Granular fertilizer

I am now growing a fair amount of vegetables. I use lots of horse manure on suitable veg as have it "on tap" plus using wood ash for increasing my fairly acid soil for the Brassica family.
I have used in the past a small amount of Growmore and another granular fertilizer (given to me by my neighbouring farmer) but that has all be used up now. If I bought say a 25kg sack of Growmore will it still be effective in a couple of years time? as won't need 25kg in 1 season. I could store it somewhere dry. Obviously the bigger the bag the cheaper it is but not if the fertilizer deteriorates over time.

 

RHS website has a blog on this:

fertliser shelf-life - My Garden

 

I make sure I use all granular fertilisers in one year silu. Organic though so it breaks up more quickly than growmore. I think fertilisers, composts, etc do change over a couple of years.
Why not buy a smaller bag?

 

@silu Granular fertilisers like Growmore will keep fairly well so long as you keep them dry and cool. I use Growmore and a 25kg sack lasts me several seasons.

 

I'm Scottish. Contrary to popular opinion we are not mean just "canny" (careful!). .
Hmm like so much of gardening, differences of opinion. Maybe I'll do a compromise and buy a 10Kg bag which will last me probably 2 to 3 seasons. I use so much organic fertilizer I only use other things for those veg which don't do well with manures. Many thanks

 

Store in air/dry tight containers it will be fine til next year

 

A 25 Kg bag is a lot to keep esp if you think a 10kg bag will last you two or three years. On that basis 25kg will last for 6 years???
Despite keeping bags dry the atmosphere, once a bag is opened, does affect the quality of fertiliser.
You could use it as a lawn fertiliser!!
Canny as well Silu. Always keen to get best value and I haggle on everything.....and I mean mosy everything. However, I think it is simply good practice to use up such consumables in 12 months

 

Glad to hear it keeps for years if stored correctly as i picked up 10 25kg sacks for £20 in a daft homebase clearance. Should last me into retirement and into my next life too

 

I buy them when reduced, then store in 10 Litrebuckets with clip down lids. If bought in smaller quantities, Growmore and BF&B are OK tipped out their boxes into plastic tubs and will last for years.

Stuff like Phostogen and Miracle- Gro are best left in their plastic packets, which I also store in 10L buckets and write the dosage on the lids before the carboard packets disintegrate.

Epson Salts are renowned for attracting moisture, another one for plastic tubs.

 

The high the Nitrogen the more problems you will get with it attracting moisture

 

Agree Jiffy......and nitrogen levels dissipate before anything else and fast. It is not easy to prevent moisture accessing dry fertiliser once opened even in secure plastic tubs.
Used to buy large quantities of fertilisers and, in my experience, the quality deteriorated if kept too long. I now only buy enough for one season. Less to store too

 

Not sure about growmore never really tried keeping that overwinter, personally I wouldn't bother.

Other straight fertilizers, ie. sulphate of potash and Ammonium sulphate do attract moisture, as does the likes of miracle grow etc. so if I have any of those left at the end of the season I bring them into the house where they keep pretty well.