What can drip irrigation contribute to the cotton industry?
History of Australian Cotton
Commercial cotton varieties arrived in Australia on the first fleet, and there were several ‘boom and bust’ periods in commercial cotton production between that time and the early 1900s. The original cotton crops were primarily in Queensland and were treated as low management rain-grown crops. It wasn’t until the 1960s, following the completion of Keepit Dam in New South Wales, that the first irrigated commercial cotton crops began in the Namoi Valley (supplied by Keepit Dam) and in southern Queensland.
Image: Key cotton-growing valleys in NSW and QLD. Not pictured are CQ (Central Queensland), and the Northern Australian cotton growing region (Far North QLD, NT, and northern WA).
With excitement building around the opportunities that irrigated cotton provided, several American families emigrated from the U.S. to the Wee Waa area of the lower Namoi valley, and we saw the combination of American expertise and Australian innovation to kick off the thriving cotton industry that Australia prides itself on today. During these first years, cotton was established as a key crop in all northern irrigation areas, from the Macquarie Valley in central New South Wales, to the Ord Valley in far north Australia. However, heavy insect pressure from Helicoverpa spp. soon saw the cotton industry in the Ord fall away. For several decades, the key cotton growing areas remained confined to Emerald in Central Queensland to the north, to the Macquarie Valley in the south.
Where are we now?
Today, with the introduction of a broader range of cotton varieties, Roundup Ready herbicide resistance traits, and the use of Transgenic Bollgard II and III traits from Monsanto (now Bayer), the cotton production areas have expanded, making Australia the 5th largest producer of cotton globally with 1,263,000 tons in 2022/2023, typically representing 10 to 13 percent of world exports and bringing the total irrigated cotton area to new heights. There are up to 1,500 cotton farmers in Australia of which 90 percent are family farms. Cotton in Australia is primarily grown in the states of New South Wales and Queensland.
With such a broad zone of production, management of cotton and the constraints growers face can vary drastically, but for the bulk of Australian cotton growers, water availability remains the key limiting factor to feasibility.
Flood furrow irrigation is currently the largest irrigation method used by Australian cotton growers, followed by bankless channel, pivot/overhead sprinkler irrigation, and a small area of drip irrigation. It’s known globally that flood irrigation methods are not the most efficient use of irrigation water, but necessity is the mother of invention, and Australian cotton growers have made great leaps in the past 30 years in water use efficiency. With innovations in technology, a strong research and development program led by the CRDC, and an industry focused on information-sharing, cotton growers have improved their Whole Farm Irrigation Efficiency from 57% in the 1990s to 81% today.
However, input prices are increasing, the government is approving further water buybacks, and labour for siphon changing and re-forming rotobucks is getting increasingly expensive and harder to attain. In 2023, diesel prices reached record-highs exceeding $2/litre, and following Russia’s invasion of Ukraine, urea prices were in excess of $1600/t. This, combined with an increasingly uncertain water market, is driving cotton growers to look at further system improvements to grow more with less.
What can Drip Irrigation Contribute?
It’s important to address the ‘Triple Bottom Line’ when looking at how investing in new technology can improve farming systems, and drip irrigation can do this.
The environmental bottom line is seemingly the most obvious improvement drip irrigation offers – saving 20-30% in water per hectare, a 25% reduction in nitrogenous fertilizer use when using fertigation, and the ability to recycle dripline back into high-quality HDPE products, including back into dripline.
Image: Drip irrigation not only saves on water use compared to flood irrigation, but also reduces labour hours, tractor hours and diesel use by eliminating the need for rotobucks, which need to be pushed down and re-formed every time machinery goes through the field.
Today, Australia and the world has an increasingly savvy consumer that cares about the environment and climate, and as we’ve seen in 2019 during the drought, irrigators often have a negative spotlight on them from the public around water use efficiency concerns. Although Australian cotton growers are some of the most efficient irrigators in the world, it’s important to continue to look for further improvements and strengthen consumer trust. As such, the utilization of drip irrigation and its resulting benefits can help to promote cotton growers to the public as the responsible, innovative water holders that they are.
Image: The Australian consumer wants to see further improvements in water use efficiency, especially following the effects the 2018-19 drought had on river systems.
Most importantly, economic viability of any new development on-farm is crucial to its long-term success. While drip irrigation can save money on water, diesel, fertilizer, and labour – can it add to growers’ bottom line through increased production? Recent trials have shown that it can. In 2022-23, compared to bankless channel irrigation, drip showed a 2.47bale/ha (19%) yield improvement, and further trials from the 2023-24 season are currently undergoing picking to support this result. With the average price per bale of $637 that cotton growers were fetching in 2023, this equates to an additional $1574/hectare on yield alone.
Aside from the benefits of reduced inputs and higher yield, cotton growers using drip have also reported on other improvements to their productivity when using drip irrigation. Many of our cotton farms are on heavier clays and vertosols, which can remain too wet to traffic for long periods after a flood irrigation event – however, drip irrigation is never over-saturating soil, allowing the use of tractors and self-propelled sprayers in-crop, saving on the expense of contracted planes for spraying or spreading.
Image: Flood furrow irrigation can impact trafficability of fields, causing a reliance on spray planes.
When cotton is flood irrigated, the root zone becomes saturated, stressing the plant and inhibiting growth and nutrient uptake, which may then lead to symptoms of disease being exacerbated, such as verticillium wilt. Additionally, when compared to overhead sprinkler irrigation, drip can also minimize the risk of quality downgrades, especially on lower canopy bolls as they’re opening, as canopy humidity is reduced in drip irrigation. By reducing plant stress from waterlogging during flowering and boll development periods has proved to be an advantage for drip irrigated cotton growers, who can boast excellent boll retention, and as a result, yield.
Image: Drip irrigated cotton in the Murrumbidgee showcases the excellent retention that can be achieved.
What drip irrigation options are available?
As Australia has such a large area planted to cotton, drip irrigation won’t be feasible for the entire industry, but it could mean less pressure on smaller, family-owned farms, when water availability is reduced and they’re trying to make hard decisions around planting areas. Drip irrigation has been used for decades, with varying levels of success – and so far, has only established a negligible market share.
Currently, the majority of cotton growers using drip irrigation, are using long-term dripline such as Aries, buried at approximately 200-250mm depth. While this achieves great results in the right circ*mstances, it relies on two things to make it economically viable: working capital to purchase and install the system, and high water reliability to ensure the system can be used year-on-year to make the most out of the investment.
In light of this, and the knowledge that most cotton valleys have low water reliability (they may not have irrigation water available to them every year), Netafim has begun to focus on low-cost, temporary irrigation systems. This involves shallow-buried, thin-wall dripline, that can be removed and recycled after 1-3years. This reduces the upfront cost of drip irrigation – with less cost in dripline, and the ability to use screen filters rather than more expensive media filters. It also allows growers to only use the system when they have water available to them – so their investment isn’t going to waste sitting in dry ground during drought periods. These systems can be sold as a complete modular unit, with a pump station containing filters, pumps, controllers, and fertigation units all included – creating a simple, ‘plug-and-play’ option for growers looking to invest in drip irrigation.
Temporary drip irrigation systems can use permanent mains with temporary Flexnet sub-mains (top), or use a completely temporary system, with temporary mains and sub-mains (bottom). Additionally, growers can adapt their existing pump infrastructure, or utilize the complete plug-and-play Modnet system, using a portable, containerized pump station complete with controls, filtration, fertigation, and diesel or electric pump.
Summary
The Australian cotton industry focuses on high yield, high quality upland cotton. Thanks to improvements in biotechnology, the Australia cotton production area has grown dramatically since the beginning of the irrigated cotton industry in the 1960s and continues to grow. The Australian water market is highly complex and variable, with government buybacks making the future of irrigation water security uncertain. To add to this uncertainty, high input and labour costs are narrowing profit margins for cotton growers. However, with drip irrigation, the Australian cotton industry may be able to maintain its current rate of growth in an environmentally sustainable way. A fully modular, simple, cost-effective system such as ModNet™, offers all the benefits of precision irrigation and fertigation, at 25% of the upfront price, without the risk involved in permanent irrigation systems in non-permanent water markets.
Image: Drip irrigated cotton near Miles, QLD.
