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Science Summary:
- Furrow sites in Home Hill recorded 13% higher deep drainage (263 mm) over the crop season compared to the drip irrigation (233 mm). Hence reduced deep drainage in drip irrigated sugarcane has been confirmed. However, the run-off in Home Hill site limited due to completely banked tail ends.
- Low soil infiltration rate (5.42 mm/hr) has been recorded for micro-sprinkler block compared to higher infiltration rate (17.89 mm/hr) recorded for drip irrigated banana in the ferrosol soil.
- Higher deep drainage noted in the Home hill site even for the drip irrigation site. Management of irrigation by frequent pulsing has been introduced this year to reduce the deep drainage from the drip irrigated crop of sugarcane.
- Higher electrical conductivity in the soil with micro-sprinkler irrigation compared to drip is related to lower plant uptake in the sprinkler plots as the crop in this treatment is still establishing. Greater EC at depths below the effective rooting zone (65 cm), imply that those nutrients are more susceptible to loss from deep drainage.
- Soil infiltration rates have a direct effect on run-off and deep drainage properties of the soil. At the current stage the infiltration rate in the drip plot is very high compared to the micro-sprinkler irrigation. It is very early to associate this to the irrigation treatment effect, as the crop with drip irrigation has substantially higher cover with plant debris (mulching effects). Research is ongoing.
- Researchers note that although drip irrigation resulted in reduced Deep Drainage compared to furrow, these deep drainage values in sugarcane sites are still high. Opportunities exist for optimization of the drip irrigation to suit to the soil, crop, growth stage and weather which will be explored out of the variable site data being collected.
Progress Update:
- The first biannual meeting of project team and other co-operators was held in December 2011.
- Experimental sites have been set up (two sugarcane in N Qld and one with banana in C Qld, all with monitoring equipment all set up for automatic and manual sampling.
- Data collection continued from two sugarcane trial sites in Burdekin. Crop at Home hill site harvest on 19-23 August (trial will continue on this site with ratoon crop for second season - 2012/13). The site at Clare will be harvested in Nov-Dec.
- Two run-off events have been recorded from the banana trial site at Bundaberg. In the Burdekin run-off associated with rainfall was noted only on the furrow site. For the same rain event no run-off was noted for the drip irrigation block. We have progressed well with data and water sample collections from deep drainage in all trial sites.
- In banana sites, piezometers for ground water, drainage lysimeters, and flumes with water height sensor for run-off control and sampling have been installed and data being collected. One new experimental area has been instrumented, with micro-sprinklers next to the drip site with banana in Bundaberg; active data collection has started from this block.
- Information about drip irrigation in sugarcane and banana which will be mailed to growers currently adopting drip (10), flood (10) and overhead sprinkler (10). The outcome of this survey will also be presented and discussed in the field day. Field day planned for December will have a complete set of crop, soil and water data from one crop cycle, which will be more meaning to the growers to discuss on the field day.
- Banana site at Bundaberg is now well instrumented and an additional block of Micro-sprinkler irrigation is establishing.
- Plant, soil and water sampling from all trials continuing for second season.
Science Summary:
- During the 2010 and 2011 hydrological years, total nitrogen loads from the butterfly pea pasture have exceeded those of brigalow scrub, grass only pasture and grass/leucaena pasture on a kg/ha basis. A lower EMC for butterfly pea in 2011 compared to 2010 indicates that the establishment phase of the pasture may be particularly susceptible to nitrogen loss.
- Bias in the load estimation techniques previously used in the 2011 hydrological year have been removed with new methodology, and the refined data is now ready for provision to users including the Paddock to Reef program. Using the refined load estimation techniques, data from the 2011 hydrological year shows similar or lower loads of TSS and nitrogen (total and species) from buffel grass and leucaena pastures compared to native Brigalow Scrub. Orthophosphate load from buffel grass pastures continues to be greater than that of virgin Brigalow Scrub. Loads of TSS, nitrogen (total and species) and phosphorus (total and species) from young (<5 year) butterfly pea ley pasture continue to equal or exceed all other catchments.
- The extension of this work into the Burnett-Mary and Burdekin catchments was undertaken using rainfall simulation. Post-wet season simulations at both sites demonstrated that more rainfall was required to generate runoff from legume based pastures compared to grass only pastures. This “sponge” effect of cracking clay soils calls in to question the suitability of rainfall simulation in these landscapes.
- Estimation of sediment and nutrient loads over time were obtained by applying EMC data collected from 2000 onward to modelled daily flow data from the catchments covering the period 1984 to 2004. Cumulative sediment loads from cropping over the 21 year period are an order of magnitude greater than pasture, with both land uses showing an increase in sediment load due to land use change. A reduction in the rate of cumulative load for cropping post 1998 coincides with a switch to minimum tillage and opportunity cropping. Total nitrogen loads over the same period show an increase in load from cropping as a result of land use change. However, loads from pasture show a reduction compared to loads from the native brigalow vegetation. The reduction of load from pasture is an order of magnitude larger than the increase in load from cropping.
Progress Update:
- A late break to the 2011 wet season resulted in no new water quality data until 2012. One communication activity has been held over into 2012 due to this lack of data. All other scheduled data collection, analysis and communication activities were completed as proposed.
- Quarterly soil and pasture sampling for the end of winter period have been completed. Sample processing is continuing and samples will be submitted for analysis in January.
- Field operations to July 2012 and data available since project commencement were reported in a combined progress report.
- The rainfall simulation component of the program has been completed well ahead of schedule. The final simulation was the Burdekin Catchment site, end of dry season, and was done in this reporting period. First cut analysis of the flow and water quality data is being undertaken.
Science Summary:
- The project has prepared a literature review that identified and characterised the factors that influence management practice adoption – such as land use practices that can be characterised by personality, education level and degree of motivation of farmers (Objective 1). Characteristics of management practices involved with land preparation, crop growing and harvesting vary over climatic zone, such as wet and dry tropics, as well as within regions depending on the land contour, soil type and traditional practices.
- Identification of the key factors affecting adoption of management practices and development of a tool to use that information are underway with farmer interviews to explore farming characteristics and factors that limit ability to manage properties according to the management practices that have water quality benefits in cane farming. A total of 17 stakeholder interviews and 116 farmer interviews (51 from Bundaberg and 65 from Mackay) have been conducted, and descriptive statistical analysis is underway.
- Preliminary results show factors – socio-demographic, cultural and economic – that influence farmer choices to adopt management practices with water quality benefits, and current uptake of practices.
Progress Update:
- The literature review is complete (Objective 1) and stakeholders are currently reviewing the document to provide feedback.
- Delays in receiving ethics approval for the farmer surveys have affected delivery of Objectives 2 & 3 that are slightly behind and a focused effort to complete surveys should catch up by the next reporting cycle.
Science Summary:
- The project has collated over 130 sites of data for runoff and water quality relating to paddock and catchment investigations. Study sites have been comprehensively reviewed using a hierarchical data structure. All of the sites have been entered into a database that identifies key characteristics of the data. Half the sites have been published to the HOWLEAKY? web portal that can be interrogated, and the project website has links to the raw data in DARTS.
- Key sites – that include cropping, pasture and horticulture land uses and a variety of management practices – have been modelled for runoff and soil loss.
- Case studies have been generated that contain files that describe time series of observed climate, runoff and soil loss. The modelling process has resulted in the development of best-bet HOWLEAKY? soil and vegetation parameters).
- HOWLEAKY? parameter files have been developed for select land use studies/sites.
- This extensive data set has not been uploaded to DARTS. At this stage DARTS is immature technology, which cannot accommodate the needs of this project (e.g. attaching key documents).
Progress Update:
- Due to the unexpected number of previous studies concerning water quality at the paddock scale, final milestone submission was extended. It is expected that final milestone will be delivered by the end of December 2012.
Conference Papers:
Freebairn DM, Cutajar J, Silburn M. (2012). Assessing water quality from farms – how much detail is required for a model to be useful?
Robinson BJ, Shaw M, Chamberlain T, Searle R, Freebairn D. (2012). A quantitative and functional soil classification for modelling the terrestrial water balance of north-eastern Australia.
Science Summary:
- A review of national and international water quality assessment frameworks has been undertaken to identify possible methods for developing a marine water quality metric for the MMP. Seven national and 5 international programs were selected as suitable for review, and similarities and differences with the MMP were documented. Five international programs were also reviewed with a focus on the procedures used for evaluating the eutrophic status of coastal and offshore waters and categories used for final classification. Recommendations from these reviews are captured in a project report and inform the selection of the preferred framework for this project.
- The review showed that none of the current frameworks in international and national programs were suitable for the GBR, so a hierarchical integration approach is being devised. Accordingly, statistical procedures to compare and then integrate the different WQ data types into an overall WQ assessment were investigated.
- A test data set is being used to trial the proposed statistical methods for the temporal and spatial aggregation. The test data comprises measurements of Chlorophyll a and Total Suspended Solids recorded by all four methods (remote sensing, fixed data loggers, regular ambient in situ sampling, and event-based in situ sampling) in the Wet Tropics region during the 2010-11 reporting year (i.e. between May 2010 and April 2011).This includes ways of augmenting the low data availability from satellite data during the wet season by using data collected during the wet season characterization fieldtrips.
Progress Update:
- All milestones have been completed in line with contractual expectations.
- The first meeting with end-users was held in May 2012 and provided the team with feedback on the progress of the framework; a second meeting was held in November 2012.
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