permaculture

[venaurafarm <venaurafarm@bellsouth.net>]

Greensand, azomite and limited quantities of wood ashes are perfectly 
good supplements supplying potassium and trace minerals. If you need to 
alter pH there are several options:
Raise pH:
dolomitic limestone
hi calcium limestone
aragonite
ground shell meal (sold as  poultry calcium supplement)
Lower pH:
wettable sulphur (sold as an ornamental shrub fungicide in garden 
centers and sometimes available in large quantities from ag supply 
stores used for other purposes
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Start with the assumption that you can render your garden soil incapable 
of growing crops if you put too much ash on too often.
You need to keep a log of how much and when. It may take quite a lot to 
have that effect but I would err on the side of caution.
An uneducated guess would be for a 4' by 30' raised bed no more than one 
1# coffee can full, dry, loose/unpacked per month, 2 at the most.
You can get the same effect with Greensand and probably Azonite if you 
use too much.
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http://apps.rhs.org.uk/advicesearch/Profile.aspx?pid=621

"Only add wood ash to the compost heap occasionally (every 15cm/6in of 
material), as heavier use risks high levels of alkalinity and soluble 
salts which could damage plants and soil.

If applying wood ash directly to soils, do this in winter and rake or 
dig it in. This will allow the compounds in the ash which could scorch 
plants to react with the moist soil and be rendered harmless before 
spring sowing or planting.

Where wood ash is applied frequently, it is worthwhile to use a pH test 
kit to monitor changes in pH and prevent levels rising over pH7.5
Wood ash may be especially useful in vegetable gardens where club root 
of brassicas is a problem

Never leave wood ash in the rain, as the potassium (a useful plant 
nutrient for flowers and fruit) is in a soluble form and is easily 
leached out

Ash produced from young sappy prunings contains a useful proportion of 
potassium and traces of other nutrients, while older wood tends to 
contain lower concentrations of nutrients.

Avoid using wood ash on areas where potatoes are to be grown the 
following spring, as the alkaline conditions can encourage potato scab."
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http://www.hort.purdue.edu/ext/woodash.html
Wood Ash in the Garden
Released 16 November 2000
by B. Rosie Lerner, Extension Consumer Horticulture Specialist

"Wood stoves and fireplaces are great for warming gardeners' chilly 
hands and feet, but what are we to do with the resulting ashes? Many 
gardening books advise throwing these ashes in the garden.

Wood ash does have fertilizer value, the amount varying somewhat with 
the species of wood being used. Generally, wood ash contains less than 
10 percent potash, 1 percent phosphate and trace amounts of 
micro-nutrients such as iron, manganese, boron, copper and zinc. Trace 
amounts of heavy metals such as lead, cadmium, nickel and chromium also 
may be present. Wood ash does not contain nitrogen.

The largest component of wood ash (about 25 percent) is calcium 
carbonate, a common liming material that increases soil alkalinity. Wood 
ash has a very fine particle size, so it reacts rapidly and completely 
in the soil. Although small amounts of nutrients are applied with wood 
ash, the main effect is that of a liming agent.

Increasing the alkalinity of the soil does affect plant nutrition. 
Nutrients are most readily available to plants when the soil is slightly 
acidic. As soil alkalinity increases and the pH rises above 7.0, 
nutrients such as phosphorus, iron, boron, manganese, copper, zinc and 
potassium become chemically tied to the soil and less available for 
plant use.

Applying small amounts of wood ash to most soils will not adversely 
affect your garden crops, and the ash does help replenish some 
nutrients. But because wood ash increases soil pH, adding large amounts 
can do more harm than good. Keep in mind that wood ash that has been 
exposed to the weather, particularly rainfall, has lost a lot of its 
potency, including nutrients.

Specific recommendations for the use of wood ash in the garden are 
difficult to make because soil composition and reaction varies from 
garden to garden. Acidic soils (pH less than 5.5) will likely be 
improved by wood ash addition. Soils that are slightly acidic (pH 6.0 to 
6.5) should not be harmed by the application of 20 pounds per 100 square 
feet annually, if the ash is worked into the soil about 6 inches or so. 
However, if your soil is neutral or alkaline (pH 7.0 or greater), find 
another way to dispose of wood ash. If you don't know your soil's 
acidity or alkalinity level, have it tested for pH.

Crop tolerance to alkaline soil also should be considered. Some plants, 
such as asparagus and juniper, are more tolerant of slightly alkaline 
conditions than "acid-loving" plants, such as potatoes, rhododendrons 
and blueberries. Wood ash should never be used on acid-loving plants."