Phosphoric Acid Potash. 7 



earth or phosphate of lime. Like ammonia, phosphoric acid 

 occurs in soils but in small quantities, and as it is required 

 abundantly not only for grain and root-crops but for all vegetable 

 produce raised as food for man or beast, the application of phos- 

 phatic manures to nearly all crops is followed with beneficial 

 results. Whilst, however, phosphoric acid benefits more or- 

 less all the crops usually grown on the farm, it promotes the 

 development of bulbous roots, such as turnips, carrots, mangold, 

 &c., in an extraordinary manner. 



3. Potash. This alkali, also, is an important fertilizing con- 

 stituent, inasmuch as it is largely required by all our cultivated 

 plants, and frequently is deficient in soils. Root-crops, and her- 

 baceous plants in particular, appear to require much potash ; for 

 which reason turnips, carrots, and other green crops are much 

 benefited by wood-ashes, burnt clay, and liquid manure, which 

 all contain considerable quantities of soluble potash. Potatoes 

 especially require a good supply of potash. Much less valuable 

 constituents of artificial manures are soda, common salt, glauber 

 salt, magnesia, lime, gypsum, oxide of iron and silica. 



Nitrogen in a proper state of combination, phosphoric acid 

 and potash, thus principally determine the efficacy of a manure. 

 We have seen, however, that the composition of the soil to 

 which it is applied, and the requirements of the crop for which it 

 is used, affect in a great measure the effects which an artificial 

 manure is capable of producing. Other circumstances, such as 

 a wet or a dry season, the time at which, and the mode in which, 

 it is applied, likewise exercise a decided influence on the efficacy 

 of a manuring substance ; and it remains, therefore, for the 

 judicious farmer to determine whether the actual fertilizing effects 

 of an artificial manure justify the expenditure of a certain amount 

 of money or not. But there is another consideration to which 

 we would direct special attention, as it is often overlooked alto- 

 gether by the practical man. As many artificial manures are 

 very efficacious, the purchasers of such manures are generally 

 quite satisfied with the results, and do not trouble themselves 

 with the inquiry, " At what price can I obtain the different fer- 

 tilizing constituents in the manure separately ?" or in other 

 words, what is its commercial value ? 



Hence we can explain that frequently fertilizing mixtures find 

 purchasers at prices twice or three times as great as their intrinsic 

 money-value. A few illustrations will show that the imme- 

 diately apparent efficacy of a manure does not necessarily deter- 

 mine its money-value. 



Nobody in his senses would think of paying the same price 

 for lime as for guano ; and yet there are instances on record in 

 which the parallel effects realised by lime were greater than 

 those of guano. It does not follow, however, that lime possesses 



