What are your magnesium levels in the soil? Gypsum is a good balancer for the Mg which makes clay sticky. There's enough sulphur in it for the following crop too.
Do be careful about where you get it from - some of the recycled plasterboard needs EA deployment licences or the RPA will be taking some of your Basic Payment.
Personally, I don't think that 1t/ac would have much effect on soils. Currently the EA pretty much accept up to 6t/ha without too much hassle. Higher rates need more justification as PTE levels can start to creep up and analysis can be very variable due to material inputs. Many years ago we used to put Tioxide 'gypsum' at 10t/ac, with some heavy coastal plain land at 20t/ac, which used to have a fairly quick response. Please bear in mind that the S in recovered plasterboard is only about 2% available.In a previous thread @York posted a cryptic message insinuating dire consequences from over applying gypsum.
I suspect its to do with damaging Mg levels, but can anyone expand on this?
FWIW, I applied 1t/acre on some index 5 Mg ground about 6 years ago and it didn't change much. Texture still poor, Mg still index 5, and no detectable difference over (poor) pre gypsum S levels when re tested 12 months later in the following crop. I would like to repeat the application but I'm wary that these Macbeth like prophecies might come to pass.
PAS109 is the Quality Protocol for recovered gypsum, but the end destination does not include agriculture. Currently, there are only two recovery routes to land for recovered gypsum, that is either by a Low Risk Waste Activity Position Statement that allows gypsum to be applied at up to 1t/ha http://1ur6751k3lsj3droh41tcsra.wpe...uploads/2015/02/Low-Risk-Gypsum-Statement.pdf or by a land spreading deployment. I am part of a small group working on a third way of getting it to land legitimately
Scotland, via SEPA, has a different approach https://www.sepa.org.uk/media/154220/recycled_gypsum_from_waste_plasterboard.pdf
Is there a difference between recycled and mined gypsum then as per paperwork? Is one waste, and the other fertiliser?