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I recently cut down and chipped a row of lilly pills and now have 4 cubic meters of wood chip. Intention is to let it decompose over a couple of years and use it to compost my garden. I originally mixed in some chicken manure to give it a head start but really not enough, and the process is slow. Is there anything I can buy which I could shovel over the top and water in to promote decomposition?

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  • Is this for a vegetable or an ornamental garden?
    – Jurp
    Dec 19, 2021 at 15:53
  • @Jurp, It is for a native garden in Brisbane Australia. Currentlly we are in a la Nina cycle so there is plenty of rain for a change.
    – Daley
    Dec 26, 2021 at 23:33
  • Personally, I use woodchips as a mulch around perennials and shrubs to conserve moisture, improve soil fertility, and improve the tilth of the soil. The only nitrogen deprivation that occurs is at the chip/soil interface, where there are no roots, and as the bacteria that remove the nitrogen die, they release it back into the soil. I use an inch around perennials and up to three inches around shrubs (but not touching the stems). I'd make this an answer but it's outside of the parameters of your question.
    – Jurp
    Dec 27, 2021 at 14:40

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Mix it with any nitrogen source. Bird manure is awesome but grass or kitchen scraps will also work. E.g. see the tables here - at the bottom or here. Not only will the chips decompose faster but will also prevent the loss of nitrogen for the other ingredients. And will prevent bad smell.

Or you can use them for mulching to inhibit water evaporation and weed growth.

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Whatever you do, don't mix it with your soil, or it'll leech the nitrogen out of the soil and cause issues. Put it on top of the soil; it'll decompose just fine on the top, without harming your soil.

Wood chip mulch is a valuable thing to have on top of your soil; plants love it. I wouldn't be worried about speeding up the process, personally. On top of your soil it should take about two to four years to decompose.

However, if you've mixed it with the soil, that's a totally different scenario than putting it on top as mulch, and you can add extra nitrogen, or something containing nitrogen, to help it decompose faster. Don't expect plants to grow particularly well in it in during this decomposition process; expect them to be stunted and get chlorosis or else to get burned by all the extra nitrogen you add; if you have chlorotic plants in such situations--and aren't adding enough nitrogen to the soil--regular foliar sprays of nitrogen can help the plants, since the soil won't have access to that).

I can't say how long it'll take to decompose if you've mixed it with the soil (but again, I don't recommend mixing it). It probably takes about 4 or 5 years for a ground Lombardy poplar or apricot stump to decompose, without adding extra nitrogen (in my experience).

I'm not familiar with the specific kind of wood chip mulch (lilly pills) you have. There may be special things about it that aren't true to wood chips generally. If they're closer to chopped up twigs than they are to wood chips, I'm not sure how that would impact the decomposition.

If you're just looking to compost the wood chips without using them before they've been composted, then yeah, adding extra nitrogen will probably help. However, I would personally want to use it as mulch instead (unless you've already got loads of mulch or have reason not to use it as mulch). If you plan to use the resulting compost in potting soil, make sure it's completely and utterly composted. Uncomposted wood chips floating around the mix can sap the mix of nitrogen for a good while.

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A little fertilizer will aid decomposition. In particular phosphorus. I use a water soluble starter; 9-45-15. I drill holes in large stumps and pour in some diluted fertilizer. I do it to all large stumps so I can't give an objective answer to how much it aids decomposition. For a pile of chips, standard composting technique of turning, and wetting when dry would also help.

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