Information
Level 2 Detail of experimental conditions (what might be found in a journal paper or project brief in Hydstra)
Description of study
What?
Erosion productivity assessments were conducted by reducing the plant available water range and the nitrogen available, and assessing the effect against non-eroded growth. Simulation was undertaken using GRASP. Model parameters were derived by combining grazier experience compared to the calculation of pasture growth for a given land type, tree density and pasture condition.
When and Where?
The study area was defined by the location of the properties of producers in the Western Downs Beef Plan group (situated between Miles, Wandoan and Roma) who were surveyed to assess land type information and stocking rates.
Rainfall is summer dominant with some winter rainfall, and simulations were based on long term climate records of the township Wandoan obtained from the SILO national interpolated climate surfaces. The recording stations is located at 149.95 E and 26.11 S.
How?
Safe carrying capacity was derived directly from graziers knowledge and experience of safe carrying capacity, and compared to the calculation of pasture growth for a given land type, tree density and pasture condition (using the GRASP model).
Erosion productivity assessments were conducted by reducing the plant available water range and nitrogen available, and assessing the effect against non-eroded growth for a 100 year period between 1900 and 2000. A scalping simulation was performed in GRASP with soil depth reduced by 50, 100 and 150 mm and compared against an uneroded profile. The plant available water content was reduced from the lower soil layers by the associated scalping depth. Nitrogen availability was reduced depending on the distribution of nitrogen for the soil type. The nitrogen distribution of the simulated land types was derived from Webb et al. (1982). Generally more nitrogen was found in the upper soil layers reducing with depth. Given this distribution of nitrogen, higher levels of soil erosion tended to have lesser effect on grass production. The resulting grass growth and carrying capacity were then re-calculated.
Project administration
Site identifier code: na
Principal investigator: C.R. Chilcott
Principal data manager:
Principal organizations: Department of Natural Resources, Mines and Energy
Data custodian: Department of Natural Resources, Mines and Energy
Key co-operators: Department of Natural Resources, Mines and Energy
Data access policy: Research has been published in soil conference bulletin
Planned pathway for data: completed study, no evidence of formal database records.
Data warehousing: for ongoing studies -na
Planned data upload frequency: for ongoing studies -na
Key references and sources of this data synthesis
These data summaries have been extracted from
- Chilcott C.R., Owens J.S., Silburn D.M., McKeon G.M. 2004. How long will soil resources last in semi-arid grazing systems? Conserving Soil and Water for Society: Sharing Solutions. 249.
Keywords:
south-east Queensland, erosion, grazing, utilisation rate