Ameliorating subsoil constraints such as compaction and acidity can enhance the yield potential of sandy soils. This study evaluated the on-farm responses of soil amelioration techniques over a ten-year period using farm yield data from two Western Australian paddocks.
We assessed amelioration effectiveness across varying seasons and crop types by setting a theoretical rain-limited yield as the benchmark for achieved yield. By mapping achieved yields against theoretical yield potential (percent achieved yield potential; AYP%), we quantified the change in productivity post amelioration.
Theoretical yield potential was calculated using equations adapted from Hunt and Kirkegaard 2015 and Oliver et al 2009: Yield potential (kg/ha) = ((0.25 × November-March rainfall + April-October rainfall) – 110) × water use efficiency (WUE); where WUE for wheat = 20 kg/ha/mm and canola = 13 kg/ha/mm.
Comparing 3-4-year-average AYP% maps before and after amelioration revealed an increase in AYP% and differential yield responses across soil types. In one case study, with varying clay contents of yellow sand (Arenosol) 90% of the paddock area increased AYP% after deep ripping with topsoil inclusion. The highest response was in the coarse acidic yellow sand. The second case study demonstrated that acidic sandy soils exhibited greater yield responsiveness to liming and deep cultivation compared to loam-clay soils.
While this AYP% benchmark has limitations in reflecting true yield potential across soil types, it provides outputs that can be interpreted across seasons and assesses proximity to water-limited yield before and after amelioration. The relative changes in AYP% were considered rather than absolute values.
This methodology offers a practical tool for evaluating amelioration effectiveness and can provide valuable insights to enable strategic targeting of soil management practices by soil type to optimise resource allocation in constrained sandy soil systems.