THE SPECIAL FERTILIZERS OF THE FARM. 



also yearly consumes cake and grain upon the farm, the use of nitrate of 

 soda becomes reasonable and right. The management is liberal and of an 

 improving character, and the nitrate of soda only brings out the artificial 

 fertility which comes of good farming, and does not prey upon the natural 

 fertility of the soil. The same remark would apply to the use of other 

 special manures, such as lime. Repeated liming, according to the old pro- 

 verb, " while it enriches the father, impoverishes the son." But lime ap- 

 plied in conjunction with liberal management cannot be objected to on the 

 score of exhausting the land. 



POSSIBLE LIMIT TO THE PROFITABLE USE OF ANY M ANUIIK. As long as 

 a soil is deficient in a particular constituent, we may expect to see benefit 

 from its application. If the land becomes sufficiently stocked with this 

 constituent, we may find a change of fertilisers desirable. If a soil con- 

 tains a sufficient proportion of phosphoric acid for the requirements of a 

 wheat crop, and at the same time an excess of potash, we cannot expect a 

 dressing of potash to be attended with any effect. A soil deficient in lime 

 may be greatly benefited by an application of lime. But a second or third 

 application of the same substance might produce but little effect, simply 

 because lime had ceased to be a deficient element. Up to the present time, 

 sh (owing to its existing in considerable quantities in farmyard man- 

 ure) has not been lacking in most of our soils. If, however, from the cul- 

 tivation of the potato, the growth of wool, or the sale of straw, the amount 

 of potash became reduced below the point required, then a demand for 

 potash salts would immediately spring up. 



In th- present treatise it will be impossible to do justice to the large 

 3 of materials employed as fertilisers, but our aim must be rather to 

 indicate the principle of their action. In the last section some substan 

 wre included which could barely be considered as coming under the 



a of general manures guano, for example, often being d. tirimt in 

 potash. Similarly, under the class of special manures certain fertili- 

 approach in complexity the composition of a true general man 



I'HM Calcium, potassium, sodium, and magnesium phosphates 



all of interest to a'jricultni Nt -< ; l-ut from our present point of vi'-w the 

 n;ini'-d is ii; My the most important. Calcium phosphat- 



a almndaner in the bones of animals, and it is also \vid.-ly 

 distrilnih-d as mini-nil phosphate and phosphorite. It o<vnr- in very .small 

 |iiantiti<- in all f.-rtil.- .soils, and it forms an important andahnnd, 



h of all our cultivated plants. In the cultivation of such 

 . crops as wheat, barl \ , an 1 oats, no constituent is more lar^ 

 drawn upon \cept nitrogen, the supply of which is derived, in a gi 

 El 



