Soil mix test results 2
Posted: September 2nd, 2010, 9:11 pm
SOIL TESTS: SECOND LOT.
The first four tests used potting mix sifted through fly wire to remove the dust. It was mixed 50/50 with Mt Sylvia diatomite, brick dust, perlite and spongalite (Richgro aquatic planting mix). This was to see whether the potting mix dust was the component that made the previous tests drain so slowly.
The next four tests used soaked and squeezed coco peat as 25% of the mix, being a more realistic mix than the previous dry 25% coco peat, which expanded remarkably when wetted. The other components, making 75%, were diatomite + perlite, diatomite on its own, brick dust and spongalite.
Two other tests contained 20% soaked and squeezed coco peat, to compare with the 25% mixes, again with diatomite + perlite and diatomite on its own.
Once again, a rough measure of drainage times was recorded. The water retained was measured differently, as damp and wet components were used in the mixes - the weight after drying for four weeks was subtracted from the weight after a one minute soak and a ten minute drain. The mixes may possibly dry even further in the next two weeks, but I got bored.
I can send the results/number salad/junk pile as a PDF to anyone who wants, but here are the conclusions.
The sifted potting mix drained more rapidly than the unsifted mix, but never as fast as the coco peat mixes.
Perlite as a component appeared to speed drainage, but reduce water retention, compared to diatomite.
None of the other grits appeared to make a great difference with drainage times - its the type and size of the absorbent component that determines the drainage speed.
Once again, coco peat (at 25%) retained as much water, sometimes more, than 50% sifted potting mix, but gave much better drainage.
Spongalite appeared to retain more water in both types of mix than diatomite, brick dust or perlite.
Diatomite appeared to hold water better over time, as a component in the mixes, with spongalite second best. Brick dust and perlite had lost more than 40% of water within a day.
If you are using the slowly absorbent grits like spongalite and diatomite, it may be worth soaking each tree once a week through summer.
A 5% addition of coco peat (from 20% - 25%) increased water retention by more than 10%. Drainage, while still good, was very slightly slower.
Adding perlite to diatomite mixes seems to reduce water retention, without any other great benefit.
So now to the Great Acid Test - my first Canberra summer. I have previously used sifted soil, composts and coarse sand, so its all going to be Verry Interresting!
TEST YOUR MIXES! And thanks for your attention.
Gavin
The first four tests used potting mix sifted through fly wire to remove the dust. It was mixed 50/50 with Mt Sylvia diatomite, brick dust, perlite and spongalite (Richgro aquatic planting mix). This was to see whether the potting mix dust was the component that made the previous tests drain so slowly.
The next four tests used soaked and squeezed coco peat as 25% of the mix, being a more realistic mix than the previous dry 25% coco peat, which expanded remarkably when wetted. The other components, making 75%, were diatomite + perlite, diatomite on its own, brick dust and spongalite.
Two other tests contained 20% soaked and squeezed coco peat, to compare with the 25% mixes, again with diatomite + perlite and diatomite on its own.
Once again, a rough measure of drainage times was recorded. The water retained was measured differently, as damp and wet components were used in the mixes - the weight after drying for four weeks was subtracted from the weight after a one minute soak and a ten minute drain. The mixes may possibly dry even further in the next two weeks, but I got bored.
I can send the results/number salad/junk pile as a PDF to anyone who wants, but here are the conclusions.
The sifted potting mix drained more rapidly than the unsifted mix, but never as fast as the coco peat mixes.
Perlite as a component appeared to speed drainage, but reduce water retention, compared to diatomite.
None of the other grits appeared to make a great difference with drainage times - its the type and size of the absorbent component that determines the drainage speed.
Once again, coco peat (at 25%) retained as much water, sometimes more, than 50% sifted potting mix, but gave much better drainage.
Spongalite appeared to retain more water in both types of mix than diatomite, brick dust or perlite.
Diatomite appeared to hold water better over time, as a component in the mixes, with spongalite second best. Brick dust and perlite had lost more than 40% of water within a day.
If you are using the slowly absorbent grits like spongalite and diatomite, it may be worth soaking each tree once a week through summer.
A 5% addition of coco peat (from 20% - 25%) increased water retention by more than 10%. Drainage, while still good, was very slightly slower.
Adding perlite to diatomite mixes seems to reduce water retention, without any other great benefit.
So now to the Great Acid Test - my first Canberra summer. I have previously used sifted soil, composts and coarse sand, so its all going to be Verry Interresting!
TEST YOUR MIXES! And thanks for your attention.
Gavin
