Advantages & disadvantages and tips for use

the essentials in brief

• Ash contains lime, potassium, iron and phosphate and is very basic with a pH of 11 to 13.
• Ash fertilizer is mainly used for liming acidic soils.
• Only ashes from pure wood without heavy metals should be used, i.e. wood whose origin you know. Ashes from charcoal, brown or hard coal and briquettes should not be used as fertilizer.
• If there is a potassium deficiency, some plants can tolerate fertilization with pure ash.

Is ash suitable as a fertilizer?

Ash is a natural fertilizer that is easy to make. Any hobby gardener can make it with a wood-burning stove or a fireplace. Ash is rich in lime and potassium. It also contains iron and phosphate, which are essential for healthy and vigorous plant growth. Ash fertilizer is mainly used for liming over-acidic soils. Since ash with a pH value between 11.0 and 13.0 has a strongly basic effect, it should not be used without restrictions for all plants.

Wood ash contains:

• 25 to 45 percent quicklime (calcium oxide)
• three to six percent magnesium and potassium oxide
• two to six percent phosphorus pentoxide
• mineral trace elements (iron, manganese, boron and sodium)

What ashes can I use?

Not all ashes should go to Fertilize of the plants are used. Fireplace ash made of wood or burned charcoal is suitable, but here too you should know exactly where the wood comes from. Both hardwood and softwood are processed into charcoal. This can be loaded differently depending on the source.

Digression

Charcoal

This is what you should pay attention to

When additives are burned in the wood, harmful substances can develop and remain in the ashes, which poison the soil. It can contain dioxin or other toxic substances. If the wood comes from an industrial region or from the vicinity of a motorway, it can be contaminated with heavy metals.

How to make perfect wood ash:

• Burn untreated and natural wood
• Wood without paintwork and Glazes(€ 65.00 at Amazon *) to use
• use dry branches, leaves or nutshells for lighting

Do not use brightly printed newspaper for lighting, as these contain chemical substances and can contaminate the ashes. Even black and white newspaper, egg boxes or toilet paper rolls should not be used. The material is often made from recycled paper, which can be contaminated with mineral oil components from colorful brochures. Also, be careful not to mix wood ash with ashes from coal.

Unsuitable ashes

Ashes from coal briquettes should not be used as fertilizer

Depending on the origin of the wood, the ash can contain heavy metals which are harmful to health and which also poison the soil and plants. Lead, cadmium or chromium can often be detected in critical concentrations. Ash made from lignite, hard coal or coal briquettes is also unsuitable as a natural fertilizer because of its heavy metal load.

Heavy metals are naturally present in wood because the tree absorbs substances from the environment as it grows. The toxic metals also come from tool wear during production by logging machines.

To be on the safe side, you should dispose of the residues of burnt charcoal in the household waste, because the origin is often unknown here. In addition, ashes from the grill contain grease residues that were created during burning. Decomposition products such as acrylamide are harmful to health and have lost just as little in the soil as cigarette ash.

Where can I use ash fertilizer?

If you can make sure that your ashes are clean, there are many uses of the natural product in the garden. It improves the lawn and can be spread in beds and under bushes. You also benefit from positive side effects.

This causes an ash fertilization:

• removes moss and algae growth
• causes root weeds to die off
• disinfects open wounds

Which plants tolerate ash?

Ash prevents potassium deficiency. In small quantities, you can fertilize various plants with pure ash. The particles are washed into the ground by rain and dissolve within a short time. This means that the substances are quickly available to the plants. Bog bed plants and plants that prefer acidic soil should not be provided with ash.

Particularly suitable plants:

• Vegetable garden: Tomatoes, Brussels sprouts, leeks
• Perennials and shrubs: Roses, Gladiolus, Phlox
• Flower beds: Geraniums, Fuchsias
• Fruit trees: Grapevines, gooseberries, raspberries
• Houseplants: all lime-tolerant crops

Fruit trees enjoy a good portion of ash

In the forest

If you have your own forest, you will appreciate the high lime content of wood ash. The majority of all German forest soils are too acidic. In a well-dosed concentration, wood ash can contribute to improving the soil in the long term. As a result, the trees can take root more deeply, which increases their stability.

Advantages of ash fertilization:

• Extension of the growing season for deciduous trees
• reduced needling in conifers
• increased fine root formation in the topsoil

Ash fertilization problems

If ash is applied in too high concentrations or in unfavorable weather, it can have negative consequences. These affect both soil life and plants. Incorrect fertilization can cause great damage, so ash should be used in low concentrations.

Plant damage

The high content of calcium, which is present as quicklime in its most aggressive form, ensures that the soil is limed. This highly alkaline quicklime can cause leaf burns if residues are left on the plants. In agriculture, calcium oxide is only distributed on ungrown areas that have a loamy to clay subsoil.

Lucky bag

Another problem is the often unknown composition of the various substances in wood ash. The proportion of minerals, like the heavy metal content, can fluctuate greatly. Without a precise analysis of the ash, fertilization tailored to the soil is not possible. You run the risk of the earth being enriched with toxic substances rather than improved.

Soil damage

If quicklime is distributed on light sandy soils, it can cause massive damage to soil life due to its low buffer capacity. Non-solidified wood ash dissolves particularly quickly if after spreading Rainfall appear. This can change the soil chemistry, so that the plants growing there can no longer absorb nutrients for a short time. Their growth stagnates and sensitive plants can die. In order to reduce the solubility and to better control the changes in the pH value in the soil, the ash should be pelleted before application.

Have the ashes tested

If you want to be on the safe side, you can have your ashes analyzed in a laboratory. There are quantitative tests that check the ash for ten to twelve common heavy metals. Ten grams of wood ash are sufficient for a precise analysis.

If you burn different tree species, you can send in the ashes as a mixed sample. However, it is then not possible to assign the ingredients to the respective ash. If you send in several samples, you must expect higher costs. A test costs between 100 and 150 euros, depending on the laboratory.

frequently asked Questions

Is ash suitable for plants that prefer acidic soils?

Ash increases the pH of the soil and should only be used for plants that prefer calcareous soils. Hydrangeas, Ferns, rhododendrons or peonies like a more acidic humus soil, which is why ash is not suitable as a fertilizer. Instead, you can fertilize these plants with coffee grounds.

How do I fertilize with ashes?

Choose a windless day so that the dust-fine ash does not spread in the garden. To be on the safe side, you can moisten the ashes a little. The high pH can damage the skin so you should wear gloves. After the application, the soil is watered. Ash should never be mixed with ammonium-containing fertilizers such as manure or liquid manure, as gaseous ammonia can be formed. Also, do not mix ash with phosphate. In the process, calcium phosphates that are difficult to dissolve and are not available to plants can develop.

How much ash should I use for fertilizing?

For liming and soil improvement, you can fertilize soils with ash every three to four years. For heavy soils with a pH value of 4.0, 200 to 400 grams per square meter is sufficient. In less acidic soils, reduce the amount to 100 to 200 grams. Light soils can quickly be limed over and should therefore not be fertilized with ash. Ground eggshells are sufficient here.

Can I put ashes on the compost?

Many microorganisms become more active at high pH. Adding ash can accelerate the decomposition processes on the compost, especially if it is acidic compost material. However, you should only sprinkle the ashes on the compost in small quantities to avoid over-lime-scale build-up. If you are not sure from which source the wood ash comes, you should dispose of it in the household waste because of possible pollution.