Thanks for the link Hazel,
There were many agricultural tools used by the Hawaiians.
The 'o'o bar a commonly known one was used for digging. They were sharpened with an adze or in some archaeological sites one can find places where there are a number of several inch long ruts in rock surfaces; these were used to sharpen the 'o'o.
A very common but not so evident tool was the Hawaiian knife. Simply a flake from a chunk of obsidian, placed between the thumb and index finger, used to cut sweet potato vines for planting, or to make taro starts. The farmer (mahi'ai) would keep an obsidian corestone (or basalt) and hammerstone (rounded basalt rock) with them while working a farm (mahi). When ever a knife was needed, a flake would be struck off the corestone.
