On May 30, 1:49*pm, stuart noble wrote:
All multi-purpose composts 'run out of steam' after 6-8 weeks

But I have proved to my own satisfaction that this is fundamentally
untrue. What you're supposedly left with after the nutrients have been
used is never explained. All I can say is that every flower I've grown
in "spent" compost has flourished, and must be feeding on something.

No it is most certainly not "fundamentally untrue". What you're left
with is a reduced level of nutrient that may be sufficient to sustain,
but not promote the same level of growth or productivity. Of course
there are plants that can perform moderately well on a sparse regimen,
but many, many more will only grow at a very modest rate and produce
fewer flowers and/or less fruit over a shorter period if not
supplemented. Your idea of 'flourishing' and mine are probably
completely different and I want the very best growth and productivity
over the entire growing cycle. This is only achievable if nutrient
levels are correctly maintained throughout the season. That is not to
say they should be over-fertilised, but sensible additional feeding
always gives consistently better results.