ADAPTATION OF MANURES TO CKOPS, 57 



these materials, which must form the basis of our judg- 

 ment. This fact has been much overlooked by many 

 scientific writers, who have counselled farmers to manure 

 their land in every case with all the constituents required 

 by the crop, a proceeding both impracticable and un- 

 necessary. In the case of a barren sand it may indeed 

 be requisite to supply all the constituents of plant food 

 before a crop can be grown, but such a case is far removed 

 from the circumstances of ordinary agriculture. 



When land is in a fertile condition the total amount 

 of plant food available for crops is very considerable, and 

 luxuriant growth may be obtained by supplementing the 

 stores of the soil with the few particular elements of food 

 which the crop it is wished to grow has most difficulty in 

 obtaining. Thus, in a large majority of cases, a dressing 

 of nitrate of sodium and phosphates will ensure a full 

 crop of wheat, barley, or oats, and in many cases nitrate 

 of sodium alone will prove very effective. These cereal 

 crops generally find the supply of nitrates in the soil 

 insufficient for their full growth, and the supply of 

 phosphates more or less inadequate ; but in a majority of 

 cases they are well able to obtain a sufficient supply of 

 potash and other essential elements of plant-food. We 

 are thus able, by supplying one or two constituents of the 

 crop, to obtain a luxuriant harvest. In the same way 

 nitrate of sodium employed alone will, in most cases, 

 produce a large crop of mangels ; superphosphate alone, 

 a large crop of turnips ; while potassium salts alone may 

 be strikingly effective with pasture and clovers. 



This special manuring for each crop is no strain on the 

 capabilities of the soil if a rotation of crops be followed. 

 If superphosphate is applied for the turnips, potassium 



