Subsoil acidity is a major constraint to crop productivity in the higher rainfall zone of south-eastern Australia; and a project funded by Grains Research and Development Corporation (GRDC) and facilitated through the NSW DPI in Wagga Wagga aims to decrease the time taken for lime to reach maximum effect.
Team leader Dr Guangdi Li said the collaborative project also involves the CSIRO and Charles Sturt University (CSU) and La Trobe University along with farmer groups, Farmlink, Southern Farming Systems, RiverinePlain and the Holbrook Landcare Group.
“The really important thing is addressing the issue of acidity that is occurring in the depth of the soil and is really impacting on crop production,” Dr Li said.
The really important thing is addressing the issue of acidity that is occurring in the depth in the soil and is really impacting on crop production
Traditionally, lime has been spread on the surface but movement into the subsoil is slow: it was felt a more aggressive method of applying lime was needed to achieve more rapid changes to soil pH at depth.
Dr Li’s team are exploring one way to deliver the lime at prescribed depth through the use of the specifically developed 3-D machine.
”We are trying to deliver the lime to where it is most needed rather than too deep,” Dr Li said.
“In our project, there are two major contrasts – we will compare surface liming and deep liming.”
Dr Li said they are curious to know if deep liming will speed the process of making lime available.
“We are also trying an alternative amendment like the addition of organic materials to compare if they will bring the nutrients into the soil and ameliorate soil acidity,” he said.
Dr Li said the industry is aware it takes a long time for the surface-applied lime to have effect on soil acidity but he expects the introduction of lime to a deeper level is also going to be slow.
“It will take years to test, and that is why we have designed this long-term experiment,” he said.
“We have developed a machine to put the lime at a level were the plants can use it.”
Specific machine to expedite soil research
Designed and built within the engineering department of the NSW DPI at Wagga Wagga, the dual depth delivery (3-D) ripping machine is being used by Dr Guangdi Li and his team in investigating the efficacy of incorporating lime at a deeper level than the normal application to the soil surface.
The unique machine is able to provide accurate placement of soil amendments at two depths from ten to 30cm.
“Designing a machine is always a challenge and we have different machines developed by various organisations,” Dr Li explained.
“We have designed a machine with two outlets to deliver materials 10 to 30cm depths.
“That is why is called a ‘dual depth delivery’ system.”
Based on the chassis of a Grizzle Ripper, the two exit points on each tyne allow lime and/or an organic amendment to be placed evenly at ten to 30cm depth.
“This is the only machine on-site and is really only for experimental purpose,” Dr Li pointed out.
“Our staff who have built it have always described the machine as ‘proof of concept’.”
It has been purely built to allow for scientific research without becoming an additional function necessary for large-scale cropping enterprises; and it can also deliver liquid fertilizers in any combination because of the twin outlets.
“With its accurate dual metering system, we know exactly how much amendment we are applying at the prescribed depth,” Dr Li said.
Although the 3-D deep ripper is not suitable for planting seed into the soil, with a front coulter attached to each tyne to break the topsoil and prevent the surface layer being lifted into clods and a backroller to compress the soil behind the ripper, the soil surface would be left prepared for sowing.