Irrigated cotton growers will this season be able to test drive a new free tool that aims to help them cut down on one of their biggest production expenses - synthetic nitrogen fertiliser application.
Condamine grower Nigel Corish is excited by the possibilities of the online tool which uses a combination of satellite imagery, predicted lint yield, and nitrogen fertiliser use efficiency (NFUE) models tailored to cotton, to generate recommendations for in-crop rates at a paddock and sub-paddock scale.
Mr Corish, whose 2014 Nuffield scholarship was on the topic of improving nitrogen use in irrigated cotton, said there were still huge efficiency gains to be made.
Newer varieties were more efficient and higher yielding, but he said many farmers were still prepared to apply more nitrogen than they needed to, with significant impacts for both their bottom line and the environment.
"It's still an area of cotton growing we need to focus on with resources and research in particular," he said.
"When I did my studies, I saw 40-50 per cent over-fertilisation for A) an insurance policy and B) to make sure that we weren't under-fertilising the crop. And unfortunately, we're seeing up to 40-50pc nitrogen losses in-crop as well."
Deakin University researchers have estimated about a third of applied nitrogen is lost in conventional cotton growing systems from volatilisation, denitrification and leaching, contributing to greenhouse gas emissions and costing the industry about $32 million a year.
Mr Corish said it cost him about $3500-$4000 a hectare to grow cotton at Lakeland Downs, with nitrogen accounting for about $600-$700 a hectare.
"Nitrogen fertiliser is a big component of our growing costs," he said.
One of the things that excites him most about the new tool, developed by a team of researchers from Queensland University of Technology and the CSIRO, is its ability to tell farmers "in real time" what plant nitrogen levels are across an entire field.
Mr Corish said this would eliminate the time lag between taking samples for petiole and leaf tissue tests, which have traditionally been used to identify nutrient imbalances, deficiencies and toxicities, and getting the results back from the laboratory.
"Quite often by the time you get the information back the decision making is a little bit too late," he said.
"So yeah, I'm quite excited. I think it's going to be of real benefit to cotton growers across Australia."
CSIRO team leader and senior research scientist Dr Tim Weaver said the free app, which can be accessed at https://qutsleo.shinyapps.io/Cotton_app/, was built as part of a Cotton Research and Development Corporation-funded project to give growers and consultants the confidence to reduce nitrogen fertiliser rates without compromising yield or depleting soil nitrogen reserves.
Dr Weaver said they calibrated the model using data from cuts of cotton taken at strategic growth stages and matched with NDVI and NDRE satellite imagery from the same dates at 35 sites across Queensland and New South Wales between 2017 and 2022.
The app, which has an accuracy of +/- 26 kilograms of nitrogen per hectare, can be used as early as squaring and at flowering, when it is more accurate at the site specific level.
Users follow an 11-step process to upload information about planting date, paddock boundaries, irrigation type, target NFUE, estimated turnout, and nitrogen fertiliser applied to date, and search for satellite images.
As well as predicting the optimal nitrogen rate, the app can generate a prescription map that can be exported and imported into MyJohnDeere for use with variable rate equipment. The recommendations are not time critical and can be applied in-field at any time throughout the season.
Dr Weaver said nitrogen fertiliser represented about 20pc of the cost of producing irrigated cotton, with growers applying rates between 18kg and 519kg per hectare.
"The endgame is it'll save dollars and emissions, because if you have a full nitrogen balance, you can look across your field with this package," he said.
"Following your crop through the satellite imagery and the models that are predicting your nitrogen in your field gives you the ability to be more efficient in the way that you apply nitrogen so you're not over supplying."
Dr Weaver said he looked forward to receiving feedback on the app from growers and consultants who tested it this season to help guide the researchers on what steps to take next.
He's also keen to adapt the concept for dryland cotton and develop a similar tool for the grains industry.
"The most exciting thing about it is I think it's a proof of concept that would be applicable across all our cropping," he said.
"With targets of zero emissions in the agricultural sector, you could be using this across all crops really - winter and summer cropping - and building interfaces for consultants and growers to really be detailed in how they target their crops and their nutrients."
