Using woody garden waste to create seed compost (and other composts) Peter Harper CAT (by kind...
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Using woody garden waste to create seed compost (and other composts) Peter Harper CAT (by kind permission of Nerds Anonymous) Daft jokes by Adam Harper
Using woody garden waste to create seed compost (and other
composts) Peter Harper CAT (by kind permission of Nerds Anonymous)
Daft jokes by Adam Harper
Slide 2
What for? Dealing with your own organic waste is a significant
contribution ordinary householders can make to sustainability Soft
garden wastes and kitchen wastes are easy to compost, but woody
wastes are not Some gardens produce an awful lots of awkward woody
material Bonfires are not cool I thought that perhaps woody waste
compost would have distinctive and useful properties So I undertook
a long-term programme of research and observation on the breakdown
of woody wastes, and how to use the resulting material
Slide 3
First trial Two adjacent open bunkers filled identically with
randomly arising woody waste. Topped up and jumped on for four
years. Urine added on one side but not the other.
Slide 4
Intermittent inspections Archaeological tunnels dug into each
bay At year 4 very little humification Dry conditions Water added
at top either runs straight through or is shed off the sides
Additions of urine seem to make no difference.
Slide 5
Section and detailed inspection at year 6 Humified zones Zone
still unhumified
Slide 6
Three composts compared for seed germination Woody waste
compost was easily the best Paper-mill de- inking sludge Seived
woody waste Commercial John Innes Seed compost
Slide 7
Trial of pure woody waste as a general garden compost
Slide 8
Courgettes as test crop: rapid growth, good yields, healthy
plants
Slide 9
Analysis of 7-year-old woody waste compost Determinand
ValueUnitRemark Density500kg/m 3 Light pH7.1 Slightly high for some
purposes Conductivity97S/cm Very low good! Dry matter31.9% Organic
matter*66.3% High NO3-N29.4mg/l Low NH4-N1.5mg/l Low Total N *2.1%
w/w Surprisingly high Total K*0.16% w/w Surprisingly low Total
P*0.26% w/w Surprisingly low * Dry matter basis
Slide 10
But who cares about the analysis? It works It is the most
brilliant lovely material Like fine malt whisky it is worth waiting
for But if we could make it quicker, wouldnt that be nice? Lets
think about why it takes so long
Slide 11
A Harpothesis Loose piles of woody material resist breakdown
because they are too dry They are too dry because Excessive
drainage (rain runs quickly through) Thatched roof effect (rain is
shed on outer layers) Open texture allows ready evaporation
Therefore decomposers (especially fungi) cannot boot up Therefore
there is a long stuck phase that might go on for years
Slide 12
continued Eventually a focus of humification develops that can
Hold moisture Act as a refugium and breeding-ground for decomposers
A wave of humification propagates from that focus Thereafter,
breakdown proceeds relatively quickly
Slide 13
Humified zones Zone still unhumified
Slide 14
Apparent progress of humification in an open woody heap 0% 100%
Humification Time in years 13524 Initial phase of bacterial
decomposition Stuck phase Adventitious formation of humification
focus Rapid spread of humification
Slide 15
How to avoid getting stuck Compress to reduce voids Shredding
Vertical stacking Prevent moisture escaping enclosure Add
moisture-retaining materials Soft wastes Soil
Slide 16
Adam always loved Shreddies
Slide 17
Shredding produces some usable compost in 18 months An unseived
mixture of all these grades has grown potatoes with good yields for
four successive years But dreadful for slugs!
Slide 18
The Stack Principle 2 x 0.75 x 0.751.5 x 1 x 1
Slide 19
Design and function of the stack Solid plastic sides Opening at
bottom Fresh material Fine material ready for use Open top >1.5m
1m Coarse pieces back to top
Slide 20
Trial of simple stack principle, using pure woody waste Woody
waste added for one year till full, then left without further
treatment for three further years Volume reduction Dismantling
upper parts of container Builders bottom
Slide 21
Appearance of surface Surface removed
Slide 22
Results This supports the theory that compression and reduced
moisture loss will accelerate humification. What about adding
moisture-retaining materials?
Slide 23
Trial of stack principle plus addition of moisture-retaining
materials Materials added randomly at top Green/woody Brown/woody
Leaves Weeds Sods Spent composts Grass clippings
(occasionally)
Slide 24
Results after two years Appearance of surfaceAppearance just
under surface
Slide 25
Progressive removal of material Homogeneous breakdown right to
the bottom
Slide 26
Close-up of texture Texture is less peaty, much more
earthy
Slide 27
Conclusion This result supports the theory that adding certain
extra materials further accelerates humification of woody wastes It
also provides a no-hassle approach to composting all but soft
wastes However.
Slide 28
We have two types of compost to test Pure woody material, peaty
and springy Call it woody waste compost or WWC Mixed garden wastes
with soil Call it soil stack compoist or SSC Trials are under way
to compare them with each other and with high fibre compost, made
with soft wastes at low temperatures (HFC)
Slide 29
Growing trials HFC wwc SSC
Slide 30
One rather clear result SSC is very weedy. WWC is remarkably
unweedy. HFC is in between
Slide 31
Other early results SSC and WWC performed equally on potatoes
and kale SSC outperformed HFC on cucumbers WWC was best for
cabbages and lettuce HFC was best for leeks and winter onions SSC
can propagate clubroot, WWC and HFC would not. WWC is especially
attractive to mice and birds, who dig up newly-planted crops
Slide 32
IMPLICATION FOR HOUSEHOLDERS Households with larger gardens
could benefit from at least two compost streams with different
qualities All are simple to operate with low maintenance
Slide 33
Possible tests of Ingham hypothesis Elaine Ingham of
soilfoodweb.com claims that composts based on woody materials would
give better results on perennials, while cellulose-based composts
are better for annuals So far, results do not support these
hypotheses
Slide 34
Kitchen waste Grass clippings High Fibre method Fast, fine
compost Other Garden wastes: Weeds Autumn leaves Spent composts
Turf and sods Slow Stack method Slow, coarse compost for general
purposes, Urine (optional!) Heavy woody waste Export to CA site for
thermophilic composting Landfill Energy-from- waste Non- recyclable
paper and cardboard Slow stack method with woody materials only
Slow, fine material for seed compost and potting mixtures
High-nitrogen wastes High-carbon wastes Principal pathways Variant
pathways Woody wastes: Prunings Hedge trimmings Twigs Lignified
stalks