriculture in the Central Peruvian Andes. J. Field Archaeol. 17, 397414.Seybold, C.A., Herrick, J.E., Brejda, J.J., 1999. Soil resilience: a fundamental compo-nent of soil quality. Soil Science 164 (4), 224234.

Silva, Y., Takahashi, K., Chavez, R., 2007. Dry and wet rainy seasons in the Mantaroriver basin (Central Peruvian Andes). Adv. Geosci. 14, 14.

Six, J., Paustian, K., Elliott, E.T., Combrink, C., 2000. Soil structure and organicmatter: I: distribution of aggregate-size classes and aggregate-associated car-bon. Soil. Sci. Soc. Am. J. 64, 681688.

Soon, Y.K. (Ed.), 1985. Soil Nutrient Availability. Van Norstrand Reinhold Soil ScienceSeries, Wokingham, UK.

Soil Science Society of America, 1996. Methods of soil analysis, part 3: chemicalmethods. In: SSSA Book Series, No. 3. SSSA, Madison, WI.

Sullivan III., A.P., 2000. Effects of small-scale prehistoric runoff agriculture in soilfertility: the developing picture from upland terraces in the Southwest. Geo-archaeology 15 (4) 291313.

Thompson, L.G., Mosley-Thompson, E., Henderson, K.A., 2000. Ice core paleoclimaterecords in tropical South America since the Last Glacial Maximum. J. Quat. Sci.15 (4), 377394.

Treacy, J., 1994. Teaching water: hydraulic management and terracing in Coporaque,

the Colca Valley, Peru. In: Mitchell, W., Guillet, E. (Eds.), Irrigation at High Al-titudes: the Social Organization of Water Control Systems in the Andes. Societyfor Latin American Anthropology Publication Series, vol. 12, pp. 99114.

Vuille, M., Bradley, R., Keimig, F., 2000. Interannual climate variability in the CentralAndes and its relation to tropical pacific and Atlantic forcing. J. Geophys. Res.105 (D10), 1244712460.

van Wambeke, A., 1974. Management properties of ferralsols. Soils Bull. 23 FAO,Rome.

Whitehead, W., 1999. Radiocarbon dating. In: Hastorf, C. (Ed.), Early Settlement atChiripa Bolivia. Archaeological Research Facility Contribution, No. 57, pp. 1722.Berkeley.

Wild, A., 1993. Soils and the Environment. Cambridge University Press, New York.Williams, P.R., 2002. A re-examination of disaster-induced collapse in the case of

the Andean highland states: Wari and Tiwanaku. World Archaeol. 33, 361374.Wilson, C., Simpson, I.A., Currie, E.A., 2002. Micromorphological evidence from

Hacienda Zuleta, Ecuador. Geoarchaeology 17, 261283.Wright Jr., H.E., Seltzer, G.O., Hansen, B.C.S., 1989. Glacial and climatic history of the

Central Peruvian Andes. Natl. Geogr. Res. 5 (4), 439445.Zimmerer, K., 1999. Overlapping patchworks of mountain agriculture in Peru and

Bolivia: Toward a regional-global landscape model. Hum. Ecol. 27 (1), 135165.


Goodman-Elgar 2008a Terraces

Documents

Transcript of Goodman-Elgar 2008a Terraces