One of the most invasive Australian weeds is being touted as a potential economic crop, with benefits for the construction, mining, and forestry industries, and potentially for many First Nations societies.
The prickly paddy melon weed, which costs the agricultural industry about $100 million a year in lost grain yields, cattle deaths, and control measures, could most probably become an unlikely money spinner as a source of urease enzymes to stop soil erosion and produce bio cement.
In a world-first study, scientists at the University of South Australia (UniSA) screened 50 natural plants and weeds to find a cheaper and more environmentally friendly source for wholesale production of urease enzymes to support soil. They presented their discoveries at The International Conference on Sustainable Civil Engineering and Architecture.
Among the weeds tested, paddy melon ticked all the boxes and was almost as effective as soybean enzymes, which are more expensive and used mostly for food.
UniSA geotechnical engineer Professor Mizanur Rahman and his students, from roadsides in Port Pirie in South Australia, collected the paddy melon weed. After crushing the seeds and taking out enzymes in a liquid form, then they freeze-dried them to make a powdered, high-concentration cementation agent.
By using this method, we cut down the cementation time from one week to six hours, says Prof Rahman.
Certain plants can produce 50 or more paddy melons, each holding up to 200 viable seeds. Taking into consideration the time that is taken to harvest, extract the seeds, and turn them into a powder, the UniSA scientists estimated a 75% saving compared to lab-grade enzyme production costs.
Plant-based urease enzymes are becoming a popular substitute for cement, lime, or artificial soil binders because they are natural and do not damage the environment. One kilogram of cement produces one kilogram of carbon dioxide making the construction industry one of the highest CO2 emitters.
Compared to the production of commercial enzymes, paddy melon enzymes are more sustainable, more efficient, and cheaper than other enzymes that are used to cement and even out soils.
Not only have we found a natural alternative to other commercial enzymes, but we could also solve a very expensive problem for the agricultural industry by harvesting these weeds, reducing the availability of seeds for preserving biodiversity, spreading, and growing paddy melon as a profitable crop.
Prof Rahman says the construction, forestry, and mining industries all have a chance to benefit from this study, but another unexpected winner could be some First Nations societies.
Paddy melon is an invasive weed on several Natural Title lands and soil erosion is another major problem. Our finding has the potential to address both of these concerns and support biodiversity conservation or rehabilitation.
The paddy melon enzymes could also be used to even out tailing dams and cover them with a thin natural crust, preventing toxic waste material from escaping.
In forest plantations, herbicide is usually applied at the base of commercially grown trees to keep weeds under control.
Herbicide is not only harmful to the environment but weeds often develop a resistance to these chemicals, says Prof Rahman. By spraying paddy melon enzyme solution around the trees would create a thin crust, preventing weeds entirely. In essence, to control a weed, we need to use a weed.
Prof Rahman says the feedback from industry sectors has been very encouraging.
In Australian summer fallow areas, paddy melon is the most important weed, affecting grain crops.Dealing with this invasive plant is crucial because of its harmful impact on biodiversity, farming systems, and grazing livestock.
I believe we have found a win-win solution that helps not only farmers but also offers a natural cementation option for many industries and may help Traditional Owners protect or rebuild the land that they manage.
