Soil
There are 15 types of Soil in existence, and 1 Crop for each Soil. More crops and plants will be added as the game grows.
Growing crops adds Experience to the Soil, the higher the Soil level is, the bigger chance of getting double harvest bonus, and double level bonus. By default, harvesting does give you only 1 crop. If your Soil level is 10 and you roll a double harvest bonus + level harvest bonus, you get 20 harvested crops in total.
Formula: (1 {default} x 2 {doubleBonus} x 10 {levelBonus})
There's also a chance to find a random item when you harvest your crops.