Many organic waste can be used in the garden as valuable fertilizer. It therefore makes sense to use coffee grounds or the ash that is produced anyway as inexpensive fertilizer. But is this advisable and how does the plant tolerate these substances?
Can coffee grounds and wood ash be used as fertilizer?
Coffee grounds and wood ash serve as fertilizer in the garden, with coffee grounds providing plants with nitrogen and preferring a slightly acidic environment, while wood ash supports lime-tolerant plants and improves acidic soil. However, both should be used sparingly and in addition to other fertilizers.
Fertilizing with ash
The fine powder is very easy to make yourself, because ash is a residual product when natural wood is burned. It is important that you know exactly the origin of the fuel, as depending on the source it can be heavily contaminated with pollutants.
Substances in wood that are hazardous to he alth, such as varnishes or glazes, also accumulate when burned and, if you then use the ash as fertilizer, can even poison the soil. Grill ash is also unsuitable as it contains degradation products such as acrylamide.
In the following table you will find the ingredients of pure wood ash:
| Ingredient in percent | Quantity |
|---|---|
| 25 – 45 | Blastlime |
| 3 – 6 | Magnesium oxide |
| 3 – 6 | Potassium oxide |
| 2 – 6 | Phosphorus pentoxide |
| different quantities | Trace elements such as iron, manganese, boron, sodium |
This shows one of the main problems that arises when fertilizing with ash: The fine powder is a surprise bag that you never know exactly how many nutrients it contains. Ash is therefore primarily used to improve acidic soil. You can also fertilize some plants that are lime-tolerant sparingly with ash:
- Choose a day with no wind so that the white powder is not accidentally spread throughout the garden.
- Wear gloves to protect your skin.
- For one square meter of soil, 100 to 400 g of ash is sufficient, depending on the pH value.
Coffee grounds as fertilizer
Coffee grounds are a good fertilizer for all plants that prefer a moderately acidic to neutral soil environment:
- It supplies the plants with plenty of nitrogen, which leads to improved growth of leaves and shoots.
- Prepare the coffee grounds and let them dry well, as the wet powder quickly begins to mold.
- Coffee grounds that you simply sprinkle on the bed have no fertilizing effect. To do this, it must first be worked into the soil and decomposed by microorganisms and earthworms.
- Coffee grounds are well suited to fertilizing grasses, as they prefer a slightly acidic environment. The same applies here: spread dry and incorporate well.
Tip
Coffee grounds and wood ash should always be used carefully. In contrast to purchased, organic fertilizers, you do not know the exact composition and do not have as good a handle on the effect of the products. Therefore, dose sparingly and use both products in addition to other fertilizers.
