If you know you really need a fast shot of potassium too, you can turn them to ashes and thats about 85-95% silica, and other stuff mostly potassium, no decomposition needed ?
Oh and since they do decompose it does help to add extra perlite in, or pummice, lava rock, heat-expanded shale whatever you got for air. I go heavier on perlite ratio near the bottom since it floats up, and heavier on the rock ratio at the top. but breaking up the soil hyphae every grow isn't good for it if 5gal+ cause it will be a living soil at that point, so i'd say just make a good soil aggregate with it initially and top ammend after, or use something to take core samples out to drop a mix of fresh hulls with soil into the core sample hole as a replacement so you don't disrupt the hyphae too much.
I think rice hulls that have decomposed from the previous fall outdoors and get planted into the next spring, help my tomatoes be more frost hardy, i'm certain of it.