Soils of Waiwhakareke

All soils found at Waiwhakareke Natural Heritage Park are typical of those found in the Hamilton Basin. The parent materials (what soils form from) found at Waiwhakareke consists of organic material (peat), tephra, alluvium and colluvium deposits.

Peat
Peat is an accumulation of partially decomposed plant material where stagnant or slow flowing water has replaced air causing slow decomposition rates. Peat can contain small amounts of alluvium or tephra deposits but must be over 50% peat to be an organic soil.

Tephra
Tephra deposits are from air-fall volcanic material from past eruptions in the North Island. Volcanic ash is tephra which consisted of particles <2mm diameter. Between 380,000 to 100,000 years ago a series of volcanic eruptions possibly from the Taupo Volcanic Zone laid down thick layers of tephra. This tephra deposit is known as Hamilton Ash and is the dominant parent material between Hamilton and the Bombay Hills.

Alluvium
Alluvium is the term for sediment that has been transported by rivers or other running water to the area. The sediment can be made up of tephra, sand, silts and clays. The alluvium of the Hamilton Basin was transported by the ancestral Waikato River system over 10,000 years ago. At this time the river brought down volcanic material from the Taupo region. This alluvium deposit is known as the Hinuera Formation.

Colluvium
Colluvium is the term for sediment transported by gravity. These often are deposits that build up at the foot of steeper slopes. Deposits can develop from avalanches, mudslides, landslides or other types of erosion.

Soils on the plain

Kaipaki Peat (organic soil)
Moderately decomposed black peat (1m+ in depth) atop alluvium. This soil type is generally found in shallow areas of ancient lakes, which gave rise to peat bogs. The soil is poorly drained with low soil fertility and a pH of 4.5 or higher.

Te Rapa Peaty Sand (gley soil)
Dark grey peat (<40cm in depth) atop alluvium of mainly pumice sands and silts. This soil is found usually surrounding large bogs in the Hamilton Basin. The soil formed under waterlogged or saturated conditions and is poorly drained with low soil fertility.

Horotiu Sandy Loam (allophanic soil)
Course alluvium of the Hinuera Formation found on undulating land. The top soil is brown with the subsoil having a yellow- brown colour. The soil is well drained, very friable with medium soil fertility.

Soils of low rolling hills

Hamilton Clay Loam (granular soil)
Found on strongly weathered, reddish-brown clayey tephra of Hamilton Ash. This is a common soils type of hills in and on the outskirts of Hamilton. The soil is well drained with medium soil fertility.

Rotokauri Clay Loam (gley soil)
Created from colluvium deposits of Hamilton Ash from the low rolling hills. This gentle sloping soil is found on foot slopes in the Hamilton area. The grey subsoil is caused by waterlogged or saturated conditions, indicating it is imperfectly to poorly drained with low soil fertility.

Kainui Clay Loam (brown soil)
Found in small patches within the Hamilton clay loam on young tephra deposits atop Hamilton Ash. This reddish brown soil has a silty top soil and is moderately well drained. Found on easy rolling slopes of low rolling hills.

References and further information

Bruce, J. G. 1979; Soils of Hamilton City, North Island, New Zealand. New Zealand Soil Survey Report 31.

Hewitt, A. E. 1998; New Zealand soil classification, second edition. Landcare Research Science Series No 1. Lincoln. 133p

McCraw, J. D. 1967; The surface features and soil pattern of the Hamilton Basin. Earth Science Journal 1: 59-74

McCraw, J. D. 2002; Physical Environment. Pp. 13-22 in Clarkson, B. D.; Merrett, M.; Downs, T. 2002; Botany of the Waikato, Waikato Botanical Society, Hamilton.

McLaren, R. G. and Cameron, K. C. 1990; Soil science: an introduction to the properties and management of New Zealand soils. Oxford University Press, Auckland. 294p.

Milne, J. D. G., Clayden, B., Singleton, P. L. and Wilson, A. D. 1991; Soil description handbook. DSIR Land Resources. 133p. ISBN 0477026168

Molloy, L. F. 1988; Soils in the New Zealand Landscape. New Zealand Society of Soil Science, Lincoln.

Selby, M. J.; Lowe, D. J. 1992; The Middle Waikato Bain and hills. Pp. 233-255 in: Soons, J. M.; Selby, M. J. (eds) Landforms of New Zealand, second edition. Longman Paul, Auckland. ISBN 0-58285929-8

Singleton, P. L. 1991; Soils of Ruakura- a window on the Waikato. DSIR Land Resources Scientific Report 5. 127p. ISBN0-477-02620-6