Wood Ash: Is It Good For Your Garden?

Gardeners all around are wondering what is the best thing for their garden. Like if coffee grounds are good for their plants or not? The questions keep coming all the time. One of the significant challenges of crop production on highly weathered soils throughout the world is acid soils‘ infertility. These acid soilsmajor attributes are their low pH, low levels of natural matter, Ca, Mg, P, or Mo shortage, Al or Mn toxicity and very low mineralization. Wood ash (fireplace ash) is a possible source of nutrients, trace elements, and lime. It can be used as an additive to fertilizer, and its addition to natural wastes before the process of composting is known to improve the quality.

An amount of wood ashes ready to be used for gardening

Several alternative uses have been developed. Land application is considered one of the best because nutrients taken from the land throughout harvest are recycled back to the land. It has often been used as a soil amendment in gardens and as a cleaning agent for having a tidy shiny pan at home. In recent years, garden enthusiasts have been given mixed signals about the safety and value of using ash on their garden soil.

Is it safe to use in the garden? You may wonder if it will have a positive or negative impact, and how it will affect your garden. Read on to learn more! 

What are the benefits of using wood ash in your garden?

A garden is a unique space reserved for the cultivation, display or enjoyment of plants and other forms of nature, as a perfect setting for a solitary human life. One of the common misconceptions for most first-time gardeners is that they believe all they require for a garden is a few plants and some soil. While this could be loosely considered to be correct, having a garden is much more than that. Gardens and gardening can be elaborate or as simple as you choose to make them, so it is an excellent idea to start a garden that fits your way of life and your peculiar needs. Here are some of the most important benefits that ash has:

1. Wood ash is beneficial to the soil

It can be a great source of potassium. To a lesser degree, it also offers some phosphorus, a little aluminium, magnesium, salt, and a couple of micro-nutrients, such as boron, copper, molybdenum, sulfur, and zinc. The amount of nutrients in the  ash is not necessarily high, and it mostly depends on the kind of wood burned. However, if your soil has a potassium deficiency, ashes can be a desirable soil amendment.

A man having soil in the palm of his hand

2. Benefits for soil pH

It mostly contains a high percentage of calcium carbonate, an ingredient present in garden lime. If you have acidic soil (5.5 or lower), your soil pH can be increased when you amend with ash. On the other hand, if your soil is neutral or alkaline, applying ash could raise the pH high enough to affect the plant’s ability to take in nutrients negatively. Wood ash needs to be avoided around acid-loving plants like rhododendrons and blueberries

Vegetables grow best in soil with a pH of 6.5, so a soil test about the pH before adding the compost is recommended in order not to raise the pH excessively (greater than pH7.0). Where club-root is present, wood ash can be used to raise the pH to as much as 7.5 to hinder this disease.

The response to that concern comes down to: What is your soil pH? Soils within the pH range of 6.0 to 7.0 are considered to be ideal for the majority of garden plants. Always remember that some plants prefer garden soil with a lower pH  (acidic) while other plants grow better in soil with more pH (alkaline).

3. Wood ash can be used as fertilizer in vegetable gardens

It is a vital source of potassium (potash) and lime for your soil. Not just that, the use of it in the garden also offers much of the trace elements that plants require to survive. However, this fertilizer is best used either gently scattered, or by first being mixed together with the rest of your compost. This is simply because it can produce salts and lye if it gets wet. In small quantities, the salt and lye will not cause any problems, but in larger amounts, they can burn your plants.

Composting ashes enables the salt and lye to be leached away. Not all ash fertilizers are equal. The type of wood plays an essential role. If the ashes in your compost pile are derived from hardwoods, like oak and maple, the minerals and nutrients in yours will be higher. If the ones in your compost are made primarily by burning softwoods like pine or firs, there will be fewer nutrients and minerals.

A vegetable garden that flourishes

4. The use of wood ash as pest control

It is also beneficial to garden plants as pest control. The salt content in the ash has the capacity to kill annoying pests like slugs, snails, and some other soft-bodied invertebrates. To effectively use it for pest control, simply spray it around the base of plants that are being attacked. If the ash gets wet, you will have to re-apply it as the water will take away the salt that is vital for pest control.

Instructions for wood ash use

It is comparable to lime which also increases pH. However, unlike lime, which can take six months or more to change the pH, wood ash is water-soluble and can amend it rapidly. It is advisable to apply approximately twice as much ash by weight as the recommendation for lime. Here are some things that you need to know while using ash:

  • Garden soils, which are already in the optimal pH range of 6.0 to 7.0,  have the capacity to handle up to 10kgs or 20 litres pail of hardwood ashes per 90 square metres yearly without raising the pH too much. Do not use more than that, as high rates of wood ashes might trigger short-term salt injury. When adding ash to your soil, be cautious.
  • Broadcast it evenly on a dry day without wind. Mix it properly with the soil before planting. You would need to wear gloves, a dust mask, and eye protection as safety measures.
  • Apply it in percentages to the compost heap so that it will mix well with other by-products. As a general rule, you shouldn’t be able to identify it after thorough mixing with the compost heap.
  • It is advisable to sieve the ash before usage to properly eliminate unwanted particles. Avoid breathing in the dust generated in this process by using face protection and limit direct exposure to your skin by wearing gloves, boots and work clothing.
  • Where it is applied regularly, it is beneficial to make use of a pH test kit to monitor changes in the pH and prevent it from rising above 7.5.
  • Never leave it in the rain as the potassium or potash can easily be leached out.
  • Limit the usage to a level that preserves the pH within the optimum range for the desired crop. The liming potential of ash is usually calculated using a laboratory-measured specification called the calcium carbonate or lime equivalent (CCE). The CCE gives information on how it will raise the pH compared to lime.
  • During the process of applying it to the soil, take special care to prevent the ash from entering any ground or surface water. You need to keep it away from any farm ditches, wells, or other sources of water
  • Ash can be spread out with a standard manure spreader or with lime application tools. It can be incorporated or top dressed. To derive the full benefit, it is better to incorporate the ash throughout the root zone whenever possible because the benefits usually occur where the ash and soil touch.
  • The fall is normally the best time for application. Applications at this time give the ash enough time to respond to the soil before fast spring growth. Soils are also generally drier and more accessible at this period.

Some wooden ashes laying on the ground 

Where wood ash should not be used

  • Wood ash, being alkaline, isn’t an ideal addition if your soil already contains a pH level of 7.5 or more. There’s no point in applying it around acid-loving plants such as blueberries. It is also not recommended for areas where you plan to grow potatoes as increased alkalinity can support the existence of potato scab, which is a fungus.
  • If you pile a large quantity of ash in one area, you run the risk of over-liming that area and damaging nearby plants.
  • Do not use it in areas with water on the soil surface. When large storms are anticipated, you should avoid applications shortly before periods of prolonged rainfall.

Can wood ash become harmful to your garden?

It has the tendency of becoming a source of heavy metals such as cadmium, lead, or chromium, which you do not necessarily want in your garden. However, there are no research findings showing that the heavy metals will not be taken in by the plants in measurable quantities if the pH level is above 6.0.

Since it often increases the pH, the existence of some heavy metals ordinarily shouldn’t be a serious problem. Do you have a steady source of wood ash and are worried about the extended application of it in your garden? You really need to consider taking it for a laboratory test. The point being made is that a percentage will include some nutrients and be advantageous to many soils. Large amounts ought to be avoided.

A plant flourishes in a garden

The process of applying wood ash is similar to the application of lime. Both procedures can enhance crop productivity, but this one provides additional nutrients. If misused or over-applied, it might trigger crop damage because it is also alkaline (without high acidity). Garden owners should comply with the recommended application rates.

Always ensure you use vigilance in managing and dealing with the ashes. They should be properly stored in a covered metal container set on the soil or concrete a few feet away from any combustible surface. Remember that even though ashes appear cold, buried embers, they remain active for days, even weeks.

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