Storing fert over the winter is no problem. It is not a fire hazard. That is a very common misconception. Fertilizer alone will not burn easily. It needs to be mixed with other things in a special way in order for it to become an explosive. This can not be done by accident, even if you were to spill gasoline on the fert.
It will not loose any of its potency, but the one thing that may happen is that the fert may become hard and rock like. If that does oocur, just put on a pair of safty glasses, and pound it with a hammer to loosen it back up again. Most of the time it will just crumble between your fingers though.
As long as it is a solid fert storing it in a dry place is best. It is okay if it freezes as long as it remains dry.
If liquid you may want to keep it in your basement or a heated garage
Hope this helps
Mike
