Cotton Australia, CRDC, ANSTO & UNSW:
R&D the key to a sustainable cotton industry
The Australian cotton industry has been managing on-farm sustainability for decades, underpinned by investments in research and development, the industry’s Best Management Practices program (myBMP), grower adoption of improved practices and innovation, and active participation in global sustainability programs. Today, Australian cotton growers produce more cotton on less land, with more efficient water use and with less impact on the environment than ever before.
Through Cotton Australia and the Cotton Research and Development Corporation (CRDC), the industry has committed to undertaking:
- Sustainability reporting every five years against agreed targets (set over five-yearly intervals from 2019 to 2029 to align with the Australian Cotton Industry 2029 Vision).
- Stakeholder engagement on industry sustainability and opportunities for improvement, including via a formal stakeholder forum.
- Independent assessments of sustainability and environmental performance every 10 years.
Sustainability in the industry is underpinned by strong R&D. For example a recent CRDC project with Australian Nuclear Science and Technology Organisation and University of NSW investigated the nitrogen cycle in rivers draining through cotton growing regions. The catchments included the Nogoa River a tributary of the Fitzroy River flowing towards the Great Barrier Reef near Rockhampton and the Namoi and Murrumbidgee rivers, part of the Murray-Darling Basin. The work included multiple river water sampling at selected sites over approximately 18 months in each catchment. Dry conditions were prevalent (2017-2020) with minor flooding only captured on one occasion in each catchment (2020-2021). The study found water quality was generally good, with some issues rising during periods of intense low flow as well as highlighting potential for fertiliser to be contaminating water during high flow events.
Water at the Lake Maraboon is good quality irrigation water with low conductivity and low sodium adsorption ratios (SAR), with dryer conditions reflected in some quality changes. Water quality downstream of Fairbairn Dam decreased sharply, particularly between the dam and the town of Emerald. The average EC
increase for surface water between Lake Maraboon and Emerald town was of 26% in a 19.6 km stretch of river, while the EC increase between Emerald and Bridge Flats Road was 18% for a 23.8 km stretch of river. Additional evaporation at Emerald weir together with inputs derived from agriculture/industry bordering the river and the urban setting could account for this increase. EC results in the Comet River were consistently well above WQO except for
the three occasions sampled with flow. Sulfate concentrations at Bridge Flats Road were always well below maximum WQO values. However, sulfate concentrations in the Mackenzie River were up to 5 times above the WQO (<10 mg/L) for the Mackenzie River while sulfate concentrations in the Comet River
were up to 20 times above the WQO (<5 mg/L) during times of no flow.
Nitrate isotopes were used to indicate likely nitrogen source. In a very generic sense, the nitrogen source as viewed by nitrate isotopes behave quite differently in the three studied catchments (sewage, grazing, fertilisers). In the case of the Nogoa, low flows during the project period restricted sampling to one high flow event, sampled in late January 2020. This event was sampled at the beginning of the flood receding phase with samples representing lower flow levels until last sample. The similarity in the concentration evolution of nitrate and phosphate during the high-flow event reinforces the nutrient’s common origin, that is fertilisers. Given the study was limited to one event restricted to Theresa Creek, the relative importance of other processes operating at the full Nogoa
catchment scale is not known. As supported by other regional studies, regardless of the source, the bulk of the nutrients transport takes place predominantly at high flow.
Historical analysis found that at Bridge Flats there has been a marked change in the baseline EC observed from approximately 2010/11. The electrical conductivity measured at Bridge Flats and that observed in the Mackenzie River, just downstream of the Comet River confluence, cannot be reconciled without additional elevated EC inputs between those two sites. Nutrients do not show a large variation in this stretch of river, neither the nitrate isotope values.
Groundwater studies have also occurred with open results available (www.sciencedirect.com/science/article/pii/S0048969721076841).