Guide to the Soils of Kaihiku-Hokonui Land Region

Manaaki Whenua Landcare R esearch NZ PRESS 1111 11 111 111 11 111 11 111 11 111 11 111 11 111 1111 111111 1111111 111 111 L000004842 NDCARE RESEARCH ~CIENCE SERIES NO. 4 Guide to the Soils of Kaihiku-Hokonui Land Region Peter D. Mcintosh Manaaki Whenua - Landcare Research Private Bag 7930, Dunedin Landcare Research Science Series No. 4 Manaaki Whenua P R E S S Lincoln, Canterbury, New Zealand 1994 © Landcare Research New Zealand Ltd 1994 No part of this work covered by copyright may be reproduced or copied in any form or by any means (graphic, electronic or mechanical, including photocopying, recording, taping, information retrieval systems, or otherwise) without the written permission of the publisher. CATALOGUING IN PUBLICATION MCINTOSH, P.O. (Peter Douglas), 1950- Guide to the soils of Kaihiku-Hokonui Land Region I Peter D. Mcintosh. - Lincoln, Canterbury, N.Z. : Manaaki Whenua Press, 1994. (Landcare Research science series, ISSN 11 72-269X ; 4) ISBN 0-478-04530-1. I. Title. II. Series. UDC 631.44(931.334.7 + 931.353.3) Cover: A typical landscape in the Hokonui land system: the central valley of the Hokonui Hills is dominated by Kaiwera soils, formed in tuffaceous sandstone and mudstone, on both the hilly land and rolling land. The deep, moisture-retentive soils are well suited to forestry plantations. Similar soils occur over large parts of the Kahiku-Hokonui Land Region described in this report. Photograph by Peter Mcintosh. Desktop publishing by John McNeil, Page Plus Ltd, PO Box 28-058, Christchurch 2. Printed by Toltec Print, 373 Wilsons Road, Christchurch. Printed on Ambassador Gloss recycled paper. Published by Manaaki Whenua Press, Landcare Research, PO Box 40, Lincoln 8152, New Zealand 3 Contents Summary 5 1. Introduction 6 1.1 Purpose 7 1.2 Area, physiography, geology and parent rocks 7 1.3 Climate 8 1.4 Vegetation 9 2. The land region and its soils 10 2.1 Definition 10 2.2 Previous research 10 2.3 Soil parent material 11 2.4 Soils 15 3. Land systems 20 3.1 Soil-landscape models 20 3.2 The Kaiwera land system 22 3.3 The Hokonui land system 25 3.4 The Owaka land system 27 3.5 The Pukepahi land system 29 3.6 The Tautuku land system 31 4. Soils and land use 33 4.1 Pastoral farming and element deficiencies 33 4.2 Horticulture 35 4.3 Forestry 38 Acknowledgements 41 References 42 Appendix 1: Brief soil profile descriptions 46 Appendix 2: Glossary 57 SUMMARY 5 Summary The Kaihiku-Hokonui land region covers about 410 OOO hectares of land underlain by predominantly tuffaceous sandstone and mudstone rocks in central and eastern Southland and south Otago, New Zealand. Previous studies have established the parent material and soil variation within the region. This report collates this research, updates the soil classification, provides keys and models for the soil distribution pattern, extrapolates the information of detailed surveys to the wider area and assesses advantages and disadvantages of land for pastoral, horticultural and forestry use. The land region is divided into the Kaiwera, Hokonui, Owaka, Pukepahi and Tautuku land systems. Within each land system there is a complex interaction of rainfall, altitude, parent material, degree of weathering and aspect. Pictorial models of soil distribution in the landscape help explain the soil pattern. Soils in the region have previously been mapped in twenty soil sets. The Kaiwera, Kaiwera hill, Kaihiku hill and Waimahaka hill sets were the most extensive. More recent detailed mapping has resulted in the identification of new soil units, most of which are classified as Brown Soils in the New Zealand Soil Classification. Allophanic Soils, Melanie Soils, Gley Soils, Recent Soils and Podzols also occur. Keys based on pedological, chemical and slope criteria enable soils to be identified. Phosphorus and sulphur deficiencies are the major nutrient limitations for improved pastures. However, sulphur may be adequate in soils near the coast. Deficiencies of cobalt and copper affect stock health, and are most severe on strongly leached upland soils. Otaraia, Owaka, Titiroa and Tuturau soils, formed in loess, are suitable for horticulture. Cool temperatures limit the range of crops that can be grown but arable crops such as vegetables are possibilities. Titiroa soils contain the least clay and most sand and after drainage are highly suitable for cultivation. A four-class system for rating soils for forestry suitability is presented. Most soils are suitable for forestry, being deep and well drained and on rolling or hilly land. Only a few soils on uplands are classed as marginally suitable or unsuitable for forestry because of steep slopes, or sites that are too exposed or too cold, or soils that are peaty or fragmental. °' ti :::~ t\to,,trf.f '9.<Jt\fG'(3' Rainfall isohyets (mm) §> ~ ~· ~ 25 km I!lll: I I I Point Kaihiku-Hokonui Land Region I I J) Service (1973). Fig. 1 The Kaihiku-Hokonui land region (shaded): location map and rainfall isohyets, from rainfall map based on data in N.Z. Meterological INTRODUCTION 7 1. Introduction 1.1 Purpose TIUs guide to the soils of the Kaihiku-Hokonui land region collates and summarises the soil information available for the region, and indicates the main limitations and potential of the region for pastoral, horticultural and forestry land uses. Many of the subjects covered in the guide (e.g. parent material origins and cause and extent of trace element deficiencies) have been dealt with in detail elsewhere. Tills guide presents the main findings of these investigations, with references to the original research, so that readers can follow up any subjects of special interest. One of the aims of the guide is to enable land users to extrapolate information from detailed surveys to the wider area. A glossary is included (p. 53) to explain technical terms. 1.2 Area, physiography, geology and parent rocks Soils developed mainly in tuffaceous (andesitic) sandstone and mudstone in the Kaihiku Hokonui land region cover approximately 410 OOO hectares of the southeast part of the South Island New Zealand (N.Z. Soil Bureau 1968) (Figs 1 and 2). The sandstone and mudstone originated as sandy and muddy sediments on the sea floor in the Triassic and Jurassic periods, 135 to 230 million years ago. While these sediments were accumulating volcanoes were active so that the sediments incorporated volcanic (tuffaceous) material. (Stevens (1980) gives a reconstruction of Triassic and Jurassic geography). The sediments later became hardened and were folded to form the Southland syncline which has its axis running through the region in a WNW-ESE direction (Wood 1956, 1966; McKellar 1966, 1969; McKellar and Speden 1978). Fig. 2 A typical landscape in the Kaihiku-Hokonui land region. Long ridges form where the underlying strata is resistant tuffaceous sandstone, while the valleys are underlain by less resistant tuffaceous mudstone. Loess, derived mainly from outside the region, mantles lower altitude undulating and rolling slopes. 8 INTRODUCTION The rocks have subsequently been uplifted and eroded. The tuffaceous sandstone rocks have resisted erosion, so that the landscape in the region is dominated by ridges of tuffaceous sandstone separated by valleys underlain by less resistant, tuffaceous mud stone. Altitudes range from sea level to 720 m on Mt Pye (3 km north of Ajax Hill (Fig. 1)), but most areas are below 600 m altitude and occur on slopes that mostly vary between rolling (8-15°) and hilly (16-25°). The tuffaceous sandstone and mudstone parent rocks contain more iron, manganese, titanium, potassium, aluminium and magnesium than the schist and greywacke typically occurring on much of the South Island hill country (Table 1), because of the andesitic ash component of the parent rocks. Although most soils are formed in parent material derived from tuffaceous sandstone and mudstone rocks, some soils of the region are formed partly in loess derived from schist and greywacke rocks occurring outside the region. Table 1. Analysis of three soil materials occurring in South Island hill country. Analyses are of deepest horizons of soils developed on these parent materials. Element Greywacke Schist Tuffaceous sandstone (%) colluvium1 colluvium2 and mudstone colluvium3 Fe 3.2 3.9 5.5 Mn 0.06 0.09 0.14 Ti 0.42 0.52 0.60 Ca 2.04 2.43 0.92 K 1.70 1.35 2.34 p 0.04 0.07 0.05 Si 32.1 29.1 26.6 Al 7.4 8.78 10.1 Mg 0.83 0.96 1.38 Na 2.09 2.34 1.84 1Profile SB10074, Benmore Range 2Profile SB09912, Hector Mountains 3Profile SB09867, Kaiwera (SB numbers refer to laboratory samples held by Landcare Research). 1.3 Climate Mean annual rainfall ranges from 800 to 1600 mm (N.Z. Meteorological Service 1973), the wetter areas being at higher altitude and near the south coast (Fig. 1). Mean annual air temperature is 9.7°C at Gore at 123 m altitude and is estimated to fall below 8°C at 560 m altitude. Most soils have a mesic soil temperature regime (mean annual soil temperature 8°C or higher) but a cryic temperature regime (mean annual soil temperature less than 8°C) may occur at altitudes above 600 m on sunny aspects and above 170 m on shady slopes (Mcintosh 1988). Further details of climate in the Kaiwera district east of Gore are given by Mcintosh (1992a). INTRODUCTION 9 1.4 Vegetation Vegetation before the arrival of humans was probably largely broadleaf-podocarp forest over all areas except for exposed and/ or poorly drained uplands such as Ajax Hill (27 km west of Owaka), and for large areas of beech forest in the east, shown by Allen (1985).

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