Golden flower cutting the cost of urea fertiliser for farmers

Sunn hemp reduces farmers' need for urea fertiliser Mon 6 Jul 2026 at 8:46am In short: A colourful crop is emerging as a solution to the rising cost of fertiliser due to conflict in the Middle East. Sunn hemp is a legume that adds nitrogen to the soil, significantly reducing the need for urea fertiliser. Growers report huge savings on urea fertiliser by including sunn hemp in their crop rotations. Fertiliser costs have surged in the wake of the conflict in the Middle East, leaving farmers searching for ways to cut input costs. Urea, a nitrogen fertiliser widely used across various agricultural sectors, has become increasingly expensive and difficult to source, prompting some growers to turn to natural nitrogen alternatives. Sugarcane farmer Neil Maitland has been planting sunn hemp as a cover crop on his farm near Cairns for several years. Cover crops are grown during breaks between main crops to improve soil health, rather than being harvested for commercial production. Sunn hemp helped improve Mr Maitland's soil health by enabling soil bacteria to convert atmospheric nitrogen into a form the plant can use. He said by incorporating the legume into his rotation, he cut his nitrogen fertiliser bill by more than $400 per hectare. "I've reduced my whole fertiliser by about 25 per cent and that's just urea,"he said. "The urea is the most expensive part of it, and that's even before the prices have gone up double. "It's not that we're not using [nitrogen], it's just that it's coming from an organic [source] instead of an inorganic fertiliser." Mr Maitland still applies other fertiliser elements, including phosphorus and potash. But, since first discovering the nitrogen-generating powers of sunn hemp, he has been involved in various trials to learn more about the best way to incorporate the crop in rotations to promote the best outcome for his sugar cane. DPI-led trials The Department of Primary Industries (DPI) has flagged sunn hemp as a useful cover crop for multiple industries. Paul Grundy from the department has tested the effectiveness of adding it to cotton rotations and has found some promising results. "Some key advantages of sunn hemp that we've been finding are associated around its nitrogen or ability to fix nitrogen," he said. "It's a legume, and that creates some potential for saving on fertiliser costs. "Essentially, what we're seeing in the tops of this legume is the equivalent of around 220 to 320 kilograms of urea, if you want to put it into fertiliser equivalents." Sunn hemp, originating from India, has been used around the world as a cover crop for years, but is a relatively new option for Australian growers. Dr Grundy said it was only made available locally about four years ago. His research has been focused on using sunn hemp to help manage reniform nematodes in Central Queensland cotton systems. The pest attacks cotton roots and reduces plant vigour and, in heavily affected crops, it can cut yields by 10 to 20 per cent, costing growers up to two bales of cotton per hectare. His trial site, set up about three years ago, started with about 3,000 nematodes per 100 grams of soil. After two and a half months of growing sunn hemp in that field, the number of nematodes dropped to 100 per 100 grams of soil. "We've got three seasons of data now, and we're reasonably confident that this particular legume has got a really good fit for that particular pest problem," Dr Grundy said. "In fact, a number of growers are using sunn hemp as part of their rotation and their farming system for managing that particular pest." Research into sunn hemp is ongoing, and Dr Grundy is keeping an eye on whether the crop might bring about a new set of challenges. "One of the things we're not clear on at this stage is whether some hemp is a host for some of the diseases that we might have, particularly in our cooler regions," he said. "The work that we've been doing so far has been largely confined to our hot areas of Central Queensland, where those diseases just haven't been a big production problem." Multi-species cover crops Near Ingham in North Queensland, some new trials are underway assessing the productivity of various cover crops in sugar cane. Lawrence Di Bella from Queensland Cane Agricultural Renewables is leading these trials, which feature about 30 species. The group with the most promising results includes sunn hemp. "We've identified in the wet tropics over summer that a cowpea, lablab, sunn hemp and soybean mix is ideal because it gives us the best odds of everything," Mr Di Bella said. "What we're trying to do is trying to quantify what the carbon build-up from cover crops is, look at the nitrogen cycling, and the biodiversity." He said with the cost of fertiliser now, he wished the trial started a year or two ago, but said he would be using the data to see where savings could be made. "The price of urea is so expensive that we can't actually afford to buy a lot of it," Mr Di Bella said. "We'll be looking at whether we can use these crops to actually help … get us through and actually use the nitrogen that's come from the cover crops in our cane program."