Seeds can be sown on a dirt tile, grass tiles needs to be packed then cultivated. The [[maximum slope]] on which you can sow seeds is 8, where 8 = (highest north-south tile border's slope) + (highest east-west tile border's slope). For example, the slope can be level EW and 8-steep NS. Or 4-steep EW and 4-steep NS, etc. Attempting to sow seeds on a greater slope results in a message "The ground is not flat enough for crops to grow. You need to flatten it first". Farm tiles function the same with a slope 8, flat or anything in between.
Note: Above is not entirely correct, game because it is using more complicated possible to sow on a tile, that has 5-steep EW and 5 steep NS. It is possible the intention was to use [[diagonal slope]] formula to calculate steepness for both diagonal directions of this, but the tile. If that value implementation is greater than 8, tile cannot be sown on. It also appears to be bugged. --[[User:Aldur|Aldur]] ([[User talk:Aldur|talk]]) 07:10, 28 September 2012 (CDT)
The current minimum harvest yield is 2.