APPLYING compost and compost-derived products to cropping soils vulnerable to erosion, especially non-wetting sands, could lead to large productivity gains through providing groundcover, arresting wind effect and long-term soil protection, according to ongoing work by Field Systems Australia.
Field Systems Australia soil scientist Ed Scott and soil systems advisor Michael Eyres have been evaluating various methods of dune capping - bulk compost application on sandy dunes at different rates and with various compost products.
"Sand dunes, especially when they're non-wetting, are very vulnerable to wind erosion and sand drift especially over summer, pre-seeding and even post-seeding," Mr Scott said.
"Given the chance they can be productive soils, but when they're constantly battered they can be a weak link in a paddock."
Mr Scott said the purpose of their work was to investigate methods of establishing cover on those vulnerable soils to help stabilisation and prevent erosion in the hope of eventually growing a healthier and more productive crop.
He said they had been working with growers on different soil specific strategies, including loose compost application and bulk granulated or pelletised compost application with a standard farm spreader.
"Compost application can certainly slow down some of that wind erosion effect," he said.
"The compost is also putting nutrients and organic matter in the soil, so once you support the plants to germinate, they'll then have more nutrients in often quite low nutrient-availability soils. We had trials where farmers put out between 3 tonnes a hectare and 10t/ha of loose compost and that was able to get plants up and germinated by providing cover.
"Some have also been going out with granulated product on the surface and because it is heavier than the loose compost, it is less prone to blowing off."
Mr Scott said while broadacre farmers were often hesitant to try compost application due to cost, he emphasised that only the problem areas in each paddock should be targeted, not the whole farm.
"It might only be 10ha of a 100ha paddock, but it becomes a big weak link that grows nothing and is cost effective to repair," he said.
While not matching it with standard fertilisers when it came to nutrient replacement, Mr Scott said the compost's primary role in the sandy soil scenario was to provide soil cover and surface protection, with the nutrient content a bonus.
Mr Scott said by providing cover initially, growers would be able to establish a crop and then retain the subsequent stubble to continue stabilising the soil.
SAND CUPPING AIDS WATER INFILTRATION
SAND cupping - the pockmarking of soils with a padfoot roller to stop water runoff - and compost product application trials by Peats Soils' Mick Wadewitz were evaluated at an Australian Organics Recycling Association field day at Langhorne Creek recently.
Mr Wadewitz had five sites - cupping with no composting, composting with no cupping, composting before cupping, composting before and after cupping and composting after cupping.
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Field Systems Australia soil advisor Ed Scott said while the best method came down to factors like paddock topography and soil type, there was evidence to suggest the treatments had a significant impact when compared to non-treated areas.
"It rained two days after the demo day and there was 2 millimetres of moisture infiltration on the no-treatment area and on the areas that had compost applied and sand cupping it went down 10 centimetres," he said.
"Having some organic matter cover helps slow that water down and allows it to infiltrate. The padfoot roller creates little cups that can hold water and slow runoff, forcing it to infiltrate rather than running to the lowest part of the landscape."
Mr Scott said the FSA team would be doing future work with growers to take the dune capping and sand cupping methods beyond a plot scale.
"In these vulnerable areas, whether it's vulnerable from a standard dune perspective or how sandy soils naturally are in the landscape or exposed landscapes like post-fire, I think there'll be some good strategies that can be implemented," he said.
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