Candy_porn
Reputation: 640

Can I use last season's compost and potting soil this year?

I have a container garden, and in my laziness left partially used bags of potting soil and planting compost out on my patio for most of the winter before moving them under cover. Will the rain have leeched out all the nutrients? Can I use what I have and amend it with fertilizer, or should I buy new compost?

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3 Answers

  • Qlandav2ex_small
    Reputation: 4209

    Dirt is dirt, use it.
    The breakdown of compost takes time, air (oxygen), warmer temperatures and appropriate moisture levels. The nutrients that it contained are still there. Mold may be present from the over moist condition, but allowing it to dry out and mixing with drier soils will ameliorate that.

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  • Dsc_0148_small
    Reputation: 840

    the only problem might be what's going on with the microorganisms in there. if it's been sitting in the bag there a chance the air holes have been blocked and it's been cooked in the sun - you might have killed off most of the aerobic bacteria.

    that's nothing that a little time and some mixing with in-the-ground dirt can't cure. if you're really worried, go buy some red wrigglers to help break things down. i've heard some folks will go the extra mile and make a diluted molasses mixture - 1/4 cup molasses to a gallon of water, spread over 30 square feet - to jump start bacteria.

    it is good to know, though, that nitrogen leaches out of your soil the fastest of all nutrients. really, nitrogen is what makes the difference between an okay harvest and a bumper crop. while its ridiculous to assume there's no nitrogen at all in those bags, I'd add a little to your beds. blood meal (available fast!) and fish meal (av bit more slow-release) work wonders, though it's crucial not to overdo it and wait until you've got a bit drier weather. fertilizing garden = good, fertilizing in the rain = fertilizing groundwater = bad.

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  • Finn3goof_small
    Reputation: 1811

    Nitrogen is water soluble and so leaches quickly. I've posted if before, but here is my fertilizer recipe:
    2 parts Blood Meal
    3 parts bone meal
    6 parts green sand.

    By "part" I mean scoop.
    This can be adjusted as needed. I often add some sort of seed meal like alfalfa for some longer term nitrogen. This basic recipe is pretty killer. I got it from the guy that started territorial seeds.

    The primary reason for adding compost to a garden is not nutrients- especially in the Northwest. It's to add well rotted organic matter. The nutrients can be added seperately and should be added seperately. Most commerially available composts need augmentation of some kind (at least in my experience). so your stuff is almost certainly just fine.

    Good luck.

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