Soil and Land Assessment of the Southern Part of Flying Fox Station for Irrigated Agriculture. Part A: Land Resources and General Land Capability.
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
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)
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
Northern Territory Government
Technical Report No. 3/2021
208 pages : colour maps and illustrations ; 30cm
Attribution International 4.0 (CC BY 4.0)
Northern Territory Government
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]
Soil and Land Assessment of the Southern Part of Flying Fox Station for Irrigated Agriculture Part A: Land Resources and General Land Capability 65 Land Unit 5c Soil pH and salinity field sites pH, EC and Cl analyses (see Appendix 2) indicate soil profiles are mostly strongly acidic to neutral (pH range 4.6-7.1), with very low mean salinity levels throughout (mean ECe <0.3 dS/m, Cl <13 mg/kg). Calculated ECe values are relatively uniform across all sites and are consistently below the critical root zone threshold (ECe 6 dS/m). Effective rooting depth (ERD) is limited only by depth to substrate. Soil chemistry Sites 117 and 187 (LU 5c) Organic carbon levels in the surface soil (0-0.1 m) are variable and range from low to high. In contrast, total nitrogen levels are consistently moderate to high. Macronutrient (calcium, phosphorous, potassium and sulfate) levels are very low to low, but micronutrient levels (copper and zinc) mostly moderate. ECEC levels are very low to low (2-6 cmol/kg) and indicate limited capacity for nutrient retention; while similar very low to low ECEC/clay ratios (0.2-0.4) confirm the clay fraction is un-reactive and wholly kaolinitic. Profiles are non-sodic (ESP < 1%) throughout (including underlying substrates). Physical soil characteristics Sites 117 and 187 (LU 5c) Soil profiles are very shallow to moderately deep (0.1-0.9 m), moderately to highly permeable and predominantly well drained. Laboratory measured clay contents are typically low (10-20%) in surface horizons/shallow profiles but increase to moderate levels (20-32%) in deeper profiles. Field textures confirm subsoil clay contents are spatially variable (within the landscape), and range from low to very high (~15-55%) depending on profile development (earthy sand, gradational earth or texture contrast profile). In each case, the surface soil to about 0.2 m (A1/A2/A3/B1 horizons) is characterised by significantly elevated levels of fine sand (57-69%) and silt (6-13%), and is unstructured (massive) with an earthy fabric and firm to hardsetting undisturbed surface condition. Subsoil materials (where developed) are either massive or structured; and typically have lower fine sand (47-48%) and silt (1213%) contents and moderate to high (but variable) clay contents (31-32% measured, likely range 1555%). Laboratory dispersion (R1) is only moderate (0.58-0.81) throughout, because of sesquioxidic influences and the relative stability of the kaolinitic clay fraction. Constraints to agricultural development Soils within Land Unit 5c are very shallow to moderately deep (0.1-0.9 m), firm to hardsetting, gravelly to very gravelly, red or brown earthy sands, sandy to clay loamy surfaced massive gradational earths or occasional texture contrast soils overlying fine-grained sedimentary rock. They are characterised by very low to low fertility and nutrient holding capacity (depending on profile development), spatially variable subsoil development (massive to structured where present) and unpredictable subsoil clay contents (range 15-55%). Important constraints include excessive slope (>2%), limited soil depth (where <0.5 m) and abundant surface rock (2->10% >60 mm). General land capability Land Unit 5c 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.