Solving the sulphur story
Data from the Monaro Farming Systems ‘Soils Club’ indicates that ~80% of the surface soils across all soil types in the Monaro region are deficient in sulphur (S) despite in some cases long histories of S fertiliser applications. It is suspected that S may be accumulating at depth in soil profiles and that this may result in poor response to S application.
This project aims to understand where S is sitting in soil profiles, whether topsoil soil S tests in the Monaro region are indicative of a pasture response to S application, and to quantify the soil test response to S application to aid fertiliser decisions.
S-response sites prepared and fertilised
In May and June 2018, 15 field sites were set up across the Monaro region.
At each of the sites an experiment was set up to investigate the response to S application of a sown subterranean clover pasture. Briefly, a 6 x 10 m area was marked out (6 plots of 2 x 5m) and lightly cultivated with a rotary hoe. Subterranean clover cv. Goulburn was sown at a high density (200 kg/ha) and basal applications of phosphorus (75 kg P/ha), potassium (50 kg P/ha) and micronutrients (boron, zinc, copper and molybdenum) were made to ensure S was the only limiting nutrient. Treatments either received ‘nil’ (i.e. 0 kg S/ha) or high S (45 kg S/ha as gypsum) with three replicates per treatment.
NB: A subterranean clover-rich pasture sward is being used a “bio-indicator” of S-responsiveness of each site. Subject to seasonal conditions, the sites will be visited in spring to assess biomass responses.
At a subset of six of the sites (two sites on each soil type) an additional experiment was set up to investigate the soil test response to S application. Briefly, an 8 x 15 m area was marked out (12 plots of 2 x 5 m) and basal nutrients applied as above to the existing pasture. Treatments received ‘nil’, 15, 30 or 45 kg S/ha as gypsum with three replicates. The sites will be visited in spring to take soil cores and determine soil test response to the different rates of S application.
Concurrent to the setup of the sites, deep soil cores were taken at each of the 15 field sites. Five replicate cores to a depth of ~80-100 cm was taken around the perimeter of the plots sown to subterranean clover. These cores will be used to assess the distribution of S in the soil profiles and contribute to understanding the potential importance of this S for pasture productivity.
See the side bar for the latest Milestone report.