Increased productivity through better design and management
of irrigated canefields
S R Raine and D M Bakker
Project completed July 1996
(This project was partially funded by the Sugar Research and Development Corporation
- Project number BS90S)
[Summary] [Background] [Objectives] [Report Outline] [Home (Raine)]
This project has obtained, for the first time, data on the performance and efficiency of furrow irrigated canefields. In particular, it has shown that water application efficiencies on high infiltration soils in the sugar industry are generally low (average approximately 30%) while on low infiltration soils it is generally high (in excess of 80%). However, irrigation efficiency has also been shown to be closely related to the irrigation design and management practices adopted with large variations both between sites and throughout the season attributed to both management and environmental differences.
Under commercial conditions, between 25 and 35 ML ha-1 annum-1 of irrigation water was applied to some canefields in the Burdekin Delta area. While these volumes are higher than would be expected in average rainfall years, they are still far in excess of the plant water requirements and are indicative of the low water application efficiencies of irrigations in much of this area. It is conservatively estimated that water application efficiencies of less than 30% are indicative of those achieved in over one-third of the Burdekin Delta area. These inefficiencies represent a considerable cost on the production of sugarcane in these areas. Howver, this project has identified a range of irrigation design and management practices that can be used to reduce water use in these areas. One particular success that has already been widely adopted was the introduction of surface compaction by changing furrow shape. This has been shown to reduce water use by up to 47% without loss of productivity on high infiltration soils. Due to the ease and negligible additional cost associated with the implementation of this practice, it has been rapidly adopted within the Burdekin Delta district and is now being practiced or trialled by inexcess of 100 growers in the area (Holden pers comm). Other management practices identified to improve water application efficiencies in high infiltration areas include using herbicides instead of cultivation for weed control, using channel water rather than underground water for some irrigations and optimising water application rates according to the field length and site characteristics . The effect of irrigation design parameters such as furrow length and slope have also been shown to have a dramatic effect on irrigation efficiency. The benefits associated with a modest 10% reduction in water use in the Burdekin Delta alone is conservatively worth inexcess of $1.1M annum-1 in direct water and pumping costs and approximately $13M annum-1 in additional productivity.
The surface irrigation model SIRMOD was identified and evaluated for use as a tool in the development of furrow irrigation design and management practices within the sugar industry. This package was found to adequately simulate irrigations where the infiltration characteristic for the site was known. The infiltration characteristic can be calculated from data on the rate of water advance down the furrow and water application rate to the furrow. Using data based on actual irrigations, this package should be an effective extension tool for the delineation of design guidelines and to assist in the demonstration to growers the effect of various management practices on irrigation efficiency. This will also enable some quantification of the economic costs and benefits of alternative irrigation designs and management practices. The package should also prove to be a useful tool to reduce the amount of field data required to be measured in similar research studies conducted either in other areas. However, it should be noted that due to the large variation in infiltration characteristic both across fields and throughout the season, the package can only be used to provide show indicative trends rather than in a quantitative role where the infiltration characteristic has not been directly measured in the field.
The results of this work have been actively
promoted to the grower, industry and research communities through field days,
tours, demonstration sites, newpaper and magazine articles, and conference
publications. This project has also provided the data necessary to
provide the solid scientific basis for the development of the specialist
extension programs conducted as part of “Watercheck” (BS127S) and “Increasing
the irrigation efficiency of the Australian sugar industry” (BSE2).
However, further research and extension is required to realise the full
economic benefit of improved water use efficiency which is estimated to be in
the order of $42M annually in the Burdekin Delta area.
Furrow irrigation is the most common form of irrigation worldwide. It has a low technology and energy requirement and requires a relatively low capital establishment cost. Approximately 30% of the Australian sugar cane crop is produced using furrow irrigation. The majority of this area is located within the Burdekin region but there is currently substantial expansion occuring in the Mareeba and Proserpine areas. Potentially 100000 ha of land will be developed for furrow irrigated sugarcane by the end of the decade.
The proper design and management of furrow irrigation systems is necessary to achieve efficient water use and maintain an adequate water supply for all growers or provide water for additional irrigations. It is also necessary to prevent salt accumulation in the root zone and rising water tables in areas irrigated from surface channels. Poor design and management may also lead to poor germination, waterlogging and losses of fertiliser and pesticides out of the root zone. While the general principles involved in the design and management of furrow irrigation systems are known, very little work has been conducted to identify the efficiency of current commercial irrigation practices in the Australian sugar industry. As there have been previously few irrigation design guidelines, and irrigation development is expensive, growers have commonly opted for the least cost design, often without considering water use efficiency or the consequences for long-term viability. As a result, long furrow lengths (> 1000 m) have become common with some furrows in the Burdekin River Irrigation Area (BRIA) inexcess of 2000 m in length.
The irrigation requirement of sugar cane in the Burdekin region is 9.8 ML ha-1 annum-1 based on the long term rainfall (Anon, 1991). However, rainfall in the past five years has been less than 500 mm yr-1 with evaporation greater than 2000 mm yr-1. This has increased the irrigation demand and raised the grower awareness of irrigation efficiency, productivity and profitability. Of particular concern to growers during this period has been the reduction in the underground water levels in the Burdekin delta and periodic demand exceeding the capacity of the surface channel system in the BRIA. The increasing irrigation demand in the BRIA resulted in above allocation water being no longer available after 1995 and the possibility of water restrictions being imposed during peak demand periods.
The direct cost of lost productivity and water
wastage from inefficient furrow irrigation practices in the Burdekin delta area
is been estimated to be approximately $3.5 M annually. However, in many
cases, low water application efficiency is limiting production through
constraints on the availability of water and the ability of growers to schedule
irrigations. Where improvements in application efficiency provide water
for additional irrigations or enable irrigation scheduling, production benefits
are conservatively estimated to be worth an additional $39M annually in the
Burdekin Delta area alone. However, only limited research has previously
been conducted to determine the efficiency of current irrigation practices and
to determine appropriate irrigation design and management practices for sugar
cane production. With this in mind, the primary aim of this project was
to “increase the productivity and sustainability of surface irrigated
canefields through improved design and management criteria”.
PROJECT OBJECTIVES AND OPERATION
This project was conducted from September 1993 to June 1996 and was funded by the Sugar Research and Development Corporation (SRDC), Bureau of Sugar Experiment Stations (BSES) and CSR Ltd (Appendix 1). The project objectives were to:
- Obtain field data on the efficiency of current
furrow irrigation practices in the Burdekin
- Identify the most suitable of the irrigation
model(s) available for simulating surface irrigation practices, and
determine the minimum number of field measurements required to operate
the model.
- Obtain infiltration estimates required by the
appropriate irrigation model for different initial soil moistures, furrow
shapes, water qualities and cultural practices.
- Produce and publicise design guidelines for furrow
length and slope for different soil types and cultural practices.
To achieve these objectives within the timeframe and resources available, the project was operated as three concurrent phases with complementary aims:
Phase A The establishment of field trials and monitoring of commercial irrigation practices to obtain baseline data on irrigation efficiency and identify methods to improve irrigation efficiency;
Phase B The identification and evaluation of surface irrigation models to assist in the design and management of surface irrigation, and the assessment of the model’s requirements for operation; and
Phase C The dissemination and publication of irrigation design and management guidelines to improve irrigation efficiency.
Each phase addressed a specific requirement within
the project but relied heavily on the other phases for input and outputs to
achieve the overall project aim. While the phases were operated
simultaneously throughout the whole project period, greater emphasis was placed
on phase A in the first year of project operation and phase B in the last year
of the project. In an effort to ensure farmer involvement in the project and
rapid adoption of project outcomes, technology transfer and extension
activities (phase C) were conducted throughout the project. In the later
years of the project, the results and extension activities arising from this
project were also integrated into the activities being undertaken by the
specialist extension projects “Watercheck - Statewide irrigation campaign”
(BS127S) and “Increasing irrigation efficiency in the Australian sugar
industry” (BSE2).
TABLE OF CONTENTS OF FINAL REPORT
NON-TECHNICAL SUMMARY
1. BACKGROUND
2. PROJECT OBJECTIVES AND OPERATION
3. PHASE A THE MONITORING OF COMMERICAL IRRIGATION PRACTICES TO OBTAIN BASELINE DATA AND THE ESTABLISHMENT OF FIELD TRIALS TO INVESTIGATE METHODS TO IMPROVE IRRIGATION EFFICIENCY
3.1 Introduction
3.2 Materials and Methods
3.2.1 Site Characteristics
3.2.2 Site Measurements
3.2.3 Calculation of application efficiency
3.3 Results and Discussion
3.3.1 Soil Type, Furrow Length and Tailwater
Recycling
3.3.2 Effect of Irrigation Cut-Off Time
3.3.3 Effect of Application Rate
3.3.4 Effect of Furrow Shape
3.3.5 Effect of Cultivation Practices
3.3.6 Effect of Trash Retention Systems
3.3.7 Effect of Water Quality
3.3.8 Alternate Furrow Irrigation
4.0 PHASE B: THE IDENTIFICATION AND EVALUATION OF A SUITABLE SURFACE IRRIGATION MODEL, AND THE ASSESSMENT OF THE MODEL’S REQUIREMENTS FOR OPERATION
4.1 Introduction
4.2 Materials and Methods
4.3 Results
4.3.1 Model Validation
4.3.2 Sensitivity Analysis
4.3.3 Empirically Fitted
Infiltration Parameters
4.3.4 Temporal Variation of Infiltration
4.4 Discussion
5. PHASE C: THE DISSEMINATION AND PUBLICATION OF IRRIGATION DESIGN AND MANAGEMENT GUIDELINES TO IMPROVE IRRIGATION EFFICIENCY
6. RECOMMENDATIONS FOR FURTHER ACTIVITES
7. ACKNOWLEDGEMENTS
8. REFERENCES
Appendix 1 Project Funding
Appendix 2 Raw data for the field sites
Appendix 3 Industry and conference
publications arising from this work
[Summary] [Background] [Objectives] [Report Outline] [Home (Raine)]