220 The Principles of Fruit-growing. 



the direct addition of nitrogenous materials, like 

 nitrate of soda, sulfate of ammonia, or some of the 

 animal compounds. 



The grower should also remember that the plants 

 need all the elements of plant growth, and not one 

 of them alone. For example, a heavy application of 

 nitrogen upon soil which is deficient in potash and 

 phosphoric acid cannot be expected to give useful 

 results. In the same way, the application of pot- 

 ash to soil which is very poor in nitrogen or phos- 

 phoric acid would be comparatively useless. The 

 heavy loamy or clay lands nearly always contain 

 an abundance of potash and phosphoric acid in 

 a more or less unavailable condition, and much of 

 these materials can be liberated to the plant by care- 

 ful tillage and the incorporation of humus. How- 

 ever, it is nearly always advisable, in orchards 

 which are bearing, to add these materials in the 

 shape of manures or concentrated fertilizers. The 

 quickest results following the use of fertilizers will 

 be seen upon the sandier lands. Two or three 

 years often elapse after the application of chemical 

 fertilizers to heavy lands before any decided results 

 are observed. In other words, clay lands ordinarily 

 show quicker results from tillage than they do from 

 the application of fertilizers. The farmer should 

 bear in mind that he should never rely exclusively 

 upon chemical plant -foods, because they contain no 

 humus, and the soil is apt to become hard and life- 

 less. They should be used in judicious rotation, or 

 in connection with cover crops, or stable manures. 



