Hello,
I´m new to this forum and to Permaculture. However I do know of a VERY effective way of controlling elephant or king grass. Currently we are working to reforest a few acres of tropical rainforest close to Bogotá, Colombia in "La Vega" area at 1,200 m. altitude (25 C average temp). We are also slowly cultivating more and more land, but the reforestation is a priority.
The whole land was completely overrun with king grass which had been planted there for bovine forage. And there is the answer to controlling it. A few cows will do short work of the grass in relatively little time. The cows will have to be removed after the grass mowed since they will eat everything else growing in between after the grass is gone. The key is planting good pioneer species after the grass has been decimated by the cows, as it will regrow quite rapidly, even from broken pieces of stem and root. There is no choice but to manually cut the grass until the pioneer species have taken hold and successfully competed with the grass. Cutting all the grass by hand without the cows will drive you nuts, you can use the cow dung later for fertilizer and compost.
It is a terrible idea to use poison, which will likely be glisophate (roundup) It will poison your land for years, which totally defeats the purpose. I´ll post some images of the land pre and post cows and also in the middle of the process soon.
Cheers,
Alejandro