Compost Heap Experiments this spring……

[RhysParticipant]

This year, I”ve built two heaps of around 1m * 80cm*80cm (size of our grids rather than optimal size I know), one month apart.

In April, I used horse manure/straw about 50:50 with the first grass cutting of the season (which had been dried out for about 10 days prior to the heap being made).

In May, I replaced about 50% of the grass cuttings with cardboard, again using well dried grass to build the heap and again having horse manure with straw rather than wood shavings.

In the April heap, the top temperature the heap reached was 60C after 6/7 days with temperature down to 55C after 10 days and ambient temperature by day 25.

I’ve just gone out and measured the May heap temperature on day 3 and it is 70C in the middle. Up to the temperatures quoted by optimal compost makers…….

This does suggest that you get heaps up to temperature quicker and more effectively if there is less grass cuttings and more cardboard.

Anyone else seen similar things or could there be other explanations for the more rapid heat-up of this second heap?? (I suppose the horse manure I got might have been fresher the second time around, but that’s just the luck of what’s there to shovel up at the stables when you go and get it)…..

[peatParticipant]

Hi Rhys
when you add grass clippings to a heap of manure you are adding more nitrogen to the heap. In so doing you are unbalancing the carbon nitrogen ratio in favour of nitrogen. By adding cardboard it increases the carbon content which needs to be significantly higher than nitrogen. This is one of the main faults in compost making, most people add too much nitrogenous material.

[RhysParticipant]

Thanks for the insight Charles – I’ll certainly use less grass in future and will add some cardboard to the first heap when I turn it at the end of May. Any other alternatives to add to up the carbon content?

[Author]

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