i have brought some ammonium sulfamate to get rid of horsetail weeds but am not sure how to use it can anyone help
Wikipedia has the details.
Please note that it will kill all plants for up to four months. You can't replant in the area until it has broken down.
On the patio, driveway and shingle path area we've found salt helpful. In the borders we're just try to keep on top of them by usual weeding.
Mix 6 parts water 1 part ammonium sulphamate and overspray. If only a small amount of the weed then nip off the tops place a small funnel over and spray each one individually...this way you can still plant non edible plants.