Invasive weed could be a viable economic crop

The prickly paddy melon weed, which costs the agricultural industry around $100 million a year in lost grain yields, cattle deaths and control measures, could have unexpected benefits for the construction, mining and forestry industries, as well as First Nations communities.

That’s according to a new study from the University of South Australia (UniSA), which saw researchers screen 50 native plants and weeds to find a cheaper and more environmentally friendly source for bulk producing urease enzymes to create bio cement and prevent soil erosion. Their results, published in the journal Géotechnique, found paddy melon was almost as effective as soybean enzymes, which are more expensive and used primarily for food.

“Paddy melon is the most significant weed in Australian summer fallow areas, affecting grain crops,” said UniSA geotechnical engineer Professor Mizanur Rahman. “Managing this invasive plant is crucial due to its detrimental impact on farming systems, biodiversity and grazing livestock.

Plant-based urease enzymes are becoming a popular alternative to cement, lime or artificial soil binders because they are natural and not damaging to the environment. Having collected paddy melon weed from roadsides in Port Pirie, Rahman and his students crushed the seeds, extracted the enzymes in a liquid form and freeze-dried them to create a powdered, high-concentration cementation agent.

“Using this technique, we cut down the cementation time from one week to six hours,” Rahman said.

Individual plants can yield 50 or more paddy melons, each containing up to 200 viable seeds. Taking into consideration the time taken to harvest, extract the seeds and turn them into a powder, the researchers estimated a 75% saving compared to lab-grade enzyme production costs.

“Compared to the production of commercial enzymes, paddy melon enzymes are cheaper, more sustainable and more efficient than other enzymes used to cement and stabilise soils,” Rahman said.

These enzymes could be used to stabilise tailing dams and cap them with a thin natural crust, preventing toxic waste material from escaping. Another potential use is in forest plantations, where herbicide is normally 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,” Rahman said. “Spraying paddy melon enzyme solution around the trees would create a thin crust, preventing weeds completely. In essence, we are using a weed to control a weed.”

Another unexpected winner could be some First Nations communities, according to Rahman. He explained, “Paddy melon is an invasive weed on many Native Title lands and soil erosion is another major issue. Our discovery has the potential to address both of these concerns and support biodiversity conservation or rehabilitation.

“Not only have we found a natural alternative to other commercial enzymes, but we could solve a very expensive problem for the agricultural industry by harvesting these weeds, reducing the availability of seeds for spreading, preserving biodiversity and growing paddy melon as a commercial crop.”

Image caption: UniSA researchers collecting paddy melons for urease enzyme extraction.