Wood ash as fertilizer

Wood Ash - a useful Agriculture input.   (Sri Lanka visit March 2013)

1. Sri Lankan plantations are generating a lot of wood ash as the stoves & boilers are fuelled by wood. This wood ash is generally being disposed in landfills or dumped into unplanted valleys. For plantations & the environment these are not good options.
2. For a long time wood ash has been used in agricultural soil applications as it recycles nutrients back to the land. Wood ash has value as a fertilizer (other than Nitrogen). Because of the presence of calcium carbonate it acts as a liming agent and will de-acidify the soil increasing its pH.
3. Wood ash has a high char content is effective as an odour control agent, especially in composting operations.
4. Typically between 0.43 and 1.82 % of the mass of burned wood (dry basis) results in ash.  Also the conditions of the combustion affect the composition and amount of the residue ash, thus higher temperature will reduce ash yield.
5. Wood ash (WA) contains:
1. calcium carbonate as its major component, representing 25 or even 45%. 
2. Less than 10 % potash,
3. less than 1 % phosphate
4. there are trace elements of iron, manganese, zinc, copper and some heavy metals 
5. However these numbers vary as combustion temperature is an important variable in determining wood ash composition. All of these are, primarily, in the form of oxides.
6. Uses:
1. Wood ashes contain potassium, calcium, phosphorus and magnesium which encourage strong root and stem growth.
2. It is water soluble & so quickly increases the soil’s alkalinity.  It’s a good substitute for garden lime / Dolomite.
3. Application rates must be determined by the pH of the soil. If pH is less than4 then 50% K can be applied as WA. If between 4 and 4.4 then 30% of the K, if between 4.4 & 4.5 then 10% of ‘K’ can be applied. However, it is best to try this out on a few sections to see how much it is affecting the pH in the particular estate’s soil.
7. How to use:
1. Broadcast evenly on the soil & then take a rake and fork it in lightly. Keep it away from the collar region of young plants. Break down any clumps since a heavy concentration will result in a potentially harmful salt spot once it gets wet.
2. Apply when the soil is dry, it’s not windy (and at least 3 weeks before planting out Young Tea). You can also add them to the compost pile (about every 6″ or so), this helps reduce odours and increase the rate of decomposition.
3. Those from hardwoods contain more nutrients than found in softwoods. Also those from young wood contain more nutrients than those from older wood. It is best to analyse these different types of wood ash to determine the nutrient contents.
4. Store WA under a shed and sealed in airtight bags. If the ash gets wet in the rain the nutrients will seep out with the water (which is fine when they’ve already been applied to the soil but not before). In inorganic estates it can be packed in old fertilizer bags & sealed.
5. PPE : Wear eye protection, a mask, shoes and gloves when handling, since it can be harmful if you breathe it in or it gets in your eyes.
6. It is also a natural pest repellent.  Bugs such as garden slugs and snails aren’t fond of scraping their bellies across the ashes so they’ll move on to find more friendlier ground.

In Organic agriculture we use a lot of Wood Ash & Urine (normally cow urine) but here is some more on human urine. There was an article on BBC website in 2011 on how human urine helps in quickly decomposing compost heaps and adding nutrition to it. Of course, we as RA can NOT recommend this, but I thought I will append this for information ONLY.

Harki Sidhu 

Just for Info:

Sustainable Fertilizer: Urine And Wood Ash Produce Large Harvest

Sep. 17, 2009 — Results of the first study evaluating the use of human urine mixed with wood ash as a fertilizer for food crops has found that the combination can be substituted for costly synthetic fertilizers to produce bumper crops of tomatoes without introducing any risk of disease for consumers.

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In the study, Surendra Pradhan and colleagues point out that urine, a good source of nitrogen, has been successfully used to fertilize cucumber, corn, cabbage, and other crops. Only a few studies, however, have investigated the use of wood ash, which is rich in minerals and also reduces the acidity of certain soils. Scientists have not reported on the combinaton of urine and wood ash, they say.

The new study found that plants fertilized with urine produced four times more tomatoes than nonfertilized plants and as much as plants given synthetic fertilizer. Urine plus wood ash produced almost as great a yield, with the added benefit of reducing the acidity of acid soils. "The results suggest that urine with or without wood ash can be used as a substitute for mineral fertilizer to increase the yields of tomato without posing any microbial or chemical risks," the report says.

Potash (/ˈpɒtæʃ/) is the common name for various mined and manufactured salts that contain potassium in water-soluble form.^[1]The name derives from "pot ash", which refers to plant ashes soaked in water in a pot, the primary means of manufacturing the product before the industrial era.

Today, potash is produced worldwide at amounts exceeding 30 million tonnes per year, mostly for use in fertilizers. Various types of fertilizer-potash thus comprise the single largest global industrial use of the element potassium. Potassium derives its name from potash, and was first derived by electrolysis of caustic potash, in 1808

Terminology

Potash refers to potassium compounds and potassium-bearing materials, the most common being potassium chloride (KCl). The term "potash" comes from the Old Dutchword potaschen. The old method of making potassium carbonate (K₂CO₃) was by leaching of wood ashes and then evaporating the resulting solution in large iron pots, leaving a white residue called "pot ash". Approximately 10% by weight of common wood ash can be recovered as pot ash.^[2][3] Later, "potash" became the term widely applied to naturally occurring potassium salts and the commercial product derived from them.^[4]

The following table lists a number of potassium compounds which use the word potash in their traditional names: