by Dr. Christopher Ballard
The complexity of the networks of natural drainage in the Tari region, which may account in part for the subterranean form of Huli sacred geography, reflects the local predominance of Miocene limestones and siltstones of the Nipa group (Davies and Eno 1980). Though limestone forms much of the surficial geology of the northern region around Dalipugua, Mogoropugua and Lebani, Pleistocene volcanic activity from five local, but now dormant, volcanic centres- Ambua, Gereba, Ne, Haliago and Yumu (Loffler et al. 1980)- has infilled this earlier landscape in the eastern basins of Tari and Haeapugua (Figure B3). Further deposits of wind-borne tephra, presumed to derive from the volcanic centre of Mt Hagen, constitute the more recent major volcanic layers (Pain and Blong 1976). The extensive cover provided by the most recent major deposit, presumed to be Tomba tephra from Mt Hagen, has produced a largely uniform parent material for the Tari region soils. Basin floors throughout the region are dominated by Quaternary alluvials, with the notable exception of a distinctive set of fans flowing off the western slopes of Ambua and extending over much of the southeastern portion of the Tari basin to. 1
In his major study of the soils of the Tari area, Wood (1984) describes the five major local soil types as alluvial, colluvial, rendzina, peaty and tephra or volcanic ash soils. 2
Figure B4 shows the distribution of these different soils over the Tari and Haeapugua basins. The most productive soils from an agronomic perspective are the colluvial and alluvial deposits restricted to river and wetland margins on the basin floors (B4.5). The colluvial soils of the southern Tari basin have developed on the mudflow deposits from Mt Ambua. The shallow rendzina soils on the limestone ridges and outcrops of the region are the least productive and, restricted to the steeper slopes where they are easily eroded, the least exploited of the Tari soils. Peaty soils are found in the swamps and are characterised by a high acidity, which is inimical to most crops, balanced to some extent by high phosphorus values and almost 20% organic content.
Topsoils developed on the volcanic ashes, characterised by Wood (1987) as humic brown soils, cover over 70% of the Tari and Haeapugua basins. Humic brown soils are notable both for their high levels of organic carbon and nitrogen and for the speed with which they degrade, rendering them unsuitable for intensive exploitation over extended periods. Most of the soils of the Tari region are developed on Tomba tephra, which covers much of the region to a depth of 2 m. Tomba tephra, dated at greater than 50 000 BP, is the uppermost of a complex series of tephras, the three upper units deriving from the volcanic centre of Mt Hagen and the basal units presumed to derive from a closer source, probably Ambua.
Overlying Tomba are at least two thin Holocene tephras: Tibito, dated to 305- 270 cal BP, and Olgaboli, dated to 1190- 970 cal BP (see Appendix A3). The distribution of these last two tephras is extremely patchy, reflecting an original estimated airfall thickness of only 1.5 em for Tibito for the Tari region (Blong 1982: Fig.29); Olgaboli has not yet been identified in the field at Tari and its presence there is only inferred by Haberle (1993:184) on the basis of a second peak of ferrimagnetic minerals lying just beneath Tibito in cores from Haeapugua. Tibito has been identified from several locations in the Tari region, where it is typically found as a discontinuous band of balled and partly cemented olive grey sand (Chapter C3). Huli appear to distinguish soils on the basis of a wide range of criteria, including colour, texture, inclusions, water content, perceived productivity and even location. Though, as elsewhere in the Highlands region (Brookfield and Brown 1963:35, Landsberg and Gillieson 1980, Sillitoe 1991), colour is the most frequent referent, Huli soil classification employs a very shallow taxonomic hierarchy, with higher-order distinctions made only between sand (mu), soil (dindi), clay (ibi dindi) and stone (tQlg.). Certainly there is no overriding consensus on soil terms; the list of Huli soil terms given in Table B3 has been compiled over time with different people, few if any of whom would agree on all of the descriptions. Instead, descriptions of soils are contingent upon the particular task at hand: principal amongst these, particularly when the question is posed standing in a garden, is the suitability of a soil for crops.
Garden site selection is based upon an appreciation of soil and vegetation qualities in combination, but certain soils are identified as uniformly favourable or unfavourable for specific crops. Dindi mindi, a rich dark brown to black humic topsoil, and dindi kabi, a yellowish brown alluvial clay, are universally preferred for sweet potato and mixed gardens. However, dindi dongoma, a hard white calcareous clay found beneath dindi mindi along the margins of Haeapugua swamp and said to be a poor soil for sweet potato, is particularly favoured for taro. Men with gardens at Haeapugua will often excavate garden ditches to a depth sufficient to enable them to heap the basal dongoma up onto the perimeter walls, which are then planted with taro. The production of ndodobai, a sticky grey clay formed by mixing dongoma and mindi topsoil, is also a technique commonly employed at Haeapugua to boost topsoil depth and reduce the acidity of the peaty topsoil.
The terms for certain soils, however, reflect ritual significance alone (see Ollier et al. 1971:40); typically, these are distinctively coloured clays. Although the favoured red, yellow, blue and white clays are quite widely available, only those clays from specific sources with intrinsic ritual significance are individually named and were formerly employed in ritual. Hence the term ambua gaga, given to a bright yellow ritual clay, refers to its source on the lower slopes of Mt Ambua. 3
Although there are no terms or phrases in the Huli language that identify soil profiles or sequences, there is a keen sense of stratigraphic position and an appreciation of the processes of soil-loss. 4 Pedogenesis is usually expressed through reference to fluvial deposition. As one person observed to me, swamp peats, once drained, dry to become firm ground (dindi kui); but floods then strip the dindi kui from the surface, exposing clay (ibi dindi) beneath. Many older Huli can identify Tibito tephra, which they refer to as mbi mu (“darkness-sand”); as Huli myths state that this sand fell from the sky (as da pindu: “sky-stuff”) and covered the surface of the land, some people have observed to me that the overlying sediments must have been washed down over the tephras.
No discussion of soils with Huli people is complete without a brief lament for the decline in the earth’s fertility, often depicted in terms of declining crop yields, the vertical or lateral movement of soil types or physical changes in soil quality. The general concept of ibane, or grease, finds its complement in soils as dindi ibane, soil grease. 5
Over time, and not solely as the result of use so much as an integral characteristic of the earth as a whole, this grease is dissipated, leaving dindi gabu (literally “dry” or “barren” ground), greaseless soil in its place. Composting of garden mounds is a recognised means of restoring dindi ibane, but is seen as a stopgap measure in a process of environmental degradation that is largely beyond the control of humans (B2.6).
See Section B5.4 for a further discussion of fertility. Huli attitudes to soil in many respects resemble those of the neighbouring Wola for whom Sillitoe (1991) describes the comparable notion of iyba or grease as it is applied to soil; apparent lexical correspondences between Huli (H) and Wola/W est Mendi (W) are suggested for at least the following soil terms: kolbatindiy (W): goloba dindi (H), tongom (W): dongoma (H) and iyb muw (W): iba mu (H).
The physical evidence of land degradation is also attested by forced changes in crop composition in gardens as the crops less tolerant of poor soils fail to yield, and by the encroaching advance of poorer soils over areas once covered with rich soil. In the following passage, a man with gardens at Haeapugua comments on the loss of topsoil (dindi mindi) and the apparent rise of basal white clays (dongoma): We used not to see dongoma. Now that it has come up the land has gone bad. Before this land was good, but soon it will all be dongoma. Dongoma lies at the base, then soft clay [ibi dindi], and on the top is topsoil [dindi mindi]. When the ground dries, the top two soils turn to dust and blow away and then dongoma comes up to the top. If the surface soil is hard, you know that dongoma is close to the surface. If it is soft, dongoma is still down some way. When dongoma is everywhere, this land will be finished and everyone will die. Kamiali 26.8.91, 91/18B:502-535
Another Haeapugua landowner expresses the belief, encoded in a short pureromo adage, that the progress of gravel and firmer, drier soil conditions across the swamp forebodes the end of the earth:
Before this gravel [gi mu] was above Mindira Togo [a bridge across the Tereba river in Haeapugua]. When the Tereba river carries the gravel down as far as [the junction with] the Tagali river, the ground will dry up completely and the world will end. Mbugua 29.7.91, Fieldnotes.
An extract from The Death of a Great Land: Ritual, History and Subsistence Revolution in the Southern Highlands of Papua New Guinea; Australian National University, Cranberra, 1995). pp. 39-42.
(Photo courtesy of Dr. Michael Main)
- The most recent of these fan deposits, the Alua mudflow, is discussed in further detail in Section B5.3.
- Wood limited his field study to an area bounded to the north and west by the Tagali river (Figure B2), consisting of the Tari basin, the Paijaka plateau and the eastern half of the Haeapugua basin; this limited area is referred to here as “the Tari area” to distinguish it from the wider “Tari region” and the more specific “Tari basin”.
- Huli use of the term ambuabi to denote the colour yellow generally implies a considerable antiquity for Huli occupation of the area, sufficient at least to permit lexical association between basic colour terms and prominent landmarks.
- This absence of terms for soil sequences appears to be common amongst other Highlands languages (Brookfield and Brown 1963:35, Oilier et al. 1971:34, Sillitoe 1991:154).
- See Section B5.4 for a further discussion of fertility. Huli attitudes to soil in many respects resemble those of the neighbouring Wola for whom Sillitoe (1991) describes the comparable notion of iyba or grease as it is applied to soil; apparent lexical correspondences between Huli (H) and Wola/W est Mendi (W) are suggested for at least the following soil terms: kolbatindiy (W): goloba dindi (H), tongom (W): dongoma (H) and iyb muw (W): iba mu (H).