Coffee grounds as fertiliser for the lawn?

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Question by: Dipl.-Ing. K.

Hello Mr. Kötter! Coffee grounds were once commonly distributed across lawns or worked into flowerbeds. The idea was to simultaneously loosen and fertilise the soil. Now I have heard from an acquaintance that this does not benefit, but rather damages the soil. Before I begin to fertilise my soil with coffee grounds, I would like to know which opinion is correct!

The GARDENA gardening expert

Dear Mr. K., this is an interesting question which once again proves how many half-truths abound, and which uncertainties and nonsensical recommendations result. Don't let yourself be made a fool of!

Basically, coffee grounds are a herbal waste product, which can be used as fertiliser as it can be decomposed by soil fauna into nutrients which plants can then utilise. However, it is not particularly different to any other plant waste.

These also have potential as fertilisers and for soil improvement. However, any compost also improves the structure of the soil. Whether coffee grounds or compost: the question is: How much should I put out? How effectively can you work the respective component into the soil?

Improving the soil structure of a lawn sustainably is certainly more complex than just distributing coffee grounds (the same applies in a flowerbed). So much to the argumentations by those advocating coffee grounds.

As far as the sceptics and opponents of the method are concerned: These refer, when talking of damage related to coffee grounds, to the residual caffeine content in coffee grounds, which might cause damage to soil fauna (after all, caffeine is, similar to nicotine, a neurotoxin).

To say more, we have to know the concentration of the residual caffeine in each particular case. Then we can estimate the suspected effects more reliably.

Snails, for example, are killed by the caffeine in any coffee grounds they eat as soon as the concentration levels rise above 2 percent. Lower concentrations will prove lethal to micro fauna in the soil. However, widely distributed quantities usual for household consumption quantities will, in my opinion, cause no damage to the living garden soil.

So where should we seek a compromise between the two sides to this argument? Add the coffee grounds in thin, widely-distributed layers onto your compost. In this way, you can utilise the fertilising effect of the brown powder without putting any of your garden soil micro fauna at risk. All you then need to do is to use the compost in your garden correctly