Comments
There has been significant influence of lime on topsoil (0-10cm) and the impact of lime on subsurface pH can be seen where incorporation has taken place, particularly with the large offset (Figure 3).
Unfortunately the influence of lime on yield was unable to be analysed in 2016 due to issues at harvest time.
The large offset disc treatment and deep ripping took place in early April 2015 and had a large impact on soil compaction.
The seeding operation in 2016 was carried out perpendicular to these incorporation treatments which caused the seeding bar to vary in depths as it crossed from one incorporation treatment to another. This may have cause the significant difference in the establishment of the crop in these treatments (Figure 1).
The low plant emergence in large offset treatments also caused a significantly lower number of heads (Figure 2). This may have caused a lower yield for the large offset areas but without harvest results, this cannot be confirmed.
The soil was very wet when the ripping treatment was applied in 2015. The ripper worked to a depth of 350mm and tines were spaced on 450mm.
As a result there was limited breakout between the tines. A cavity was created around the foot of the tyne, smearing the furrow wall with little fracturing.
Break out of the soil was estimated to be less than 50% between the base of the tines.
Very little mixing of the lime occurred as surface soil was too damp to fall in behind the tine before the trench closed.
Lime appeared as if adhered to the surface soil.
No significant subsoil pH difference was seen according to the 2016 soil results. However, the increase in subsoil pH where the large offset machine was used to incorporate lime can be seen in Figure 3, even though it may not be significant.
Acknowledgements
Thanks to Peter Stickney for managing the trial; also to DAFWA technical services staff for their assistance and SoilTech for soil sampling.
This project is supported by the Northern Agricultural Catchments Council, through funding from the Australian Government’s National Landcare Programme.