Giacomo (Jack) Betti and Steve Davies (DAFWA)
|Contributor||West Midlands Group|
Site 2, Moora, WA
To compare different clay spreading and tillage methods for the amelioration of water repellent gravel soils.
A summary of the main results from the first season at the Moora trial are presented in Figures 1 and 2. Due to technical issues, the trial was not seeded at the same time as the rest of the paddock, which was supposed to be used as an untreated control. For this reason, a comparison of the treatments to a control treatment without tillage and clay spreading is not available. A statistically significant effect of tillage on early plant establishment was found when analysing the plant counts measured about four weeks after sowing (Figure 1, left). All the treatments with the off-set disc (in combination or not with clay spreading) had more plants per linear meter in comparison to the one-way plough treatments. This is likely due to uneven seeding depth following tillage with the one-way plough (deep tillage) compared to the shallower tillage with the off-set disc. Surprisingly, incorporation of subsoil clay at any given rate did not show any significant effect on early plant establishment although this result could be explained by the wetter than usual weather in April-May reducing the severity of soil water repellence.
Again, when looking at the tiller counts recorded 8 weeks after sowing (Figure 1, right) the addition of clay at different rates did not affect the number of tillers. However, the wheat growing in the one-way plough treatments overcame the initial delay in germination giving higher tiller number than those recorded in the treatments with the off-set disc (except for the treatment with 250 t/ha of clay). This trend continued at harvest, with the one-way plough treatments producing higher yields (4.5-4.6 t/ha on average) than the off-set disc treatments (4.1-4.3 t/ha on average) at any given rate of subsoil clay.
Due to the low rates of clay spreading and the low cost of the incorporation methods, all treatments provided a positive return of investments in the first year (ROI= ($/ha gain – $/ha total direct costs) / $/ha total direct costs), based on mean values in Table 1. Not surprisingly, the best ROI in the first year was obtained by the one-way plough treatment without clay spreading (1.42 $/ha), followed by the off-set disc without clay spreading (1.22 $/ha) and the treatments clay spread at 50 t/ha incorporated with one-way plough (1.17 $/ha). These estimates are indicative only, as indirect costs and interests on the initial capital investment are not included in the calculations. For more accurate estimates of ROI, yield results from multiple seasons and crops will be collected in the next 3 years.
|Lead research organisation||
Department of Agriculture and Food WA
|Host research organisation||
West Midlands Group
|Trial funding source||GRDC DAW00244|
This research is funded by DAFWA and GRDC through DAW00244 soil water repellency, part of GRDC’s Soil Constraints West portfolio of projects. Thanks to Graham White and Erin Cahill for clay spreading, undertaking tillage treatments and provision of trial sites. Thanks also to Joanne Walker, Chad Reynolds and Larry Prosser (DAFWA) for technical support.
|Other trial partners||Not specified|
Nufab multi-spreader, one-way disc plough, off-set disc, digger (clay pit excavation and clay spreader loading).
|Sow date||1 June 2016|
|Harvest date||Not specified|
|Plot size||17m x 18.3m|
SILO weather estimates sourced from https://www.longpaddock.qld.gov.au/silo/
Jeffrey, S.J., Carter, J.O., Moodie, K.B. and Beswick, A.R. (2001). Using spatial interpolation to construct a comprehensive archive of Australian climate data , Environmental Modelling and Software, Vol 16/4, pp 309-330. DOI: 10.1016/S1364-8152(01)00008-1.