Queensland Government Technical Report

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© State of Queensland 1984

For information about this report contact [email protected] Queensland Department of Primary Industries Bulletin QB84006

SOILS OF THE KAIRI RESEARCH STATION, ATHERTON TABLELAND, NORTH QUEENSLAND

L.A. Warrell W.P. Thompson (Agricultural Chemistry Branch) M.G. Cannon (Division of Soils, CSIRO)

Queensland Department of Primary Industries Brisbane 1984 ISSN 0155-221X Agdex 524 ACB/9

Queensland Department of Primary Industries GPO 8ox 4 6 Brisbane. 4001. CONTENTS

Page

1. INTRODUCTION 1

2. HISTORY 1

3. METHODS 2

4. PHYSICAL ENVIRONMENT 2

4.1 Climate 2 4.1.1 General 2 4.1.2 Climate in Relation to Soils 2

4.2 Geology and Geomorphology 4 4.2.1 General 4 4.2.2 Geology in Relation to Soils 5

5. SOILS - MORPHOLOGY AND CLASSIFICATION 6

5.1 Soil Profile Class and Mapping Unit Definitions 6

5.2 Soil Profile Classes 6 5.2.1 Soils Derived from Barren River Metamorphics 8 5.2.2 Soils Derived from Atherton Basalt 8

5.3 Classification of the Soils 9 5.3.1 Relationship Between Great Soul Group and 9 Local Terminology 5.3.2 Classification of Krasnozems and Euchrozems 9 5.3.3 Great Soil Groups 10 5.3.4 Soil Taxonomy 11 5.4 Detailed Soil Profile Class Descriptions 12

5.5 Mapping Units 17

6. SOILS - CHEMICAL AND PHYSICAL ATTRIBUTES 17

6.1 Introduction 17

6.2 Soil Chemistry and Fertility 18 6.2.1 Electrical Conductivity (EC) and Chloride 18 6.2.2 pH 18 6.2.3 Exchangeable Cations 19 Page

6.2.4 Extractable Potassium 21 6.2.5 Exchangeable Sodium 22 6.2.6 Exchangeable Acidity and Exchangeable Aluminium 22 6.2.7 Cation Exchange Capacity (CEO 22 6.2.8 Base Saturation 27 6.2.9 Organic Carbon and Nitrogen 28 6.2.10 Phosphorus 28 6.2.11 Trace Elements 30

6.2 Physical Attributes 30 6.3.1 Particle Size Distribution 30 6.3.2 CEC/Clay Ratio 31

7. ACKNOWLEDGEMENTS 32

8. REFERENCES 32

APPENDIX 1 : Morphological and Analytical Data for 35 Representative Profiles

APPENDIX 2 : Selected analyses for soil profile classes 40 1. INTRODUCTION

Kairi Research Station services the Atherton Tableland dairying and crop industries. Total area of the research station is 243 hectares lying along the western edge of Tinaroo Dam.

The Atherton and associated Evelyn Tablelands have never been soil surveyed at scales that are of relevance to the intense land use of the area.

Detailed soils data were required to meet the immediate needs of research on the station itself and associated extension. This survey is aimed at meeting these needs but will also act as a suitable reference area for any future regional surveys.

The major research and extension requirements are:

comprehensive description and classification of soils, soils map at a scale suitable, for planning trials, and chemical and physical characterization of the soils.

2. HISTORY

The Kairi Research Station began as a State Farm in 1910. It was partly cleared of the original rainforest (known locally as "scrub") in that year. It continued as a State Farm until 1929, when it was closed, except for the piggery, which continued for a few years longer.

Commercial interests operated the farm from 1929 to 1944, when it was taken over by the Australian Military Forces for vegetable and egg production for the forces. Irrigation from a well was used in the vegetable production.

On the 6th July 1946 it was reopened by the Department as a Regional Experiment Station. Its primary purpose was to find a practical, economic solution to the declining productivity of the soils of the Atherton Tableland. Because of the growth of the station to meet the various agricultural needs of the district, it was raised to Research Station status in March 1962.

Lhtil the filling of the Tinaroo Falls Dam in the late fifties, a large area of rainforest along the left bank of the Barron River was included in the station reserve. In 1963 Tinaroo Falls Dam reached its fully supply level for the first time and only approximately two hectares of the original rainforest was left.

Extra area was added to the station from portions of resumed farms not inundated by the waters of Tinaroo Falls Dam, by inclusion of land from the closed railway from Tolga to Malanda and by purchase of land from adjacent farmers. The last purchase was made in November 1975.

The names of the previous owners have been preserved in the names given to some of the soil profile classes e.g. McDonald, Pope, Drysdale and Godfrey. - 2 -

3. METHODS

3.1 Field Methods

Detailed descriptions were taken at 89 sites at 100 m intervals along selected traverses. Descriptions were to 1.5 m and surface (0 - 0.1 m) samples were taken for fertility analyses.

The site descriptions were grouped into soil profile classes which formed the basis of the mapping units.

Mapping was done with a further 145 sites hand augered to 0.9 m and allocated to soil profile class and mapping units. At each of these sites bulked surface samples were taken for analyses. These sites were located on a 100 m grid in most areas and on a 150 m grid in others. The average sampling density is 1 site per 1.2 hectares.

Mapping unit boundaries were defined by interlining between grid points and limited air photo interpretation.

Eight representative profiles were then sampled for detailed chemical and physical analyses. Bulked surface samples were also taken at these sites.

4. PHYSICAL ENVIRONMENT

4.1 Climate

4.1.1 General

The climate of the Kairi area shows a marked seasonal pattern of both rainfall and temperature. (Figure 1). The months December to March account for almost 747o of the total annual rainfall of 1 248 mm. This coincides with the highest temperatures and highest pan evaporation. In essence the district has warm subhnmid summers and relatively dry, significantly colder winters.

The winter rainfall component is relatively small, hence both pasture and crop production are limited by moisture stress over this period.

4.1.2 Climate in Relation to Soils

The soils of the Kairi area are characterized by deeply weathered low activity clays. Such features are the product of extensive periods of high rainfall and high temperatures during the Tertiary.

The present climate bears little, if any, relationship to the conditions under which such weathering occurred as it is considerably colder and drier than the Tertiary. - 3 -

300

250 -

§ 200 -

_j < 150 -

<100-

50 -

0 M A M J J 0 N D MONTH

30 -

25 -

o LU 20 CC D ^ 15 (Z LLJ Q. 10

5 -

M A M J J N D MONTH

MEAN SOIL TEMPERATURE AT 0.2m MAX. AIR TEMPERATURE

MIN. AIR TEMPERATURE

Figure 1 Meteorological data for Kairi Research Station, 1955-1978

The work of Kershaw (1970, 1971, 1974 and 1975) is of particular relevance to the survey area. Kershaw's climatic vegetation relationship for the late Pleistocene and Holocene on the Atherton Tableland have been summarized by Bowler et at. (1976). While much of the discussion of Kershaw and Bowler et al. is peripheral to pedogenesis, it is relevant that both precipitation and temperature regimes in the survey area have changed markedly not only from the Tertiary to Quaternary, but also during the late Quaternary. Figure 2 suggests that a six fold change in precipitation has occurred in the last 15 000 years. - 4 -

Precipitation as % of Present 0 25 50 75 100 125 150 175 200

5 - tin g

T3 O 10-

15 -

20- Indicates direction esen t Q. of change only.

or e 25 - CD .Q

CO 30- O

X 35- \

Yea r 40

Figure 2 Changes in precipitation at Lynch's Crater, Atherton. Data are derived from pollen analysis according to A.P. Kershaw and quoted in Bowler et. al. (1976).

While classification systems like the great soil groups (Stace &t al. 1968) and principal profile forms (Northcote 1979), have no direct, or at best have indirect, implied pedogenetic connotations, Soil Taxonomy (Soil Survey Staff 1975) has climatic parameters as a major component of its hierarchical system. Within this survey area, while present temperature and rainfall regimes may well be of land use significance (and hence are arguably valid classification tools) they are unlikely to have major pedogenetic connotations.

Soil Taxonomy classification based on present data for' the Kairi soils is given in Appendix 1 and Table 2.

4 .2 Geology and Geomorphology

4.2.1 General

The survey area occurs on part of the Atherton Tableland. The formation and geological history of this tableland is well described by De Keyser (1972). Two major geological formations are present on the station. - 5 -

Metamorphics

The Barron River metamorphics include phyllite, slate, schist, greywacke, etc. These were laid down in the mid Palaeozoic and uplifted during Permo-Carboniferous times. Following a period of dissection during the Tertiary the Atherton basalts were extruded.

Basalts

The Atherton olivine basalts were extruded into the major valleys of the uplifted tableland during the late Tertiary and early to mid Quaternary.

Relief and climatic conditions of the Tertiary were conducive to deep in situ chemical weathering. Such processes may result in the loss of silica and cations by solute movement (Oilier 1978). The end result is often the development of low activity clays with low base saturation. Soils of this survey area possess these features (Table 1). Higher values recorded for the 0 - 0.1 m depths reflect higher organic matter contents.

Table 1. Base saturation and clay activity ratios of Kairi soils at two depths

0 - 0.1 m 0.5 - 0.6 m

Base saturation % 11 - 70 14 - 47

CEC/clay (m. equiv. g~x) 0.3 - 0.8 0.2 - 0.3

4,2,2 Geology in Relation to Soils

On Kairi Research Station eight soil profile classes were identified:

Soils Derived from Barron River Metamorphics

Bolygum - - Red rough-ped earth (krasnozem) McDonald - Krasnozem and weakly to moderately structured krasnozem variant. Decomposed metamorphics at <1.5 m.

Soils Derived from Atherton Basalt

Kairi - Subplastic krasnozem. Hoop - Krasnozem. Pope - Subplastic euchrozem-krasnozem intergrade. Drysdale - Euchrozem. Godfrey - Euchrozem-krasnozem intergrade. Yungaburra - Euchrozem-krasnozem intergrade with decomposed basalt at £1.5 m. - 6 -

The soils derived from metamorphics have markedly higher total potassium and coarse sand contents and lower total phosphorus contents than those derived from basalt (Figure 3). This may be explained by the difference in primary mineral contents of the metamorphics and basalts, the intermediate metamorphics being higher in silica and potassium bearing minerals.

The basaltic soils also divide into two basic groups, krasnozems and euchrozem-krasnozem intergrades. The euchrozem-krasnozem intergrades have generally lower coarse sand and total potassium contents than the krasnozems. Total phosphorus levels are generally higher for euchrozem-krasnozem intergrades, although the range in values overlaps with the krasnozems (Figure 3).

The difference in total K and coarse sand contents between the basaltic krasnozems and euchrozem-krasnozem intergrades, however, suggests that variation within the basalt flow or between flows may also be contributing to the genesis of euchrozems and krasnozems in this survey area.

De Keyser (1972) states that there is often a good relationship between soils and geology in the Atherton Tableland. While the soils can be readily grouped on a geological basis, which is reflected in certain analytical data of possible pedogenetic significance, the geology map is not a valid instrument for defining soil. Within Kairi Research Station itself no metamorphics have been mapped (De Keyser 1972). This reflects the extensive nature of the geological mapping. One of the soil profile classes that occurs on the metamorphics (McDonald) is morphologically broadly similar to the basalt soils, but has the higher coarse sand and total potassium, and lower total phosphorus and clay contents diagnostic of metamorphic soils.

5. SOILS - MORPHOLOGY AND CLASSIFICATION

5.1 Soil Profile Class and Mapping Unit Definitions

Soil profile classes (Beckett 1971; Beckett and Burrough 1971, Beckett and Webster 1971; Burrough et al. 1971) are groups of soil of similar morphology such that the variation of certain profile characteristics within a group is less than the variation among groups. Soil profile classes have a range of variation of profile attributes.

Mapping units are areas or groups of areas coherent enough to be represented to scale on a map, which can be adequately described in a simple statement in terms of their main soil profile classes (Beckett and Webster 1971). A mapping unit thus can contain an association of soil profile classes. The composition of the mapping units is given in Section 5.5.

5-2 Soil Profile Classes

Eight soil profile classes have been described on two geological formations. Detailed descriptions are given in Section 5.4. Total K%

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.< 0.9 1.0 1.1 1.2 1.3 1.4 1.5 1.6 1.7 1.8 1.9 2.0 2.1 2.2 2.3 2.4 2.5 2.6 2.7 2.8

30-

60-

90- Range Q. d) Q 120-

150

Total P% c.s. % .04 .05 .06 .07 .08 .09 .10 .11 .12 .13 .14 .15 .16 .17 .18 .19 .20 .21 .22 .23 .24 .25 0 10 20 30 40 50 60

30 - 30- o x o X 60- ^QO° 60 - % * E o x o 2 x 90 - g-90 CL X Q X Q -I- 120 l-g

o 150 «> X. 150

SOILS DERIVED FROM BARRON RIVER METAMORPHICS Bolygum, McDonald - krasnozems

SOILS DERIVED FROM ATHERTON BASALT x x x x x Kairi, Hoop - Krasnozems

OOOO4O40O Drysdale, Pope, Yungarburra, Godfrey - Euchrozem and euchrozem - krasnozem intergrades

Figure 3 Total potassium (K%), phosphorus (P%) snd coarse sand (0.2~2mm)% contents of the soil - 8 -

5,2.1 Soils Derived from Barron River Metamorphics (Bolygwn and McDonald)

Bolygum occurs on the upper and mid slopes of the metamorphic hills. Some rock outcrop is common, and was probably more evident before agricultural development.

They are normally gradational, gritty and gravelly red clay soils with rough ped fabric and dark, yellow-brown or red-brown surfaces. They are normally <1.5 m deep.

They can readily be identified from the basalt soils by the presence of quartz-rich grit and gravel and by their yellower hues and lighter textured surfaces.

McDonald occurs on the lower and mid slopes of the metamorphic hills. The soils are krasnozems and weakly to moderately structured variants of krasnozems. Decomposed metamorphics are evident below 1.0 to 1.5 m, and some quartz-rich grit of metamorphic origin is found throughout the profile. This is a definitive characteristic of this soil profile class.

5.2,2 Soils Derived from Atherton Basalt (Kairi, Hoop, Pope, Drysdale, Godfrey and Yungaburra)

There are three major groups of soils derived from weathered basalt.

Krasnozems subplastic soils - Kairi - weakly subplastic or plastic soils - Hoop

Euchrozem-Krasnozem Intergrades and Euchrozems subplastic soils - Pope weakly subplastic or plastic soils - Drysdale

Euchrozem-Krasnozem Intergrades - soils with decomposing basalt at <1.5 m - Yungaburra soils with surface horizons derived from alluvia eroded from surrounding basalt areas - Godfrey

There is no consistent relationship between slope position and soil profile class for Kairi, Hoop, Pope or Drysdale.

Yungaburra is found associated with basalt outcrops. In some areas most of the gravel, cobble and boulder has been removed. While profiles were not examined below a depth of 1.5 to 2 m, road cuttings in the vicinity of the survey area show considerable depths of soil for soil profile classes other than Yungaburra. - 9 *

Godfrey is found only in small valleys between hills where siltation has occurred. Its distribution is patchy in the small valley basins, but can normally be found associated with low mounds (<0.6 m high) on the valley floor.

There is no significant difference in surface appearance between Kairi, Hoop, Pope and Drysdale.

The krasnozems can, however, be easily separated from the euchrozem- krasnozem intergrades by obtaining the field pH of the 0.1 m, 0.2 - 0.3 m, 0.5 - 0.6 m and 0.8 - 0.9 m layers. The euchrozem-krasnozem intergrade {Pope) and euchrozem (Drysdale) will have a pH >7.0 at one or more of these depths. The krasnozems (Kairi and Hoop) will have a pH of <6.8 at all of these depths.

The subplastic soils (Kairi and Pope) can readily be separated from the weakly subplastic and plastic soils (Hoop and drysdale) by texturing the 0.05 - 0.1 m layer.

Subplastic soils will field texture as clay loams after 1 minute of working and increase to light clay or finer after 10 minutes working.

Plastic soils will field texture as light clay soils after 1 to 2 minutes .and not significantly increase in field texture with working.

For a definition of field texturing technique and subplasticity see Northcote (1979, p 30).

5.3 Classification of the Soils 5.Z.I Relationship Between Great Soil Group and Local Terminology

Up to the present time the soils of Kairi have been loosely considered as "krasnozem red basaltic soils" and "granitic" soils.

McDonald, Kairi, Hoop, Pope, Drysdale, Godfrey, Yungaburra contain soils that fall into the local "krasnozem red basaltic soil" group. Not all of these soils are krasnozems while McDonald is derived from metamorphic parent materials. Drysdale is a euchrozem (neutral soil similar to krasnozems). Pope, Godfrey and Yungaburra are euchrozem-krasnozem intergrades.

5.3.2 Classification of Krasnozems and Euchrozems

While krasnozems are a distinctive group of soils some difficulty was found in classifying the Kairi soils to principal profile forms (Northcote 1979).

Gn 4.11 soils similar to Bolygum have been described elsewhere (Northcote et al. 1975) as belonging to the krasnozem great soil group and more generally as red rough-ped earths. Because of the lower grade of structure and surface colours of yellower hue, Bolygum will be described as a red rough-ped earth in this survey though classified as a krasnozem.

The more strongly structured, deeper and redder Uf 5 and Uf 6^soils have been described as krasnozems, euchrozems or euchrozem-krasnozem intergrades, depending on their pH profiles and base saturation. - 10 -

Isbell et al. (1967) described krasnozems of the Atherton Tableland as Gn 3 soils and more recently profiles of similar location and particle size to the Kairi Uf 5 and Uf 6 soils have also been described as Gn 3 soils (Isbell et al. 1976).

Such discrepancies between field pedologists can be explained by different field texturing techniques or soil variability. The latter can be eliminated in this instance as ten profiles examined in the Millaa Millaa, Yungaburra, Walkamin and Herberton areas were described as Uf 5 or Uf 6 by the authors.

The Factual Key (Northcote 1979) is not clear on the description of 'subplastic soils. Two fcield textures are required to define subplasticity - an initial field texture after 1 to 2 minutes working and a final field texture after 10 minutes working.

The accepted practice by most users of the Factual Key is to code on the initial field texture (R.C. McDonald, personal communication). On this basis soils in the survey area with initial field texture of clay loam would be coded as Gn. Soils with initial field texture of light clay would be Uf 6 or would have to increase in texture after 10 minutes working to medium heavy clay to be coded as Uf 5 (subplastic non cracking clay soils). (Medium heavy clay is defined as a field texture intermediate between medium and heavy clay).

Contrary to the Factual Key, a precedent has been set for including those subplastic soils with initial field textures in the clay loam to light clay range in the Uf 5 group (Northcote et al. 1975, p. 48). This precedent has been followed in this survey as the authors found <57o of the subplastic soils to initially field texture as definitive loams or clay loams (Gn 3 soils).

5.3.3 Great Sotl Groups

As indicated in Section 5.3.1, the loosely applied terms "krasnozem red basaltic soils" and "granitic soils" are not an acceptable means of describing the soils of Kairi Research Station.

All soils in this survey belong to the krasnozem or euchrozem great soil groups (Stace et al. 1968) or intergrades between the two. Unfortunately the definition of these great soil groups is based on relative criteria of poorly specified lower base saturation ("usually less than 50 per cent throughout") and higher acidity for the krasnozems.

Table 2 contains summary data for CEC, base saturation and pH for the profiles sampled (Appendix 1). In thellegend making stage of this survey, an arbitrary figure of field pH 6.8 was selected as the cut off point between euchrozems and krasnozems, as at this stage in a survey there is no other diagnostic chemical criteria available to the field pedologist.

Profiles sampled under this criterion and assigned to one of the great soil groups or an intergrade, exhibited the following chemical criteria:

Krasnozems (Bolygum, McDonald, Kairi, Hoop) - Low CEC with <367« base saturation below A horizons and pH <6.7 on a glass electrode 1:5 pH. - 11 -

Table 2. Soil classiftcatlon, pH, CEC and base saturation data for Kairi soils

CEC meq/100 g soil Base saturation 7. pH (1:5)

SPC GSC PPF 0-0.1 m 0.5-0.6 m 1.1-1.2

Bolygum Krasnozem Gn 4.14 11 5 4 28 23 12 5.7 5.7 5.3 Tropeptlc Haplustox

-McDonald Krasnozem Uf 6.31 14 5 22 14 17 5.4 5.2 5.1 Tropeptic Haplustox

Kairi Krasnozem Uf 5.21 19 9 36 36 35 6.2 6.4* 5.9 Tropeptic Haplustox

Hoop Krasnozem Uf 6.31 15 8 25 25 : 5.8 5.8 5.1 Tropeptic Haplustox

Pope Intergrade Uf 5.21 20 9 70 37 29 6.8 6.7 5.9 Tropeptic Haplustox

Drysdale Euchrozem Uf 6.31 17 9 52 47 60 6.5 7.0 7.3 Tropeptic Eutrustox

Godfrey Intergrade Uf 5.31 16 16 19 48 40 50 6.5 6.4 6.6 Ustic Dystropept

Vungaburra Intergrade Uf 6.31 31 13 15 64 41 38 6.8 6.7 6.0 ultic Haplustalf

Euchrozem (Drysdale) Low CEC, with base saturation of between 47 and 607> below A horizons and pH >6.8 throughout the B horizons.

Intergrades (Pope, Godfrey, Yungaburra) - Low to slightly higher CEC, with base saturation of between 28 and 507. below A horizons and pH of between 5.7 and 7.0 in the B horizons.

Stace et aim (1968) do not specify definite pH, CEC or base saturation limits to the great soil groups and their published type profiles exhibit a much wider range in these properties (overlapping between great soil groups) than the profiles from this survey. The allocation of these soils to their respective great soil groups (or intergrade) is thus fraught with problems.

Within the context of this survey, soil profiles with pH <6.7 and base saturations <367o are considered krasnozems. Soil profiles with pH >6.8 and base saturation ^477o are considered euchrozems. The remainder of our population is scattered across these arbitary boundaries and are hence considered intergrades.

5.3,4 SoiX Taxonomy

Soil Taxonomy classification for the sampled profiles is given in Table 2 and Appendix 1.

The classification can only be regarded as tentative as a lack of soil moisture and temperature regime data and the use of NH4C1 CEC techniques limit the accuracy of our classification.

This requires the adoption of certain assumptions (e.g. ustic moisture regimes and similarity between CEC results by the two methods). - 12 -

As in the great soil groups, those soils which were regarded as being spread over the arbitary krasnozems (Tropeptic Haplustox) euchrozem (Tropeptic Eutrustox) boundary, have a wide range in classifications including Oxisol, Inceptisol and Alfisol.

5.4 Detailed Soil Profile Class Descriptions

Introductory Notes to Soil Profile Class Descriptions

Principal Profile Form: As in Northcote (1979).

Great Soil Group: As in Stace et al. (1968).

Soil Colours: Colour names from Reid et al. (1979).

Soil Names: Moist soil colours from Oyama and Takehara (1967). pHi Average Inoculo field kit pH. Some of the soils behaved inconsistently when tested with a field pH kit. It was found that for those soil profile classes where strongly acid pH's were encountered (Bolygum, McDonald, Kairi and Hoop) pH-continued to become more acid by up to 2 units after 1 minute. pH readings were taken after 30 seconds. In the neutral to weakly acid soils, pH continued to increase by up to 2 units after 1 minute. After 3 minutes readings normally were acid. Readings were standardized on 30 seconds as this best equated with the glass electrode (1:5) pH.

Field Texture: As in Northcote (1979).

Unless otherwise stated all field textures are taken after 1 to 2 minutes of working.

Pope and Kairi have subplastic surface textures. The 1 to 2 minute field texture is 1 texture group (Northcote 1979) lower than the field texture after a working of 10 minutes.

All other soils are weakly subplastic or plastic - the change in texture between 1-2 minute and 10 minute is less than 1 texture group.

Fabric: The term matt smooth ped is used for smooth ped surfaces that lack the gloss, sheen or shine exhibited by some soils (notably black earths and krasnozems). SOIL PROFILE CLASS: BOLYGUM Principal Profile Form: Gn 4.11 SOIL PROFILE CLASS: McDONALD Principal Profile Form: Uf 6.31

Great Soil Group: Krasnozem Great Soil Group: Krasnozem and some Parent Material: Barron River meta- weakly to moderat- morphics intruded by Parent Material: Barron River metamorphics intruded by granite ely structured granite variants Brief Description: Red rough-ped earths (Northcote et al. 1975) Brief Description: Deep acid strongly and weakly to moderately structured red clay soils Modal Profile:

Modal Profile: Au: Dark to red-brown (10YR to 5YR 3/2 to 2/4) gritty sandy clay loam to clay loam with pH gravel (rarely fine sandy clay loam), weak 005 60 - 6 5 A,: Red (2.5YR 2/4 to 3/4), light clay to fine blocky, hard setting, dry soft. light medium clay (rarely gritty), strong very fine to fine crumb, dry slightly A or A,: Red to brown (2.5YR to 7.5YR 4/4 to l2 hard. 3/6) gritty clay loam to light clay with 5-0-6-2 0 3 gravel, weak blocky, rough ped, dry soft. B^ Red (2.5YR 3/4), light medium clay to 055 04 • medium clay, strong very fine subangular B : Red to red-brown (2.5YR to 5YR 3/6 to 4/6) •05 2 B2I / blocky, matt smooth ped, dry slightly light clay to medium clay, moderate medium 5-0-6-8 0 6 hard. subangular blocky, breaking to fine, rough ped, dry slightly hard to hard. 5 0- 5 8 09 B2l: Red (2.5YR 3/4 to 3/6), medium clay normally with trace amounts of quartz grit, B B or C: Strongly (B ) to weakly (C) decomposed &O-6O 0 9- 1( s strong fine subangular blocky, matt smooth parent material. NormaLly red to red-brown /over ped, dry slightly hard. (10R to 5YR 3/6 to 5/6), occasionally weakly 5 0- 58 0 12- / mottled, sandy clay to medium clay, may be B : Red to red-brown to brown (2.5YR to 7.5YR very gravelly (C), weakly structured. 5O-56 12 22 55-5 8 1-5 J 3/4 to 4/6), light medium to medium clay with trace amounts of grit, strong fine 52-58 15 subangular blocky to blocky, matt smooth Variants: Gn 4.14 - A horizon may occur between 2 ped,^dry slightly hard. 0.05 and 0.35 m.

B : Strongly decomposed metamorphics. Gn 4.10 ~ Surface pH may be >7.0. 3

BC or C: Weakly to moderately decomposed white mottled brown to red (2.5YR to 7.5YR 4/3 to 4/6) metamorphics. Normally gritty. Textures range from sandy clay to medium clay.

Variant: Uf 4.41 - A2 horizon may occur between

0.05 and 0.4 m and Bt horizon is absent.

Uf 6.31 - Profile may have a moderate grade of structure. SOIL PROFILE CLASS: KAIRI Principal Profile Form: Uf 5.21, Uf 5.22 SOIL PROFILE CLASS: HOOP Principal Profile Form: Uf 6.31

Great Soil Group: Krasnozem Parent Material: Atherton basalt Great Soil Group: Krasnozem Parent Material: Atherton basalt

Brief Description: Deep structured subplastlc red clay soils with Brief Description: Acid deep structured red clay soils pH <7.0 throughout

Modal Profile: (Refer introductory notes on field texture and field pH) Modal Profile: (Refer introductory notes on field texture and field pH)

pH A : Red to red-brown (7.5R to 5YR, 2/3 to 3/3), PH x A : m m light clay to light medium clay, strong m m An, P Red (7.5R to 2.5YR 2/3 to 3/6), sub- 6 0 - 68 0 5 6 - 7 0 0 plastic clay loam to light clay increasing 005 very fine crumb, dry soft. to light medium to medium heavy clay, strong 02 0 25 A12 or"' very fine crumb, dry soft to slightly hard. B2l: Red to red-brown (7.5R to 5YR 2/3 to 3/4), 5 7 - 6 8 O 3 4 8 - 68 03- light medium clay to medium clay, strong A,2, A,: Red (7.5R to 2.5YR 2/3 to 3/6), sub- fine subangular blocky, dry soft to plastlc clay loam to light clay increasing slightly hard. to light medium heavy clay, strong very 4 8 - 6 8 0-6- 6 8 - 6 5 0 6 fine to fine crumb, dry slightly hard to 0 75 B22: Red to red-brown (10R to 5YR 3/3 to 3/6), hard. light medium clay to medium heavy clay, strong medium prismatic, polyhedral or 5-5 - 6 5 0 9 4 8 - 6 5 09 B2l: Red (10R to 2.5YR 2/3 to 3/6), light medium subangular blocky breaking to very fine clay to medium clay, strong medium poly- subangular blocky, matt smooth ped, dry I I hedral and subangular blocky breaking to soft to slightly hard. very fine blocky and subangular blocky, matt 48 - 6 5 12 B22 5O - 58 12 smooth ped, dry slightly hard to hard. / B21: Red to red-brown (10R to 5YR 3/4 to 4/4), / B23 light medium clay to medium heavy clay, 4> strong medium angular blocky to polyhedral, B22: Red (10R to 2.5YR 3/5 to 4/6), medium clay, 4 8 - 60 !5 I 4 7 - 58 15 strong medium polyhedral to subangular breaking to very fine subangular blocky, blocky breaking to very fine subangular matt smooth ped, dry slightly hard. blocky, matt smooth ped, dry slightly hard to hard. Variant: Gn 3.11 - A, horizon of red (2.5YR 2/4) clay loam may occur between

Variant: Uf 4.41 - A2 may occur between 0.15 and 0 and 0.05 m. 0.45 m. Uf 4.41 - A2 horizon of red (7.5R 2/3)

Gn 3.11 - At textures are subplastic light clay may occur between and increase from loam to 0.05 and 0.3 m. light medium clay. pH of whole profile may be between 4.8 A] textures are subplastic and increase and 4.0 below 0.2 m. from clay loam to light medium clay. Uf 6.31 - B21 and B2J horizons may

B21 textures are subplastic and increase contain trace amounts of from light clay to medium clay. manganiferous concretions - B22 large amount. Dr 2.21 - A, textures are subplastic and increase from loam to light medium clay (0-0.05 m).

B, occurs from 0.05 to 0.2 m. Textures are not subplastic, light medium clay. SOIL PROFILE CLASS: POPE Principal Profile Form: Uf 5.21, Uf 5.22 SOIL PROFILE CLASS: DRYSDALE Principal Profile Form: Uf 6.31

Great Soil Group: Euchrozem - kras- Parent Material: Atherton basalt Great Soil Group: Euchrozem Parent Material: Atherton basalt nozem intergrades Brief Description: Deep structured red clay soils with pH >7.0 at 60 cm. Brief Deacriptlon: Deep structured subpla6tic red clay soila with pH >7.0 at 60 cm

Modal Profile: (Refer introductory notes on field textures and field pH)

Modal Profile: (Refer introductory note on field textures and field pH) 0: Decomposing plant litter (scrub areas pH only). 58 - 6-8 pH Alt: Red (7.5R to 2.5YR 2/3 to 3/4), m m 005 6 2 - 78 subplastic clay loam to light clay All ' Alt: Red to red-brown (7.5R to 5YR 2/3 to 3/3), 005 increasing to medium clay to medium heavy light clay to light medium clay, strong clay, strong fine crumb, dry soft. 0 25 fine crumb, dry soft. 0 15 t 0 2 Al2: Red (7.5R to 2.5YR 2/4 to 3/4), 035 Al2 or A3: Red (10R to 2.5YR 2/3 to 3/3), light 63 - 7 ) 0 3 subplastic light clay increasing to medium clay, strong fine crumb, dry B2I ' medium heavy clay, strong fine crumb, slightly hard. 04 dry soft. 6 8 - 7 7

6 8 - 75 0 6 B2l or B,: Red (10R to 2.5YR 2/4 to 3/4), Red (7.5R to 2.4YR 2/4 to 3/4), light medium clay, strong medium subangular medium clay to medium clay, strong fine 6 8 -7 8 blocky to prismatic breaking to fine 0 8 subangular blocky, matt smooth ped, dry blocky, matt smooth ped, dry slightly 6 8 - 80 0 9 slightly hard. hard.

Red (7.5R to 2.5YR 3/3 to 4/6), medium B2 or B22: Red (10R to 2.5YR 2/3 to 3/4), medium 6 8 - 78 12 clay (rarely medium heavy clay), strong clay to medium heavy clay, strong medium medium prismatic to subangular blocky polyhedral breaking to fine blocky and breaking to fine subangular blocky, dry subangular blocky, matt smooth ped, dry 5 3 - 78 I 5j hard. slightly hard.

Variant: B22fm horizon may occur below B2l Variant: Uf 4.41 - A3 horizon may be replaced

horizon of similar morphology to B21 by colour A2. but with trace amounts of manganifetous soft patches (207. of sites). Uf 4.41 - A, horizon may occur between 0.1 and 0.4 m.

In such profiles (<5% of sites) At horizon has small amounts of manganif-

erous concretions and A2 large amounts,

Bi horizon is absent, B2i horizon has trace amounts of manganiferous concret-

ions, B22 small. All of these sites occur close to Tinaroo Dam high water level and may reflect periods of waterlogging. SOIL PROFILE CLASS: GODFREY Principal Profile Form: Uf 6.31 SOIL PROFILE CLASS: YUNGABURRA Principal Profile Form: Uf 6.31

Great Soil Group: Euchrozem-kras- Parent Material: Lower horizons are Great Soil Group: Euchrozem-krasnozem Parent Material: Basalt nozem intergrades sedentary on Atherton intergrades basalt. Surface horizons are alluvia eroded from Brief Description: Relatively shallow structured neutral to weakly acid red surrounding basalt areas clay soils with evidence of decomposing basalt within 1.5 m Brief Description: Deep structured neutral to weakly acid red clay soils.

Modal Profile: (Refer introductory notes on field textures and field pH) Modal Profile: (Refer introductory notes on field textures and field pH)

Scattered surface basalt cobble to A,: Red (2.5YR 2/4), light clay to light PH boulder - occasionally no stone present medium clay, strong fine crumb, dry soft. on the surface. 6 2 - 70 005 0 1 A,: Red (7.5R to 2.5YR 2/3), light medium A,: Red to red-brown (2.5YR to 5YR 2/3 to 2/4), clay, strong fine crumb, dry soft. subplastic, light clay increasing to medium clay, strong fine crumb, dry slightly hard. 6 5 - 6 8 0 3 B2l: Red (10R to 2.5YR 2/3 to 2/4), light medium clay to medium clay, strong crumb, 0 45- A3: Red to red-brown (2.5YR to 5YR 2/3 to 3/4), dry soft. B2I / medium clay, strong very fine crumb, dry /B22 5 8- 7 0 0 6- slightly hard. B22: Red (10R 2/3 to 2/4), medium clay to medium heavy clay, strong medium subangular B2l: Red to red-brown (2.5YR to 5YR 3/4 to 3/6), 60 - 70 0 9 blocky breaking to fine crumb, dry slightly 5 3 - 7 2 0 9 medium clay to medium heavy clay, strong hard. 10 medium subangular blocky breaking to fine subangular blocky, matt smooth ped, dry i 58 - 72 12 hard. Variant: B22 horizon may be replaced by a 5 0 - 7 0 12- buried soil with the following morphology: 14 B22: Red to red-brown (2.5YR to 5YR 3/4 to 4/6), 55 - 72 15 medium clay, strong medium subangular 5 5 - 68 15 blocky to prismatic breaking to fine sub- 0.9-1.2 m: 2 A - Red (10R 2/3), sub- u t angular blocky, matt smooth ped, dry hard. plastic, clay loam increasing to light medium clay, strong very fine structure, BC: As for B , but with inclusions of decomposed dry soft. 2 basalt. Amount of inclusions increases 1.2 m: 2uBj - Red (10R 2/3), medium with depth and texture gradually decreases heavy clay, strong medium structure, to light clay. dry slightly hard. C: Basalt. pH of buried soil may increase to 7.5 at 1.5 m. Variant: A horizon may be replaced by an A Neutral or weakly alkaline pH may occur 3 12 horizon of similar colour, consistence below 0.6 m (Euchrozems). and structure but with texture light clay. pH below 0.3 m falls to <5.5 (Krasnozems). - 17 -

5.5 Mapping Units

Each mapping unit contains more than one soil profile class. Mapping unit composition is given in Table 3. Mapping units are named after the dominant soil profile class.

Table 3. Mapping unit composition

Dominant soil Minor soil Mapping unit :profile class profile class

Bolygum (Bo) Bolygum 80% McDonald 207,

McDonald (Me) McDonald 70% Bolygum 107, Hoop 20% Kairi

Kairi (Ka) Kairi 70% Hoop 20% Pope 10%

Pope (Po) Pope 707, Drysdale 20% Kairi 10%

Drysdale (Dr) Drysdale 707, Pope 20% Hoop 10%

Godfrey (Go) Godfrey 70% Yungaburra 207, Drysdale 10%

Yungaburra (Yu) Yungaburra 707, Drysdale 20% Pope 10%

6. SOILS - CHEMICAL AND PHYSICAL ATTRIBUTES

6.1 Introduction

Chemical and physical data and descriptions for the eight representative soil profiles sampled are given in Appendix 1. Methods used were those of Bruce and Rayment (1982) unless otherwise stated.

Certain of the physical analyses and total chemical analyses (P and K) have been used to assess pedogenetic differences between the soil profile classes.

To distinguish between krasnozems and euchrozems, cation exchange capacity and pH have been used in accordance with the definitions of those great soil groups given by Stace et at* (1968) as discussed in section 5.3.3. - 18 -

6.2 Soil "Chemistry and Fertility

Eighty-five single surface samples (0 - 0.1 m) and 138 bulked surface samples (n = 10), together with profile samples from the eight soil profile classes (Appendix 1) were available to indicate trends in soil chemistry and major nutrient problems likely to be associated with plant growth on the station.

6.2.1 Electrical Conductivity (EC) and Chloride

The mean values of EC for surface soils of all soil profile classes are low (0.1 - 0.2 mS cm l). Where individual sample values were much higher (0.7 and 0.9 mS cm J°), animals were grazing and urine patches are a likely cause•

Mean chloride values of all surface soils are very low, all. being less than 0.017, chloride.

In profiles, EC and chloride decreased with depth, without exception, to very low values. Consequently, salinity is unlikely to affect crop growth.

6.2.2 pH

The pH values of 83 per cent of the bulked surface samples for all soils were medium acid to slightly acid (5.6 - 6.5). Surface samples of soil profile classes derived from Barron River Metamorphics (Bolygum and McDonald) had mean values significantly lower than those classes derived tram Atherton Basalt, with the exception of Kairi (Table 4). This is due to a greater percentage (approx. 307«) of the samples from Bolygum and McDonald having strongly acid pH values (5.1 - 5.5). Yungaburra bulked surface samples had the highest mean value for pH, 6.3.

Table 4. Percentage distribution of pH of bulked surface samples (0 - 0.1 m) from Kairi Research Station

Distribution of values Soil profile No. of Range Standard class samples of pH <5.5 5.5-6.5 >6.5 Mean deviation

Bolygum 7 5.4-5.9 29 71 - 5.58 0.214 McDonald 23 5.3-6.6 26 69 4 5.75 0.388 Kairi 8 5.4-6.7 12.5 75 12.5 5.85 0.460 Hoop 20 5.0-6.5 15 85 - 5.93 0.457 Pope 14 5.5-6.4 - 100 - 6.03 0.336 Drysdale 45 5.3-6.9 2 89 9 6.24 0.264 Yungaburra 21 5.9-6.6 - 81 19 6.34 0.227 "All soils" 138 5.0-6.9 9.4 83.3 7.3 6.05 0.401 - 19 -

Single surface sample pH means for the classes showed reasonable agreement with those of bulked surface samples (Table 5). Therefore bulking of say ten single site samples could be expected to give a reasonable estimate of surface pH.

Table 5. Comparison of pH means from single surface samples and bulked surface samples (0-0 .1 m)

Single samples Bulked samples Soil profile No. of Standard No. of Standard class samples Mean deviation samples Mean deviation

Bolygum 11 5.50 0.195 7 5.58 0.214

McDonald 9 5.81 0.460 23 5.75 0.388

Kairi 21 6.00 0.360 8 5.85 0.460

Hoop 9 5.80 0.265 20 5.93 0.457

Pope 17 6.11 0.270 14 6.03 0.336

Drysdale 12 5.94 0.315 45 6.24 0.264

Yurigaburra 5 6.46 0.279 21 6.34 0.227

All soils 85 5.93 0.383 138 6.05 0.401

Figure 4 shows the distribution of pH values for bulked surface samples over the whole station.

All the krasnozems (including red rough-ped earth krasnozem) show a decrease in pH from slightly acid to strongly acid with depth (Table 2).

The euchrozem increases in pH from slightly acid to neutral with depth, and the euchrozem-krasnozem intergrades tend to be mainly slightly acid to neutral throughout, becoming slightly acid to medium acid in the lower depths (Table 2).

6.2.3 Exchangeable Cations

Calcium is the dominant exchangeable basic cation in all surface soil samples Values range from 2.0 to 15 m. equiv. 100 g"1. The euchrozem (Drysdale) and euchrozem-krasnozem intergrades (Pope, Godfrey and Yungaburra) are much higher in calcium in the surface than the krasnozems (McDonald, Kairi and Hoop) and red rough-ped earth krasnozem (Bolygum) (Appendix 1).

There is a very strong association between exchangeable calcium and ^ organic carbon for surface soils derived from Atherton Basalt, (r2 = 0.83 , n = 12), illustrating the importance of organic matter in preserving the levels of divalent cations in these soils. - 20 -

25 - 25

20 - n = 138 19

15 - CO

Q. E 13 C/5 "o 12 12 6 10 - 10 9

7 6 6 6 5- T 3 Pl m 2 n 5.0 5.5 6.0 6.5 7.0

pH H00 Figure 4 Frequency histogram of pH of bulked samples (0 -0.1m) of all soils.

Below 0.6 m calcium content decreases, this being most marked in Bolygum and McDonald, where magnesium becomes the dominant basic cation at lower depths. The one exception is Godfrey where calcium increases with depth (Appendix 1).

Soils derived from metamorphics have a significantly higher total potassium than the soils derived from basalt (Figure 3). This is not true for exchangeable potassium (Appendix 1).

Both metamorphic derived soils (Bolygum and McDonald) have up to approxi- mately 0.30 m. equiv. 100 g l soil exchangeable potassium in the surface and less than 0.1 m. equiv. g"1 soil at depth.

Krasnozems on Atherton Basalt (Hoop and Kairi) have a similar exchange- able potassium status to the metamorphic derived soils, with the exception of the surface soil of Kairi, which has 0.86 m. equiv. 100 g~l soil. - 21 -

High exchangeable potassium (>1 m. equiv. 100 g x) in the surface of euchrozems and euchrozem-krasnozem intergrades (Pope, Drysdale, Yungaburra, Godfrey) is thought to be associated with concentration at the surface by return of maize residues during a long history of maize growing on these soils (Warrell unpublished data). Euchrozem and euchrozem-krasnozem intergrades also have a reasonable supply of exchangeable potassium to at least 0.9 m.

Potassium deficiencies in crops are probably unlikely, but metamorphic derived soils would be most susceptible.

6.2.4 Extractable Potassium

Table 6 lists extractable potassium found in the bulked surface soil samples of the various soil profile classes. Only two values were recorded for Godfrey and these are not presented.

Table 6. Extractable potassium in bulked surface samples (0 - 0.1 m)

Soil profile Number of Mean Range CV classes samples meq 100 g~l meq 100 g"1 7,

Bolygum 6 0.47 0.28 - 0.68 34

McDonald 22 0.72 0.24— 1.70 61

Kairi 7 0.60 0.20 - 1.20 58

Hoop 16 0.95 0.20 - 2.30 65

Pope 13 0.76 0.22 - 1.40 52

Drysdale 44 1.24 0.38 - 3.10 43

Yungaburra 19 1.31 0.54 - 3.30 51

Values for exchangeable potassium and extractable potassium on these soils show good agreement, as evidenced by the corresponding values for the various profile samples (Appendix 1).

Rayment (19 77) suggests that at an exchangeable potassium level of 0.20 m. equiv. 100 g x soil, a potassium response in tropical legumes is unlikely and even at levels less than this, a response is uncertain.

As can be seen from Table 6 none of the one hundred and twenty samples analysed have values less than 0.20 m. equiv. 100 g 1 -soil. It therefore seems unlikely that tropical legumes would give a growth response to potassium fertilization of any of the soils.

It is once again suggested that the high extractable potassium status of many of the bulked surface soils is evidence of a long history of maize growing. - 22 -

6.2.5 Exchangeable Sodium

Characteristics of all the survey soils are their low exchangeable sodium and low salt content. Tropical legume species have in general, a low sodium content, particularly when grown on a soil low in exchangeable sodium and salt (Andrew and Robins 1969). Consequently mixed tropical pastures with a large legume component, growing on these soils, could be expected to be low in sodium and may be unable to supply a grazing animal's sodium requirement.

6.2.6 Exchangeable Acidity and Exchangeable aluminium

Exchangeable acidity and exchangeable aluminium (Table 9) were found in significant amounts only in soils derived from Barron River Metamorphics (Bolygum and McDonald) and only then at lower depths (below 0.5 m). This appears to coincide with the occurrence of decomposing parent material in the profiles.

At the depths found, exchangeable aluminium should have little effect on annual crops, but may effect deep rooted perennial crops, particularly during dry periods. However, it is believed that the soils derived from metamorphic rocks are more susceptible to erosion than soils derived from basalt. It is therefore possible that,in eroded profiles of Bolygum or McDonald,toxic amounts of-aluminium may be found closer- to the surface.

Aluminium toxicity is further discussed in section 6.2.7.

6.2.7 Cation Exchange Capacity (CEC)

The origin of cation exchange capacity lies in the negative electric charges on the colloidal clay surfaces, oxidic surfaces associated with the clay, and humus particles of the soil matrix. There are two main components of charge: a constant negative charge ,and a variable charge which may be negative or positive depending on the pH and salt concentration of the soil solution.

CEC measurements

CEC measures the ability of a soil to adsorb cations in exchangeable forms. It corresponds to the negative charge of the soil and is normally expressed in m. equiv. 100 g x soil.

In soils having both constant and variable charge surfaces, such as the soils of the Kairi survey, the use of an extractant for determining CEC differing in pH and salt concentration from the soil solution,alters the net negative charge on the variable charge surfaces. Such an extractant is 1 M NH^Cl pH 7, that was used initially for these soils.

The method using 1 M NH4C1 pH 7 as the extractant,has been widely used for classifying soils, but when such measurements are used for soil fertility predictions, interpretations can be very misleading. For this reason such CEC values have been called'apparent CEC values '(Buol 1980). - 23 -

Another method, called the effective cation exchange capacity (ECEC) (Buol 1980) measures CEC at the pH of the soil. It was also used for the soils of the survey because it is believed to give values closer to the actual capacity of the soils to retain cations under field conditions (Appendix 2).

Buol (1980) has used the difference between CEC pH 7 (extracted with a strong salt solution) and ECEC as a measure of the presence of variable charge surface in soils. CEC — ECEC In Appendix 2 it can be seen that the ratio ( vnvn ) exceeds unity (except in some subsoils) and is greatest in the surface horizons of all the soil profile classes. This indicates that cation exchange capacity in these surface soils is dominated by variable charge surfaces. This is due to the presence of organic matter, which is a variable charge colloid, and also to the sesquioxides present in the soils.

In general, subsurface soils with less organic matter, have less variable charge.

pH and variable charge

Because the variable charge of soils is pH dependent, there is a particular pH (pH0) where the net charge of the variable charge surface is zero, i.e. where cation exchange capacity and anion exchange capacity on the variable charge surfaces are equal and any net negative charge present would be associated with constant charge surfaces in the soil (Uehara and Gillman 1981). In soils dominated by variable charge (all surface soils of the survey), pH0 is an important parameter, as it determines the sign of the net variable surface charge (Uehara and Gillman 1981, p. 65).

If soil pH is less than pH0 the difference (pH0 - pH) is positive, the variable charged surface has a net positive charge and will exhibit anion exchange. Conversely, if soil pH is greater than pH0, these surfaces have a net negative charge and will exhibit cation exchange.

The pH0 is also important as it corresponds to a point of maximum chemical stability in soils dominated by variable charge, for at that pH value the net variable surface charge is zero. With continued weathering of soils dominated^by variable charge there is a tendency for soil pH to move towards the pH0 value (Mattson 1932).

From the difference between the soil pH value in a very dilute electro- lyte (H20) and in a more concentrated solution (1 M KC1), e.g. A pH = - pHjj Q> the sign of. the net surface charge can be determined.

Positive, zero, or small negative (0 > ApH >-0.5) values generally indicate a soil dominated by variable charge minerals. Where A pH values are large negative (<-0.5) nothing can be said about whether charge is variable or permanent, but a high negative surface-charge density is indicated. The above statements are incorporated in Table 7. - 24 -

Table 7. Interpretation of soil pH measurements at two electrolyte

concentrations (e.g. H20 and 1 M KCl)

Sign of Indication A pH net surface of variable Inferred

charge charge surface pH0 small + yes H + P H20

o o yes H = H £p H20 P KCl)

0 > A pH > -0.5 - yes PHKCl

<-0.5 large - can be EITHER unknown constant OR variable charge but soil has a high negative surface charge density

Inference of pH0

An approximate value of pH0 can be inferred from pH values in the two different electrolytes. This is best explained in tabular form. TaDle 7 gives all the information that can be obtained from two such pH measurements

An example of where A pH is positive is the surface soil (0 - 0.1 m) of Hoop, and its approximate pH0 would be about 5.8. For all the other soil profile classes, the surface soils have a negative A pH.

Table 8 lists the approximate pH0 value of surface soils (0 - 0.1 m) for all soil profile classes.

Table 8. Inferred pH0 values of surface soils (0 - 0.1 m) for all soil profile classes

Soil profile class Approximate inferred pH0 values

Bolygum 5.5 McDonald 5.1 Kairi 6.0 Hoop 5.8 Pope 6.7 Drysdale 6.0 Godfrey 6.1 Yungaburra 6.7 - 25 -

Where other information (ECEC, CEC pH 7) is not available, 'the measure- ment of the pH of a soil at two different electrolyte concentrations may be a useful tool in determining whether variable charge minerals are present in the soil and if so inferring pH0 values (Uehara and Gillman 1981) (Table 7).

As stated above, all the surface soils of the soil profile classes (except Hoop) have a negative A pH and soils will tend to accumulate cations.

The pH0 values of all the soil profile classes (except Hoop) would be close to the corresponding pH in KC1, while the value for Hoop would be close to the pH in water (Table 7). It is to be expected that, with time, the surface soil pH of all soil profile classes would tend towards their respective pH0 values. Except for Hoop whose pH -is approximately at pH0, the surface soils will tend to become more acid. Other factors, such as the amount and type of fertilizers applied will have an effect on the actual soil pH, but in general the tendency will be for the surface soil pH to decrease.

Aluminium toxiclty

In the soils derived from metamorphic material (Bolygum and McDonald) the negative value of A pH increases down the profile (Table 9) indicating a high net surface-charge density, shown by ,CEC - ECECs ratio to be mainly ^ ECEC due to variable charge minerals. Where the water pH, taken to be the soil pH, was less than 5.5, appreciable amounts of exchangeable aluminium were found.

Table 9. Exchangeable aluminium in Bolygum and McDonald profiles

Soil profile Depth pH Exchangeable aluminium A pH class cm 1:5, H 0 m. equiv. 100 g l H H 2 P KC1 " P H20 Bolygum 0-10 5.7 0.01 -0.2 20-30 5.6 0.03 -0.3 50-60 5.7 0.03 -0.5 80-90 5.3 0.59 -0.8 110-120 5.3 1.04 -0.9 140-150 5.3 1.25 -l.Oy

McDonald 0-10 5.4 0.05 -0.3 20-30 5.5 0.23 -0.8 50-60 5.2 0.62 -0.7 80-90 5.0 1.54 -0.7 110-120 5.1 1.51 -0.8 140-150 5.1 1.60 -0.8 - 26 -

The pH of the 0.2 - 0.3 m depth of McDonald is now 5.5. A slight decrease in this soil's pH, say 0.2 units, would cause a large increase in exchangeable aluminium within the rooting zone of most plants - resulting in aluminium toxicity. Such a pH decrease in time is (without intervention) suggested as the inferred pH0 of soil is about 4.7.

In Figure 5 two points (Q) corresponding to pH of 5.4 and 5^3 respectively, give an indication of likely exchangeable aluminium levels which could be expected in McDonald at 0.2 - 0.3 m depth as pH decreases. These aluminium levels correspond to about 247« and 357o aluminium saturation in the soil - 207o aluminium saturation is regarded a safe upper level for oxidic soils. Applications of ammoniacal and potassium fertilizers would exacerbate the problem. This effect is unlikely to occur at the same 0.2 - 0.3 m depth in Bolygum, as it has a low net negative charge at this depth. This also applies to the 0 - 0.1 m depths of both profiles.

A - -8)

A ( J) 1.5- " " A( - -8) ( -.8) ApH =PHKC1 - pH|_|2o 1 A Bolygum • Me Donald + Q Likely A1 ^ levels in (-1.0) McDonald at 0.2 - 0.3m as pH decreases

• (-9) 1.0-

o o \

0) \ B(-.6)

ro (-.7) A V»(--8) LU 0.5- -.7)

-•8) \ A(

\ A(

5.0 5.5 6.0

pH H20

Figure 5 Extractable A13+(KC1) plotted against pH for all depths, Bolygum and McDonald. - 27 -

Anion retention

At the lower depths of Kairi, Pope and Yungaburra, A pH becomes positive and anions would be expected to be held on the variable charge surfaces. This has a beneficial effect of retention of nutrient anions, such as nitrate and sulphate, provided plant roots can reach the zones of accumulation (1.1 - 1.2; 1.4 - 1.5 m).

The surface soil of Hoop has a small positive A pH value (anion retention on variable charge surface) and a pH0 value of about 5.8. In fact, throughout the whole profile the pH values in water and 1 M KC1 are almost equal, and therefore the soil pH is very near pH0 at all depths, suggesting that this soil profile is well weathered and extremely stable.

6,2.8 Base Saturation

Base saturation of these soils calculated as a per cent, using CEC (deter- mined at pH 7 with 1 M NH^Cl) was one of the factors used to place the soils in the various great soil groups (see section 5.3.3).

On this basis, surface soils of euchrozems and euchrozem-krasnozem intergrades all have a base saturation greater than 487<> whereas krasnozems and red rough-ped earth krasnozem are less than 367o base saturated in the surface (Table 2).

Apart from a minor response in maize to lime, no cation responses have been reported in the maize growing areas of the Atherton Tableland (Cartmill 1953).

Kerridge st at. (19 72) reported some responses to lime with pasture legumes on some Atherton Tableland soils.

When base saturation is calculated using ECEC all the soils have a base saturation greater than 907,,, with the exception of- the two soils derived from metamorphic material. These two classes (Bolygum and McDonald) decrease sharply in base saturation below the 0.6 - 0.9 m depth; the level at which decomposing material is found.

Should the upper horizons of Bolygum and McDonald become depleted of cations, lower depths would be unlikely to supply cations necessary for plant growth, remembering the increasing presence of extractable aluminium at these lower depths.

This depletion is most likely to occur as the soil pH decreases towards the soil's respective pH0 value. It would therefore seem prudent to ensure that the pH of the surface horizons of Bolygum and McDonald remain at or above pH 5.5 by the use of small quantities of lime or dolomite (500 kg/ha). This amount would need to be increased if ammoniacal or potassium fertilizers are used.

The use of lime or dolomite would not be expected to provide any beneficial effects for any of the other profiles, because of their cation status and the absence;of extractable aluminium. - 28 -

While general statements could be made on the effect of_-other fertili- zers on variable charge soils, further chemical data on the survey soils would be needed for the statements to be more specific (Uehara and Gillman 1981). To obtain the best information from such determinations, they would need to be supported by laboratory experiments, detailed field histories of fertilization and plant growth data.

6,2.9 Organic Carbon and Nitrogen

Organic carbon contents of the surface soils (Appendix 2) range from 1.3 to 3.37o, the lowest value being found in Hoop (1.37o), and the highest in Yungaburra. For surface soils, total nitrogen content shows a similar pattern, with a range of values from 0.12 to 0.427o N, the lowest value being associated with Hoop and highest with Yungaburra (Appendix 1).

C:N ratio divides the soils on parent material. Bolygum and McDonald (metamorphics) have a ratio in surface soils of about 13, while the rest of the soil profile classes range from 7.5 to 10.

As all soils, except Pope, are at present under improved pasture, comparisons are reasonably valid, and hence soils with a lower C:N ratio would be expected to mineralize nitrogen more readily.

The fact that Pope under rainforest and Yungaburra under improved pasture have similar organic carbon and nitrogen values suggest a large contribution from the legume component in the pasture.

Without detailed histories of the pastures on other soils, little more can be added to the above.

6,2.10 Phosphorus

Some bulked surface samples obviously have been collected from fertilized areas. This must be taken into account when interpreting the extractable phosphorus content of the soils, as 100 kg ha'1 of superphosphate will supply about 8 ppm of phosphorus to the surface 0.1 m of soils (bulk density taken as 1.2 g cm 3).

Figure 6 shows the distribution of acid extractable phosphorus in 127 bulked surface samples (11 bulk surface samples were not analysed for phosphorus).

Rayment, Bruce and Robbins (1977) found Siratro was most likely to respond to superphosphate at acid extractable phosphorus levels below 13 ppm P, uncertain to respond in the 13^22 ppm P range, and unlikely to respond above 22 ppm P. Rayment, Bruce and Cook (1980) suggest responses to superphosphate when acid extractable phosphorus is below 22 ppm P and no response above 29 ppm P.

Forty per cent of surface samples analysed had acid extractable phosphorus values 20 ppm P or less, suggesting a likely response to super- phosphate by tropical legumes (Figure 6). - 29 -

35 -

5 25 45 65 85 105 125 145 165 185 205 225

ppm P (0.005 M H2SO4)

Figure 6 Frequency histogram of acid extractable P for bulked samples (0-0.1m) analysed.

Bolygura, McDonald and Hoop soils had over 707o of their samples with less than 20 ppm P, suggesting that the majority of these soils would require phosphorus application for successful tropical legume growth (Table 10).

Drysdale and Yungaburra appear to be the only soils with adequate phosphorus in the surface.

Samples from representative soil profile classes appear to follow a similar trend in extractable phosphorus to the bulked surface samples,with low values for Bolygum, McDonald and Hoop and higher values for Drysdale and Yungaburra (Appendix 1). - 30 -

Table 10. Acid extractable phosphorus (ppm P) in bulked surface samples (0 - 0.1 m)

Soil profile Mean Range CV % below classes^ Number ppm P ppm P % 20 ppm

Bolygum 6 16 8-35 64 71

McDonald 22 22 7-96 103 77

Kairi 7 21 8-38 59 57

Hoop 16 26 5-106 101 75

Pope 13 32 10-64 55 31

Drysdale 44 54 10-175 75 16

Yungaburra 19 59 17-230 82 16

$ Only two samples were collected in Godfrey : 39 and 1320 ppm P

Extractable phosphorus in the surface seems to be related to the soils total P content. However, this apparent relationship should not be inter- preted as the soil's ability to supply phosphorus, for, as shown by Standley and Moody (1979), the basaltic soils of the Atherton Tableland have high sorption abilities for phosphorus.

6.2.22 Trace Elements - Fe, Mn3 Cu3 Zn

The only samples analysed for these elements were the surface samples of the representative soil profiles (Appendix 1).

All profiles on Atherton Tableland Basalt had low D.T.P.A. extractable iron (range 10-34 ppm Fe) compared to samples on Barron River Metamorphics, even though basaltic soils contain large quantities of iron oxides (Standley and Moody 1979).

At the pH of the soils the levels of manganese extracted would be unlikely to prove toxic. Viets and Lindsay (1973) suggest a toxic value of greater than 500 ppm Mn.

The levels of copper and zinc found should prove adequate. However, it may be possible to induce zinc deficiencies by heavy fertilization with lime or superphosphate (Lindsay 1972). Copper is less likely to be affected by fertilization.

6.3 Physical Attributes 6.3.1 Particle Size Distribution

All soils described are ferruginous (i.e. rich in sesquioxides). Those derived from Atherton Basalt contain 6-770 dithionite extractable iron, while those derived from Barron River Metamorphics, 2-37» iron. - 31 -

For over fifty years (Groves 1928) it has been recognized that the physical analyses of ferruginous soils (particularly those of tropical origin) have presented difficulties. There are two main problems in particle size determinations of ferruginous soils: a) They are difficult to disperse,which leads to under estimation of clay fraction and over estimation of fine sand and silt (due to incomplete dispersion). In the method used for survey soils (modification of Day 1956), if a breakdown of undispersed particles occurs during washing then the total percentage (CS + FS + Si + Cl) will be <1007o. This effect would be expected to be small. b) Density of particles in sesquioxide rich soils can be greater than the assumed density of 2.65 g cm 3 at which the hydrometer is calibrated.

This results in:

(i) Changes in settling velocity,which will affect readings depending on the silt and clay distribution of the soil. This effect is usually considered to be small and of little consequence.

(ii) The density of the suspension read by the hydrometer is greater if particles have densities greater than 2.65 g cm 3,which results in over estimation of silt and clay. This effect is thought to be the major effect in the survey soil samples.

As can be seen from Appendix 1, soils derived from Barron River Metamorphics (Bolygum and McDonald) have a much higher sand fraction throughout the profile than soils derived from Atherton Basalt.

Clay percentages in Bolygum and McDonald are lowest in the surface and approach 30-407o only in Bolygum in the presence of decomposing parent material.

Surface soils of soil profile classes derived from Atherton Basalt range in clay from 40 to 597o, with Godfrey (derived from alluvia) having the highest value. These profile classes appear to have a zone of maximum clay accumulation at 0.5 - 0.6 m. Exceptions are Kairi and Pope, where clay percentage in the lower part of the profile remains reasonably constant.

6.3.2 CEC/Clay Ratio

The ratio CEC/clay m. equiv. per g clay, gives an indication of clay mineralogy in soils with a constant charge.

In soils with a large variable charge component the values obtained from these calculations are dependent on the pH of the extractant used to determine CEC. The higher the pH of the extractant the larger the CEC value obtained, hence the higher the ratio CEC/clay for a given clay percentage.

Bearing this in mind, all values for subsurface soils are less than 0.2 with the exception of Godfrey where the value is approximately 0.28. It would be inferred from these values that the clays present are dominantly kaolinitic. - 32 -

7. ACKNOWLEDGEMENTS

Staff and funding assistance was provided by the Research Station Section of the Department of Primary Industries.

The assistance of Dennis Baker and the staff of the soil chemistry laboratory of Agricultural Chemistry Branch is also gratefully acknowledged,

Thanks are also extended to Lyn Landers for typing this report and the staff of the Drafting Section, Division of Land Utilisation for map production.

Editorial comment of Ron McDonald and Robin Bruce (QDPI) and Ray Isbell (CSIRO) is also gratefully acknowledged.

8. REFERENCES

Andrew, C.S., and Robins, M.F. (1969). The effect of potassium on the growth and chemical composition of some tropical and temperate pasture legumes. II. Potassium, calcium, magnesium, sodium, nitrogen, phosphorus, and chloride. Australian Journal of Agricultural Research 20 : 1009-21.

Beckett, P.H.T. (1971). The cost effectiveness of soil survey. Outlook on Agriculture 6 : 191-8.

Beckett, P.H.T., and Burrough, P.A. (19 71). The relation between cost and utility in soil survey. IV. Comparison of the utilities of soil maps produced by different survey procedures, and to different scales. Journal of Soil Science 22 : 446-80.

Beckett, P.H.T., and Webster, R. (1971). Soil variability : A review. Soils and Fertilizers 34 : 1-15.

Bowler, J.M., Hope, G.S.S., Jennings,J.N., Singh, G., and Walker, D. (1976) Late Quaternary climates of Australia and New Guines. Quaternary Research 6 : 359-94.

Bruce, R.C., and Rayment, G.E. (1982). Analytical methods and interpre- tations used by the Agricultural Chemistry Branch for soil and land use surveys. Queensland Department of Primary Industries Bulletin QB 82004.

Buol, S.W. (1980). Morphological characteristics of Alfisols and Ultisols. In "Soils with Variable Charge". (Editor B.K.G. Theng), pp 3-16 (New Zealand Society of Soil Science : Lower Hutt, New Zealand).

Burrough, P.A., Beckett, P.H.T., and Jarvis, M.G. (1971). The relation between cost and utility in soil survey. I. The design of the experiment. II. Conventional or free survey. III. The cost of soil survey. Journal of Soil Science 22 : 359-94. - 33 -

Cartmill, W.J. (1953). Maize fertilizer and rotation trials on the Atherton Tableland. Queensland Agricultural Journal 76 : 249-63.

Day, P.R. (1956). Report of the committee on physical analyses, 1954-5, Soil Science Society of America. Soil Science Society of America Proceedings 20 : 167-169.

de Keyser, F. (1972). 1:250 000 Geological Series - Explanatory Notes. Innisfail, Queensland. Bureau of Mineral Resources Geology and Geophysics.

Isbell, R.F., Webb, A.A., and Murtha, G.G. (1968). "Atlas of Australian Soils". Sheet 7, North Queensland. With explanatory data. (CSIRO Australia and Melbourne University Press : Melbourne).

Isbell, R.F., Stephenson, P.J., and Murtha, G.G. (1976). Red basaltic soils of north Queensland. CSIRO Australia, Division of Soils, Technical Paper No. 28.

Kerridge, P.O., Andrew, C.S., and Murtha, G.G. (1972). Plant.-nutrient status of soils of the Atherton Tableland, north Queensland. Australian Journal of Experimental Agriculture and Animal Husbandry 12 : 618-27.

Kershaw, A.P. (1970). A pollen diagram "from Lake Euramoo, north east Queensland, Australia. New Phytologist 69 : 785-805.

Kershaw, A.P. (1971). A pollen diagram from Quincan Crater, north east Queensland, Australia. New Phytologist 70 : 669-81.

Kershaw, A.P. (1974). A long continuous pollen sequence from north eastern Australia. Nature (LondonX_251 : 222-3.

Kershaw, A.P. (1975). Late Quaternary vegetation and climate in north eastern Australia. Bulletin of the Royal Society of New Zealand 13 : 181-8.

Lindsay, W.L. (1972). Inorganic Phase Equilibria of Micronutrients in Soils. In "Micronutrients in Agriculture". (Ed. Richard C. Dinauer). Ch. 3 (Soil Science Society of America, Inc. : Madison, Wisconsin).

Mattson, Sante. (1932). The laws of soil colloidal behaviour: IX. Amphoteric reactions and isoelectric weathering. Soil Science 34 : 3: 209-240

Northcote, K.H. (1979). 'A Factual Key for the Recognition of Australian Soils'. 4th Ed. (Rellim Technical Publications : Glenside, S.A.).

Northcote, K.H., Hubble, G.D., Isbell, R.F., Thompson, C.H., and Bettenay, E. (1975). 'A Description of Australian Soils' (CSIRO : Melbourne).

Oilier, CD. (1978). Silcrete and weathering. In "Silcrete in Australia". (Ed. Trevor Langford-Smith) (Department of Geography, University of New England).

Oyama, M., and Takehara, H. (1967). 'Revised Standard Soil Colour Charts'. (Fujihira Industry Co. Ltd. : Tokyo).

Rayment, G.E. (1977). Maintenance fertilizers for Siratro pastures. Tropical Grasslands 11 : 216-220. - 34 -

Rayment, G.E., and Bruce, R.C. (1979). Effect of topdressed phosphorus fertilizer on established white clover based pastures in south- east Queensland. I. Prediction of yield responses using soil tests. Australian Journal of Experimental Agriculture and Animal Husbandry 19 : 454-62.

Rayment, G.E., Bruce, R.C, and Cook, B.G. (1980). Prediction of yield responses to phosphorus by established Greenleaf desmodium/grass pastures in south-east Queensland using chemical tests. Australian Journal of Experimental Agriculture and Animal Husbandry 20 : 477-85.

Rayment, G.E., Bruce, R.C., and Robbins, G.B. (1977). Response of estab- lished siratro (Macroptilium atropurpureum cv. siratro) pastures in south-east Queensland to phosphorus fertilizer. Tropical Grasslands 11 : 67-77.

Reid, R.E., Shaw, R.J., and Baker, D.E. (1978). Soils and irrigation potential of the alluvial flats of the Byee Area, Barambah Creek, Murgon, Queensland. Queensland Department of Primary Industries, Agricultural Chemistry Branch, Technical Report No. 14.

Soil Survey Staff (1975). 'Soil Taxonomy : A Basic system of Soil Class- ification for Making and Interpreting Soil Surveys'. United States Department of Agriculture Handbook No. 436. (United States Government Printing Office : Washington, D.C. ).

Stace, H.C.T., Hubble, G.D., Brewer, R., Northcote, K.H., Sleeman, J.R., Mulcahy, M.J., and Hallsworth, E.G. (1968). 'A Handbook of Australian Soils'. (Rellim Technical Publications : Glenside, S.A.).

Standley, J., and Moody, P.W. (1979). Phosphorus sorption studies on some north Queensland soils. Queensland Department of Primary Industries, Agricultural Chemistry Branch, Technical Memorandum 4/79.

Uehara, G., and Gillman, G. (1981). "The Mineralogy, Chemistry, and Physics of Tropical Soils with Variable Charge Clays". (Westview Press : Boulder, Colorado).

Viets, F.G. Jr., and Lindsay, W.L. (1973). Testing soils for zinc, copper, manganese and iron. In "Soil Testing and Plant Analysis". (Ed. L.M. Walsh and J.D. Beaton). Revised Edition, Chapter II. (Soil Science Society of America Inc. : Madison, Wisconsin). - 35 -

APPENDIX 1

Morphological and Analytical Data for Representative Profiles

Classification to categories of Soil Taxonomy (Soil Survey Staff 1975) are based on limited data and are thus approximations. - 36 -

BOUGUM Map Unit: Site No: Bo jreat Soil Group: Kraanozem 3til ~---.iz~.z~: Tropeptle Haplustox P.P.F.: On 4.11 aarent Material: Barron River metamorphles A.M.6. Kef: Topography: Ridges and Low hills on dissected tablelands Air Photo Ref: Location: Kairi Research Station

Vegetation: Cleared. Improvtd tropical pasture. Rainfall: 1248 mm

Profile Morphology: 17. silica rich gravel and cobble on soil surface. Depth

At 0-10 cm Very dark reddish brown (5YR 2/3), clay loam with grit »nd gravel, weak fine blocky, dry soft. Clear to Aj 10-30 cm Dark reddish brown (2.5YR 3/4), clay loam with grit and gravel, weak blocky, dry soft. Clear to -

3,v 20-40 em Dark reddish brown (5YR 3/6), light clay with grit and gravel, moderate medium subangular blocky breaking to fine, rough ped, dry slightly hard. Diffuse to - 3,, 40-70 cm As above but dark reddish brown (2.5YR 3/6), light medium clay. 3,j 70-150 cm Aa above but dark red (10R 3/6), light to light medium clay.

Laboratory Data: ++ Lab.No. Depth pH f 5) Cl Dispersion C.S. F.S. Si C C.E.C . Ca :<• P K S Moisture t CIS 1:5 aSem"1 Ratio (Hi) Particle Size * 0 .D. Sxch. Cations m. aquiv/100 g O.D. * O.D 15 A.D. bar bar 364 0-10 ' 5.7 0.06 0.003 0.19 45 22 13 21 11 2.3 0.7 0.05 0.19 0.080 1.57 0.048 1.7 17 10 366 20-30 5.6 0.04 0.002 0.20 37 26 8 29 10 2.0 0.4 0.05 0.09 0.076 1.79 0.039 1.5 20 10 369 50-60 5.7 0.01 0.001 0.05 31 26 15 32 5 1.0 0.1 0.05 0.05 0.055 1.81 0.017 1.3 18 10 372 80-90 5.3 0.01 0.001 27 18 12 47 4 0.5 0.2 0.05 0.05 0.054 1.71 0.037 1.4 21 14 3 75 110-120 5.3 0.01 0.001 27 20 9 47 4 0.1 0.3 0.05 0.04 0.052 1.92 0.030 1.2' 378 140-150 5.3 0.01 0.001 27 21 13 42 4 0.1 0.3 0.05 0.05 0.049 2.04 0.026 1.2 Lab.No. Depth Org. 0 Tot . N Acid Bicarb Repl. K te Cu a jm i Extr. P ppm m.equiv/lOOg D.T .P.A . Extr. ppm ppm 364 0-10 1. 3 0 .13 7 11 0 22 56 63 1.1 1.1 365 10-20 1. 7 0 .13 5 12 0 12

McDONAU) Map Unit: Site No: M- Great Soil Group: Krasnoiera 5-iZ. '.«.:•"r.o^r: Tropeptlc Haplustox P.P.F-: U£ 6.31 Parent Material: Barron River metamorphlcs A.M.G. Ref: Topography: Dissected tablelands Air Photo Ref: Location: Kairi Research Station

Vegetation: Cleared. Improved tropical pasture. Rainfall: 1248 ran

Profile Morphology: Depth Ai 0-10 cm Dark reddish brown (5YR 3/4), light clay with grit, strong very fine crumb, dry slightly hard. Diffuse to -

BL 10-25 cm Dark reddish brown (2.5YR 3/4), light medium clay with grit, strong very fine subangular blocky, matt smooth ped, dry slightly hard. Diffuse to -

3I; 25-50 cm Dark reddish brown (5YR 3/6), medium clay with grit, strong fine subangular blocky, matt smooth ped, dry slightly hard. Diffuse boundary to 3,, 50-90 cm Reddish brown (2.5YS 4/6), light medium clay with grit, strong fine subangular blocky, matt smooth ped, dry slightly hard. Diffuse to - C 90-150 cm As above but with 207. white and grey mottles of gritty and gravelly light medium clay.

Laboratory Data: Lab. No. Depth H S.C.( 1:5) Cl Dispersion C.S. F.S. Si C C.E. C. Ca** + P K S Moisture % P 1 Mg* Ma* K* cm 1:5 mScm" S Ratio (R|) Particle Size * O.D. ixch. Cations a. aquiv/100 g * O.D 15 O.D. A.D. bar bar 252 0-10 5 .4 0.10 0.006 0.25 37 18 14 32 14 2.0 0.8 0.05 0.33 0.110 1.50 0.043 2.2 25 16 254 20-30 5 .5 0.03 0.002 0.18 32 21 12 35 10 1.2 0.4 0.05 0.13 0.065 1.75 0.026 1.8- 23 15 25 7 50-60 5 .2 0.01 . 0.001 0.33 29 23 17 35 5 0.5 0.1 0.05 0.05 0.043 2.28 0.015 1.2 22 15 260 80-90 5 .0 0.01 0.001 0.05 21 23 18 36 4 0.3 0.2 0.05 0.03 0.037 2.22 0.019 0.95 23 14 263 110-120 5 .1 0.01 0.001 30 26 19 31 4 0.1 0.5 0.05 0.04 0.035 2.72 0.017 0.33 266 140-150 5 .1 0.01 0.001 0.04 31 23 15 34 4 0.2 0.5 0.05 0.05 0.033 2.46 0.019 0.38 21 13 Lab.No. Dep^h Org Cu in B on Extr. P ppm m.equiv/lOOg D.T.P.A . Extr. ppm ppm 252 0-10 2 .3 0.16 16 15 0 36 74 11 0.9 0.8 253 10-20 1 .4 0.12 8 11 0 17 - 37 -

i;il :-r-.-:i-i :^sss: KAIRI Site No: Ka Great Soil Group: Krasnozem ..::r.^~: Tropeptlc Haplustox P.P.F.: Uf 5.21 Parent Material: Atherton basalt A.M.G. Ref: Topography: Dissected tablelands Air Photo Ref: Kaiti Research Station

1248 mm

Profile Morphology: Depth

At 0-10 cm Very dark Teddish brown (10R 2/3), clay loam to light clay Increasing to medium clay, strong very fine crumb, dry slightly hard. Clear to - 10-40 cm Very dark reddish brown (7.5R 2/3), light clay increasing to light medium clay, strong fine crumb, dry slightly hard. Diffuse to -

40-90 cm Very dark reddish brown UOR 2/3), medium clay, strong medium polyhedral to subangular blocky breaking to very fine blocky and subangular blocky, matt smooth ped, dry slightly hard. Diffuse to - 90-150 cm As above but dark red (10R 3/5).

Laboratory Data: Lab.Mo. Depth pH 5) Cl Dispersion Co. F.S. Si C C.E.C Ca** Mg+* Na* X* P K S ifoisture % cm 1:5 mScm. ' Ratio (Ri) Particle Size % 0 .D. Zxch. Cations m. equiv/100 g t O.D '15 O.D. A.D. bar bar 268 0-10 5.2 0.11 0.008 0.17 18 17 23 46 18 4.6 1.3 0.05 0.36 0 .137 0.59 0.055 3.2 28 20 270 20-30 6.2 0.05 0.002 0.13 14 18 0 51 15 4.9 3.6 0.05 0.21 0 .122 0.57 0.038 2.7 27 19 273 50-60 6.4 0.03 0.001 11 18 ] 8 60 9 3.0 3.2 0.05 0.07 0 .090 0.54 0.017 2.3 26 20 276 80-90 6.5 0.02 0.001 11 17 'l 57 7 2.4 3.3 0.05 0.06 0 .077 0.63 0.020 2.2 26 20 279 110-120 5.9 0.03 0.001 9 17 ' 0 61 7 1.5 3.9 0.05 0.07 0 .083 0.67 0.046 2.4 282 140-150 5.5 0.03 0.001 7 14 2 62 7 0.9 L.9 0.05 0.05 0.094 0.52 0.052 2.3 29 24 Lab.No. Depth Org. C Tot . H Acid Bicarb Repl. K Mn Cu Zn 3 cm Extr. P ppm m. equiv/lOOg D.T .P.A . Extr. ppm ppm 268 0-10 1. 9 0 25 29 24 0 75 20 141 4.6 1.9 269 10-20 1. 4 0 20 25 21 0 34

HOOP Map Unit: Site No: Ho Great Soil Group: Krasnozem •--.I- ~'^:cz::o~;: Tropeptlc Haplustox P.P.F.: uf 6.31 Parent Material: Atherton basalt A.M.G. Ref: Topography: Dissected tablelands Air Photo Ref: Location: Kalri

Vegetation: Improved tropical pasture (ex rain-forest). Rainfall: 1248

Profile Morphology: Depth Ai 0-30 cm Very dark reddish brown (5YR 2/4), light clay to light medium clay, strong fine crumb, dry soft. Diffuse to -

B2l 30-50 cm Dark reddish brown (5YR 3/4), light medium clay, strong fine subangular blocky, matt smooth ped, dry soft. Diffuse to -

B12 50-90 cm Dark reddish brown (2.5YR 3/3), medium clay, strong medium prismatic to subangular blocky breaking to very fine subangular blocky, matt smooth ped, dry soft. Diffuse to B,, 90-150 cm As above but 10R 3/3.

Laboratory Data: Lab. No. Depth pH E.C.(1:5 ) Cl Dispersion C .5. F.S. 51 C C.E.C «(g" Na* K* P K S Moisture % 1 cm 1: 5 mScrn" Ratio (Ri) Parti cle Size X O.D. Sxch. Cations m. jquiv/100 g 0 % O.D 15 .D. A.D. bar bar 348 0-10 5 3 0.07 0.001 0.15 15 17 23 51 15 2.7 D 6 0.05 0 .23 0 .114 0.58 0.039 2.9 26 19 350 20-30 6 0 0.04 0.002 0.05 13 14 20 58 11 2.2 3.4 0.05 0 .10 0 .108 0.54 0.029 2.4 26 21 353 50-60 5 8 0.04 0.002 0.03 11 13 21 59 8 1.3 3 2 0.05 0 .05 0 .085 0.54 0.045 2.5 27 22 356 80-90 5 4 0.02 0.001 10 14 22 60 7 0.7 3 6 0.05 0 .04 0 .080 0.58 0.059 2.5 26 22 359 110-120 5 1 0.01 0.001 13 15 26 53 7 0.1 3 3 0.05 0 .06 0 .084 0.60 0.055 2.5 362 140-150 5 0 0.02 0.001 11 14 22 58 7 0.1 3 1 0.05 0 .07 0 .088 0.59 0.063 2.7 Lab.No. Depth Oi g- C Tot. N Acid Bicarb Eepl. K re Mn Cu Zn 3 cm Extr. P ppm m.equiv/lOOg D.T.P.A . Extr. ppm ppm

348 0-10 1. 3 0 12 10 25 0. 20 35 127 2.5 0.8 349 10-20 1. 2 0 13 9 24 0. 15 - 38 -

POPE Site No: po Great Soil Group: Euchrozem - Krasnoiem lntergrade Iropeptic Haplustox P.P.F.: Uf 5.21 Parent Material: Acherton basalt A.M.G. Ref: Topoqraptiy: Dissected tablelands Air Photo Ref:

Rainfall: 1248 mm

Profile Morphology: Depth

Atl 0-10 cm Very dark reddish brown (2.5YR 2/4), clay loam to light clay increasing to medium clay, strong fine crumb, dry soft. Gradual to

Al2 10->40 cm As above but light clay increasing to light medium clay. Diffuse to - • B, 40-90 cm Very dark reddish brown (2.5YR 2/4), light medium clay, strong fine subangular blocky, matt smooth ped, dry slightly hard. Diffuse to - * Dark reddish brown (2.5YR 3/4), medium clay, strong medium prismatic to subangular blocky breaking to fine subangular blocky, mact smooth ped, dry hard.

Laboratory Data: Lab.No. Depth pH 5) Cl Dispersion C.S. F.S. Si C C.E.C CaTT Mg** Na" P K S Moisture $ cm 1:5 mScm"1 Ratio (Ri) Particle Size S 0.D. 2xch. Cation s m. aquiv/100 g o'.D. * CD 15 A.D. bar bar 316 0-10 6.8 0.22 0.006 0.16 15 14 J3 47 20 10 2.0 0.05 1.70 0.202 0.43 0.067 3.6 32 23 318 20-30 7.0 0.07 0.002 0.14 9 13 24 64 11 3. 7 0.3 0.05 0.91 0.144 0.38 0.032 2.7 28 22 321 50-60 6.7 0.05 0.002 0.09 10 14 22 63 9 2. 5 0.2 0.05 0.66 0.127 0.36 0.022 2.4 28 22 324 80-90 6.2 0.03 0.004 8 10 L7 67 7 1. 7 0.2 0.05 0.31 0.108 0.36 0.015 2.0 28 24 327 110-120 5.9 0.02 0.002 5 3 22 71 7 1. 6 0.4 0.05 0.08 0.114 0.24 0.021 2.1 330 140-150 5.7 0.02 0.001 3 11 25 66 7 0. 9 0.9 0.05 0.10 0.129 0.17 0.036 2.7 35 29 Lab.Mo. Depth Org. C Tot . N Acid Bicarb Repl. K Fe Mn Cu Zn d cm % Extr. P ppm m.equiv/lOOg D.T .P.A . Extr. ppm ppm

316 0-10 3. 2 0 32 120 + 94 1 7 13 218 5.4 4 317 10-20 1. 7 0 23 56 46 0

DRYSDALE Map Unit: Site No: Dr Great Soil Group: Euchrozem 3 : il ~--::ZT.O~: Tropeptic Eutrustox P.P.F.: Uf 6.31 Parent Material: Atherton basalt A.M.S. Ref: Topography Air Photo Ref: Location: Kairi Research Stati

Vegetation: Improved tropical pasture (ex rain-forest). Rainfall: 1248 mm

Profile Morphology: Depth A, 0-10 cm Very dark reddish brown (5YR 2/4), light clay to light medium clay, strong fine crumb, dry soft. Diffuse to - A, 10-30 cm Very dark reddish brown (2.5YR 2/4), medium clay, strong fine crumb, dry soft. Diffuse to -

B2l 30-60 cm Very dark reddish brown C2.5YR 2/4), medium clay, strong medium subangular blocky breaking to fine blocky, matt smooth ped, dry slightly hard. Diffuse to B,j 60-150 cm Very dark reddish brown (2.5YR 2.5/4), medium clay, strong medium polyhedral breaking to fine blocky and subangular blocky, matt smooth ped, dry slightly hard.

Laboratory Data:

Lab. No. Depth OH 5) Cl Dispersion C.S. F.S. Si C.E. C. Ca** Mg** Na* X* ? K S Jfoi sture cm 1:5 mScm ' Ratio (Ri) Particle Size t O.D. Exch. Cations m. equiv/3.00 g O.D. * O.D 15 A.D • ba» 284 0-10 6.5 0.20 0.007 0.16 11 11 28 57 17 5.9 ] .0 0.05 1.56 0.144 0.35 0.04 7 3.2 31 24 286 20-30 6.7 0.11 0.008 0.08 8 12 19 67 10 3.2 C .2 0.05 0.99 0.113 0.31 0.023 2.6 29 24 289 50-60 7.0 0.04 0.002 0.12 7 15 21 65 9 3.8 C .2 0.05 0.33 0.097 0.25 0.018 3.0 31 26 292 80-90 7.3 0.04 0.001 0.11 4 16 12 66 7 3.6 C .3 0.05 0.27 0.092 0.17 0.014 2.8 34 28 295 110-120 7.3 0.04 0.001 3 20 26 56 7 2.8 1 .0 0.05 0.44 0.102 0.12 0.023 2.8 298 140-150 6.3 0.06 0.001 2 22 28 54 4 1.3 C .8 0.05 0.31 0.105 0.08 0.036 3.1 Lab.No. Depth Org. C Tot . N Acid Bicarb Repl. K Ke Sftl Cu 3 cm * Extr. P ppm m.equivnoog D. T.P.A . Extr. ppm ppm 284 0-10 2. 2 0 .27 27 24 1.6 10 131 3.4 1.3 285 10-20 1. 4 0 .17 24 24 1.3 - 39 -

i:il .-rtf;.:* :i;ss: GODFREY Site No: ck> Great Soi1 Group: Euchrozem - krasnozem intergrade :::*o~: Ustic Dystropept P.P.F.: Uf 6.31 Parent Material: Alluvia eroded from soil developed on A.M.G, Ref: _ Atherton basalt Topography: Dissected tablelands Air Photo Ref: Location: Kalrl Research Station

Vegetation: Improved tropical pastures (ex rain-forest). Rainfall: 1248 mm

Profile Morphology: Depth 0-10 cm Very dark reddish brown (2.5YR 2/4), light clay to light medium clay, strong fine crumb, dry soft. Gradual to 10-50 cm As above but 2.5YR 2/3. . 50-120 cm As above but 2.5YR 2/4. 120-150 (10R 2/4), medium clay, strong medium subangular blocky breaking to fine crumb, dry slightly hard.

Laboratory Data: Lab. No. Depth PH E.C.U: 5) Cl Dispersion C.S. F.S. Si C C.E.C. Ma- P K S Moisture % cm 1:5 mScm"1 Ratio (R,) • Particle Size S O.D. Sxch. Cat ns m. equd v/100 g O.D. % O.D 15 A.D. bar bar 332 0-10 6.5 0 .13 0.004 0.19 7 14 21 63 16 4 .9 0.9 0.05 1.56 0.158 0.29 0.044 2.8 31 24 334 20-30 6.5 0 .05 0.001 0.18 6 15 26 60 16 3 .5 0.2 0.05 1.15 0.154 0.27 0.037 2.7 30 24 33 7 50-60 6.4 0 .04 0.001 0.18 7 17 23 59 16 5 .1 0.6 0.05 0.50 0.165 0.21 0.042 2.6 31 24 340 80-90 6.5 0 .04 0.001 0.16 10 16 26 52 17 6 .1 0.4 0.05 0.42 0.167 0.21 0.043 2.9 30 23 343 110-120 6.6 0 .06 0.001 8 17 28 52 19 8 .3 0.5 0.05 0.50 0.192 0.21 0.052 3.1 346 140-150 6.9 0 .05 0.001 5 16 25 62 14 4 .7 0.3 0.05 0.40 0.175 0.21 0.036 3.1 Lab.No. Depth Org . C Tot . N Acid Bicarb Repl. K Fe Vh Cu Zn B cm i Extr. P ppm m. equi v/lOOg D. T.P.A . Extr. ppm ppm

332 0-10 2.0 0 .22 41 42 1.5 12 94 2.7 1.7 333 10-20 1.6 0 .16 33 33 1.1 c:l. _-r::i-; Ciajs: YUNGABURRA Map Unit- Site No: Yu Great Soil Group: Euchrozem - krasnozem intergrade 3-il ^:—ozy: Ultic Haplustalf P.P.F.:' uf 6.31 Parent Material : Atherton basalt A.M.G. Ref: Topography: Dissected tablelands Air Photo Ref: Location: Kairl Research Station

Vegetation: Improved tropical pasture (ex rain-forest). Rainfall: 1248 mm

Profile Morphology: Basalt outcrop 30 m away. 17. surface cobble and stone cover Depth Ai 0-10 cm Very dark reddish brown (5YR 2/4), light clay to light medium clay, strong fine crumb, dry slightly hard. Diffuse to - A, 10-30 cm Dark reddish brown C2.5YR 3/4), medium clay, strong fine crumb, dry slightly hard. Diffuse to - B, 30-60 cm Dark reddish brown (5YR 3/4), medium clay, strong medium subangular blocky breaking to fine subangular blocky, matt smooth ped, dry hard. Diffuse to BC 60-100 cm Dark reddish brown (5YR 3/6), with 107. grey weathered basalt inclusions, medium clay. Diffuse to - C 100-150 cm As above but with 507. grey weathered basalt inclusions.

Laboratory Data: Lab.No. Depth PH E.C.I 1:5) Cl Dispersion C.S. F.S. Si C C.E. Mg" Na* :<• P K S Stoi sture i cm 1:5 mScm"1 Ratio (R ) Particle Size % O.D. Sxch. Cations m. squi v/100 g * 0 D. ! 1-5 l O.D. A.D • bar 300 0-10 6.8 0.19 0.003 0.24 12 17 33 44 31 15 3.2 0.05 1.70 0.317 0.25 0.059 5.0 39 28 302 20-30 7.0 0.19 0.002 0.17 2 12 30 54 20 7 .4 1.6 0.05 0.40 O.204 0.11 0.046 4.6 39 31 305 50-60 6.7 0.06 0.003 0.09 1 16 26 66 13 3 .6 0.7 0.05 0.87 0.133 0.10 0.029 3.7 40 32 308 80-90 6.6 0.06 0.002 0.12 <1 21 30 55 14 ' 4 .3 0.7 0.05 0.60 0.126 0.09 0.025 3.9 • 41 31 311 110-120 6.0 0.03 0.003 1 23 38 47 15 4 .4 1.0 0.11 0.24 0.135 0.03 0.016 4.2 314 140-150 6.0 0.02 0.003 2 28 32 44 13 3 .4 0.9 0.11 0.40 0.145 0.05 0.019 4.2 Lab.No. Depth Org . C Tot. N Acid Bicarb Repl. K Fe Jfti Cu Zn B cm J Extr. P ppm m.equiv/lOOg D.T.P.A . Extr. ppm ppm 300 0-10 3 .3 0.42 12f 105 1.6 29 165 4.3 13 301 10-20 2 .9 0.39 10 105 0.62 - 40 -

APPENDIX 2

Selected analyses for soil profile classes

Organic Ratio Base L:5 a Soil profile Depth Clay carbon ptl J ECEC Variable CEC-ECEC saturation l b 0 class cm 7. 7. H20 KCl tneq. 100 g~ CEC charge EC EC 'L

3olygum 0-10 21 1.8 5.7 5.5 3.3 11.2 7.9 2.4 28 20-30 29 1.7 5.6 5.3 2.6 10.2 7.6 2.9 25 50-60 32 5.7 5.2 1.2 5.1 3.9 3.3 23 80-90 47 5.3 4.5 1.5 4.1 2.6 1.7 20 110-120 47 5.3 4.4 1.7 4.1 2.4 1.4 12 140-150 42 5.3 4.3 1.8 4.1 2.3 1.3 11

McDonald 0-10 32 2.3 5.4 5.1 3.4 14.4 11.0 3.2 22 20-30 35 1.4 5.5 4.7 2.1 10.2 8.1 3.9 18 50-60 35 5.2 4.5 1.8 5.1 3.3 1.8 14 80-90 36 5.0 4.3 2.3 4.1 1.8 0.8 14 110-120 31 5.1 4.3 2.4 4.1 1.7 0.7 17 140-150 34 5.1 4.3 2.6 4.1 1.5 0.6 20

Kairi 0-10 46 1.9 6.2 6.0 6.8 18.7 11.9 1.8 36 20-30 51 1.4 6.2 5.6 5.9 15.5 9.6 1.6 37 50-60 60 6.4 6.0 3.4 9.3 5.9 1.7 35 80-90 57 6.5 6.1 2.8 7.2 4.4 1.6 39 110-120 61 5.9 6.0 2.5 7.2 4.7 1.9 35 140-150 62 5.5 5.6 2,9 7.3 4.4 1.5 40

Hoop 0-10 51 1.3 5.8 6.0 3.6 14.6 11.0 3.1 24 20-30 58 1.2 6.0 6.0 2.8 11.4 8.6 3.1 24 50-60 59 5.8 5.8 2.1 8.3 6.2 3.0 25 80-90 60 5.4 5.5 1.4 7.3 5.9 4.2 20

110-120 53 5.1 5.1 0.60 7.3 6.7 11.2 7 140-150 58 5.0 5.0 0.48 7.3 6.8 14.2 4

Pope 0-10 47 3.2 6.8 6.7 13.9 19.9 6.0 0.4 69 20-30 64 1.6 7.0 6.6 5.0 11.4 6.4 1.3 44 50-60 63 6.7 6.3 3.4 9.3 5.9 1.7 36 80-90 67 6.2 6.4 2.2 7.2 5.0 2.3 21 110-120 71 5.9 6.5 2.1 7.3 5.2 2.5 29 140-150 66 5.7 6.2 2.0 7.3 5.3 2.7 28

Drysdale 0-10 57 2.2 6.5 6.0 8.6 16.7 8.1 0.9 51 20-30 67 1.4 6.7 6.0 4.5 10.3 5.8 1.3 43 50-60 65 7.0 6.3 4.4 9.3 4.9 1.1 47 80-90 66 7.3 6.7 4.3 7.3 3.0 0.7 58 110-120 56 7.3 6.7 4.4 7.3 2.9 0.7 59 140-150 54 6.8 6.2 2.5 4.2 1.7 0.7 58

Godfrey 0-10 63 2.0 6.5 6.1 7.5 15.6 8.1 1.1 48 20-30 60 1.6 6.5 5.7 4.0 15.6 10.6 2.1 32 50-60 59 5.4 5.9 6.3 15.6 9.3 1.5 40 80-90 52 6.5 6.0 6.9 16.7 9.8 1.4 42 110-120 52 6.6 6.2 • 9.3 18.8 9.5 1.0 50 140-150 62 6.9 6.3 5.5 13.6 8.1 1.5 40

Yungaburra 0-10 44 3.3 6.8 6.7 19.9 30.9 20.0 1.0 64 20-30 64 2.9 7.0 6.6 9.9 20.2 10.3 1.0 47 50-60 66 6.7 6.3 5.3 12.7 7.4 1.4 41 80-90 55 6.6 6.4 5.7 13.7 8.0 1.4 42 110-120 47 6.0 6.4 5.7 14.9 8.2 1.4 38 140-150 44 5.0 6.2 4.8 12.7 7.9 ' 1.6 37

Footnote: a Sum of cations + KC1 extractable acidity b Determined with 1 M NH.C1 c (CEO - (ECEC)