THE USE OF WOOD ASHES FOR MANURIAL 

 PURPOSES. 



By Arthur Stead, B.Sc, F.C.S. 



In using wood ashes as a source of potash it is necessary to 

 consider the climate. In moister climates, a thorough incorpora- 

 tion with the soil is all that is necessary, but in dry climates like 

 that of Bloemfontein and other parts of South Africa, special 

 precautions must be taken to prevent harmful effects. The fact 

 is that potash salts are " brack " salts, and any addition of them 

 to the soil results in an increase of the amount of " brack." 

 There are several kinds of brack salts ; but the commonest are 

 sulphates, chlorides, and carbonates of soda and potash. Of 

 these the sulphates are the least harmful, while the carbonates 

 are very injurious. Now wood ashes contain a large percentage 

 of carbonate of soda and potash (i.e., Ganna Bosch ash contains 

 about 40 per cent, of these substances), therefore in applying 

 wood ashes as manure the farmer must always remember that he 

 is adding excessively injurious substances to his soil. The car- 

 bonates of soda and potash injure the bark tissue and some- 

 times destroy it altogether. Such a plant, if pulled up, will be 

 found to have a dark ring of varying width rounid its stem, 

 usually just below the surface of the soil. This dark ring is 

 easily rubbed away, because the alkali has softened it. The 

 plant is, in a word, ring-barked, which is one reason why it dies. 

 Carbonates of soda and potash are also able to prevent the ger- 

 mination of seeds. Seeds are also softened and destroyed just 

 in the same manner as the bark of the plant is. Lucerne seeds, 

 and also the young plants, are very liable to destruction if any 

 appreciable quantity of these compounds is present in the soil. 

 The drier the weather, the nearer the surface and the more con- 

 centrated will these compounds be, and the more destruction will 

 they cause. These same carbonates, of soda and potash also 

 prevent the growth of certain soil organisms which are necessary 

 for abundant growth. Among these organisms are the inhabi- 

 tants of the tiny nodules to be found on the roots of peas, beans, 

 lucerne, sainfoin, etc. These organisms obtain nitrogen for the 

 plant from the air. If therefore their growth is prevented the 

 plant suffers. Again, very small quantities of these carbonates 

 of. soda and potash have a bad effect on the texture of the soil. 

 They tend to puddle it. Now a completely puddled soil will let 

 neither water nor air pass. If, now, one portion of a field is 

 dressed with ashes and another not, that which is not treated 

 will remain more open than the other, and air and water will 

 therefore pass through it more easily. 



This may be what is causing the trouble with lucerne patches 

 that have been treated with ashes. On that portion where the 



