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Soil and Land Assessment of the Southern Part of Flying Fox Station for Irrigated Agriculture. Part A: Land Resources and General Land Capability.



Soil and Land Assessment of the Southern Part of Flying Fox Station for Irrigated Agriculture. Part A: Land Resources and General Land Capability.

Other title

Agricultural Land Suitability Series, Report 14A


Andrews, K; Burgess, J; McGrath, N; Wright, A; Walton, S; Northern Territory. Department of Environment, Parks and Water Security


Hill, J.V.


E-Publications; E-Books; PublicationNT; Technical Report No. 3/2021




Flying Fox Station; Roper River Region


This report presents findings from a 52 938 ha soil and land resource mapping investigation of the southern part of Flying Fox Station, in the Roper River Region of the Northern Territory. While the study area was primarily selected because of its diverse geology, terrain and soils, it is also representative of the central Roper River region, and findings from the investigation will underpin and guide future agricultural development in the region.


Made available by via Publications (Legal Deposit) Act 2004 (NT)

Table of contents

Executive Summary; 1. Introduction; 2. Previous land resource investigations; 3. Methodology; 4. Climate; 5. Geology; 6. Landscapes; 7. Land units; 8. Land capability assessment; 9. Land management; 10. References; Appendices.




soil survey; land resource assessment; land units; land capability assessment

Publisher name

Northern Territory Government

Place of publication





Technical Report No. 3/2021


208 pages : colour maps and illustrations ; 30cm

File type





Attribution International 4.0 (CC BY 4.0)

Copyright owner

Northern Territory Government



Related links

http://www.ntlis.nt.gov.au/metadata/export_data?type=html&metadata_id=6589A5D125EFB385E050CD9B2144202B; https://hdl.handle.net/10070/820014 [Report_print_Soil Land Assessment Flying Fox - Part A Land Resources General Land Capability]; https://hdl.handle.net/10070/820013 [Report_screen_Soil Land Assessment Flying Fox - Part A Land Resources General Land Capability]; https://hdl.handle.net/10070/829192 [Soil and Land Assessment of the Southern Part of Flying Fox Station for Irrigated Agriculture. Part B: Digital Soil Mapping and Crop Specific Land Suitability]

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Soil and Land Assessment of the Southern Part of Flying Fox Station for Irrigated Agriculture Part A: Land Resources and General Land Capability 83 Land Unit 9a Analytical data for Land Unit 9a is unavailable. Soil chemistry and physical attributes described below come from Land Unit 1a (Site 180) which is the source of alluvium, and also Land Unit 9c1 (Site 85) which occupies equivalent creek flats and has similar soil morphology and mineralogy. Both units possess characteristics considered indicative of Land Unit 9a. Soil pH and salinity field sites pH, EC and Cl analyses (see Appendix 2) from Land Unit 1a suggest soil profiles are strongly acidic to slightly acidic (pH range 4.6-6.6), with very low mean salinity levels throughout (mean ECe <2 dS/m, Cl <9 mg/kg). Calculated ECe values are below the critical root zone threshold (ECe 6 dS/m), and effective rooting depth (ERD) is >1.5 m (or depth to substrate where present). Soil chemistry Site 180 (equivalent LU 1a), Site 85 (equivalent LU 9c1) Organic carbon and total nitrogen levels in the surface soil (0-0.1 m) are likely to be moderate (compared with high levels in Land Units 1a and 9c1) because more frequent fire, less litter accumulation and very sandy textures. Macronutrient (calcium, phosphorous, potassium and sulfate) and micronutrient (copper zinc) levels are low, and similar to those measured in Land Unit 9c1. ECEC levels are very low to low (<6 cmol/kg) and reflect low clay content and very limited capacity for nutrient retention. ECEC/clay ratios are likely to be very low (<0.2) and confirm the clay fraction (albeit small) is un-reactive and wholly kaolinitic. Profiles are non-sodic (ESP 2%) throughout (including underlying substrates). Physical soil characteristics Site 180 (equivalent LU 1a), Site 85 (equivalent LU 9c1) Field observations indicate soil profiles are deep to very deep (1.0->1.5 m) earthy sands, that are highly permeable and moderately well to well-drained. Laboratory measured clay contents from Land Units 1a and 9c1 suggest levels are very low to low (<5-20%) throughout. Profiles are dominated by elevated levels of coarse sand (59-64%) and also significant fine sand (29-32%), and are unstructured (massive) with sandy or earthy fabric. Surface horizons will be loose or soft when undisturbed, and will be subject to incoherent behaviour following tillage (because of limited clay fines with which to bind the soil matrix). Laboratory dispersion (R1) is likely to be similar to that seen in Land Unit 1a, with low levels (0.53) in the immediate surface soil (due to organic influences), and high or extreme levels (0.83-0.97) in subsurface/subsoil layers (because of an unstable sand fraction and minimal sesquioxides). Constraints to agricultural development Soils within Land Unit 9a are deep to very deep (1.0->1.5 m), soft to firm, brown or grey earthy sands developed on local coarse sandy alluvium. They are characterised by low fertility and nutrient holding capacity, massive structure and very low to low clay contents (range <5-20%). Important constraints include regular short duration high energy erosive flooding and excessive slopes (locally >2%) around incised stream channels. General land capability Land Unit 9a has extreme constraints (Class 4) that preclude agricultural development. Where other forms of development such as infrastructure must proceed, detrimental effects to the environment would need to be fully mitigated. Land capability criteria and contributing data are presented in Appendices 4 and 5 and discussed further in Chapter 8.

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