Trials look at paddock pH variances
TRIAL sites throughout the North East – including at Devenish, Lilliput and Miepoll – are helping arm growers with information on how much soil pH can vary within a paddock; and the acidic patches by applying lime at variable rates.
The ‘Spatial variability of soil acidity and response to liming in cropped lands of the Victorian HRZ’ project, a GRDC investment made in conjunction with Agriculture Victoria, is investi ing variable lime rates when the costs and returns vary.
Soil acidity is a major soil limitation in many cropping soils of the HRZ, with many growers liming the whole paddock with one blan- ket rate to treat surface acidity.
However, growers are looking for a more economical way to do this.
Agriculture Victoria soil scientist Doug Crawford says the raw data available to growers on how variable soil pH can be is limited.
“There is information available from previous research about lime application responses, how to test pH and the movement of lime through soils, but not a lot on within-paddock variability of pH,” he says.
The project is testing 10 paddocks from different high-rainfall areas of Victoria, including the North East, Gippsland and Western Districts.
In each paddock, 100 soil cores have been taken in a grid pattern down to 30 centimetres, which have then been cut into 10cm and the pH analysed in each 10cm increment.
Mr Crawford says they have seen a considerable range in soil pH values across the paddocks sampled so far.
“The most acidic paddock we have sampled was also the least variable, but in the less-acidic paddocks, which had more variation, there were patches which were strongly acidic,” he says.
“In addition to the soil sampling we are also using EM38, EM31 and GIS mapping to help us better determine the pH values between sample points.
“We are also using satellite imagery to examine the variation in biomass across the crops and analysing grain yield data so we can map out soil pH and how it relates to crop growth.
“This will help us get a better handle on the economic effects of variable-rate liming.
“In that economic analysis we also consider the extra cost of getting pH mapped and consider the extra savings from not liming the parts of the paddock that don’t need it.”
The project will conclude next year.
It aims to reduce the uncertainty in lime decision-making in the HRZ and enable growers to better manage risks, both to farm
This story is reprinted from GRDC GroundCover, issue 137.
TRIALS UNDER WAY: Acidity is a major limitation in many cropping soils in the North East, with many growers liming the whole paddock with one blanket rate to treat surface acidity to try to overcome the constraint. Research considering the variances are now under way at Devenish, Lilliput and Miepoll.
THIS month, we take a look at some of those who work tirelessly behind the scenes at the Ellinbank Research Centre.Researcher Profile: Meaghan Douglas.Job title: Research Scientist with Agriculture Victoria.How long have you worked at Ellinbank: Four years.Qualifications: Bachelor of Science (Honours).Where studied: The University of Melbourne.Current field of research: Dairy cow nutrition. I am two years into a PhD investigating the nutritive and rumenal degradation characteristics of perennial ryegrass pasture throughout the year, in order to formulate optimal supplementary grain rations for grazing dairy cows.