I use this stuff all natural maybe once a month. Works good.
We use similar stuff you posted on our irrigated cow pasture twice a year so your probably ok to use it if the grass is tall enough so your tort won't ingest it accidentally.
I would not use any fertilizer IN the enclosure where a tortoise would have access to it. The link won't open for me, but if the fertilizer is marketed as safe for a pasture, it should be fine to grow tortoise food in it.
I use the organic fertilizers from Armstrong Nursery. They work well and the tortoises can't ingest it as I use a cultivator to work the matter into the soil followed by a good soaking. I have to be sure that the tortoises don't drink from any puddles for a week ir so.