Deuteronomy 23:13

And you shall have a trowel with your tools , and when you sit down outside , you shall dig a hole with it and turn back and cover up your excrement .

As part of your equipment have something to dig with, and when you relieve yourself, dig a hole and cover up your excrement.

And thou shalt have a paddle upon thy weapon; and it shall be, when thou wilt ease thyself abroad, thou shalt dig therewith, and shalt turn back and cover that which cometh from thee: