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Thread: Is the coffee as fertilizer debate settled?

  1. #17
    Hello, I must be going... Not a Number's Avatar
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    Quote Originally Posted by BigBella View Post
    Coffee is particularly high in phenolic compounds -- some twelve percent of dry weight in unroasted beans -- which have a role in breaking down decaying plant material; thereby, freeing up some complex organic nutrients.

    As far as commercial nurseries are concerned, the local one here not only uses and sells compost "teas" but also brings in spent grounds from Starbucks and Peets by the wheelbarrow load, to add to their composts . . .
    Aren't many phenolic compounds volatile? The roasting process would remove the volatile compounds.

    The operative word here is "compost". Composting releases or transforms the nutrients in the "compost materials" so they can be utilized by the plants. The primary nutrient being nitrogen. All the literature I've read about using coffee as a fertilizer refer to using the grounds which are a good source of nitrogen as it breaks down.

    Quote Originally Posted by theplantman View Post
    It isn't that coffee doesn't work at all. It's like Paul seconded: it's a lackluster solution to achieve greater, healthier plant growth. And therefore in my opinion, it's an obsolete idea that isn't productive to play with anymore. Let's say a person is early into this hobby and wondering how to improve the health/vigor of their plants as well as expand their horticultural skillset. Assuredly, the payoff is higher to spend time experimenting with fertilizers over coffee.
    There is also the cost if you are using just the brew - if you look up the cost per gallon for coffee you'll see estimates from $0.50 to $100 per gallon. Assuming you get some low-cost brand like Folger's the cost per gallon ranges from around $0.50 to $0.75. I estimated that with a fertilizer like MaxSea the cost is about $0.05-$0.20 per gallon depending on what strength you use.
    Grand Hotel... always the same. People come, people go. Nothing ever happens.

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    Analysis of spent coffee ground (from the lettuce paper):

    N 1.2%
    P 0.02%
    K 0.35%
    Mg 0.1%
    Caffeine 0.18%

    N is slightly higher than typical peat-based potting soil, but P K Mg isn't higher. Also all N is in organic form (immobilized), so it isn't immediately available. Some epiphytes can directly absorb some amino acid. Indeed in a Brazilian study of some orchids, it has shown that inorganic (chemical) fertilizer + organic fertilizer did better than the case when they were used separately. So nutritional content is very small. Actually, in the lettuce study, N-content from the leaf analysis shows that N concentration in the leaf decreases with more coffee in the soil.

    Additionally, caffeine can influence some soil microbes because it is toxic to microbes and plants, and it can influence the microbe fauna. This could have negative or positive effects to the potted plants.

  3. #19
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    Quote Originally Posted by naoki View Post
    Analysis of spent coffee ground (from the lettuce paper):

    N 1.2%
    P 0.02%
    K 0.35%
    Mg 0.1%
    Caffeine 0.18%
    Useful information, to be sure. But the "Nepenthes coffee treatment" doesn't involve spent grounds, it employs brewed coffee, as if you were making it for your own consumption (however, for use on plants, it gets diluted significantly).

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    I just "coffee'd" my plants after reading this. I hadn't done so in a long time. Typically, it's something I do once a year or so, while relying on fertilizer every two months or thereabouts (it used to be every two weeks, but I get lazier the longer I grow these things).

    In the past, I've been part of this debate, using plant physiology jargon as well as firsthand experience to make my case. However, the topic has acquired the scent of a bloated, decaying horse (for me, anyway). That being said, David (Big Bella) has eloquently summed up why many of us use coffee in as concise a description as I could imagine, and he has done so in numerous posts over the years. Regarding my experience with this form of supplemental nutrients, I do notice improved growth in certain plants, whether some species simply metabolize these compounds more effectively, appreciate the acidity, or perhaps are benefiting because of the media they're in - I'm not entirely sure. I have noticed that species found naturally in serpentine soils benefit conspicuously more from this than others, but again, I'm not sure why, and perhaps the results won't be the same for others who follow suit.

    As a note for new growers who are curious about trying this nutrient regimen, I will say that it doesn't harm the plants, which is something that can occur when inexperienced growers decide to "experiment" with synthetic fertilizers. But as with any nutrients introduced into a contained substrate, flushing is always recommended to improve airflow and reduce growth of unwelcome guests. This applies to both coffee and synthetic fertilizers.

    I'll probably continue to use both synthetic fertilizer (Grow More urea-free or Maxsea all purpose) and coffee for the foreseeable future, but I don't put too much stock into it these days. There are factors in the environment that I have more trouble maintaining than nutrients, such as temperature, root space, light, humidity, pests, etc.. All of which have profound effects on the health and growth rate of these plants. It's often recommended that you should only supplement nutrients once your plants are already healthy, as you will be able to gauge how much, or how little, is needed (as Butch (Av8tor) touched upon above). In addition, these application rates further depend on factors such as temperature, light, media, moisture,, CO2 availability, etc., which are all limiting factors in almost the same way nutrients are limiting factors.

    A pretty good rule of thumb for those "new" growers reading this now or years from now: Make sure your thumb is green before you purport to have one.

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    Whimgrinder's Avatar
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    Quote Originally Posted by mato View Post
    A pretty good rule of thumb for those "new" growers reading this now or years from now: Make sure your thumb is green before you purport to have one.
    Hear hear. And learn to walk before you run, etc.

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