Do you apply gypsum every time you plant canola? Are you sure you need to?
Gypsum can supply sulphur (S), calcium (Ca), and treat sodic (dispersive) soils.
Some growers use gypsum to both improve soil structure and supply S. Gypsum only improves soil structure in dispersive soils. A simple DIY dispersion test can identify dispersive soils.
In many cropping paddocks, repeated gypsum treatments have significantly improved dispersive topsoils. These topsoils’ structure may not improve further with more gypsum.
If the soil is not dispersive, the only potential benefit of applying gypsum is to supply S and Ca.
A typical application of 2.5 t/ha of gypsum supplies enough S to balance the needs of several cropping cycles (including canola).
2.5 t/ha gypsum = 475 kg/ha S
You don’t automatically need to apply gypsum before every canola crop if better S nutrition is your sole aim. Soil testing and paddock history of gypsum applications can predict if your crop is likely to need extra S.