Soil trends examined
A soil survey of agricultural land in East Gippsland is set to be revisited in spring with the re-sampling of 50 sites previously tested in 2014–15.
The survey is part of the 10 year-long East Gippsland TopSoils Project, a collaboration between Agriculture Victoria, the East Gippsland Catchment Management Authority, local Landcare networks, Southern Farming Systems, and the National Landcare Program.
The project began in 2013 and is due to conclude in 2023.
Agriculture Victoria meat and wool team leader, Keren Walker said the TopSoils Project focused on protecting and improving the health of productive soils.
“As part of the 2014–15 survey, soil from 214 randomly selected farms was tested for soil acidity, salinity and nutrients to provide a snapshot of soil fertility across East Gippsland and a baseline for future monitoring.
“Results from the re-sampling of the 50 sites this coming spring will be compared with 2014–15 sampling results,” she said.
Data gathered from the 2014 soil survey has already been used to advise farmers on how best to manage their soils and maintain ground cover. The information from 2014–15 soil survey data is contained in an Agriculture Victoria Information Note: Acidity of grazing soils in East Gippsland.
“Sixteen of the paddocks sampled in 2014 had also been tested 30 years prior and the results from the 2014–15 survey were compared with the available historical data sets from 1975– 1982, to determine the likely trends of soil fertility in the region,” Ms Walker said.
“The results indicate nearly all the tested paddocks in East Gippsland were acidic, and half were strongly to very strongly acidic.
“Generally, soils with a pH (water) below 6 are considered acidic and the pH (water) range from 5.5 to 7 is considered as favourable for most plants, though at the lower end of the range, if other soil conditions are limiting, plants may become less productive.
“Eighty-seven per cent of the tested surface soils had a pH (water) below 6 and about 45 per cent were found to have a pH (water) below 5.5. It was also found that paddocks which recorded low acidity levels 30 years ago had become more acidic, suggesting the acidification process of soils is continuing in East Gippsland,” she said.
While acidity is not directly responsible for restricting plant growth, it can decrease the availability of plant nutrients such as phosphorus and molybdenum and can increase other elements, particularly aluminium and manganese to levels that become toxic to plants.
Acidity can also lead to the leaching of essential plant nutrients from the soil and make the soil environment less favourable for nitrogen fixation and soil organisms.
Ms Walker said the acidification process is gradual and may not be identified until pastures show clear acidification symptoms, such as poor/stunted growth, difficulty with establishment or persistence of species sensitive to increased aluminium levels such as Phalaris, lucerne and some clovers.
“Producing and removing large quantities of hay or silage from an area can also contribute to the acidification process, so maintaining organic matter will provide a buffer against soil acidity and alkalinity,” she said.