Re-using old compost

I emptied out a large terracotta container so that I could move it. It would easily take an 80L bag of compost.
Should I add fertiliser to all of the old compost? It looks like it might have been sylvagrow so it was good stuff or should I go half and half with new compost? If yes, should I keep most of the new stuff at the top or mix it in?
I'm only going to plant annuals in it so I doubt the roots will get to the bottom.

 

If the old compost is still friable and drains well @BB3, I’d be inclined to leave half of it at the bottom and add fresh compost on the top, and not mix them. Your annuals will only need extra tomato feed later to encourage more flowering.

 

I always re-use my old compost. I mix it with Coir and my own compost,
with added feed.

 

That makes sense - financially as well as horticuturally!
thank you @Plantminded

 

I used to put garden soil at the bottom of large pots, for summer display, and potting compost on top, until I noticed that the roots never went into the garden soil.

I think you need to mix whatever you use so that the pot contains the same stuff top to bottom.

 

You are welcome @BB3. You could mix it all together if you like but my logic is that annuals have shallow roots so they will benefit from all the nutrients in the fresh compost at the top while they are producing leaves, stems and roots. Nutrients wash down with watering, which is why I would then supplement with tomato food later on for flowering. If you were growing a woody plant, I’d always use fresh compost and use the old compost as a mulch on borders. In a smaller container than the one you are using, I would mix everything up and add some slow release fertiliser as well.

 

I was thinking of adding fertiliser to the bottom layer. Would summer bedding plants like petunias, verbena and bidens' roots go down 2ft anyway?
Cross posted @Plantminded

 

There’s no harm in adding extra fertiliser @BB3, greedy annuals will seek it out .

 

@BB3, if I was planting annuals in a pot that size I would probably half fill it with bits of polystyrene at the base, to save on using compost.

 

The thing is garden centres are going greener. Not so much polystyrene about
Loads of pots were damaged by the weather this winter so I'm not short of crocks!

 

Unless you experienced diseases or root pests last year, the only missing ingredient is likely to be nutrient. Its simple to add slow release capsules, mixed into the remaining compost, and top up with either more commercial compost or better still, introduce some home made if it is likely to be weedfree and healthy. Even Jacks contains no magic......

 

I have a pile where I empty all my pots after the growing season, it tends to be a right old mixture of differing composts, some with sand some with grit or soil, it lays there all the winter, I broke some of it down yesterday and it looks like good stuff, it has a nice texture.

So I will reuse it during this summer with an addition of fertiliser for things that might need it.

 

I've been bunging everything from my containers in a wheelbarrow , mixing it up with fertiliser. I reckon it's no worse than some of the stuff you buy which is often suspect organic matter and fertiliser anyway .
Worms chucked into mix. Snails in council bin.
After 50 years of gardening it's only just occurred to me that moving empty containers about is much easier than moving full ones.
If only I was an organised gardener, life would be simpler and my back would appreciate it. But I'm more content with serendipitous laissez faire ( sorry feeling pretentious. It'll wear off soon)