The wood ash is an excellent organic fertilizer to use in your organic garden. Those living in the countryside or simply having a wood stove or fireplace often have large quantities at their disposal. Using it as fertilizer in the garden makes disposal easy while nourishing the soil and crops simultaneously. However, it’s crucial to know precisely how wood ash affects the soil and plants. Understanding these details will enable you to use it correctly. A common question among gardening enthusiasts is whether it’s safe to use in the garden.
As with most agricultural questions, the answer is “it depends.” Before using it, it’s essential to understand the characteristics of your soil. Additionally, you need to know which plants you’re growing and the content of the ash itself. Let’s clarify further.
Which Wood Ash to Use in Your Garden
The wood ash you want to use in your garden is nothing more than the solid residue from wood combustion. It has a very fine powdery texture, with shades of gray.
The best wood ash for your garden comes from pruning trees and hedges, as well as from stove and fireplace residues. For domestic heating, people typically use wood from trees like oak, beech, fir, pine, poplar, chestnut, and acacia. In pruning, olive and laurel trees are known for producing significant amounts of waste.
Using this type of wood ash in your garden serves two purposes. It solves the disposal problem and allows you to fertilize the soil with the natural elements found in the plants themselves, closing an eco-friendly cycle. It’s a similar principle to compost: what you consume returns to nature in a different form.
Elements Found in Wood Ash
Wood ash contains four main elements, which are:
- Calcium, ranging from 25 to 40%
- Potassium, from 5 to 30%
- Phosphorus, from 1.3 to 20%
- Magnesium, from 1.3 to 16%
These substances are beneficial for most plants, ensuring healthy and balanced growth. For example, phosphorus is essential during the flowering periods, while potassium greatly aids in fruit ripening.
The nourishment wood ash provides to the soil is not complete because it lacks nitrogen, but it contains a significant amount of calcium. The other elements (potassium, phosphorus, and magnesium) are mineral salts gradually made available by the slow degradation of ash. This allows plant roots to absorb nutrients at the right time.
In an organic cultivator’s garden, the lack of nitrogen in wood ash can be compensated for with home compost, mature manure, or earthworm humus (the latter can be purchased here).
Nitrogen is a crucial element for vegetative growth, and common vegetables like tomatoes, eggplants, peppers, and zucchinis suffer when it’s lacking.
Effects of Ash on Soil and Plants
Previously, we discussed the various soil types and their structures. Another essential factor to consider in evaluating your field is the chemical reaction, in essence, measuring the pH to understand whether you have acidic, neutral, or alkaline soil.
Most horticultural and fruit species thrive in neutral to slightly alkaline soils (pH between 6.6 and 7.8). Wood ash, as a primary component, adds calcium, which has a basic effect on the soil, increasing its alkalinity.
So, if you have slightly acidic soil, using ash for fertilization is advantageous, and you can use higher doses. However, if your soil is already chalky, alkaline, and compact, using ash can create unfavorable conditions for plants.
Ash should be avoided, especially if you grow acid-loving plants, which prefer acidic soils (pH below 5.5). Here’s a list of the main acidophilic plants and trees:
- Azalea
- Camellia
- Strawberry Tree
- Heather
- Gardenia
- Magnolia
- Mimosa
- Blueberry
- Hydrangeas
- Rhododendrons
- White Fir
- Red Fir
- Japanese Maple
- Birch
- Chestnut
- Beech
How to Apply Wood Ash to Soil
Wood ash is produced and used in the garden during winter. It’s excellent for preparing resting soils before spring and summer crops. You can distribute it evenly on the ground as you collect it, allowing it to rest and dissolve. During spring land cultivation, it will be incorporated, nourishing plant roots.
In practice, if there’s a lot of pruning material to dispose of, make piles and burn them where you know you need fertilizer. Check local burning legislation, and always work safely to avoid harm to people or property.
If you have fruit trees, hedges, or roses, you can use ash by sprinkling it near the main trunk and all around. In this case, it’s beneficial to mix the ash with the soil through light hoeing.
The recommended dosages not to exceed are 25 kg per 100 sqm of land, approximately 200/300 g per sqm. To fertilize winter crop soil, it’s useful to spread some ash before earthing up. This is done for crops such as cauliflower, broccoli, savoy cabbage, and cabbage.
According to the European directive, the use of ash as a fertilizer is allowed in organic farming (Reg. Cee 2092/91). However, the ash must come from “wood not chemically treated after felling.” Let’s see what this implies.
Ashes Not to Use
Not only European directive but also common sense suggests not using ash from chemically treated wood. Paints, adhesives, plastic materials, etc., are toxic substances for our soil, and thus, they should be avoided.
Certainly, the ash from fossil carbon should not be used, as it contains heavy metals that can damage plants. Moreover, these metals can persist in the substrate for a long time.
Some argue that charcoal residues, for example, after a barbecue, can be used. We do not recommend it. Many also wonder if it’s possible to use ash from pellet stoves. These stoves are prevalent in domestic settings and are gradually replacing the traditional fireplace. Pellets are a commercial product derived from wood sawdust. They undergo various industrial processes that theoretically do not involve the use of chemicals. However, we do not recommend using them in the garden. Observationally, pellet ash is almost black and very fine, and it doesn’t give the same clean feeling as wood ash. The almost pristine gray of the latter, in our opinion, is preferable to the almost black coloration of pellet ash.
Other Uses of Wood Ash
In rural life, ash has always accompanied farmers and housewives. Lye, for instance, is a well-known soap made easily from wood ash. This soap was used in the past for laundry and more. Ash can also play an anti-parasitic role in the soil, as seen in the biological defense against snails. It can be used in domestic compost, helping to eliminate bad odors from compost bins. It’s often used in manure piles because it absorbs manure moisture, promotes organic mass ventilation, and improves fermentation. The ash and manure mix is perfect for natural fertilization, being complete in all the main nutrient elements.
