The value of native vegetation for storing carbon is well accepted by farmers as a form of greenhouse gas mitigation on their farms; but its capacity to increase soil carbon is largely unknown.
A project undertaken by Rutherglen Landcare Group has seen North East farmers conduct a series of detailed soil tests to determine the effects of different forms of native vegetation and exotic pastures on soils in the area.
Project manager with Rutherglen Landcare Group, Philippa Noble, said more than 200ha had been revegetated around Rutherglen in the past 22 years.
“Reintroducing perennials, including native trees and shrubs, back into the landscape, is important for improving our wildlife, water quality and climate change mitigation, but the effect of revegetation on our soils is not known,” Ms Noble said.
The Rutherglen project is supported by North East Catchment Management Authority, with funding from the Australian Government’s National Landcare Program.
“We wanted to compare the soils of our native bush areas; that is, the original soils, with soils under revegetation, agroforestry and pasture areas in close proximity to see what changes have occurred from clearing to reintroduction of native vegetation,” Ms Noble said.
The group chose four locations around Rutherglen; two in grey box country, one in native pine, and one in red gum country. All four sites, which had bush, revegetation, agroforestry and pasture within 100 metres of each other were soil sampled to a depth of 10cm and tested for pH, nutrients such as phosphorus and nitrogen, soil carbon and cation exchange capacity.
Ms Noble said preliminary results from testing in September found the soils were mostly acidic (pH 5-6 in water), with no real trend from bush to pastures except where pastures had been limed.
Organic carbon levels in the bush ranged from 1.5 to 2.5 per cent. Plantations had a little less organic carbon and the highest value was a pasture site at 2.7 per cent. The native pine country sites tended to have the lowest organic carbon, and the redgum country the highest.
The testing found zinc was deficient at most sites. Most samples of bush, plantation and shelterbelts had very low levels of phosphorus, but fertiliser had again lifted levels in some pastures.
All four sites had high iron, potassium and copper levels, with other elements at satisfactory levels.
Ms Noble said a planned field day would discuss the findings and how farmers can improve soil health and organic matter levels.
Further details are available on request from Philippa Noble by email to firstname.lastname@example.org
Caption: Philippa Noble presents the soils project interim results to the Rutherglen Landcare AGM.