Information
Level 2 Detail of experimental conditions (what might be found in a journal paper or project brief in Hydstra)
Description of study
What?
Transport of herbicides in runoff and sediment was measured during simulated rain and furrow irrigation on a hill-furrow system typically used for cotton and row-crop production in Australia.
When and Where?
The soils chosen (vertosols) are typical of many areas used for cropping in central and southern Queensland. The soils within the study are Black Vertosol, Udic Haplustert, Halic Vertosol and is a strongly self mulching and strongly cracking with some thin surface crusting. Surface soil properties (0-25mm depth, mean of the three samples each from hills and furrows) are clay 67%, silt 15%, fine sand 13.5% and coarse sand 5% pH (1:5 soil:water) 8,1, organic carbon 1.1%, cation exchange capacity 53cmol (+)kg-1 .
Climate is subtropical and semi arid with summer dominated rainfall. Mean annual rainfall is 639mm, with 59% of the rainfall occurring within the warmer seasons (between November and March). Mean annual potential evaporation is 1885mm. The average temperature at the site was 21.1oC with a maximum and minimum temperature of 13.2 and 29.0oC.
How?
The transport of herbicides in runoff and sediment was measured during simulated rainfall and furrow irrigation on a hill furrow system. The rain and irrigation were applied within the first five weeks after cotton planting and herbicide application. The main treatment for this experiment include the following:
- Time between herbicide application and the runoff producing events (rainfall or irrigation) referred to as day after treatment (DAT);
- Banded verses blanket application; and
- Wheel tracks versus non wheel track (rainfall simulation study).
Herbicides were applied to the site, this includes:
- Staple herbicide- It was applied at 2-3 were intervals to different areas and rainfall simulations and irrigation were run during a two week period starting 5 weeks after the first application; and
- Diuron and Metolachlor herbicides- Were applied on the rainfall simulation plots to provide a contrast with pyrithiobac sodium/ These herbicides were applied at >10 times the rate recommended on the label.
The rainfall simulation uses 13 inline oscillating flat fan Veejet 80100 nozzles, on an area of ~2m by ~12m. The rainfall simulation applied rain with drop sizes and kinetic energy consistent with natural rainfall in Eastern Australia. Low EC rain water was used. Rain was applied to two neighbouring plots (a non wheel track and a wheel track) simultaneously. The intensity of ~70mmh-1 for more than 40min. Total rain in 40 min was ~47m. Storms of this intercity and duration occur about once every 5 years on average on the Darling Downs.
Runoff rate and sediment concentration were measured every 1-2mins from the outlet of each plot by recording the time it took to fill the bottle. Runoff rates (Ls-1) was calculated from mass of water and sampling duration. Sediment concentrations (gL-1) was calculated from mass of oven dried sediment and mass of water.
The pesticide analysis of runoff water was collected from the furrow outlet in plastic/glass bottles as 7, 10, 13, 16, 19, 22, 27, 32, 37, 40min after rain started, if runoff was occurring.
Runoff transport of pyrithiobac sodium (alone) was studied for furrow irrigation. These were 1m crop rows on 2m wider beds, with irrigation furrow each 2m. The beds were carried over from cotton the previous year. The furrows were carried over from measurements were made 50m up from the traidrain. The irrigation were run at three times after herbicide application each for blanket and banded (40% band on the hills) herbicide application. Runoff and sediment concentrations were measured by taking a sample of all runoff from the furrow over a known time at 1, 2, 5, 10, 15, 20, 30, 40, 50, 60, 90 min after the runoff started and until outflow ceased.
Project administration
Site identifier code: N/A
Principal investigator: Silburn DM
Principal data manager: N/A
Principal organizations: Department of Environment and Resource Management
Data custodian: Department of Environment and Resource Management
Key co-operators: N/A
Data access policy: Research has been published but base data is not archived
Planned pathway for data: completed study, no evidence of formal database records.
Data warehousing: for ongoing studies N/A
Planned data upload frequency: for ongoing studies N/A
Key references and sources of this data synthesis
These data summaries have been extracted from:
SIlburn DM, Foley JL, deVoil RC. 2011. Managing runoff of herbicides under rainfall and furrow irrigation with wheel traffic and banded spraying.
Keywords:
Great Barrier Reef, Vertosol, Queensland, Water quality, Partition coefficient, Pyrithiobac sodium, Metolachlor, Diuron