Kevin, You can add supplies as you plant the field. When you start a task you have the ability to "Save for later". You can then resume the task and make any changes. When you select a material, you can enter the area covered for it. To add another material just tap on the name of the first material. This will bring up a box where you can add other materials to the list. Each material can have a different area covered.
Regarding scale tickets, this is on the development list for the future.