Since most agricultural soils in Western Australia are already below the recommended targets, treating soil acidity to remove it as a production constraint often produces a yield response. Wheat yields in WA increase by 12% on average after the application of 2t/ha or more of good quality lime to acidic soils, based on Department of Primary Industries and Regional Development (DPIRD) data from hundreds of trial-years (Table 1).
|Crop||Lime rate (t/ha)||Grain yield response (% yield change) 0 years after liming||Grain yield response (% yield change) 1-4 years after liming||Grain yield response (% yield change) 5+ years after liming|
|Wheat||1-1.5||1 (16 trials)||8 (34 trials)||6 (11 trials)|
|Wheat||2-2.5||2 (19 trials)||13 (35 trials)||12 (18 trials)|
|Canola||1-3||21 (3 trials)||15 (18 trials)||12 (7 trials)|
|Barley||1-3.2||-4 (1 trial)||7 (18 trials)||47 (5 trials)|
The time taken to observe this response depends on many factors, such as the starting pH profile; the amount, frequency and quality of lime applied; the sensitivity of the rotation; and the degree of reliance on subsoil moisture at the end of the season. Typically, amelioration and potential yield responses can take four or more years after liming.
In DPIRD trials, there is consistently little or no yield response for wheat in the year of lime application, but on average, there is a yield increase in the following years. Canola appears to have a large initial response to liming, although this has only been looked at in a limited number of field trials (Table 1). For all crops in Table 1 with sufficient lime and time to treat subsurface acidity, responses are significant. Where pasture is a part of the rotation, production is usually increased after liming.