The straw golem is your farming friend. If placed near any growing crop, when that crop is mature, he will break it. If you add an intelligence core to your straw golem, he will attempt to replant the crop that he broke, assuming of course there was a replantable item dropped. However, the straw golem does not actually collect anything, so a fully automatic farm would also require a wooden golem attached to a nearby chest to collect the crop drops. Intelligent straw golems will replant whatever they just harvested, dropping any excess seeds.
Straw Golems can harvest Sugar Cane, Nether Wart, Wheat, Potatoes, Pumpkins, Melons, Cocoa, Carrots, Flax, and Cacti, but unless they are the intelligent variety, they will knock out the entire plant without leaving the base block or any planted seeds for continued growing, with the exception of pumpkin/melon stalks. Below is an example image of an intelligent straw golem breaking a cacti block while leaving the bottom of the plant. They can also harvest crops that you have to right-click on, like, for example, berry bushes from Natura.
"The Straw Golem can be placed anywhere and as long as there are fully grown crops, reeds or plants nearby, it will harvest them. Unfortunately straw makes a poor construction material which means the golem cannot carry anything - harvested materials simply fall to the ground.
Smart versions of the straw golem can also instantly replant what they just harvested on the same block as well as nearby blocks."
Required Research: Golemancy