Fertilizer Bin
A Fertilizer Bin is a Building in FarmVille 2 that produces additional 12 
Fertilizer and gives a 25% chance of obtaining a single 
Speed-Grow. It is filled by fertilizer produced by adult animals and become available for emptying once the treshold of 40 has been reached.
For a visual presentation of the build process, see here
Fertilizer Bin[]
After placing the Fertilizer Bin, some building materials are needed to finish the Building.
10 Green Paints- 10 Grass Clippings
- 10 Wood Planks
After that, 4 Neighbors are needed to hire for constructing the Fertilizer Bin. If you have little neighbors, you might already get neighbors filled in.
This building can be stored in inventory. It will still fill up with fertilizer when stored in the inventory, but you will not get a notice about it being full.
Known glitches[]
While only one Fertilizer Bin is available to be built, more than 4 can be placed on the farm.
Currently there is a glitch known which sometimes requires multiple time emptying the bin to be able to obtain the fertilizer.
Pictures of the Fertilizer Bin build process[]
When you are at level 9 this screen will pop up, making you able to build a Fertilizer Bin.
You will need a set of materials to get through the first building phase of the Fertilizer Bin.
At the second building phase, you will need to ask neighbors to help in finishing the Fertilizer Bin.
Once finished, the Fertilizer Bin will be able to hold fertilizer produced by at least 1 adult animal on your farm. Rakes are needed to empty a full bin. You currently can have unlimited rakes at any given time. It shows 60 on this screen, that was later adjusted to 40.