Physical mass difficult to haul, store and distribute within commercial grape vine trellis systems. Unknown amounts needed to control weeds. Unknown repeat application timing. Compost sources see it as disposal problem, but growers see it as a cash flow issue. With our wet winters and clay loam soils we have access with heavy equipment for only a short time after harvest.
Research needs to be done about surface soil benefits over time.
Clyde Elmore and I have talked about this with Pritchard, et al and may submit a DANR grant to explore this. I note Oregon St Univ seems to be studying impacts of weed management practices on surface biomass and microbe populations. Big grower fear up here is not heavy metals, but is soil active root pathogens such as Oak Root Fungus.