58 THE CHEMISTRY OP THE FAEM. 



salts for the seeds, and a nitrogenous manure for the cereal 

 crops, the more important elements of plant food con- 

 tained in the soil will not be diminished at the end of the 

 rotation. At the same time the most economic result will 

 have been obtained from the manures employed, for each 

 manure will have been supplied to that particular crop 

 with which it yields the most remunerative result. 



It is doubtless possible by means of rotations manured 

 on the above principles to farm successfully with the sale 

 of all the crops produced, and without the use of farm- 

 yard manure ; this is possible at least so long as artificial 

 manures can be obtained at a low price. In the majority 

 of cases, however, the special manuring will only be 

 required to supplement the general manuring by farmyard 

 manure. Under these circumstances it would seem best, 

 from a chemical point of view, to apply the farmyard 

 manure to those crops which most require potash, or 

 which stand most in need of a general manuring ; such 

 crops would be pasture, artificial grasses, turnips and 

 potatos. 



As the whole object of artificial manuring is to supple- 

 ment the deficiencies of the soil, it is highly desirable 

 that a farmer should ascertain by trials in the field what 

 is the actual amount of increase which he obtains from 

 the application of the manures he purchases. A few 

 carefully made experiments will teach him what his land 

 and crops are really in need of. Should he add super- 

 phosphate with the nitrate of sodium for his wheat ? 

 What dressing of the nitrate is most economical ? Is 

 superphosphate alone sufficient for his turnip crop, or 

 should guano or nitrate be employed as well ? What is 

 the smallest quantity of superphosphate sufficient for the 



