Information
Level 2 Detail of experimental conditions (what might be found in a journal paper or project brief in Hydstra)
Description of study
What?
This study monitored water infiltration and nutrient leaching in black Versotols under different long-term fallow management practices.
When and Where?
From 1969 and 1998 a study was undertaken on two sites (Project 1 and Project 2) within the Hermitage Research Station near Warwick on the Southern Darling Downs. A permanently grassed area (1000 m by 50 m), 1600 m north-east of the trial was also used to represent the trial site prior to cultivation and is referred to as the Hermitage virgin site. Two farms located approximately 90 km north-east of the Hermitage trial site were selected for their long history of regular fertiliser use, both using conventional tillage with stubble retention and fertiliser-N applied annually. The fifth site was a permanently grassed area approximately 10 m by 1000 m adjacent to farm site 2, referred to as the farm virgin site. All 5 sites were Black Vertosols.
Project 1, Hermitage trial site 1, Farms and Virgin Sites
Hermitage trial site 1 had a permanent winter cereal (wheat or barley) – summer fallow rotation over the life of the study with 12 different management treatments: zero (Z) or conventional (C) tillage x stubble retention (R) or burning (B) x 3 nitrogen fertiliser rates 0, 23, and 69 kg N/ha.
The hermitage trial site 1 was sampled on the 12th and 13th of December 1989 1 month after the barley harvest. The site had received 66mm of rainfall since harvest and soil sampling. Both farm and virgin sites were sampled in May 1990 following fallow for 6 months at farm 1 after wheat harvest and 12 months fallow at farm 2 after sorghum harvest.
Project 2, Hermitage trial site 2
Hermitage trial site 2 also had a permanent winter cereal (wheat or barley) followed by a summer fallow rotation. A total of 12 trial treatments were used combining 2 tillage methods conventional (CT) and zero (ZT) and 2 stubble management strategies, stubble burned (SB) and stubble retained (SR) x 3 nitrogen fertiliser rates 0, 23, and 69 kg N/ha.
How?
Project 1, Hermitage trial site 1, Farms and Virgin Sites
Soil Sampling
Soil samples were obtained using hydraulic sampling tube, which allowed a sampling depth of 5.4m. The sampling was carried out in 3 stages: 0-1.8m x 36-mm (internal diameter), 1.8-3.6m x 25-mm, and 3.6-5.4m x 25-mm. Core samples taken at the Hermitage site were divided into 0.3-m increments to make 18 depth intervals. At both farm and virgin sites, the top 0.3m of the soil was divided into 0-0.15 and 0.15-0.3m making 19 depth intervals.
Chemical Analysis
Soil samples for chemical analysis were dried at 40°C for 4 days then ground to <2 mm diameter, and stored in air- tight jars. Dried soil for nitrate-N analysis was extracted with 2M KCL using a 1: 10 soil solution ratio. Soil was then filtered through No. 40 filter paper. The solutions were then analysed for nitrate-N using a modified Griess-Ilosvay method in an automated spectrophotometer. Soil for chloride analysis was prepared into a 1 : 5 soil water solution then stirred for 30 minutes and allowed to stand for 1 hour before analysis. Chloride concentrations were determined by potentiometric titration with AgNO3 using a quinhydrone half-cell and Ag/AgCL electrode.
Project 2, Hermitage trial site 2
Subsurface Cracking Patterns
Cracking patterns were photographed in October 1991 after a period when no crop had been planted due to prolonged drought. An industrial vacuum cleaner was used to remove the fine dry aggregates of the self-mulching surface layer leaching the wetter subsurface. This allowed subsurface exposure, without physical disturbance, and a clear view of cracking within the soil. A 1-m square quadrat was used to define the photographic boundary. The photographs were assessed visually.
Hydraulic Conductivity
Hydraulic conductivities of the surface soil were measured using disc permeameters in January 1991 following the December wheat harvest. Permeameter measurements were conducted at supply tensions -1 and -3 cm H2O at each site. The January Measurements were conducted at antecedent moisture contents ranging from 0.054 m3/m3 (CT-SB) to 0.094 m3/m3 (ZT-SR) in the surface and 0.202 m3/m3 (CT-SB) to 0.359 m3/m3 (ZT-SR) in the subsoil. As the volume of crack macropores varies with moisture content, the permeameter measurements were conducted again in February 1991 with moisture content ranging from 0.398 m3/m3 (ZT-SB) to 0.465 m3/m3 (ZT-SR).
Bromide Tracer Infiltration (24 hr)
Measurement of bromide infiltration within the soil was conducted in June 1992 using a ring infiltrometer which supplied solution at a constant positive potential for 24 hrs, and a disc permeameter which supplied solution at -3cm potential until the solution supply was exhausted after 20-80 min. Depth increments for sampling were smaller near the top of the profile. Samples were collected with a 50-mm-diameter sampling tube driven into the soil 5-10 times per permeameter / infiltrometer site. The experiment was conducted following rain when soil moisture was near field capacity. After 24 h, the infiltrometer and permeameter sites were sampled for analysis of water and bromide. Soil moistures were determined by oven drying at 110°C and bromide concentrationswere analysed using ion chromatography
Bromide Tracer infiltration (6 months)
Subplots, 4 by 5 metres, were established midway along the plot length within each of the 69kg N/ha plots for each surface management treatments. The subplots had 100 kg/ha of bromide dissolved in 25L of water applied by a watering can over the 20-m2 area. The subplot was designed to include areas of intensive sampling (2x1 m2 microplots) and areas sampled less frequently (the rest of the subplot area). Bromide was applied to the subplots on 8 January 1990. Soil samples for moisture and bromide analysis were taken with steel push tubes to a depth of 1.5 m at 4 dates following application. The first sampling on the day after application (9 January 1990) involved taking two 36-mm-diameter cores within each microplot and another 2 cores from positions external to each microplot. This allowed establishment of initial soil concentrations of bromide for the microplot and external areas. Subsequent sampling dates during the 1990 fallow were 22 February, 3 May, and 22 June. Only the initial (9 January) and the final (22 June) sampling included sampling external to the microplot area.
Project administration
Site identifier code: N/A
Principal investigator: JE Turpin
Principal data manager: -N/A
Principal organizations: Department of Agriculture, University of Queensland
Data custodian: Department of Agriculture, University of Queensland
Key co-operators: Queensland Wheat Research Institute, CSIRO Division of Land and Water, Leslie Research Centre
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:
- Turpin JE, Thompson JP, Waring SA, and Mackenzie J. (1998). Nitrate and chloride leaching in Vertosols for different tillage and stubble practices in fallow-grain cropping. Australian Journal of Soil Research 36: 31 – 44
- Turpin JE, Bridge BJ, Orange D, and Thompson JP. (1999). Water and bromide movement in a Vertosol under four fallow management systems. Australian Journal of Soil Research 37: 75 - 89
Keywords:
Nitrate, chloride, leaching, bromide, vertosol, fallow management, tillage, stubble