Agricultural Land Suitability of the Wet Tropical Coast

QO91010

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Agricultural land suitability of the wet tropical coast

Mossman-Julatten area

P.R. Wilson Land Resources Branch

Q QueenslandDepartment of PrimaryIndustries Queensland Government Technical Report

This report is a scanned copy and some detail may be illegible or lost. Before acting on any information, readers are strongly advised to ensure that numerals, percentages and details are correct.

This report is intended to provide information only on the subject under review. There are limitations inherent in land resource studies, such as accuracy in relation to map scale and assumptions regarding socio-economic factors for land evaluation. Before acting on the information conveyed in this report, readers should ensure that they have received adequate professional information and advice specific to their enquiry.

While all care has been taken in the preparation of this report neither the Queensland Government nor its officers or staff accepts any responsibility for any loss or damage that may result from any inaccuracy or omission in the information contained herein.

For information about this report contact [email protected] Project Report QO91010

Agricultural land suitability of the wet tropical coast

Mossman-Julatten area

P. R. Wilson Land Resources Branch

Queensland Department of Primary Industries Brisbane ISSN 0727-6281 Agdex 526/515

This publication was prepared for Queensland Department of Primary Industries officers. It may be distributed to other interested individuals and organisations.

...... F ...... iii CONTENTS Page

LIST OF ILLUSTRATIONS iv

LIST OF TABLES iv

ABSTRACT

1. INTRODUCTION

2. CLIMATE

3. GEOLOGY AND LANDFORM

4. HYDROLOGY

5. SOILS

6. LAND USE 14

0 CONCLUSIONS 36

81 ACKNOWLEDGMENTS 39

9. REFERENCES 39

10. APPENDIXES

Land suitability classification scheme 41

II Agricultural land suitability classes 63

III Explanation of codes for the UMA record type (not included in report, accessed through the Director, Land Resources Branch, Queensland Department of Primary Industries)

IV Unique map area record type (not included in report, accessed through the Director, Land Resources Branch, Queensland Department of Primary Industries)

V Land use specifications of agricultural crops 64

VI Pasture management categories 80 iv

LIST OF ILLUSTRATIONS Page

Figure 1. Locality plan

Figure 2. Monthly pan evaporation at Port Douglas and median monthly rainfall at Daintree, Mossman and Julatten

Plate 1. Small but widespread areas of salt affected caneland in 21 the Clifton soil mapping unit on the eastern side of Cassowary Range

LIST OF TABLES

Table 1. Median monthly rainfall (mm)

Table 2. Mean monthly maximum and minimum temperature (°C)

Table 3. Mean monthly 9 am and 3 pm relative humidity (%)

Table 4. Distinguishing attributes of the dominant soils 10

Table 5. Soil drainage and permeability categories for the 22 dominant soils

Table 6. Limitations and land attribute levels occurring in each 28 soil mapping unit

Table 7. Area (ha) of suitability classes for each crop and soil 30 mapping unit ABSTRACT

The Wet Tropical Coast from Ingham to Cape Tribulation is utilised for sugar-cane, horticultural crops, tea, field crops, exotic pine plantations and cattle. A majority of the coastal lowlands is developed creating land use problems and competition for land. The expanding urban developments are also competing for land. This report on the area from Cape Tribulation to Julatten is a companion to other reports on the Wet Tropical Coast.

A soil survey at 1:50 000 (Murtha 1989) was conducted over an area of about 105 000 ha. The lands were assessed in terms of land suitability for growing sugar-cane, bananas, papaw, mango, lychee, citrus, avocado, rambutan, tea, vegetables, cucurbits, pineapple, maize, sorghum, sweet corn, soybean, peanut, sweet potato, rainfed rice, Pinus caribaea and improved pastures.

Each of the 520 unique map areas were individually assessed for their suitability for each crop using a suitability classification scheme. The limitations assessed were climate, water availability, soil nutrient supply, salinity, wetness, flooding, landscape complexity, soil physical conditions, topography, rockiness and water erosion. A 1:100 000 agricultural land suitability map accompanies this report.

The report identifies the areas of land suitable for agricultural development and the management needs of these lands for agricultural uses and the likely impact of other land uses on these lands. The guidelines are aimed at promoting improved productivity while avoiding degradation of the land resources.

The information in this report will be useful to industry groups, land holders, local authorities and government departments who have a commitment to maintain the land in a highly productive state.

1. INTRODUCTION

Mossman is situated 67 km by road north of Cairns and is the centre for Queensland's most northerly sugar-cane growing area. There were several unsuccessful attempts to establish a sugar-cane industry in the Mossman area during the 1880s and 1890s. The Mossman Central Milling Company was formed in 1894 and began crushing in 1897.

Prior to 1980, cane growing was restricted to the narrow coastal lowland from Oak Beach in the south to the Daintree River in the north. Cane production expanded into the Julatten area and on to the northern bank of the Daintree River after 1980.

A soil survey by Murtha (1989) provides a morphological description of the soil series and a description of the mapping units. A sugar-cane land suitability study by Capelin and Murtha (1983) identified the lands suitable for growing sugar-cane in the Julatten area and identified the constraints to crop production.

The main concerns affecting the sugar industry and other land uses at the time of this study were the limited suitable land available for expansion the competition for land and expansion onto less suitable land. The expanding urban developments, including tourist developments, were also competing for land. This study covers the coastal lowlands from Oak Beach to Cape Tribulation and the Julatten uplands south to Mount Molloy (Figure 1). It includes all land presently assigned to the Mossman sugar mill except for a small area on Rifle Creek downstream of Mount Molloy.

The approach adopted for the study was to assess the suitability of the land resources for various agricultural uses.

2. CLIMATE

2.1 Rainfall and evaporation

A rainfall gradient exists on the coastal lowlands with median annual rainfall decreasing from 3000+ mm in the area from Daintree to Cape Tribulation area to 2000 mm in the coastal strip south from Port Douglas.

A sharp rainfall gradient exists on the Julatten uplands. Median annual rainfall ranges from 1542 mm at Julatten to 1082 mm at Mt. Molloy.

Rainfall in the region has a strong summer dominance. For example, 81% and 87% of the mean annual rainfall for Mossman and Mt. Molloy respectively occurs from December to April.

Rainfall data are presented in Table 1. COOKTOWN 1.5 KM Scale in Kilometres 1050 10 20 30 40 50 L i I i i I I I

Rossville ~o Hope Islands

River

CORAL SEA

STUDY AREA

'MOSSMAN Mitchell N JULATTEN

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ATHERTON

Figure 1. Locality Plan Table 1. Median monthly rainfall (mm)

Cubbagudta* Daintree Whyanbeel Mossman Port Julatten Mount Valley Douglas Molloy

January 476 366 489 439 364 307 210 February 706 668 567 525 378 373 275 March 671 423 515 418 387 273 193 April 427 404 291 170 152 99 4 May 222 144 104 68 55 48 19 June 90 34 68 49 36 41 16 July 67 37 35 9_5 16 19 7 August 57 49 39 26 16 18 4 September 65 40 42 34 24 12 4 October 51 49 62 44 30 19 8 November 116 124 110 103 76 56 31 December 204 218 189 171 126 94 81

TOTAL 3654 2689 2896 2321 1964 1542 1082

* Location 16°12'S, 145°24'E (Cape Tribulation area)

Source: Bureau of Meteorology

Figure 2 compares monthly class A pan evaporation for Port Douglas and median monthly rainfall at Daintree, Mossman and Julatten. Evaporation is at a maximum from September to December corresponding to lower relative humidity and increasing temperatures. The decreasing evaporation from January to March corresponds to maximum humidity and higher rainfall.

Assuming evaporation does not vary greatly over the study area due to proximity to the coast, the monthly moisture balance shows a deficit from May to December for all centres except the higher rainfall Cape Tribulation area. Here, a deficit occurs from June to December. 700 MEDIAN MONTHLY RAINFALL

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.... Port Douglas

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Figure 2. Monthly pan evaporation at Port Douglas and median monthly rainfall at Daintree, Mossman and Julatten.

2.2 Temperature

Port Douglas is the only centre with long term climatic records other than rainfall. Mean monthly maximum temperatures range from 30.3°C during December and January to 24.6°C during July (Table 2). Mean monthly minimum temperatures range from 23.8°C in January to 16.8°C in July. Occasional light frosts may occur on the Julatten uplands. The incidence and severity of frosts generally increases to the south-west and are generally confined to the level plains along Rifle and Bushy Creeks.

Table 2. Mean monthly maximum and minimum temperature (°C)

Port Douglas max. min. January 30.2 23.8 February 29.9 23.6 March 29.2 23.0 April 28.1 21.8 May 26.3 19.7 June 25.0 18.1 July 24.4 16.8 August 25.0 17.0 September 26.5 18.7 October 28.0 20.8 November 29.1 22.5 December 30.1 23.4 Source: Bureau of Meteorology

2.3 Relative humidity

Relative humidity at Port Douglas shows the same seasonal pattern as rainfall. The 9 am mean relative humidity ranges from 81% in February to March to 69% in September (Table 3).

Table 3. Mean monthly 9 am and 3 pm relative humidity (%)

Port Douglas 9 am 3 pm January 78 73 February 81 76 March 81 75 April 78 72 May 77 72 June 77 71 July 75 69 August 73 66 September 69 64 October 70 65 November 71 67 December 72 68 Source: Bureau of Meteorology 3. GEOLOGY AND LANDFORM

3.1 Geology

The geology of the study area has been mapped by Amos and de Keyser (1983) at 1:250 000 scale. The geology comprises:

• Hodgkinson formation • Barron River metamorphics • Mareeba granite • Quaternary alluvium and beach sands

3.1.1 Hodgkinson Formation

The Hodgkinson Formation is a highly folded, thick and fairly uniform geosynclinal deposit of rhythmically alternating arenite and slate with inter-calcated beds of chert, volcanics and limestone. Low grade metasediments form the dominant parent material of the uplands. The Hodgkinson Formation contains some interbedded basic volcanics.

3.1.2 Barron River metamorphics

These consist of interbedded phyllite, foliated and massive quartzite, schist, slate, metagreywacke, greywacke, minorchert and greenstone, with minor levels of marble and ultrabasic schist.

The contact zone between the Barron River metamorphics and Hodgkinson Formation is ill-defined.

3.1.3 Mareeba granite

The Mareeba granite includes a large intrusion comprising the high mountain ranges west of Mossman and in the Thornton Peak area.

It consists mainly of adamellite but ranges from granodiorite to granite. The rock is porphyritic and medium to coarse grained•

3•1•3 Quaternary alluvium and beach sands

Alluvia has been deposited as alluvial fans and as alluvial plains• The alluvia on the alluvial fans has been transported only short distances and is associated with adjacent geology. The stream alluvia has been transported over some distance and may contain sediments from various origins, mainly from the Hodgkinson Formation and Mareeba granite.

Beach ridges and/or dune sands occur along the coastline. The most extensive areas occur in the Wonga and Port Douglas areas. 3.2 Landform

The study area comprises eight landform patterns (McDonald et al. 1984):

• Mountains • Hills • Low hills • Rises • Alluvial fans • Alluvial plains • Beach ridge plains • Tidal fiats

3.2.1 Mountains and hills

These landform patterns have high to very high relief (90 to > 300 m) with moderately inclined to precipitous slopes and fixed erosional stream channels•

There is continuously active erosion by wash and creep. The geology is typically Hodgkinson Formation, Barron River metamorphics and Mareeba granite. The main occurrence of mountains and hills include the Great Dividing Range, Main Coast Range, Cassowary Range, Dagmar Range and Thornton Range. Numerous hills occur in the Julatten area. An extremely large old landslip occurs at the base of Thornton Peak near Cooper Creek.

3.2.2 Low hills and rises

These landform patterns have very low to low relief (9 to 90 m) and very gentle to steep slopes, with fixed erosional stream channels. There is continuously active sheet flow, creep and channelled stream flow. Low hills and rises in the Julatten area are formed from the Hodgkinson Formation and Barron River metamorphics.

3.2.3 Alluvial fans

This landform has very gently to gently inclined slopes of extremely low to very low relief (< 30 mm). The alluvial fans have formed from the deposition of material at the base of the hills and mountains by channelled stream or sheet flow. The fans form a continuous apron fronting the hills and mountains along the coastal lowlands. The boundary between the hills and/or mountains and the alluvial fans has been delineated in most areas by a sharp change in slope. The slopes of the hills and mountains are generally greater than 20%. Slopes on the fans are generally concave with 5 to 10% on upper slopes and < 1% on lower slopes.

The alluvial fans have formed predominantly from the Hodgkinson Formation and Barron River metamorphics with minor areas formed from Mareeba granite• 3.2.4 Alluvial plains

This landform pattern has formed from alluvia derived from the alluvial fans, low hills, hills and mountains. It includes the landform elements; plains, levees, terraces, channel benches, prior streams, stream channels and swamps.

Most alluvia is a mixture of sediments from granitic and metamorphic rocks with varying contributions from each.

3.2.5 Beach ridge plains

Beach ridges consist of relict parallel linear ridges built up by waves and modified by wind.

Beach ridge systems and a dune system are evident and indicate several stages of coastline development. The youngest system occurs as an almost continuous landform pattern along the coastline. Older systems occur more sporadically and it is evident that some areas have been destroyed by stream migration and to a lesser extent shoreline erosion.

3.2.6 Tidal flats

The alluvial plains at the mouths of creeks and rivers grade into tidal flats colonised by mangroves. The largest areas of mangroves occur at the mouth of the Daintree River and in the shallow embayment west of Port Douglas.

4. HYDROLOGY

4.1 Surface hydrology

The Daintree, Mossman and Mowbray Rivers and Stewart, Saltwater and Whyanbeel Creeks are the major drainage systems on the coastal lowlands. The Daintree River has an extensive catchment while the remaining creeks and rivers are relatively short and fast flowing. Floods are generally confined to the channel benches on the plains in the lower reaches of the rivers and creeks. Floods are usually of limited duration (< 2 days) but depend on flood characteristics.

The Julatten area is drained by Rifle and Bushy Creeks which are tributaries of the Mitchell River. Flooding along these creeks is usually of limited duration.

Water from the Daintree River is not used for irrigation due to salinity from tidal influence in the vicinity of existing cropping. Irrigation is usually possible above Stewart Creek but this area is largely occupied by improved pastures. Very limited use is made of surface waters from the Mossman and Mowbray Rivers above the tidal influence. Cropping in the Julatten area makes limited use of water in Rifle and Bushy Creeks. This includes two cane farms.

4.2 Subsurface hydrology

Subsurface water on the coastal lowlands is not widespread and is of varying quality and yield (Queensland Water Resources Commission personal communication).

The alluvial sediments which are up to 40 m thick, can supply water at 8 to 14 1/second. Water is usually brackish close to the coast with quality improving further from the coast.

The sediments of the alluvial fans generally supply little subsurface water. Water may be supplied at 6 to 8 1/second from the fractured metamorphic rocks below the sediments but the water is usually high in iron.

The limited economic supplies of good water are usually sufficient for strategic watering of crops.

5. SOILS

A report on "Soils of the Mossman-Cape Tribulation Area, North Queensland" (Murtha 1989) describes the soils of the study area.

A total of 47 soil series were recognised. These have been mapped as 25 soil mapping units. Mapping units are associations, that is they contain several soil series. Each occurrence of a mapping unit is a unique map area (UMA). Each UMA was given a unique number and individually described on a UMA record type (Appendix IV) in terms of soils and landform. The dominance of the major soil and the range of associated soils may vary among the UMAs of each mapping unit.

A brief description of the dominant soil series in the soil mapping units together with the Great Soil Group, dominant principle profile form and landform, are listed in Table 4.

5.1 Soils formed on beach ridges

Two distinct beach ridge systems and one dune system are clearly evident and indicate several stages of coastline development. Three mapping units have been named after the dominant series.

A rudimentary podzol (Hull series) forms the youngest system and ranges from less than 100 m to about 1.5 km wide. It forms an almost continuous zone along the coastline. The red earth/yellow siliceous sand/yellow earth of the Brosnan/Spanos 10

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P, ..~ "~ ~ 0 >'- 0 2 r~ Z 13 association generally occurs inland of the Hull association between Rocky Point and the Port Douglas road. Brosnan and Spanos series occur in about equal proportions with the red earth generally occupying the higher areas. The podzol of the Daintree series is restricted to the sands immediately to the south of Baileys Creek Road turnoff.

The soils are dominantly rapidly drained but are occasionally poorly to imperfectly drained in low lying areas. Available soil water capacity is very low on the podzols to low on the red earths but fluctuating watertables within a metre of the surface in some soils supplies water to plants. Salinity is only a problem where sea water intrusion occurs close to the coast.

5.2 Soils of basaltic origin

No basalt was mapped in the study area but basic volcanics are interbedded in the Hodgkinson Formation.

Three mapping units include soils formed/n situ and on alluvial fans. The krasnozem formed in situ (Pin Gin series) occurs near the crest of the Main Coast Range on the Mossman to Mount Molloy Road. The krasnozem on the alluvial fans (Kimberley series) is restricted to the lower slopes of the Thornton and Alexandra Ranges. The red and brown clay (Pera series) occurs as small areas throughout the Hodgkinson Formation south of Weatherby homestead.

The rapidly drained krasnozems and moderately well drained red clay have good available water capacity. The pH of all soils is usually less than 5.5. Slopes greater than 3% are dominant. Rock fragments increase in size and amount on the upper slopes of the alluvial fans.

5.3 Soils of metamorphic rock origin

Five mapping units include soils formed/n situ and on alluvial fans. The red podzolic soil (Galmara series) was mapped as small areas to the north of Alexandra Range. A xanthozem (Bicton series) and a soloth (Weatherby series) dominate the rises, low hills and hills of the Julatten to Mount Molloy area. The soloth dominates the drier areas. A red earth (Mission series) and a yellow podzolic soil (Clifton series) dominate the alluvial fans on the coastal lowlands. The red earth occurs on the upper slopes while the yellow podzolic soil dominates the lower slopes and overlies marine sediments in places.

Available water capacity is generally high on the red podzolic soil and xanthozem but shallow soil depths on the xanthozem may lower the available water capacity. The red earth, yellow podzolic soil and the relatively shallow, coarse structured soloth have moderate available water. The pH of all soils is usually less than 5.5 except the alkaline phase of the Weatherby series which increases in occurrence towards Mount Molloy. Salinity is a minor but common problem on the Clifton series along the eastern side of Cassowary Range. Soil drainage ranges from well drained to imperfectly drained with more poorly drained soils usually occurring at the base of the slopes or on the 14 soloth soil. Massive, very hardsetting surface horizons are typical of the soloth and yellow podzolic soil. Broken topography (creeks, gullies), rock fragments and water erosion are common problems on the rises, hills and upper slopes of the alluvial fans.

5.4 Soils of granitic origin

Mareeba granite occurs mainly as inaccessible mountains. One small area of yellow earth (Thorpe series) occurs in the upper reaches of Whyanbeel Creek.

The well drained soil has moderate available water capacity. Granite boulders are common. Slopes are mainly 5 to 8%.

5.5 Soils formed on alluvium

These soils have formed on alluvia chiefly containing material of granitic and metamorphic rock origin with varying contributions from each. The dominant soils in the mapping units include soils with no suitable great soil group (Tully, Mossman, Liverpool series), a red earth (Virgil series), a yellow earth (Somerset series), a gleyed podzolic soil (Coom series), soloths (Ponzo, Rumula, Holloway series), a solodic soil (Gariock series) and humic gleys (Newell, Timara, Bulguru series).

The earths (Virgil, Somerset) and solodic soil (Gariock series) have moderate available water capacity while the remaining soils have high capacities. Liverpool series may have moderate available water capacity due to a shallow sandy subsoil. All soils except Gariock and Rumula series near Mt. Molloy have a pH of 5.5 or less. The Rumula soil has a neutral subsoil pH in the drier areas near Mount Molloy. Soils range from well drained to very poorly drained. Floods are generally restricted to the channel benches and the plains in the low reaches of the larger rivers. Broken topography due to narrow alluvial plains and numerous stream channels is common in the upper catchments. Massive very hardsetting surface horizons are typical of the soloths and solodic soil. Rock fragments usually occur only in the upper catchments.

6. LAND USE

6.1 Introduction

Agriculture in the study area is dominated by the sugar industry and beef cattle. Other relatively minor or potential industries include lychees, avocados, bananas, papaws, tea, rambutans, pineapples, peanuts, citrus, vegetables, small crops and broad acre crops such as maize, sorghum and soybeans.

The higher hills and mountains are generally inaccessible and are largely covered by national parks and state forests. The dramatic increase in tourism recently has resulted in an increased demand for urban and rural residential subdivision. 15

The sugar industry dominates the coastal lowland from the Daintree River to Yule Point. One grower is located north of the Daintree River and several growers are in the Julatten to Mt. Molloy area. The district has 9547 ha of assigned land supplying cane to the Mossman Central Mill. The average long term yield per harvested area is 74.6 t/ha with an average CCS 1 of 13.7 units. The improvement in cane productivity in recent years has come mainly from a more intensive utilisation of the gross assigned area. The average assigned area per assignment is 54.5 ha. The incidence of green cane harvesting is increasing and represented 73.9% of the total harvest in 1989.

Beef cattle are grazed predominantly on improved pastures along the Daintree River and Stewart Creek and in the Julatten area. The undulating rises and low hills south of Julatten are predominantly under native pastures.

Lychees, avocados and papaws are grown on small scattered areas in the Julatten area. Small areas of papaws are also grown on the coast.

Bananas are grown to a limited extent mainly in the upper Whyanbeel Creek area and north of the Daintree River.

Tea is grown on a range of soils in the Mackenzie Creek area north of the Alexandra Range. Current yield levels are about 3000 kg/ha but the harvested leaf has to be sent approximately 250 km to Nerada for processing.

Coffee is grown to a very limited extent in the Stewart Creek area and another plantation is being established on Bushy Creek.

Pineapples are grown on a small area in the Miallo area. Fruit goes to the local fresh fruit market.

6.2 Methods of evaluating land suitability

6.2.1 Assessing land suitability

A total of 520 unique map areas (UMAs) have been delineated in the study area.

The UMAs have been individually assessed for their relative suitability for growing sugar-cane, bananas, papaw, mango, lychee, citrus, avocado, rambutan, tea, vegetables, cucurbits, pineapple, maize, sorghum, sweet corn, soybean, peanut, sweet potato, rainfed rice, Pinus caribaea and improved pastures using the land suitability classification scheme described in Appendix I.

The significant limitations to production were identified for each UMA. The severity of each limitation was assessed on a 1 to 5 scale coinciding with the scheme's five suitability classes (Appendix II). The land was then allocated to one of the five

1 CCS" Commercial cane sugar 16 classes:

Class 1 Suitable with negligible limitations Class 2 Suitable with minor limitations Class 3 Suitable with moderate limitations Class 4 Marginal/presently unsuitable Class 5 Unsuitable

The significant limitations to production in the study area were identified following discussions with BSES, Mossman Mill, industry groups, Forestry Department, QDPI, farmers, a literature review and field experience gained during the study.

The suitability classes and relevant limitations to production of the various crops have been recorded on the UMA record file.

6.2.2 Use of suitability classes

Land has a wide range of properties which affect yields, costs and efficiency of production and land degradation. The land suitability classification simplifies these complex interactions so that a comparative overview can be gained of the lands.

In general, as the degree of limitation increases, yields decline and/or costs of production increase and thus efficiency declines. However, the farmer has a major effect on yield and economic efficiency and it cannot be assumed that the highest yields will always be achieved on class 1 land. Lands with the same suitability class for a crop may have different yields and/or production costs because of inherent soil properties.

Considerable information is lost when simplifying the resource inventory into land suitability classes, hence the classes should be interpreted with care.

6.2.3 Effective agricultural land

The effective agricultural land factor (EALF) is intended to account for loss of land to headlands, drains, soil conservation works, general infrastructure and small unmapped, unusable areas such as creeks and gullies. For every hectare of suitable land only a proportion will be used for arable cropping, tree crops or pastures and this proportion varies according to the mapping unit, type of limitation, land use and land suitability class. The concept of EALF has been used to examine the potential increase in useable land for arable cropping, tree crops and pastures.

As the severity of some limitations increases, more land is consumed in overcoming those limitations. For example, increased wetness requires a greater density of drains; increased erosion hazard requires more erosion control measures. However, the amount of land consumed in overcoming a limitation is also dependent on the crop. In general, arable crops require more land to overcome limitations such as rockiness, erosion and topography. Whereas tree crops are less sensitive and pastures are very tolerant and little land will be lost in overcoming the limitation. Some UMAs vary greatly in the amount of land lost to creeks and gullies. Therefore, the land use 17 efficiency will vary between UMAs with similar mapping units and crops. Effective agricultural land factors are recorded on the UMA record file.

6.2.4 Mapping assigned land

The assigned land was mapped so that location, size and relative suitability of assigned and unassigned land could be compared.

The assigned land was delineated onto aerial photographs. These were compiled onto 1:50 000 working maps and overlaid on to the UMA working maps. In each UMA, the area of land assigned to the Mossman Mill was measured with a digitiser and the area of unassigned land calculated.

Assigned land is measured by the cane inspectors at a scale of 1:4 000, thus the digitised areas measured at 1:50 000 overestimate the actual assigned area. In order to estimate the actual assigned area, the 1:50 000 measured area was compared with that measured by the cane inspectors at 1:4 000 and this ratio was called the mill factor.

6.2.5 Storing and extracting data

The UMA record file consists of 4 record types. Record type 1 contains location data and land resource inventory. Records 2 to 4 contain the land suitability assessment of the various crops. Record type 4 contains the UMA areas, cane assigned areas, mill factors and land use efficiency factors. The UMA codes are described in Appendix III and the UMA record file is given in Appendix IV.

All the data can be manipulated and extracted in any combination. It can be printed out in tables or in overlay form.

Using the tabular form of data presentation, the required information can be sorted into groups, listed and areas calculated. Using the overlay method of data presentation, a plotter plots any of the UMA data at the grid coordinates of the UMA labelling points. The plot can then be overlayed on an appropriate base map.

The information on computer files can be accessed through the Director, Land Resources Branch, Department of Primary Industries, Meiers Road, Indooroopilly, 4068.

6.3 Land use specifications for agricultural crops

A brief outline of the land use specifications of the agricultural crops for which suitability was assessed are described in Appendix V. Specifications briefly outline the climatic adaptations, soil requirements, management practices, varieties and yields. Specific tolerance levels for each limitation are listed in the suitability classification scheme (Appendix I). 18

6.4 Limitations to agriculture

Rainfed agriculture within the study area will be affected by the following limitations:

Climate Water availability Soil nutrient supply Salinity Wetness Flooding Landscape complexity Soil physical condition Topography Rockiness Water Erosion

These limitations affect crop production through influences on crop growth, machinery operations and land degradation.

6.4.1 Climate

The climate varies over the study area (see Section 2) but it is difficult to compare climatic conditions within the area because of the shortage of data. Rainfall, temperatures and the occurrence of frosts were assessed for particular areas largely based on local knowledge. The information was then allocated to UMAs.

High humidity is associated with the incidence of disease and high or low temperatures may preclude, or diminish the quality or quantity of production of certain crops. Annual rainfall was used as an indicator of high humidity for extended periods. The incidence of frosts was assessed on the basis of local knowledge. Frosts in the Julatten to Mount Molloy area are generally light and are not considered to be a significant limitation to most crops. Exceptions are some horticultural crops and tea.

Strong winds from cyclones can cause severe crop damage. Crops which may be affected during the summer period are sugar-cane and tree crops. Tree crops are particularly sensitive when soils are saturated.

6.4.2 Water Availability

Plant yield will be decreased by periods of water stress, particularly during critical crop growth periods. The water availability to plants is determined by the interaction between soil attributes, climate, landform and effective rooting depth of a crop.

Attributes which determine soil water include texture, pedality, minerals in the clay size fraction, organic matter, grade of structure, depth, infiltration rate, permeability, salinity, sodicity, compaction, occurrence of impermeable layers and rock fragments. Climatic factors include rainfall, temperature and evapotranspiration. Landform will influence water supply through watertable effects and run-off. For example, well drained 19 upland soils dry out prior to the well drained level alluvial soils with similar profile attributes. The effective rooting depth of a crop will determine how much of the soil profile can be utilised.

Climatic factors are restricted to wet or dry season. The monthly moisture balance shows a deficit from May to December for the Julatten to Mount Molloy area (Capelin and Murtha 1983). Supplementary irrigation is required by crops until the wet season to achieve optimum yields. Cane assignments on Rifle Creek below Mount Molloy are irrigated. Landform, effective rooting depth for the various crops and the soil attributes have been incorporated into the suitability classification scheme (Appendix I). Clay mineralogy for all soils is fairly uniform and is dominated by kaolinite (Murtha 1989).

In general, the deep (> 1 m), pedal, fine structured, uniform to gradational, medium to heavy textured soils have negligible limitations for wet season crops. This may be modified by the occurrence of rock fragments. Light textured soils such as the rudimentary podzols on the beach ridges have severe limitations for most crops. This may be modified by the occurrence of a fluctuating watertable shallower than one metre. Crops which require irrigation are less dependent upon soil moisture but irrigation frequency and management effort are related to the method of irrigation and soil attributes described in the suitability classification scheme.

6.4.3 Soil nutrient supply

The effect is reduced plant growth associated with a shortage or over supply of nutrients. Suitability assessment accounts for requirements additional to standard rates and practices.

On strongly acid soils (pH < 5.5), aluminium toxicities may result in sensitive crops. Increased exchangeable aluminium has occurred in cultivated land over time when compared to uncultivated land (Wood 1985). Although sugar-cane (Hetherington et al. 1986) and tea (Eden 1965, Harler 1956) are tolerant to aluminium, other crops may be sensitive to aluminium in the highly leached, strongly acid soils which predominate in the study area. No measurements are available on the type of aluminium and concentrations in soils.

Nutrient sorption can be a problem on acid soils or soils high in organic matter. Phosphorus sorption arises in acid soils where iron oxides often react strongly with phosphate (Taylor et al. 1983). The amount of phosphorus retained by iron oxides depends on the amount available, surface area of the oxides, pH, competition for surface charge by organic matter and other anions. Phosphate sorption is reduced by the competitive influence of organic matter. The cation exchange capacity of organic matter and therefore, the ability of surface soils to retain nutrient cations, can be considerably decreased by interaction of the organic matter and iron oxides. Also if organic matter is removed by erosion, the iron oxides cannot retain cations. Phosphate sorption may occur on the iron rich basaltic and metamorphic soils but no measurements are available.

Aluminium oxides behave in a similar way to iron oxides and have the ability 20 to sorb phosphate (Norrish and Rosser 1983). In acid soils, aluminium hydroxy polymers occupy exchange sites on organic matter. These hydroxy - aluminium species are able to react with phosphate (Norrish and Rosser 1983). This could possibly explain the high phosphate sorption of the humic gley soils (Newell, Bulguru series).

Many trace elements, such as copper, zinc, cobalt, iron and manganese, react with organic matter in soils and often cannot be exchanged easily from soils (Beckwith and Butler 1983).

In this high rainfall area, nutrient leaching from highly permeable, low cation exchange capacity soils is suspected but there is a lack of knowledge on the fate of nutrients. Some control of nutrient leaching may be achieved by:

raising the cation exchange capacity by increasing organic matter, raising pH where variable charge soils exist, applications of silicates and phosphates

managing the low cation exchange capacity by split applications and slow release fertilisers.

High soil pH suppresses tea growth. Tea ideally requires a soil pH < 5.5. A soil pH > 6.5 is unsuitable. High pH (>6.5) only occur in the neutral and alkaline phases of the soloths (Weatherby, Rumula series) and the solodic soil (Garioch series) south-west of Julatten. These soils are also unsuitable for tea due to a wetness limitation while the area is unsuitable due to low rainfall.

Excessive levels of elements such as sodium, chloride or boron are not considered to be a limitation to crop growth in the study area.

6.4.4 Salinity

Soluble salts affect plants through the osmotic effects on water uptake, toxicity caused by specific ions and the effects of high exchangeable sodium percentage (ESP). Toxicity effects are covered in Section 6.4.3, while ESP effects are covered in other sections (see Sections 6.4.2, 6.4.5).

Plant responses to salt are conditional on tolerance levels, climate, evapotranspiration, moisture regime of the soil, composition of the salts, nutrient status of the soil and soil physical properties, particularly permeability.

The relative salt tolerances for a range of plants (Shaw et al. 1986) have been used to determine suitability subclasses (Appendix I).

Minor salinity problems occur in the Mossman area. Primary or natural salinity is a result of marine intrusion and is restricted to areas along the coast. Secondary salinisation occurs on seepage slopes. This is restricted to minor but widespread areas in the Clifton soil mapping unit on the eastern side of Cassowary Range south of Mossman (see plate 1). Widespread clearing of the vegetation has probably resulted in rising watertables with salts accumulating on the surface and in the soil profile where 21 alluvial fan sediments overlie strongly sodic D horizons possibly of marine origin. The location of the Captain Cook highway may have contributed to the problem by restricting lateral seepage. The cause of salting requires investigation.

The aim of reclamation is to leach the salts out of the rooting profile while retaining soil permeability. On impermeable soils (Clifton series), permeability can be improved by the addition of a soluble form of calcium. Salt water disposal can be achieved by;

local surface drains to protect saline areas from additional saline run-off water

planting deep rooting vegetation on catchment areas to increase evapotranspiration and therefore lower the watertable

installing deep drains to intercept groundwater. Deep drains will lower the water-table and encourage leaching.

Plate 1. Small but widespread areas of salt affect caneland in the Clifton soil mapping unit on the eastern side of Cassowary Range. 22

6.4.5 Wetness

Waterlogging reduces plant growth by affecting soil aeration, increasing the incidence of diseases and causing delays in machinery operations.

Internal and external drainage were assessed. Indicative attributes of internal drainage include texture, the presence of pedality, grade of structure, mottles, segregations and impermeable layers. Laboratory data such as exchangeable cations, pH, salinity and dispersability can also be used as indicators. Soil attributes determine or indicate soil permeability and soil drainage. Slope and topographic position were used to assess external drainage capacity.

Crop sensitivity to wetness was the overriding criteria for determining suitability subclasses.

The timing of mechanical operations, such as cultivation, disease and pest control and harvesting, is an important consideration. Harvesting operations can be severely restricted on poorly drained soils, especially for wet season crops. Some crops, such as bananas and tea, require all year round mechanical operations for harvesting or disease and weed control.

The soil drainage and permeability categories, crop sensitivity, and flexibility of mechanical operations have been used to assess the suitability subclasses (Appendix I). Table 5 shows the drainage and permeability categories for the dominant soils. Seepage areas on the alluvial fans are particularly troublesome due to their small size, frequency and randomness.

Table 5. Soil drainage and permeability categories for the dominant soils

Soil drainage Soil Permeability

Slowly Permeable Moderately Permeable Highly Permeable

Very poorly drained Bulguru

Poorly drained Holloway Timara

Imperfectly drained Weatherby, Clifton, Weatherby, Clifton, Ponzo, Rumla, Garioch Somerset, Coom, Newell

Moderately well drained Pera, Weatherby Bicton, Weatherby, Liverpool, Tully, Mossman, Somerset

Brosnan, Pin Gin, Kimberly, Well drained Thorpe, Liverpool, Somerset Mission, Galmara, Virgil,

Hull Rapidly drained Daintree 23

6.4.6 Flooding

Flooding is defined here as overflow from natural water courses as distinct from surface water ponding due to insufficient drainage capacity.

The effect of flooding is yield reduction or plant death through water characteristics such as silt content and water temperature, lack of aeration and the physical removal or damage from flowing water. The extent of crop damage is largely dependent upon the type of crop.

The effects of flooding on an individual piece of land are difficult to predict. Flood frequency was used to distinguish between suitable and unsuitable land only in extreme frequency situations or for intolerant crops. Where flood frequency is significant, but not extreme, the "f' symbol was used in the UMA record file to indicate the occurrence of flooding, but due to insufficient knowledge, it does not downgrade the classification (Appendix I).

Floods in the study area are mainly associated with cyclones or monsoonal activity with major floods usually associated with cyclones.

All coastal rivers and creeks, except the Daintree River, are short and fast flowing. Flooding is usually restricted to the channel benches and is of limited duration. The Daintree River has a relatively large catchment with floods occurring on the channel benches and on the plains in the lower reaches of the river. Flooding along Rifle and Bushy Creeks in the Julatten area is usually restricted to the channel benches and is of limited duration.

Few land use and development options are available. Land management should aim at stabilising the flood plain in high risk areas. This includes not clearing and cultivating within 40 metres of the river bank or 20 metres for small creeks, maximising height and cover of crops during the flood prone time of the year to protect the soil against water scouring, and establishing permanent pastures or other vegetation where deposition and scouring regularly occur.

6.4.7 Landscape complexity

Landscape complexity includes dissected land (topographic complexity) and complex distribution of different soils (soil complexity).

The dissection of flat land by streams and gullies resulting in small and/or narrow, and/or isolated areas, will restrict farm layout and the efficiency and ease of machinery use. It is desirable to have continuous unbroken land for effective crop production. Assessment of the topographic complexity limitation is based on size and isolation of the mapping units (Appendix I) and type of agricultural enterprise. For example, broad acre crops, such as maize and sorghum, will be more severely affected on small areas than high value horticultural crops. 24

The mapping units regularly affected by dissected land include the soils of metamorphic rock origin on the hills and rises, and upper slopes of the alluvial fans. Soils of alluvial origin are sometimes affected where the plains are dissected by numerous gullies (Ponzo series) or in upper catchments where the alluvial plains are narrow and/or dissected by stream channels.

Mapping units are associations, that is, they contain several soil series. Farm layout and general efficiency are affected when a soil occupies a small area and/or when the component soils have different suitability classes (Appendix I). Where the area of contiguous suitable soils in a UMA is less than a minimum production area, the area of any contiguous suitable soil in adjacent UMAs is also included in the assessment of the minimum production area. When soils of different suitability classes are present, the highest suitability class is downgraded according to the proportional area of each soil. This is done once the subclasses for all other limitations are determined.

Where complex soil patterns are a problem on the alluvial plains, areas of individual soils were estimated rather than accurately delineated.

6.4.8 Soil physical condition

This limitation applies to soils where;

surface condition influences seedling emergence and establishment, and root crop development;

the moisture content of the soil determines the ability to cultivate a soil to achieve a favourable tilth;

• adhesive soils affect the harvest of root crops.

Hardsetting surfaces, stiff clays and coarse structure affect root crop development and seedling emergence and establishment. Hardsetting surfaces are a feature of the earths (Mission, Virgil, Somerset series), the yellow podzolic soil (Clifton series), the soloths (Ponzo, Rumula, Weatherby series) and the solodic soil (Garioch series). Stiff clays and coarse structure within the plough layer may be a problem on the solodic soil (Garioch series).

It is desirable that a soil can be cultivated over a wide moisture range to give a favourable tilth and some flexibility in the timing of operations such as planting. The clay soil (Pera series) has a narrow moisture range while the gleyed podzolic soil and humic gley (Coom, Timara series) have a moderate moisture range. The hardsetting yellow podzolic soil (Clifton series) and texture contract soils (Weatherby, Garioch series) also have a moderate moisture range for cultivation because they have very firm consistency when dry and are spewey when wet.

Adhesive soils affect the recoverability and condition of root crops. Root crops ideally require friable soils so harvest machinery can easily lift and remove the root crops from the soil. A majority of the massive surfaced soils or poorly to imperfectly drained 25 soils with clay textured surface are adhesive to varying degrees. In general, the degree of adhesiveness increases as clay content and/or consistency increase and degree of pedality decreases.

All these factors, together with the type of agricultural enterprise, will determine suitability (Appendix I).

6.4.9 Topography

The topography limitation covers the slope limits for safe machinery use and effects of complex slopes on the efficiency of machinery use on sloping arable land.

The slope limit for safe machinery use is 15% when machinery is used on the contour because of conventional soil conservation measures. An upper slope limit of 20% and 30% exists for tree crops and pastures respectively. This is because tree crops and pastures have permanent grass cover and machinery can be used up and down the slopes. The lower slope limit of tree crops compared to pastures represents unsafe use of machinery on wet slippery slopes over 20%.

The moderately inclined (slopes 10 - 20%) rises, low hills and hills with either a xanthozem (Bicton series), red podzolic soil (Galmara series), krasnozem (Pin Gin series) or a soloth (Weatherby series) are the landforms and soils with slopes regularly above 15%.

Complex slopes, which have variable downslope angles and orientation across the slope, cannot be used effectively by machinery when conventional erosion control measures are implemented. Erosion control layouts on complex slopes cause short rows and sharp curves. Complex slopes do not downgrade the suitability class of a UMA. Assessment of complex slopes is subjective only and was recorded on the UMA record file to indicate that minimum tillage, surface management practices and modified erosion control structures have to be applied in lieu of conventional erosion control structures. The soils which regularly have complex slopes are the krasnozem of basaltic origin (Pin Gin series), the xanthozem (Bicton series) and the soloth (Weatherby series) of metamorphic rock origin. The red podzolic soil of metamorphic rock origin (Galmara series) often has complex slopes but is a minor arable soil in the study area.

6.4.10 Rockiness

Rock fragments (pebble, gravel, cobble, stone, boulder) will interfere with the use of, and may cause damage to agricultural machinery. The volume of rock fragments within the soil is extremely variable and difficult to estimate. Tolerance levels vary among farmers and for different agricultural uses.

In general, crops which require several cultivations annually and have a low harvest height (sugar-cane, soybeans) have a low tolerance to rock fragments. Root crops (peanuts, sweet potatoes) will not tolerate any rock fragments. Crops with higher harvest heights (rice, maize, sorghum) can tolerate more rock fragments. Horticultural tree crops (avocados, papaws, citrus, mangoes, lychees, rambutans) can tolerate 26 considerable amounts. Bananas, pineapples and exotic pines, although tolerating considerable amounts of rock fragments, are slightly more sensitive to mechanical operations during establishment than other tree crops.

Surface rock fragments in tea plantations interfere with harvest machinery by creating irregular harvest heights and reducing tea quality. This aspect is particularly important in erosion prone areas where rock fragments may become concentrated on the surface.

Improved pastures are very tolerant of rock fragments.

The size and abundance of rock fragments, as defined by McDonald et al. (1984) were used to determine suitability subclasses (Appendix I). The limitation increases with the size and/or amount encountered.

Rock fragments are a problem on the rises, low hills and hills with soils of metamorphic rock origin (Weatherby, Galmara series), the upper slopes of the alluvial fans (Mission, Kimberley series) and in the upper catchments of the alluvia (Liverpool, Virgil series). Generally, the size and abundance increases on upper slopes and in upper catchments.

6.4.11 Water erosion

Water erosion causes soil degradation and long term productivity decline on unprotected sloping arable land through loss of soil, organic matter and nutrients. Crop damage, higher working costs, uneven harvest heights and damage caused by silt deposition also result from soil erosion.

Soil loss will depend on rainfall erosivity, soil erodibility, slope gradient and management practices.

Rainfall erosivity is very high on the wet tropical coast (Rosenthal and White 1980) with the major distribution of erosive rainfall occurring during the summer months. Consideration of this factor is particularly important in the management of summer crops.

Soil erodibility depends on infiltration characteristics, permeability, water holding capacity, structure and stability. These factors are relatively uniform within each soil series. Slope gradient cannot be modified.

Necessary measures to control water erosion may be divided into surface management (such as contour farming, maintaining maximum surface covers, minimum tillage, maintaining the soil surface in a rough condition if cultivated) and structural works (such as contour banks, waterways and diversion banks). Soil loss can be reduced to acceptable levels on simple slopes by erosion control structures and surface management practices up to the maximum slope limits (Appendix I). Slope limits were determined in consultation with soil conservation extension and research personnel and extension and research agronomists. The slope limit for a particular use is the slope 27 beyond which erosion cannot be reduced to acceptable levels (20 t/ha/year).

The soils prone to water erosion are the soils of basaltic origin (Pin Gin, Kimberley, Pera series), soils of metamorphic rock origin (Galmara, Bicton, Weatherby, Mission, Clifton series) and soils of granitic origin (Thorpe series). The soloth of metamorphic rock origin (Weatherby series) is more erodible than other soils of metamorphic rock origin and has been placed into a separate soil group (Appendix I). The red and brown clay of basaltic origin (Pera series) has soil attributes indicating higher erodibility than other basaltic soils and has been placed into the slope categories of the granitic soils.

6.5 Suitability of soils for agricultural crops

A summary of the limitations and attribute levels occurring in the soil mapping units is given in Table 6. The limitations are not necessarily present in every UMA.

The limitations (Appendix I) assessed for each UMA (Appendix 4) are related to soil or landform attributes or both. Water availability and soil nutrient supply are largely soil related. Landscape complexity, topography and flooding are landform related. Salinity, wetness, erosion and rockiness are largely a result of both landform and soil attributes. The degree of the limitation related to soil attributes is normally constant between UMAs while the degree of the limitation related to landform can vary between UMAs.

Table 7 summarises the area (ha) of the suitability classes for each crop and each soil mapping unit.

6.6 Alternative land uses

There is competition for agricultural land on the lowlands and in the Julatten upland area. Alternative uses to agricultural crops include urban, rural-residential and tourist developments and other subdivisions which are generally considered too small for viable agricultural production.

As agricultural production, particularly sugar-cane, is a major contributor to the economy of the area, it is important that the Mareeba and Douglas Shire Councils accept the responsibility for coordinating an orderly and balanced development taking into account the requirements of all the competing land uses.

The coastal lowland from the Daintree River to Oak Beach has been almost completely utilised for growing sugar-cane. There is virtually no potential for expansion or substitution from existing sugar lands other than to the more remote and fragmented lands in the Julatten area, up the Daintree River or north of the Daintree River. The Mossman Mill which crushes all the sugar-cane in the study area requires a minimum throughput of cane to remain viable. The long term viability of the mill is in doubt if existing or potential lands are subdivided. 28

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i=..d ~ ¢~1 ~ ~_ (~ ~, ~ ~ ~1(~1,,~. ~ ~ ~ ~ ~ '~'='1'~ 36 It is important to protect valuable agricultural land from subdivision or urban development. The subdivision of valuable agricultural lands (class 1, 2 and 3 land) into small blocks generally renders these areas too small for viable agricultural production. The minimum subdivision area should correspond to the minimum area for viable agricultural production unless subdivision blocks are to be used as expansion areas or used for cropping in conjunction with adjoining areas. Urban, rural-residential and tourist developments should be directed to the marginal/currently unsuitable (class 4) or unsuitable (class 5) agricultural lands such as the coastal beach ridges and the steep (> 15%) lands adjacent to the hills and mountains.

7. CONCLUSIONS

The lowlands from Cape Tribulation to Oak Beach and the Julatten uplands were assessed in terms of land suitability for growing sugar-cane, bananas, papaw, mango, lychee, citrus, avocado, rambutan, tea, vegetables, cucurbits, pineapple, maize, sorghum, sweet corn, soybean, peanut, sweet potato, rainfed rice, Pinus caribaea and improved pastures. Each of the 520 unique map areas (UMAs) were individually assessed for their suitability for growing the crops.

A total of 24127 ha is suitable (class 1, 2 and 3 land) for sugar-cane, 20548 ha for bananas, 13381 ha for papaws, 14328 ha for mangoes, 16343 ha for lychees, 13382 ha for citrus, 0 ha for avocados, 17418 ha for rambutans, 7741 ha for tea, 23815 ha for vegetables, 21275 ha for cucurbits, 16053 ha for pineapples, 20380 ha for dry season maize, 17512 ha for wet season maize, 20380 ha for sorghum, 23484 ha for sweet corn, 16234 ha for soybeans, 13639 ha for peanuts, 15799 ha for sweet potatoes, 19723 ha for rainfed rice, 22840 ha for Pinus caribaea, 31684 ha for improved pastures. A 1:100 000 agricultural land suitability map accompanies this report.

An effective agricultural land factor was allocated to each UMA to account for the varying proportions of the gross areas actually useable for growing the various crops. There is sufficient land to accommodate an increase of 3712 ha (after the effective agricultural land factor is taken into account) in cane assigned land. Most of this land is located up the Daintree River, north of the Daintree River and in the Julatten area. However, no account was taken of the availability of the land. The potential assigned land is on average further from the mill than the assigned land. The Julatten area is generally fragmented while the steep Main Coast Range poses transport problems. The land north of the Daintree River is largely subdivided into small blocks while distance and transport of cane across the Daintree River are also problems. There is virtually no unassigned suitable cane land available to the sugar-cane industry between the Daintree River and Oak Beach.

All land considered marginal/currently unsuitable for any agricultural use is of dubious benefit due to the high cost of and/or unreliable production and land degradation. Future changes in technology may prove these lands to be suitable. 37 The significant limitations to production were identified and assessed for each UMA. The limitations assessed were climate, soil water availability, soil nutrient supply, salinity, wetness, flooding, landscape complexity, soil physical condition, topography, rockiness and water erosion.

Climatic factors were assessed for particular areas and then allocated to UMAs. High humidity is associated with a high incidence of disease and high or low temperatures may preclude or diminish the quality or quantity of production of certain crops.

Crops grown during the moisture deficit period from May to December must rely on soil water or supplementary irrigation. This is particularly the case in the drier Julatten to Mount Molloy area. The water availability limitation is most severe on the sandy soils of the beach ridges, and with the shallow rooted crops.

A majority of the soils in the study area are strongly acid (pH < 5.5) and aluminium toxicity could result in some crops. The use of nitrogen fertilisers has aided the acidification of soils, particularly in the sugar industry. Soil pH should be raised (pH > 5.5) not only to reduce aluminium to low levels but also to increase cation exchange capacity where variable charge characteristics exist. The humic and organic soils have high phosphorus sorption capacities. Heavy initial phosphorus applications are necessary. Nutrient leaching in the high rainfall areas on highly permeable low cation exchange capacity soils is suspected but there is a lack of knowledge on the fate of nutrients.

Secondary salinisation is restricted to relatively minor but widespread areas in the Clifton mapping unit on the eastern side of Cassowary Range south of Mossman. Widespread clearing of vegetation has probably resulted in salts accumulating on the soil surface and in the soil profile where alluvial fan deposits overlie strongly sodic D horizons, possibly of marine origin. The exact cause, extent and rehabilitation methods of these saline areas needs to be evaluated.

Coordinated drainage programs need to be implemented on wet soils. The mapping of soils enables areas which require drainage to be readily distinguished and allows the coordinated planning of drainage works on soils with similar drainage attributes. Drainage works need to be coordinated with soil conservation works and flood management. The recognition of soils with different drainage characteristics allows more efficient farm layout and management. A uniform soil is important for efficient cultural and harvesting operations. Overuse of machinery and the mistiming of cultural and harvesting operations on waterlogged soils can result in compaction, structural degradation and reduction of organic matter. Soil degradation can be minimised by avoiding cultivation, harvesting and other heavy equipment operations on moist or wet soils, improving soil drainage, minimising the number of passes of equipment and using equipment with adequate flotation characteristics. The loss of organic matter can be reduced by the use of cover crops and trash farming.

Flooding is usually restricted to the channel benches of the creeks on the coast and in the Julatten area and is of limited duration. The Daintree River has a large catchment with floods occurring on the channel benches and on the plains in the lower 38 reaches of the river. There should be an awareness that agricultural benefits of farming on the flood plain carry costs associated with flooding. Land management should aim at stabilising the flood plain in high risk areas. This includes not clearing and cultivating within 40 metres of the river banks or 20 metres for small creeks, maximising height and cover of crops during the flood prone times of the year and establishing permanent vegetation where deposition and scouring occur.

Landscape complexity, either dissected land or soil complexity, will restrict farm layout and the efficiency and ease of machinery use. The mapping units regularly affected by dissected land include the soils of metamorphic rock origin on the hills and rises, and upper slopes of the alluvial fans. The alluvial plains are sometimes affected by gullies or narrow plains. Complex soil patterns are a problem on the alluvial plains.

Soil physical condition affects a range of soils. Seedling emergence and establishment problems are associated with the hardsetting soils. The soils with clay surface texture and some of the texture contrast soils have a moderate to narrow moisture range for cultivation. A majority of the massive surfaced soils or soils with clay surface texture are adhesive to varying degrees, affecting the recoverability and condition of root crops.

The slope limit for safe machinery use is 15 % for arable agriculture, 20% for tree crops and 30% for improved pastures. Complex slopes, which cannot be used effectively by machinery when conventional erosion control measures are implemented, regularly occur on the rises and low hills with soils of metamorphic rock origin.

The rockiness limitation is generally a problem only on the rises, low hills and hills with soils of basaltic and metamorphic rock origin, the upper slopes of the alluvial fans and in the upper catchments of the alluvia. Generally, the size and abundance increases on upper slopes and in upper catchments.

The problems of soil erosion have been recognised by the sugar industry and other industry groups. The adoption of conventional soil conservation measures in combination with trash retention and minimum tillage practices need to be encouraged on all erosion prone land. The increase in trash retention and minimum tillage in the cane industry in recent years is encouraging.

An increase in demand for urban, rural-residential and tourist development subdivision is competing for agricultural land, primarily sugar-cane lands. It is important to protect valuable agricultural lands from subdivision. Development should be directed to the marginal/currently unsuitable agricultural lands such as the coastal beach ridges and the steep lands (> 15%) adjacent to the hills and mountains.

The system of recording resource data in this study allows rapid reassessment for the suitability of new crops or where changing technology alters suitability. It is also compatible with the computer aided drafting system whereby resource data or suitability information can be printed in map or overlay form. 39

8. ACKNOWLEDGMENTS

The author wishes to thank:

• G. Murtha, CSIRO, Townsville for assistance with the recognition of soils and supplying soils information.

• A. Ford, Mossman Central Mill and A. Rudd, BSES, Mossman for supplying information on the sugar-cane industry.

• R. McDonald (deceased), M. Grundy and V. Eldershaw for editorial comment.

• C. Hill and P. Cass for typing of the report.

• Land Resources Branch Cartographic Section for compiling figures and maps.

9. REFERENCES

Amos, B. J. and de Keyser, F. (1983), Mossman, Qld., 2nd edition, 1:250 000 Geological Series - Explanatory Notes, Australian Bureau of Mineral Resources, Geology and Geophysics, Canberra

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

Beckwith, R. S. and Butler, J. H. A. (1983), Aspects of the chemistry of soil organic matter, in Soils: An Australian Viewpoint, Division of Soils, CSIRO, CSIRO: Melbourne/Academic Press: London, 565-582.

Capelin, M. A. and Murtha, G. G. (1983), Julatten sugar-cane land suitability study, Queensland Department of Primary Industries, Project Report QO83015.

Eden, T. (1965), Tea, 2nd edition, Longmans, London.

Hackett, C. and Carolane, J. (1982), Edible horticultural crops. A compendium of information on fruit, vegetable, spice and nut species, Academic Press, Sydney.

Harler, C. R. (1956), The culture and marketing of tea, 2nd edition, Oxford University Press, London.

Hetherington, D. J., Asher, C. J. and Blamey, F. P. C. (1986), Tolerance of sugar-cane to aluminum in soil and solution culture, Proceedings Australian Society of Sugar- Cane Technologists, 1986 Townsville Conference, 63-68. 40 McDonald, R. C., Isbell, R. F., Speight, J. G., Walker, H. and Hopkins, M. S. (1984), Australian soil and land survey field handbook, Inkata Press, Melbourne.

Murtha, G. G. (1989), Soils of the Mossman - Cape Tribulation area, North Queensland, Division of Soils, CSIRO, Divisional Report No 102.

Norrish, K. and Rosser, H. (1983), Mineral phosphate, in Soils: An Australian Viewpoint, Division of Soils, CSIRO, CSIRO: Melbourne/Academic Press: London, 335-364.

Northcote, K. H. (1979), A factual key for the recognition of Australian soils, 4th edition, Rellim Technical Publications, Glenside, S.A..

Rosenthal, K. M. and White, B. J. (1980), Distribution of a rainfall erosion index in Queensland, Queensland Department of Primary Industries, Division of Land Utilisation Technical Report 80/8.

Shaw, R. J., Hughes, K. K., Dowling, A. J. and Thorburn, P.J. (1986), Principles of landscape, soil and water salinity - processes and management options, Part A, in Landscape, soil and water salinity. Proceedings of the Burdekin Regional Salinity Workshop, Ayr, April 1986, Queensland Department of Primary Industries Conference and Workshop Series QC86003.

Stace, H. C. T., Hubble, G. D., Brewer, R., Northcote, K. H., Sleeman, H. R., Mulcahy, M. J. and Hallsworth, E. G. (1968), A handbook of Australian soils, Rellim Technical Publications, Glenside, S.A.

Taylor, R. M., McKenzie, R. M., Fordham, A. W. and Gillman, G. P. (1983), Oxide minerals, in Soils: An Australian Viewpoint, Division of Soils, CSIRO, CSIRO: Melbourne/Academic Press: London, 309-334.

Wilson, P. R. (1982), The relationship between soil characteristics, watertable heights and sugar-cane yields in the Macknade mill area, Proceedings of the Symposium on Rural Drainage in Northern Australia, Darling Downs Institute of Advanced Education, 1982, 53-66.

Wood, A. W. (1985), Soil degradation and management under intensive sugar-cane cultivation in North Queensland, Soil Use and Management 1 (4), 120-124. 41

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APPENDIX II

LAND SUITABILITY CLASSES

Class definitions

Five land suitability classes have been defined for use in Queensland, with land suitability decreasing progressively from Class 1 to Class 5. Land is classified on the basis of a specified land use which allows optimum production with minimal degradation to the land resource in the long term.

Class 1 Suitable land with negligible limitations. This is highly productive land requiring only simple management practices to maintain economic production.

Class 2 Suitable land with minor limitations which either reduce production or require more than the simple management practices* of class 1 land to maintain economic production.

Class 3 Suitable land with moderate limitations which either further lower production or require more than those management practices of class 2 land to maintain economic production.

Class 4 Marginal land which is presently considered unsuitable due to severe limitations. The precise effects of these limitations on the proposed land use are unknown. The use of this land is dependent upon either undertaking additional studies to determine its suitability for sustained production or reducing the effects of the limitations(s) to achieve production.

Class 5 Unsuitable land with extreme limitations that preclude its use.

Land is considered less suitable as the severity of limitations for a land use increase, reflecting either (a) reduced potential for production, and-or (b) increased inputs to achieve an acceptable level of production and-or (c) increased inputs required to prevent land degradation. The first three classes are considered suitable for the specified land use as the benefits from using the land for that land use in the long term should outweigh the inputs required to initiate and maintain production. Decreasing land suitability within a region often reflects the need for increased inputs rather than decreased potential production. Class 4 is considered presently unsuitable and is used for marginal land where it is doubtful that the inputs required to achieve and maintain production outweigh the benefits in the long term. It is also used for land where reducing the effect of a limitation may allow it to be upgraded to a higher suitability class, but additional studies are needed to determine the feasibility of this.

Class 5 is considered unsuitable having limitations that in aggregate are so severe that the benefits would not justify the inputs required to initiate and maintain production in the long term. It would require a major change in economics, technology or management expertise before the land could be considered suitable for that land use. Some class 5 lands however, such as escarpments, will always remain unsuitable for agriculture.

* Where more than simple management practices are required, this may involve changes in land preparation, irrigation management, the addition of soil ameliorants and the use of additional measures to prevent land degration. 64

APPENDIX V

LAND USE SPECIFICATIONS OF AGRICULTURAL CROPS

Sugar-cane

The sugar-cane industry in the Mossman Mill area is rainfed, fully mechanised, traditionally under intense cultivation, and burnt cane. Recent trends include green cane harvesting, trash retention and minimum tillage. Average assignment is 54.5 ha on individually owned land.

Climatic adaptation: Suited to study area.

Soil requirements and management practices:

Irrigation beneficial in low rainfall areas (Mt. Molloy area) or on dry soils (Hull soil series) during water deficit period. Bulk of growth during wet season.

Fertiliser rates as per BSES recommendations. High rates of nitrogenous fertiliser have acidified soils. Aluminum tolerant.

Moderately sensitive to salinity. Basic management includes underground pipes (for small areas), crossdrains and possibly gypsum application.

Moderately tolerant of waterlogging. Variety selection enables use of a wide range of soils. Basic management includes bedding, surface drains and possibly levelling.

Moderately tolerant to flooding. Damage depends on cane variety and flood characteristics.

Large contiguous areas required.

Desirable that soil can be cultivated over wide moisture range to give flexibility to timing of operations.

Machinery use up to 15% slope. Unstable on steeper slopes.

Moderately sensitive to rock fragments due to low harvest heights and regular cultivation. Basic management includes raising cutting height at harvest and rock picking during fallow. Minimum tillage reduces rock fragments brought to surface.

Conventional soil conservation measures, minimum tillage and surface management practices required on erosion prone land.

Varieties: As per BSES approved varieties.

Yields: Average yields per harvested area 74.6 t/ha. Average ccs 13.7 units.

Bananas

The banana industry is irrigated and mechanised in combination with manual harvesting. Farms individually owned.

Climatic adaptation: Requires high temperatures (mean maximum temperatures > 25°C) for optimum growth. Sensitive to frost. 65

Soil requirements and management practices:

Irrigation essential to offset water deficit period in latter half of year, during critical stages and to maximise yields.

Fertilise rates: 500 kg N/ha/year) 300 kg P/ha/year) 5 to 8 split dressings 800 kg K/ha/year)

1.5 t granomag/ha (depends on soil pH).

Sensitive to salinity. Avoid saline areas.

Plant moderately tolerant to waterlogging but mechanical operations moderately sensitive. Basic management includes bedding, surface drains and levelling.

Moderately tolerant to flooding.

Moderately large contiguous areas required.

Moderately tolerant of soil physical conditions. Cultivation and other soil disturbance mainly during land preparation and planting phase of four year cycle.

Machinery use up to 15% slope. Unstable on steeper slopes.

Moderately tolerant of rock fragments. Cultivation and other soil disturbance mainly during land preparation and planting phase of four year cycle. Basic management includes stone picking.

Conventional soil conservation measures, minimum tillage and surface management practices required on erosion prone land.

Varieties: Mons Marie, Williams.

Yields: 2130 to 5000 cartons/ha.

Mango

The mango industry is irrigated and mcchanised in combination with manual harvesting. Farms individually owned.

Climatic adaptation: Severe disease problems in areas receiving > 2500 mm. Frost sensitive.

Soil requirements and management practices:

• Irrigation essential during fruit development, especially on light textured soils. Moisture stress prior to flowering beneficial to induce flowering. Light textured soils preferred for easier soil moisture control.

Fertiliser rates:

1 to 4 old trees 0.1 kg urea, 0.5 kg 10:2:17 mixture/tree/year. 15 year old trees 4 kg urea, 10 kg 10:2:17 mixture/tree/year.

0.13 to 1 kg dolomite/tree every 3 years. 66

• Moderately sensitive to moderately tolerant to salinity. The deep rooting tree makes reclamation difficult.

Moderately sensitive to waterlogging. Deep rooting. Basic management includes bedding, surface drains and levelling.

Moderately tolerant to flooding.

Tolerates small areas originating from broken land or soil complexity.

• Machinery use up to 20% slope. Unstable on steeper slopes when grass or soil wet.

Very tolerant to rock fragments. Minimal soil disturbance.

Permanent grass cover reduces erosion to minimal levels.

Varieties: Mainly Kensington Pride.

Yields: Tree age Yield/tree (kg) 0 to 4 0 to 5 5 to 9 5 to 100 10 to 14 20 to 200 15 to 19 50 to 500 > 25 50 +

Papaw

The papaw industry is irrigated and mechanised in combination with manual harvesting. Farms individually owned.

Climatic adaptation: Generally suited to study area. Sensitive to frosts and strong winds.

Soil requirements and management practices:

Irrigation essential during drier periods.

• Fertiliser rates: applied as monthly split dressings.

Preplant: 52 kg N, 168 kg P, 48 kg K, 40 kg borax, 2 t dolomite/ha/year.

Non-bearing plants: 164 kg N, 30 kg P, 144 kg K, 40 kg borax, 2 t dolomite/ha/year.

Bearing plants: 256 kg N, 30 kg P, 244 kg K, 60 kg borax, 2 t dolomite/ha/year.

Sensitive to salinity. Avoid saline areas.

Sensitive to waterlogging. Requires moderately well drained to rapidly drained soils. Basic management includes bedding, surface drains and levelling.

Sensitive to flooding. Requires flood free land.

• Tolerates small areas originating from broken land or soil complexity.

Machinery use up to 20% slope. Unstable on steeper slopes when grass or soil wet. 67

• Very tolerant to rock fragments. Minimal soil disturbance.

Permanent grass cover reduces erosion to minimal levels.

Varieties: No specific varieties.

Yield: 35 to 50 t/ha. Depends on plant spacing.

Lychee

The lychee industry is irrigated and mechanised in combination with manual harvesting. Farms individually owned.

Climatic adaptation: Generally suited to lower rainfall areas (<2500 mm). Tolerates light frosts. Variety selection important.

Soil requirements and management requirements:

Irrigation essential during fruit development. Moisture stress prior to flowering beneficial to induce flowering.

Fertiliser rates at four month intervals.

First year: 0.2 kg 10:2:17 mixture/tree 4 year old trees: 0.6 kg 10:2:17 mixture/tree Older trees: 1.5-4 kg 10:2:17 mixture/tree (depends on size)

1 t dolomite/ha/year

Sensitive to salinity. Avoid saline areas.

Moderately tolerant of waterlogging. Tolerates a wide range of soils as long as the soil dries out prior to flowering.

Moderately tolerant to flooding.

Tolerates small areas originating from broken land or soil complexity.

Machinery use up to 20% slope. Unstable on steeper slopes when soil or grass wet.

Very tolerant of rock fragments. Minimal soil disturbance.

Permanent grass cover reduces erosion to minimal levels.

Varieties: Tai So, Kwai May Pink (B3)

Yields: 5 to 6 year old trees 1750 kg/ha 10 to 12 year old trees 4900 kg/ha 20 year old trees 14000 kg/ha 68

Citrus

The citrus industry is irrigated and mechanised in combination with manual harvesting. Farms individually owned.

Climatic adaptation: Generally suited to study area. Produce good quality fruit but poor colour. Require protection from strong winds.

Soil requirements and management practices:

Irrigation essential during periods of year when flowering and fruit development occurs.

• Fertiliser rates:

Young trees: 100 g N, 10 g P, 50 g K/tree/year Mature trees (older than eight years): 200 kg N, 20 kg P, 100 to 200 kg K/ha/year, 2 to 5 t dolomite/ha used to raise pH where Mg deficiency occurs.

Moderately sensitive to salinity. Avoid saline areas.

Sensitive to waterlogging. Requires moderately well drained to rapidly drained soils. Basic management includes bedding and surface drains.

• Sensitive to flooding. Requires flood free land.

Tolerates small areas originating from broken land or soil complexity.

Machinery use up to 20% slope. Unstable on steeper slopes when soil or grass wet.

Very tolerant to rock fragments. Minimal soil disturbance.

Permanent grass cover reduces erosion to minimal levels.

Varieties: A wide range of varieties are available.

Yields: Depends on variety and age.

Avocado

The avocado industry is irrigated and mechanised in combination with manual harvesting. Farms individually owned.

Climatic adaptation: Generally not suited to study area. Requires mean maximum summer temperatures < 25°C, severe disease problems associated with extended periods of rain and high humidity, requires protection from strong winds.

Soil requirements and management practices:

Irrigation essential during drier periods of year when flowering and fruit development occur.

Fertiliser rates:

One year old trees: 0.1 kg 13:2:14 mixture, 25 g potassium-magnesium sulphate, 20 g borax, 0.1 kg zinc sulphate, 0.25 kg super, 25 g potassium sulphate/tree/year 69

Four plus year old trees: 0.5 kg 13:2:14 mixture increasing 0.5 kg/year to maximum 6 kg, 0.1 kg potassium sulphate, 0.1 kg potassium-magnesium sulphate, 40 g borax, 0.5 kg zinc sulphate/tree/year, 2 t dolomite/ha

Sensitive to salinity. Avoid saline areas.

Sensitive to waterlogging. Requires moderately well drained to rapidly drained soils. Basic management includes hilling and surface drains.

Sensitive to flooding. Requires flood free land.

Tolerates small areas originating from broken land and soil complexity.

Machinery use up to 20% slope. Unstable on steeper slopes when soil or grass wet.

Very tolerant to rock fragments. Minimal soil disturbance.

Permanent grass cover reduces erosion to minimal levels.

Varieties: Mainly Fuerte, Sharwil, Hass, Sheperd.

Yields: five year old trees 4 to 10 cartons/tree 10 year old trees 20 to 30 cartons/tree 15 year old trees 40 to 60 cartons/tree

Rambutan

The rambutan industry is irrigated and mechanised in combination with manual harvesting. Farms individually owned.

Climatic adaption: Sensitive to low temperatures and frosts. Requires mean maximum summer temperatures >25°C and mean minimum winter temperatures > 14°C. Some varieties can withstand 3 to 4°C for short periods. Wind breaks essential•

Soil requirements and management practices:

• Irrigation essential during fruit development. Flowering initiated by moisture stress for four weeks.

Fertiliser rates:

First 4 years: 200 kg N, 35 kg P, 100 kg K/ha/year Bearing trees: 200 kg N, 25 kg P, 130 kg K/ha/year applied quarter at fruit set, half after harvest, quarter 9 weeks after harvest.

Sensitive to salinity. Avoid saline areas.

Moderately tolerant to waterlogging. Tolerates a wide range of soils, beneficial if soils dry out prior to flowering.

Moderately tolerant to flooding.

Tolerates small areas originating from broken land or soil complexity.

Machinery use up to 20% slope. Unstable on steeper slopes when soil or grass wet. 70

Very tolerant to rock fragments. Minimal soil disturbance.

Permanent grass cover reduces erosion to minimal levels.

Varieties: Peng Thing Bee (R3) (variety evaluated at Kamarunga).

Yields: 5 year old trees 20 kg/tree (Malaysian figures. 10 year old trees 110 kg/tree Australian figures not 17 year old trees 220 kg/tree yet established)

Tea

The tea industry is mainly rainfed and fully mechanised. All weather road access is required to allow regular harvesting, transport of harvested leaf to processor and the bringing in of labour and supplies.

Climatic adaptation: Requires >2000 mm annual rainfall. Sensitive to frosts.

Soil requirements and management practices:

• Plant deep rooted and drought tolerant but irrigation beneficial during establishment and in drier periods to maintain production and leaf quality.

• Requires very strongly to strongly acid (pH 4.5 to 5.5) soils for optimum growth, unsuitable if soil pH >6.5. Aluminum tolerant.

Fertiliser rates. Applied as several split dressings

345 kg N, 11 kg P, 64 kg K/ha/year

Moderately sensitive to salinity. Avoid saline areas. Difficult and expensive to reclaim soils to rooting depth and/or difficult to re-establish affected areas.

Sensitive to waterlogging. Requires moderately well drained to rapidly drained soils. Basic management includes surface drains and levelling: Underground pipes beneficial in small areas.

Sensitive to flooding. Requires flood free land.

Large contiguous areas required.

Tolerates soil physical conditions. Land preparation only at beginning of a very long crop cycle (100+years).

Machinery use up to 15% slope. Unstable on steeper slopes.

Moderately sensitive to rock fragments during land and seed bed preparation phase of tea establishment, interferes with harvest machinery by creating irregular harvest heights and reducing tea quality, particularly important in erosion prone areas. Basic management includes stone picking prior to planting and manual stone picking after establishment.

• Conventional soil conservation measures, minimum tillage and surface management practices required on erosion prone land.

Varieties: No specific varieties available. Variety selection presently under evaluation.

Yields: Approximately 3000 kg/ha/year. 71 Vegetables

The vegetable industry is irrigated, mechanised in combination with manual harvesting for some crops and under intense cultivation. Farms are individually owned.

Climatic adaptation: Dry season crops only. Disease and pest control very important.

Soil requirements and management practices:

• Irrigation essential• Crops shallow rooted.

Fertiliser rates depend on crops and soil fertility.

Sensitive to salinity but shallow rooting allows reclamation with the use of underground pipes for small areas, surface drains and possibly gypsum applications. Avoid saline areas.

Sensitive to waterlogging but tolerate a wide range of soils in the dry season. Bedding and drains usually part of basic management.

Flooding not a problem in dry season.

Tolerate small areas originating from broken land or soil complexity.

Require fine seed bed. Seedling emergence and establishment problems occur on hardsetting massive or coarse aggregate soils. Desirable that soils can be cultivated over wide moisture range to give flexibility to timing of operations.

Machinery use up to 15% slope. Unstable on steeper slopes.

Sensitive to rock fragments. Interferes with cultivation, planting and mechanical harvesting.

Conventional soil conservation measures and surface management practices required on erosion prone land. Cover crops required on fallow land during wet season.

Varieties: A wide range of varieties are available for crops such as tomatoes, capsicums, beans.

Cucurbits

The cucurbit industry is mainly irrigated and mechanised in combination with manual harvesting. Under intense cultivation. Farms are individually owned.

Climatic adaption: Dry season crops only. Disease control very important.

Soil requirements and management practices:

Irrigation required during drier periods. Shallow rooted crops.

Fertiliser rates depend on crop and soil fertility.

Moderately sensitive to salinity but shallow rooting allows reclamation with the use of underground pipes for small areas, surface drains and possibly gypsum applications. Avoid saline areas.

Sensitive to waterlogging but tolerate a wide range of soils in dry season. Bedding and drains usually part of basic management for more intensive crops. 72

• Flooding not a problem in dry season.

• Watermelons and pumpkins require moderately large contiguous areas. Other more intensive crops tolerate small areas originating from broken land or soil complexity.

Require fairly fine seed bed. Seedling emergence and establishment problems on hardsetting massive or coarse aggregate soils. Desirable that soil can be cultivated over wide moisture range to give flexibility to timing of operations.

• Machinery use up to 15% slope. Unstable on steeper slopes.

• Sensitive to rock fragments due to regular cultivation.

Soil conservation measures and surface management practices required on erosion prone land. Cover crops required on fallow land during wet season.

Varieties: A range of varieties are available for crops such as watermelons, pumpkins, rockmelons, zucchinis, cucumbers.

Pineapple

The pineapple industry is irrigated and mechanised in combination with manual harvesting. Fruit goes to local fresh fruit market. Farms individually owned.

Climatic adaptation: Suited to study area. Sensitive to frosts.

Soil requirements and managements practices:

Drought tolerant and can be grown on a range of light textured soils. Irrigation desirable during dry periods.

• Fertiliser rates apply to nutrient deficient soils for plant and first ratoon crops.

1200 kg N, 100 kg P, 1200 kg K, 350 kg Ca, 300 kg Mg, 15 kg Fe, 7 kg Zn, 7 kg Cu, 1 to 3 kg B/ha/year.

Sensitive to salinity. Avoid saline areas.

• Sensitive to waterlogging. Shallow rooted and will tolerate imperfectly drained soils provided bedding is practiced and soil can be drained effectively with drains or underground pipes for small areas.

Sensitive to flooding. Requires flood free land.

• Tolerates small areas originating from broken land or soil complexity.

Machinery use up to 15% slope. Unstable on steeper slopes.

Moderately tolerant to rock fragments. Affects land preparation and planting operations every three to four years.

Conventional soil conservation measures, minimum tillage and surface management practices required on erosion prone land.

Varieties: Queensland Cayene, common rough, MacGregor, Alexandra. 73

Yields: Smooth leaf varieties: plant crop 55 t/ha ratoon crop 45 t/ha

Rough leaf varieties: plant crop 35 to 40 t/ha ratoon crop 45 to 50 t/ha

Maize

The maize industry is rainfed and fully mechanised. Under intense cultivation. Farms individually owned.

Climatic adaptation: Mainly dry season crop. Sensitive to frosts. Poor pollination when temperatures > 38°C. High temperatures unlikely in dry season up to November.

Soil requirements and management practices:

Dry season crops rely on soil moisture.

Fertiliser rates 80 kg N/ha, 35 kg P/ha.

Moderately sensitive to salinity. Avoid saline areas.

Requires moderately good drainage. Tolerates a wide range of soils in dry season.

Moderately sensitive to flooding but not a problem in dry season.

Requires large contiguous areas where machinery can be used effectively and soil conservation measures implemented. Broadacre crop.

• Requires moderately fine seedbed. Seedling emergence and development problems on hardsetting massive or coarse aggregate soils. Desirable that soil can be cultivated over a wide moisture range to give some flexibility to timing of operations.

Machinery unstable on steeper slopes > 15%.

• Moderately sensitive to rock fragments due to regular cultivation.

Conventional soil conservation measures, minimum tillage and surface management practices required on erosion prone land.

Varieties: Pioneer 6875, QK958, QK657, Sloan.

Yields: 3 to 5 t/ha.

Sorghum

Grain and forage sorghum is rainfed and fully mechanised. Under intensive cultivation. Farms individually owned.

Climatic adaptation: Mainly dry season crop. Sensitive to frosts. Poor pollination when temperatures > 38°C. High temperatures unlikely in dry season up to November.

Soil requirements and management practices:

Dry season crops rely on soil moisture. 74

• Fertiliser rates: Mainly N and P. S, K, Zn as required.

Moderately tolerant to salinity.

Requires moderately good drainage. Tolerates a wide range of soils in dry season.

• Moderately sensitive to flooding but not a problem in dry season.

Requires large contiguous areas where machinery can be used effectively and soil conservation measures implemented. Broadacre crop.

Requires moderately fine seedbed. Seedling emergence and establishment problems on hardsetting massive or coarse aggregate soils. Desirable that soil can be cultivated over a wide moisture range to give some flexibility to timing of operations.

Machinery unstable on steeper slopes > 15%.

Moderately sensitive to rock fragments due to regular cultivation.

Conventional soil conservation measures, minimum tillage and surface management practices required on erosion prone land.

Varieties: Mainly hybrid E57, others SM8, Solo H, new tropic, DK55, Triumph.

Yields: 2 to 4 t/ha.

Sweet corn

Thc swcct corn industry is irrigatcd and mechanised in combination with manual harvcsting. Undcr intcnsc cultivation. Farms are individually owned.

Climatic adaptation: Poor pollination when tcmpcratures > 38°C. Scnsitivc to frosts.

Soil rcquircmcnts and managcmcnt practices:

• Irrigation essential during moisture sensitive stages at establishment and from tasseling to harvest.

Fertiliser rates:

Prcplant: 750 to 100 kg 5:7:4 mixture Side dressing: 200 kg 11:2:15 mixture

• Moderately sensitive to salinity. Avoid saline areas.

• Rcquires modcratcly good drainage but will toleratc a wide rangc of soils during dry season.

Moderatcly sensitive to flooding by not a problem in dry season.

Moderately tolerant to small areas originating from broken land or soil complcxity.

• Requires modcratcly f'mc seedbed. Sccdling emergence and development problems on hardsctting massive or coarse aggregate soils. Desirable that soil can be cultivated over a widc moisture range to give some flexibility to timing of opcrations.

• Machinery unstable on steeper slopes > 15%. 75

• Conventional soil conservation measures, minimum tillage and surface management practices required on erosion prone land.

Varieties: Style Pack, Golden Fancy, NK 195, Midway.

Yields: 800 to 1200 cartons/ha, approximately 30 cobs/carton.

Soybean

The soybean industry is rainfed, fully mechanised. Under intensive cultivation. Farms individually owned.

Climatic adaptation: Photoperiodic. Wet season crop only. Planting mid December to mid January, harvest May.

Soil requirements and management practices:

Shallow rooted crop but moisture availability generally not a severe problem during wet season, provided there is adequate moisture at planting.

Sensitive to aluminum toxicity. Fertiliser rates of P and K as required. Plants nodulate to supply adequate N.

• Moderately tolerate of salinity.

• Plants moderately tolerant to waterlogging but machinery operations such as planting, pest control and harvesting are likely to be restricted during the wet season.

Moderate tolerance to flooding (1 to 2 days).

Large contiguous areas required where machinery can be used effectively and soil conservation measures implemented. Broadacre crop.

Moderately fine seedbed required. Seedling emergence and development problems on hardsetting massive or coarse aggregate soils. Desirable that soil can be cultivated over a wide moisture range to give some flexibility to timing of operations.

Machinery unstable on steeper slopes > 15%.

Sensitive to rock fragments due to low harvest heights and regular cultivation.

• Conventional soil conservation measures and surface management practices required on erosion prone land.

Varieties: Fitzroy, Canapolis.

Yields: 1.75 to 2.5 t/ha.

Peanut

The peanut industry on the Wet Tropical Coast is irrigated and fully mechanised. Under intense cultivation. Farms individually owned.

Climatic Adaptation: Disease control very important. Dry season crop only. Rotation necessary to reduce disease incidence. 76

Soil requirements and management practices:

• Shallow rooted crop. Irrigation essential to supplement soil moisture deficit during dry season.

Fertiliser rates: 200 to 400 kg super/ha 0 to 80 kg K/ha (depending on soil fertility) Lime as required.

Sensitive to salinity. Avoid saline areas.

Sensitive to waterlogging. Requires well drained soils.

Flooding not a problem during dry season.

Large contiguous areas required for effective machinery use and implementation of soil conservation measures.

Hardsetting massive and/or stiff clay soils restrict peg development. Desirable that soil can be cultivated over wide moisture range to give flexibility to timing of operations. A relatively deep (> 0.5 m) friable soil important for removal of soil from peanuts during harvest.

Machinery unstable on steeper slopes > 15%.

Very sensitive to rock fragments. Interfere with cultivation, planting and harvest.

Conventional soil conservation measures required on erosion prone land.

Varieties: Virginia Bunch, Red Spanish.

Yields: 1.5 to 2.5 t/ha.

Sweet potato

The sweet potato industry is irrigated, fully mechanised. Under intensive cultivation. Farms individually owned.

Climatic adaptation: Dry season crop only to limit pests and diseases.

Soil requirements and management practices:

Shallow rooted crop. Irrigation essential to supplement soil moisture deficit during dry season.

Fertiliser rates:

375 to 500 kg N:P:K: mixture (depends on soil fertility), dolomite applied prior to planting.

• Sensitive to salinity. Avoid saline areas.

• Sensitive to waterlogging. Requires well drained soils.

Flooding not a problem during dry season.

Tolerates small areas originating from broken land or soil complexity. 77

• Hardsetting massive and/or stiff clay soils restrict tuber development. Desirable that soil can be cultivated over wide moisture range to give flexibility to timing of operations. A relatively deep (> 0.5 m) friable soil important for removal of soil from tubers during harvest.

• Machinery unstable on steeper slopes > 15%.

• Very sensitive to rock fragments. Interferes with cultivation, planting and harvest.

Conventional soil conservation measures required on erosion prone land.

Varieties: Mandy Co-323, Beerwah gold, NC-3, Centennial.

Yields: 25 to 40 t/ha.

Rice

The rice industry on the Wet Tropical Coast is rainfed, fully mechanised. Under intense cultivation. Farms individually owned.

J Climatic adaptation: Wet season crop. Planted December to January, harvested May to June. Strong winds cause lodging. Weed and pest control generally more expensive than Mareeba-Dimbula area due to wetter climatic conditions.

Soil requirements and management practices:

Shallow rooted crop but severe soil moisture restrictions unlikely during wet season provided there is adequate moisture at planting.

• Fertiliser rates:

90 to 135 kg N, 25 kg P/ha. K and trace elements as required.

Moderately sensitive to salinity. Management includes underground pipes (for small areas) and drains. Gypsum applications may be beneficial on some soils.

Plants tolerate waterlogging but machinery operations such as planting and harvesting may be restricted during wet season. Basic management includes surface drains and levelling.

Moderately tolerant to flooding but lodging causes harvesting problems.

Large contiguous area required for effective machinery use and implementation of soil conservation measures.

Moderately fine seed bed required. Seedling emergence and establishment problems on hardsetting massive or coarse aggregate soils. Desirable that soil can be cultivated over wide moisture range to give flexibility to timing of operations.

• Machinery unstable on steeper slopes > 15%.

Moderately sensitive to rock fragments due to regular cultivation.

Conventional soil conservation measures, minimum tillage and surface management practices required on erosion prone land. 78

Varieties: Bluebonnet 50.

Yields: Approximately 3 t/ha.

P/nus car~baea

The forestry industry is based on exotic pines which are rainfed and growing predominantly on crown land. The industry is fully mechanised with a 25 year (approximate) crop cycle.

Climatic adaptation: Suited to study area receiving > 1600 mm annual rainfall. Strong winds combined with waterlogging can cause windthrow. Requires frost free conditions.

Soil requirements and management practices:

Deep rooted but approximately 90% of roots in top 0.25 m. Adapted to light textured soils but trees particularly susceptible to water stress during establishment•

Can utilise low nutrient soils. P fertiliser not normally applied and occasionally N, Cu, Zn, B, S applied to more nutrient deficient and highly leached soils. Sensitive to soils with pH > 7.

Very sensitive to salinity. Avoid saline areas.

Moderately in tolerant to waterlogging. Grows best on well drained soils, soils with >0.3 m of topsoil to an impervious layer and with potential drainage problems are high mounded (profile cross semon• of 0.8 m-).9 Mounding• conducted to supply sufficient" so il depth and to raise roots above watertable.

Moderately tolerant to flooding. Damage mainly in first few years of establishment.

Moderately sensitive to small areas resulting from broken land or soil complexity. Minimum area 5 ha with minimum width 100 m.

Machinery use up to 20% slope. Unstable on steeper slopes.

Moderately tolerant to rock fragments. Cultivated and mechanically planted only at beginning of 25 year crop cycle. Herbicides and hand planting employed on small, very rocky areas.

Erosion is of concern only in first 2 to 3 years of establishment prior to establishment of permanent grass cover. Clearing, raking, ploughing, mounding and planting carried out on the contour on erosion prone land.

Varieties: Pinus caribaea var. hondurensis (Honduras Caribbean pine).

Improved pastures

The beef industry on the Wet Tropical Coast is based on improved and native pastures. Improved pastures are rainfed and established mechanically usually with minimal cultivation. Properties are freehold and leasehold.

Climatic adaptation: Species selection enables adaptation to a wide range of conditions. The species mentioned here are suited to the Wet Tropical Coast areas which receive light to no frosts. 79

Soil requirements and management practices:

Although most species are shallow rooted and susceptible to moisture stress, pasture production and recoverability depends on management practices and stocking rates.

Fertiliser rates depend on natural soil fertility which can be determined by soil type and native vegetation (see pasture management categories Appendix VI).

Species vary in their sensitivity to salinity. Basic management includes drains and use of tolerant species. Clearing of intake and seepage areas should be avoided.

Species vary in their sensitivity to waterlogging (see pasture management categories Appendix VI).

Flooding is generally not a problem. Improved pastures are used to stabilise areas prone to erosive flooding.

Management is very tolerant of small but contiguous areas resulting from broken topography.

Seedling emergence and establishment problems may result with small seeded species on hardsetting massive or coarse aggregate soils.

Machinery use up to 30% slope. Unstable on steeper slopes.

Very tolerant of rock fragments. Soil disturbance minimal.

Permanent grass cover reduces erosion to minimal levels.

Pasture species: See pasture management categories (Appendix VI). 80

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