200 BOAKD OF AGRICULTURE 



while those containing less (like wheat, for instance) receive greater 

 benefit from its use. The function of nitrogen seems rather to yield 

 force, or to stimulate growth, than to supply plant food. 



Second, our soils lack potash in an available form. New Eng- 

 land soils generally contain enough, but it is there as a silicate, in a 

 combination so nearly insoluble that it is virtually locked up. It is 

 liberated thence only by slow degrees ; by freezing and thawing, 

 air and rain, especially by rain water, containing, as it does, a little 

 carbonic acid.* 



The third want is phosphoric acid. All soils capable of pro- 

 ducing crops contain more or less of this, but nearly all in bo 

 scanty measure that it is more frequently needed than any other ash 

 constituent of plants ; and when present in insufiicient quantity, 

 plants make a feeble growth, are liable to many casualties which 

 healthy and vigorous plants escape, and cattle fed upon the herbage 

 of such land are subject to what is known as "bone disease.!' 



These three substances, Potash, Nitrogen, and Phosphoric acid, 

 are the most important and the most expensive which the farmer 

 has need to buy ; and all commercial fertilizers sold, whatever the 

 name they bear, be it ground bone, guanos, of whatever name or 

 kind, phosphates, or super-phosphates, or "perfect manures," or 

 whatever else, which are really woi'th more than half a cent per 

 pound, owe their value mainly to the presence of one or more of 

 these substances. 



An interesting question relative to means of fertilization is, 

 whether it be the better policy for the farmer to buy manures 

 directly or indirectly ; that is to say, whether to buy commercial 

 fertilizers, or commercial articles of cattle food, to be converted 

 partly into meat or dairy products, and partly into manure. It is 

 too broad a subject for discussion here, but it deserves more con- 

 sideration than it receives. The true answer I believe would vary 

 with circumstances, sometimes one and sometimes the other, and 

 it should be the business of each farmer to ascertain which would 

 be best for him. 



The term "Commercial Manures " may be understood as em- 

 bracing all those manurial substances which are usually purchased 

 by the farmer, in distinction from those usually obtained from his 

 own resources. 



* Late investigations have shown that potash is liberated frum its insoluble connections 

 by the agency of acid phosphate of lime, and to this fact, probably, is due a considerable 

 degree of the surprising efficacy of a genuine Super Phosphate in not a few instances. 



