RATIONAL FERTILIZATIOX. 181 



A close examination of these analytical results reveals in many 

 instances remarkable variations in regard to almost every essen- 

 tial fertilizing constituent of plants. Some contain one part of 

 phosphoric acid to one part of potash, others one of the former 

 to two, three, four, and even as high as five parts of the latter. 

 A similar variation ma}- be noticed as regards the relative propor- 

 tions of phosphoric acid and nitrogen ; in most instances we find 

 more phosphoric acid than sulphuric acid and chlorine, yet in some 

 species of plants more sulphur and chlorine than phosphoric acid 

 may be noticed. Similar circumstances exist as regards the pro- 

 portions of lime and magnesia. 



The recognition of these conditions obliges us to concede that 

 none of our ordinary manures, composed of refuse matters, can 

 be considered in the majority of cases the most suitable fertilizer 

 without the addition of some one or more articles of plant food 

 in a suitable and available form. Good economy and a regard to 

 healthful conditions of the soil advise that course. 



There still remains one point of importance to which I desire to 

 call your attention in this connection, namely, the careful selection 

 of manurial substances with reference to the most advantageous 

 form. 



A productive agricultural or horticultural soil implies, for vari- 

 ous reasons, the presence of decaying vegetable matter ; this 

 condition we secure either by a direct addition in the form of 

 barnyard manure, or some other vegetable refuse material inciden- 

 tal to our industries, or by green manuring, or a judicious system 

 of rotation of crops. The latter course is in man}- instances the 

 safer one, as far as the preservation of a healthful condition of 

 the soil is concerned. 



An excessive accumulation in the soil of either animal or vege- 

 table matter, or of both, is apt to turn it into a breeding place of 

 injurious parasitic growths. For this reason it is not advisable 

 to secure a liberal supply of the various essential articles of plant 

 food b}' the use of an exceptionally large quantity of barnyard 

 manure or of any organic refuse material of a similar character. 



A moderate use of these substances, supported by a proper ad- 

 dition of concentrated commercial articles of plant food for the 

 purpose of rendering them complete fertilizers, deserves in the 

 majority of cases particular commendation on account of the di- 

 rectness and certainty with which we can reach the object in view. 



