Information
Level 2 - Detail of Experimental Conditions
What
This project measured the range of nutrients and suspended solid concentrations that exist in plot scale drainage and urban lakes during rain events in the wet season within two distinct river catchments in Queensland.
The study provided unique information on cane farms, detailing the amount of nutrients and sediment that exist in runoff draining..
The strategies developed for the cane field sites are:
- Maintain sound soil management practices, including maintenance of green cane trash blanketing and use of minimal tillage;
- Management of fertiliser application based on soil and plant nutrients status and crop productivity requirements. Fertiliser sources vary markedly in form and variety and landholders preferentially use conventional granular forms over other sources (e.g. Liquid fertilisers such as Liquid One Shot);
- Maintaining grassed buffer strips on the blocks and grassed drainage channels to reduce sediment losses and enhance assimilation of nutrients in sub surface drainage. Using slashing and occasional use of knock down herbicides to maintain soil integrity;
- Using cultivated soy beans during fallow periods to enrich soil N. This will result in soil N levels that may exceed plant cane requirements (circa up to 300kg N/ha) so soy beans density may need to be managed.
When and Where
The project started on June 2002 and concluded in June 2003.
The watershed for the study region was 13.67 hectares, which drains a number of cane blocks (4F-5.5ha, 5B- 2.97ha and 5C- 5.2ha).
The slope of the block is estimated to be 5% with cane representing 95% of the block under cultivation. The soil on the block was characterised as a mix of soil types that include:
- Warrami;
- Hillview;
- Fine Variant;
- Thorpes;
- Felug Red Variant;
- Malbon; and
- Hewitt.
How
Harvest of the cane crop on the block was conducted in October of each year with planting and fertilising application usually carried out in the first week of November.
Weir Infrastructure
A crump weir was installed at the drainage points at each site. The weir was a TB3 weir with 1 mm tipping bucket rain gauge with additional instrumentation including:
- 3.5 meter range Druck PTX1830 pressure transducer coupled to a RRDL-A data logger.
Depths and discharge were measured to the nearest 0.0001 point (or cumec) and were recorded every two minutes, but reporting data has been limited to 15 minute intervals.
A number of sampling strategies were used on the cane field site, these include:
- 2002/03 and 2003/04 seasons, water samples were collected by the landholders and project catchment coordinators;
- 2004/05 seasons, modified rising stage samples (CASPER) were used in conjunction with landholder sampling; and
- 2005/06 an autosampler was used to collect event flows in the 2005/06 CASPER was also maintained at the cane field, but to only validate autosamples.
Flow and rainfall data were logged between 11 January 2003 and 30 June 2006.
Physio-Chemical and nutrient data that was collected from the samples include:
- pH;
- Nitrogen;
- Conductivity;
- Phosphorus; and
- Total Dissolved Solids.