CHAP. II. POTASH MANURES. 



used for feeding purposes. This kind of cake is generally ground up 

 and sold as "rape-dust" for manurial purposes. It yields, on 

 decomposition, from 5 to 6 per cent, of ammonia, and also contains 

 3 or 4 per cent, of phosphate of lime. It may be used on all crops, 

 but resembles other organic nitrogenous manures in its slowness of 

 action; it is therefore unsuitable for a top-dressing and should 

 generally be applied in autumn, in quantities ranging from a few cwt. 

 to | ton per acre. It is much used for hops, and is also generally 

 regarded as a preventive of wire-worm. It probably acts by affording 

 a palatable food on which this pest feeds instead of on the young 

 growing crop, which is thus indirectly protected. 



SOOT. Soot is a manure much valued for top-dressing wheat. Its 

 efficacy is entirely due to the sulphate of ammonia that it contains. 

 The percentage of ammonia in it commonly ranges from about 2 to 5, 

 and is determined mainly by the degree to which the actual soot itself 

 is mixed with ashes, chimney-mortar, &c. 



POTASH MANURES. Potash in former years was a comparatively 

 rare and expensive commercial article, being made mainly from the 

 ashes of plants. For a long time past, however, a plentiful supply has 

 existed in the mineral potash salts raised from mines in Germany. 

 The potash salt most familiar to the farmer is the compound salt 

 known as kainit, which contains about 23 per cent, of sulphate of 

 potash. More concentrated forms of sulphate of potash, and also 

 muriate of potash (chloride of potassium), are likewise sold for manure, 

 and numerous experiments have shown that either is more effective for 

 some crops than kainit in quantity sufficient to afford an equal amount 

 of potash. 



While phosphatic and nitrogenous manures tell on practically all 

 soils, potash is much less certain in its action. Heavy land is generally 

 independent of artificially applied potash, though clays are sometimes 

 found in which potash is deficient. It is usually on light land, however, 

 that potash salts are most effective. As an example we may mention 

 that on some of the light Norfolk soils potash acts on almost all crops, 

 affecting their yield very largely. On peaty land, too, as on the reclaimed 

 boglands of Ireland, potash is very generally found, when tried, to be 

 beneficial. For potatoes potash in artificial manure usually pays well, 

 with other manures, on all classes of soil, particularly when no farm- 

 yard manure is used. 



SALT. Chloride of sodium, or common salt, is a material which has 

 been for many years recognised as a useful manure, though we are 

 still in the dark as to the precise mode in which it acts. Sodium, 

 though always present in plants, is not an essential ingredient of their 

 food, nor is chlorine, the other element of which salt is made up. 

 Furthermore the soil always contains a supply of sodium, and a 

 good deal is applied year by year in farmyard manure, while the rain 



