IN a trial in the north-east Wheatbelt, a single lime application significantly increased grain yield and profitability, resulting in a cumulative net benefit of $800 to $1100 per hectare after seven seasons of wheat.
The purpose of liming is to help deal with issues of soil acidity by increasing pH which helps to improve plant establishment and root growth, meaning plants are able to gain more moisture and nutrients from the soil, ultimately leading to an increase in yield.
The trial was run at Tardun, about 50 kilometres south east of Mullewa, by the Department of Primary Industries and Regional Development (DPIRD) since 2013, with seven seasons being sown to wheat and one year, in 2018, being fallow.
Over the eight years, soil tests for pH have been conducted in 10 centimetre increments down to 40cm, while yield data from the site after each season has also been compiled.
DPIRD research scientist Chad Reynolds said the purpose of the trial was to address the soil acidity problem and evaluate the economic return, while also assessing if tillage instruments could be utilised to address subsoil acidity at a faster rate.
"Results from seven crops grown over eight seasons at Tardun have shown that applying lime to the surface of an acid soil increased crop yield and hence cumulative profitability by up to $1100/ha in this low rainfall environment," Mr Reynolds said.
"The greatest yield benefit from lime application occurred in the lower growing season rainfall years, such as 2017 and 2019, with what had been limed showing over a tonne per hectare improved wheat yield when compared to what hadn't been.
"This suggests that the wheat was able to get better root establishment on the soil with better soil pH profile and was able to access more of the moisture and nutrients at depth, thereby improving the yield."
In the other trial results, lime incorporation through suitable tillage treatments did increase subsoil pH to the depth of incorporation faster than application to the surface.
Unfortunately, incorporating lime with tillage treatments did not further increase production and profitability at Tardun, but the reduction in subsoil acidity did stretch down to 20cm.
"Soil tests need to be carried out because growers need to know if there is a soil acidity problem, not only in the topsoil, but down in the profile to 40cm," Mr Reynolds said.
"If there is a problem, one of our key messages is that growers should take the opportunity to throw lime out in front of whatever the tillage treatment might be, whether that be spading, mouldboard ploughing or deep ripping.
"If they apply the lime first, the tillage can help it to get down to depth to help address the subsoil acidity issue faster and the sooner the lime is applied, the sooner the benefits will be seen and returned in terms of yield and therefore profit."
The large scale experiment at Tardun clearly shows the benefits of lime application on crop yield where soil acidity is a constraint.
The wheat yield benefits received over a number of seasons resulted in a significant cumulative benefit and this demonstrates that sufficient lime application to acidic soil results in a positive economic outcome and shows that yield potential will not be gained if soil acidity is not addressed.
"The grower who's farm we've been hosting the trial on said liming was a 'no-brainer' as the benefits were clearly evident - whatever had been limed was far better than what hadn't," Mr Reynolds said.
"Visually the results of the trial were clear in terms of the lime runs versus no lime, and that was before you even start looking at yield results."