Information
Level 2 Detail of experimental conditions at Wallumbilla
Description
What?
The study monitored the effects of a range of soil conditions (chisel tillage, sweep tillage, minimum tillage and pasture) on runoff and soil erosion over an eighteen year period.
When and Where?
From 1982 to 2000 a study was undertaken 10km north of Wallumbilla and approximately 45 km ENE of Roma. Climate of the region is described as semi-arid sub-tropical climatic statistics can be viewed in Figure 1.
The predominant soil type is a grey vertosol with alkaline surface horizons over strongly acid clays. The surface varies from weakly self mulching to moderately crusted to weakly hard setting depending on recent environmental conditions. The soil has a plant-available water capacity of 140-160 mm in the top 1.5m, with 70% of the potential water held in the top 0.60m. Infiltration rates are considerably high during dry and cracked soil conditions’, however sealing occurs during prolonged periods of rainfall.
How?
The study used a set of 4 paired contour bay catchments (approximately 1 ha each, 2% sloping, Figure 1) to monitor soil water, catchment hydrology and water quality aspects of different land management options (chisel tillage, sweep tillage, minimum no tillage and pasture) within a real farm context. Further catchment details are featured in Table 1.
Rainfall was measured via a network of three tipping bucket recording rain gauges, a manual rain gauge at each side of the catchment and a gauge at the farm residence, approximately 2 km south (Figure 2). A trapezoidal weir design was chosen to measure total runoff and peak discharge. Samples of runoff were collected at the weir outlet to determine suspended sediment concentrations. Rising stage samples were collected automatically at 5, 10, 20, 30, 40 and 50 cm stage heights with samples being drawn from mid flow depth. Weighted mean sediment was calculated at each height weighted by its relative discharge at each stage. Total suspended sediment from the hillslope was measure from water samples collected on the rising limb of hydrographs.
Surface cover and surface roughness were measured concurrently after each runoff event, after cultivation and at soil sampling and periodic visits. Surface cover was measured visually using a 1m2 quadrat at 20 random locations in each bay, while surface roughness was described on a visual scale. The scale ranged from 1 (smooth surface no microrelief) to 5 (surface with large clods, distinct furrows and maximum potential for surface storage). Soil moisture was determined at 9 locations on 3 separate occasion (post harvest, mid fallow and pre-planting) in each bay at a depth of 1.5m with the use of a hydraulically driven 30mm diameter steel tube. Each core was separated into intervals of 0.1-0.10, 0.10-0.30, 0.30-0.60, 0.60-0.90, 0.90-1.20 and 1.20-1.50m and moisture content determined gravimetrically. Bulk density was measured on several occasions using 0.10m diameter corers, and used to convert gravimetric values to a volumetric basis.
Wheat was sown annually in the crop catchments, planted in May-June. Wheat was typically harvested within 2 weeks of the beginning of November using the land owner’s harvester. Pastures were established in Bay 2 in 1990 and bay 1 in 1996 with buffel grass and snail medic. Pastures were grazed when sufficient feed was available and crops were not growing. Grain yield was determined by harvesting 400m long strips in each bay using a commercial harvester (6m wide). Evaporation in fallows was determined by difference where E = rainfall – runoff – change in soil water over the fallow.
Project administration
Site identifier code: na
Principal investigator: David Freebairn
Principal data manager: -na
Principal organizations: Queensland Department of Natural Resources and Mines
Data custodian: Queensland Department of Natural Resources and Mines (DNRM)
Key co-operators: Viv and Barbara Taylor, "Fairlands" Wallumbilla
Data access policy: Research has been published in Aust. J Soil Research 2009 and all data available as supplimentary material (Open access)
Planned pathway for data: DARTS and this site
Data warehousing: DARTS and this site
Planned data upload frequency: for ongoing studies - na
Key references and sources of this data synthesis
- Freebairn DM, Wockner GH, Hamilton NA, Rowland P (2009). Impacts of soil conditions on hydrology and water quality from a brown clay in the north-eastern cereal zone of Australia. Australian Journal of Soil Research. 47: 389-402.
- Cawley ST, Hamilton NA, Freebairn DM, Markey LJ. Viable Farming Systems Group Project: Evaluating fallow management options by using rainfall simulation. Queensland Department of Primary Industries October 1992.
Keywords
Cropping, Southern Queensland, runoff, soil erosion, crop yield, tillage methods, ground cover, participative research