AN EFFECTIVE APPROACH TO DELIVERING SUGARCANE IRRIGATION EXTENSION AT BUNDABERG BASED ON REAL TIME WEB-BASED TECHNOLOGY By MG HAINES Bundaberg Sugar Services Ltd, Bundaberg mhaines@sugarservices.com.au KEYWORDS: Soil Water Balance, Real Time Information, Irrigation Web Centre, Stress Factors, Stress Days. Abstract BUNDABERG HAS A supplementary irrigation water supply capable of supplying approximately one third of the potential annual crop moisture demand and rainfall is often insufficient or inappropriately timed for the seasonal requirements of the sugarcane crop. This situation lead to the development of an extension program designed to improve scheduling techniques to maximise crop utilisation of both water sources. There are several locations across the world where field monitoring of soil moisture is practiced and data are received through web technologies (Kenana Sugar Company, Sudan, Indonesia, Murray Darling Irrigation Area, Australia) but discussions with these groups indicate that data are generally delivered to the primary user for the specific use of the company, agronomy department or the specific farming operation. A modern interpretation of the role of agricultural extension is one that enables change in individuals, communities and industries involved in the primary industry sector and in natural resource management. The concept of identifying champions with the intention that other farmers will be encouraged to adopt similar goals and practices is a longstanding extension method. However, when dealing with issues of irrigation, promoting outcomes after the event does not alert the target group to the need for timely change and therefore is unlikely to successfully achieve the desired outcome. A Bundaberg web-based extension program designed to draw all farmers in the district into a technology group of likeminded users was developed. Monitoring systems located on the farms of high performing enterprises provide a constant flow of real time information which enables the industry as a whole to react to climatic influences. The potential outcomes of this program are a sustainable increase in productivity, a reduction in irrigation input costs and a greater understanding of factors that impact on the local environment. Introduction A pattern of increased temperatures and a range of adverse weather conditions that are either dryer or wetter than usual are predicted for the future. This prospect of climate variability is focussing the future of agricultural management on change, particularly in irrigation water use and drainage. With this in mind a proposal for a new extension delivery framework to enhance the capacity of sugarcane growers in the Bundaberg mill area to adapt to the predicted change was developed by Bundaberg Sugar Services Limited (BSSL). This paper describes this program, which includes a web-based concept designed to provide daily Bundaberg-specific irrigation and climate information to irrigators. The delivery mechanism developed provides a guide to soil moisture change as determined by in-field monitoring systems in the Bundaberg mill area. 140
The purpose of this information is to provide an opportunity for neighbouring irrigators to review situations similar to their own, so as to be able to identify the rate of water use by a similar crop on a similar soil type on the same day. Strategically located automatic weather stations are also linked to this web system to provide a continuous feed of important crop management information including, rainfall, wind speed/direction, air temperature and soil temperature. Background Benchmarking programs comparing sugarcane yield to effective rainfall and applied irrigation water that commenced at Bundaberg in 1989 have continued to highlight the impact of management decisions on the relationship between rain, irrigation and sugarcane yield at Bundaberg. The benchmarking concepts applied to this program have been reported by Kingston (1994), Willcox et al. (1997) and Haines and Linedale (2006). Information presented in this paper will highlight the potential for yield improvement when irrigation efficiency extension programs are focused on applying irrigation to manage the soil water balance relative to the water holding capacity of the soil, and daily crop requirement. During the long running Rural Water Use Efficiency Initiative (RWUEI) program, which has been widely reported by Baillie et al. (2001), Linedale et al. (2001), Baillie (2002), and Newell et al. (2002), irrigators appear to have understood extension that focused on reducing application inefficiencies. Investment in low pressure booms, lateral move and centre pivot irrigators to reduce wind effect on irrigation application efficiency has increased. However, the concept of right amount at the right time does not appear to have been as widely embraced. A comparison of tc/ha between individual farms with comparable applied irrigation rates for crops harvested from 1998 to 2002 is presented in Figure 1 and shows yield variations of up to 50 irrigated fields may not be utilising rain or irrigation to its full potential. 140 120 100 t cane/ha 80 60 40 y = -1.3588x 2 + 16.296x + 53.002 R² = 0.5751 20 t cane/ml 0 0 1 2 3 4 5 6 7 ML/ha Fig. 1 Bundaberg irrigation water applied (ML/ha) and sugarcane yield (tc/ha) for 1998 to 2002. Where no irrigation is applied there is little control over crop water availability and it could be expected that variation due to different soil types or timing of rainfall events is likely to occur. 141
However, where irrigation is applied, particularly at quantities that are likely to raise the total crop available water to close to optimum it could be expected that with effective scheduling, issues of soil type and seasonal effect would be less dominant. These data suggest that this may not be the case. Haines and Attard, (2010) provided examples of two Bundaberg case studies over four seasons (2005 2008) showing irrigation schedules based on the web scheduling tool WaterSense (developed by CSIRO and industry participators) that was verified by EnviroSCAN (Sentek Pty Ltd, Australia) capacitance field probes. The WaterSense model uses reference ET (Allen et al., 1998) and daily factors to calculate ET C. Mean data for the case studies indicate gross rain plus gross irrigation of 1304 mm/year with crop utilisation of available soil water 1228 mm ET C for a yield of 132.14 tc/ha. Mean application of irrigation was 3.4 ML/ha as irrigators responded to the timely directives of the modelling process which resulted in high level (94%) utilisation of rainfall and applied irrigation. This indicates that detailed attention to managing the soil water balance can lead to higher yield potential, which in the case study situations improved the mean yield from 9.1 to 10.76 tc/100 mm of ET C (+ 18.2%). This information also raised questions about the most effective way to increase farm-level uptake of water balance farming concepts. With this in mind it was decided to investigate options that created a timely visual reference to a measured infield response to contributing factors. The plan was to develop a system that provided real time indicative advice to irrigators showing the range of management practices in the region and highlighting the benefits or down side of each practice. Modelling tools such as WaterSense were considered for the Bundaberg irrigation information web site, however, irrigators generally did not respond well to the concept of modelling. There was a need for regular input of data to maintain model records and the probability that a computer could emulate the field situation was difficult for the irrigator to accept. Bundaberg CANEGROWERS and Bundaberg Sugar Services Ltd (BSSL) commenced an Irrigation Planning and Management Project in 2011 to develop the capacity and/or skills of sugarcane farm managers to efficiently schedule for increased crop utilisation of irrigation and/or rainfall. To address the issues identified, funding was sought from the Australian Government funded Caring for Our Country grants program for a pilot project titled Improving skills in sugarcane irrigation planning and management for increased environmental sustainability and economic viability of irrigated farming enterprises. Project outline This pilot project proposal outlined a unique and new extension service delivery framework to enhance the capacity of sugarcane growers in Bundaberg to adopt an adaptive strategies approach to managing the impact of a changing and increasingly variable climate. This approach focused on optimising climatic influences to maximise crop water use efficiency and economic return. This goal required the right amount of water be available to the crop at the right time. The future of economically viable irrigated sugarcane production at Bundaberg may well depend on how effectively the crop utilises both rainfall and irrigation. This concept required that information such as real time weather interpretation relative to daily crop needs (e.g. water, temperature and radiation) and real time indicative soil moisture status be readily available to irrigators to ensure that rainfall is fully utilised but also that irrigation is not withheld so long as to lose the benefit of growth gained from a rainfall event. This proposal set out a plan to develop a specific web-based information centre providing locally relevant updates to support the adaptive strategies concept. Implementation plan The project plan proposed a central point of communication called the Bundaberg Climate and Crop Water Use Information Centre (a one-stop-shop web site) delivering soil moisture updates, crop water use rate and weather related information based on data gathered from infield 142
soil monitoring activities, local weather stations and national weather sources. Capacitance soil moisture monitoring systems and a network of local automatic weather stations were planned to collect and transfer data via phone modem to a processing location which then supplies soil water balance graphs and weather information to the web site. Soil moisture data are updated every two hours and weather station data are refreshed every 15 minutes for access by BSSL members. Extension plan Extension professionals have for some time utilised various methods of estimating daily sugarcane water use as a tool for scheduling of irrigation in sugarcane farming. Most systems are based on crop factors relative to the long term mean of pan evaporation (EP) or calculated reference evapotranspiration (ET 0 ) and rely on the reliability of the crop factor estimates for accuracy. The weakness in these methods is that the water use calculations depend on historical information for canopy development not current weather for a specific day which does not always relate well to the long term data, thus when the situation calls for an adaptive strategy, monitoring is more reliable. The overriding problem with estimates and calculations is that irrigators are generally more likely to be attuned to visual signals than estimates and calculations. There will be situations where temporary midday stress can occur with adequate soil moisture if Et demand exceeds capacity of the root system to access moisture but the concern is that some irrigators are likely to rely on more permanent levels of leaf stress or watch for dryness of the soil before commencing irrigation, both of which are signals of cessation of growth not the onset of stress. Daily crop water use will vary according to specific daily weather conditions, the soil water balance and crop size. The extension plan implemented by the Bundaberg Irrigation Planning and Management Project is modelled on the Diffusion process (Van den Ban and Hawkins, 1996), which is based on the principle that when an innovation is adopted by some, others may follow. It is well known that farmers have a keen interest in what other farmers are doing. This concept is often applied when case studies illustrating adoption of innovation or reward for high achievement are highlighted through media and other extension events e.g. award presentations. When extending irrigation fundamentals like adaptive scheduling through the case study process often the time lag between the action that influenced the high performance and the outcome negates the value of the demonstration. The goal of the web based extension plan is to provide an opportunity for farmers to observe activities of neighbouring farmers in a time frame that allows for timely adjustment in practice. The key to this plan is that farmers are able to compare situations similar to their own in real time to identify the rate of water use per day by a similar crop on a similar soil type on the same day. The objective is to create an on-line irrigation extension group comprising all 230 members of BSSL. Extension methodology In recognition of the diversity of knowledge and skills within the group, information provided by the Bundaberg irrigation information web site is designed to deliver its message via a visual concept as opposed to a highly technical approach. Graphical presentations are based on the illustration of water dynamics in the crop root zone shown in the schematic example of the relationship between the rate of soil moisture infiltration and extraction in each of three soil moisture phases (Figure 2). The three phases of the soil water balance are presented as: Phase 1: soil moisture increase due to irrigation or rainfall Phase 2: soil water saturation and drain down to field capacity unrestricted crop use of Readily Available Water (RAW) Phase 3: restricted crop water use as moisture content declines crop moisture uptake ceasing indicating that the crop has reached permanent wilting point (Plant Available Water (PAW) now exhausted). 143
The intended message is: Phase 1, water is entering the field; Phase 2, the crop is growing; and Phase 3, growth is slowing and yield is being irretrievably lost. Fig. 2 Soil water phases. Extension delivery Nineteen (19) capacitance probes were installed across the Bundaberg sugarcane production area. Eight of the 19 probes are owned by BSSL and the remainder have been purchased by irrigators. Probes owned by irrigators are managed by BSSL and information from these sites is also available through the Bundaberg irrigation information web site. Monitoring at each site shows the relationships between changes to the soil water balance caused by management practice or other events that facilitate change e.g. rainfall, irrigation timing and volume applied, ET C and drainage. For the purpose of illustrating the impact of root development on soil water availability, sensors within each probe are placed at different depths to capture the impact of root density on moisture uptake as the sugarcane plant develops. Sensors are placed at depths of 10 cm, 30 cm and 60 cm to record moisture extracted from the highly active root zone in most soils (0 60 cm) and at 100 cm to monitor extraction of moisture from deep profile soils. The 100 cm sensor also serves as a monitor of deep drainage and is useful as a tool to minimise losses from inefficient irrigation systems. An interpolated volumetric measure of moisture in one cubic metre of soil is determined from this data. Most soil types, crop sizes and irrigation systems are represented and it is envisaged that over time the district coverage will be improved as more members purchase a soil monitoring unit to monitor their individual situation which will increase the opportunities offered by this project. Eight automatic weather stations are also located in the Bundaberg sugarcane production area. Weather station reports are continuously updated on the web site showing factors that influence crop production, including current temperature, 24 hour rainfall and current rain, wind 144
speed/direction and soil temperature. A map locating each probe and weather station site (Figure 3) is included on the web site to provide a simple means of accessing a monitoring point closest to each member s farm. Users of this web tool are able to select a monitoring site with a click on the site number on the map display. Fig. 3 Monitoring site location map. The selected site will open the web page (Figure 4) showing a photograph of the crop being monitored with information about the crop, the soil and a graphic report of the monitoring outcomes. Each report contains two graphs: The upper graph shows separate levels in the soil which illustrates moisture change at different depths usually 10 cm, 30 cm, 60 cm and 100 cm; The lower graph is a sum of the total amount of water in a cubic metre of the soil at the monitored point (0 100 cm depth). The page also displays current four-day rainfall and temperature forecasts. A link to a comprehensive weather information site is also available. Field Capacity in the summed graph is established from the information collected by the monitoring process and Refill Point (on set of stress) is based on the Readily Available Water Content (RAWC) of the soil derived from Bundaberg soil mapping units (Donnollan et al., 1998). Graph interpretation The staircase pattern shown in the soil moisture graph illustrates influences affecting the soil water balance. The steep part of each step is associated with daylight hours (transpiration and evaporation) and the flat section denotes night when there is little or no demand for moisture by the crop. A sloping trend can occur directly after rain or irrigation when the soil profile is draining down to field capacity. Larger steps indicate hotter days and smaller steps cooler days. These daily affects are shown in Figure 5. 145
Fig. 4 Web page. Fig. 5 Summed graph illustration. 146
Onset of stress is shown in Figure 6 as smaller steps indicating reduced water use below the onset of stress line. Below this line daily crop water use is less than 50% of the non stressed rate. Fig. 6 Onset of stress illustration. Discussion The Bundaberg Climate and Crop Water Use Information Centre is providing both extension and benchmarking capabilities. Web based extension activities have a distinct advantage over traditional extension methods through their ability to simultaneously communicate with a large target audience and the ability to track uptake of the information provided. Analytic reports indicate that the number of visits to the Bundaberg CANEGROWERS web site (www.bdbcanegrowers.com.au) continues to increase. During March 2014 visits were 2930 per month and by December 2014 monthly visitations increased to 3705. Approximately 60% of all visits to the web site were related to the irrigation scheduling information contained on the Climate and Crop Water Use Information Centre page. Periods of crop stress during the most critical growth period of each season (e.g. mid November to end April) and yield outcomes have been compared by accessing soil monitoring records from 18 probe sites during 2012 and 2014 and corresponding annual yield for each field supplied from mill records. Information relating the effect of stress on the final crop yield was analysed by comparing the number of days that soil water remained below the RAWC for each particular field with yield from that corresponding field to determine if the correlation of days of stress and tc/ha is sufficiently reliable for the Bundaberg sugarcane industry to apply the outcomes to future extension programs. The correlation of stress days and yield which is illustrated in Figure 7 shows that for each day that soil moisture remains below RAWC a potential exists for an irretrievable yield loss of 0.78 tc/ha. Conclusion The aim of the Bundaberg irrigation scheduling program is to enhance district yield through improved crop utilisation of available water resources. It has been shown that stress days can be linked to a loss in crop potential and if stress days during the critical maximum growth months could be eliminated this program has the potential to significantly increase annual production. The potential for stress factors to contribute to significant production loss at Bundaberg was highlighted by Inman- Bamber (2007) when the influence of crop stress on sugar yield at Bundaberg was analysed. Bundaberg benchmarking records and simulated crop production with APSIM (Agricultural Production Systems Simulator; McCown et al., 1996) established a mean 147
simulated stress factor (0.723) and mean sugar yield 11.4 t/ha that compared favourably to 11.1 t/ha for the mean of historical records. Tonne Cane/ha 180 170 160 150 140 130 120 110 100 90 80 70 60 50 40 30 20 10 0 y = -0.7843x + 140.43 R² = 0.7468 0 20 40 60 80 100 120 Stress Days tc/ha Fig. 7 Illustrating impact of days of stress on sugarcane yield. Application of the water stress factor (0.723) to historical yield of 11.1 t/ha indicates that, if no water stress occurred and other limiting factors were eliminated, a mean sugar yield of 15.4 t/ha (=11.1/0.723) would be possible. Application of a base CCS (13.5 units) to the sugar yield of 15.4 t/ha would relate to cane yield of 114.0 tc/ha which, when compared to the mean Bundaberg yield of 82 tc/ha, would represent a productivity gain of 39%. The Climate and Crop Water Use extension program is a major step forward in addressing the challenge of translating this potential into outcomes for the Bundaberg sugarcane industry. Acknowledgements I acknowledge and am grateful to the Bundaberg farmers who have shown faith in the development of the web plan by purchasing additional equipment to expand the monitoring footprint and the patience of the staff at Bundaberg CANEGROWERS who have persevered with the development issues that commonly occur when technology is expanded into new concepts. REFERENCES Allen RG, Pereira LS, Raes D, Smith M (1998) Crop evapotranspiration: guidelines for computing crop water requirements. FAO Irrigation and Drainage Paper 56. Baillie CP, Gordon G, Smith RJ (2001) Performance of travelling gun irrigators. Proceedings of the Australian Society Sugar Cane Technologists 23, 469. Baillie C (2002) Yield reduction due to non-uniformity of travelling gun irrigators. Proceedings of the Australian Society Sugar Cane Technologists 24, 241 245. 148
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