334 TALKS OX MANURES. 



The actual cost of tlic ingredients, therefore, in the crop ot 

 twenty buslielsitf wlu-at, would be about ten to twelve dollars. 

 But as this manure would furnish the injj^redients for the 

 growth of both straw and grain, and it is customary to return 

 the straw to the laud, after tlie tirst crop, fully one-third of the 

 cost of the manure might, in consequence, be deducted, which 

 would niiike the ingredients of the twenty bushels amount to 

 six dollars. Twenty bushels of wheat in Kngland would sell 

 for twenty -eight dollars ; therefore, there woukl be twenty-two 

 dollars left for the cost of cultivatitm and profit. 



A French writer on scientific agriculture has em])loyed 

 figures very similar to the above, to show liow Fiench farmers 

 may grow wlieat at less liian one dollar per bushel. At this 

 jirier they might ct-rtaiidy defy the comp<'tition of the United 

 States. It is one thing, however, to grow crops in a lecture 

 room, and (piite another to grow them in a field. In ilealing 

 with artificial .nanures, furnishing jihosphoric acid, i)ot;ush, 

 and nitrogen, we have substances which act upon the soil in 

 very (lifTerents ways. Phosphatt^ of lime is a very insoluble 

 substance, and nnjuires an enormous amount of water to dis- 

 solve it. Salts of potash, on the other hand, are very 8()lu])le in 

 water, but fi>rm very insoluble com])ounds with the soil. Salts 

 of ammonia ami nitrate of soda an- perfectly soluble in water. 

 U hen applied to the land, the ammonia of the former sulv 

 stance forms an insoluble compound with the soil, but in avery 

 short time is converted into nitrate of lime ; and with this sjxlt 

 and nitrate of soda, remains in solution in the soil water until 

 they are either taken up by the plant or are washed away into 

 the drains or rivers. 



Crops evaporate a very large amount of water, and with this 

 water they attract the soluble nitrate from all ])arts of the soil. 

 Very favorable sci-sons are therefore those in which the soil is 

 n«'ither too dry nor too wet; as in one case the solution of 

 nitrit)^ becomes dried up in the soil, in the other it is either 

 waslied away, or the soil remains so wet that the plant cannot 

 evaporate the water sufKciently to draw up the nitrates which 

 it contains. 



The amount of potash and phosphoric acid dissolved in the 

 water is far too small to supi)ly the requirements of the plant, 

 and it is probable that what is required for this puqwse is dis- 

 .^^olved by some direct action of the roots of the plant on com- 

 ing in contact with the 'nsoluble phosphoric acid and potash La 

 the soil. 



