A group of farmers in South East Queensland has been looking at a method of controlling soil erosion and the associated run-off of nutrients and pesticides with a product that has proved successful in the construction industry.
Soil erosion is an issue which has long been a concern for pineapple growers. The Australian pineapple sector has expanded considerably over the last 15 years. 48,000 tonnes of fresh pineapple were produced and sold on the domestic market with a farm gate value of $57.5 million during the 2012-13 season alone.
When the pineapple beds are first profiled ready for planting usually during the summer months, the soils are vulnerable to erosion from heavy rain events which have been noticeably increasing in intensity throughout the last decade.
Access to good healthy soil is needed to be able to continue on this trajectory, which led some local Pumicestone Passage farmers to start trialling a novel environmental technology, a biodegradable polymer.
Produced by Vital Industries, Stonewall is a non-hazardous water-based co-polymer used in the coating and binding of dust particles where properties of high water and wind resistance, elasticity and tensile strength are required. It biodegrades with UV light, soil microbes and moisture.
Over the last six years, pineapple farmers at Glass House Mountains have been trialling various methods of application of the biodegradable polymer product Stonewall. The polymer reduces the loss of soil and pollutants to the Pumicestone Passage, part of the Moreton Bay Ramsar Wetland.
Growers have also been trailing various products, application rates, slopes and soils to optimise the investment. Through years of trialling, the application of polymer is becoming more strategic, so more ground can be effectively covered per unit cost.
To help make this initiative affordable, considering the considerable cost to farmers, Healthy Land and Water is offering farmers in the Pumicestone catchment a subsidy to trial the polymer on their crops. This subsidy is being offered through National Landcare Program funding available until 2023. For more information please contact Healthy Land & Water on firstname.lastname@example.org.
The soil on Keith’s property is very sandy and moves very easily with the flow of water, but according to Keith, the polymer has made it easier to control this movement of soil. Keith says the polymer also effectively holds the pesticide in the ground, reducing run off and reducing the number of applications, cutting costs in the process.
“It’s been very impressive. When you compare where it has been applied and where it hasn’t, you can see the results.” Says Keith.
“I think other pineapple growers should definitely use the polymer while the subsidy is still available.”
“The subsidy is a great idea, it’s helped us reduce the movement of sediment.”
Sam has also experienced multiple benefits of using the polymer on his crops including less time spent cleaning silt traps and relocating soil to the beds. Using the polymer has become general practice on his property.
“The polymer seals in the herbicide, so it doesn’t get affected by rain. It doesn’t wash away, it stays on the hill,” says Sam.
“Most of the time we are doing two or three less passes with herbicide.”
“On some crops, we applied the polymer ten months ago and incredibly, we haven’t lost any soil.”
Sam has found that the pre-emergent herbicide spray is held in place, eliminating the need for follow-up spraying, saving both on chemical costs and labour.
“When you add it all up, the figures stack up,” Sam said.
How the biodegradable polymer works
The polymer product is mixed with water and is then sprayed over the beds after they have been formed, planted and following pre-emergent herbicide application. Once the polymer has dried, it forms a hard crust which helps to hold the crop together, preventing it from crumbing and washing away when it rains.
According to the manufacturer, moisture in the ground to the equivalent of 5 millimetres of rain is needed before the polymer is applied. Instead of relying on the weather, Sam’s process involves spraying water over the crop (5 – 6,000 litres per hectare) using a generic spray boom just prior to the polymer application. Sam then blanket sprays using cone jets at 7.5%, with two passes.
For the polymer to form a thicker, more effective crust it is best if it is able to set in dry, sunny weather for a minimum of two days.
Keith’s process differs to Sam’s. He applies the polymer to only the walkways using jets because this is where most of the water runs on his farm, effectively being able to cover twice the area for the same amount. He reports that because there is no polymer on top of the beds, moisture can get in.
Keith has found the best time to apply the polymer is after rain, once the soil has had time to settle.
Dr Javier Leon from the University of the Sunshine Coast has been undertaking drone monitoring for the project to help quantify rates of soil erosion across different polymer application treatments to inform the future use of polymer.
A survey-grade drone is used to collect imagery from above, measuring the precise rates of erosion with an average of 1,000 images per site, undertaken around midday to ensure best light. Flights are pre-programmed to achieve maximum precision yet remain cost-effective.
Due to the recent heavy rain and flooding, unfortunately some trials were unable to be completed. Stay tuned for more updates about this project.
This project is supported by Healthy Land & Water through funding from the Australian Government’s National Landcare Program.
This project is supported by the Morgan family, Sandy Creek Pineapple Company, G.O. Pike and Son and Vital Industries.
The project forms part of a collaborative approach to achieving environmental sustainability in the pineapple industry with a team involving Growcom, the Queensland Department of Agriculture and Fisheries and Agri-Supply Global, with support from the Queensland Department of Environment and Science and the Horticulture Industry Association.