THE CULTURE OF CORN. 403 



quantities of silica in the ash possess properties in common, 

 one of which is, that, when liberally supplied with nitrogen, 

 they are capable of outgrowing and overpowering all other 

 species of plants. It is quite true that corn is less dependent 

 upon an artificial supply of nitrogen than wheat, oats, or 

 barley, and the reason for this fact I have frequently pointed 

 out : viz., that, after the other crops are ripe, corn continues 

 its growth during the exact period when the liberation of 

 nitric acid in the soil is most active ; and it. is this circum- 

 stance that enables the United-States farmer to sell corn so 

 much cheaper than wheat. 



At Rothamsted we have abundance of evidence to show 

 how large is the quantity of nitric acid liberated during the 

 summer months. For example : the water collected from 

 the drains of our experimental wheat-field in July contained 

 no nitric acid ; while the soil of the adjoining held, where 

 no crop was grown, contained in September as much nitric 

 acid as would have supplied the nitrogen contained in fifty 

 bushels of corn. The United-States farmers are now em- 

 barking largely in the use of artificial manures, and therefore 

 may possibly be glad to hear the views of one who has been 

 studying their properties for more than forty years. 



First, they will find a very great difference between the 

 amount of ingredients which is supplied in a manure and 

 that obtained in the produce ; then two of the ingredients 

 generally supplied in manure — viz., phosphoric acid and 

 potash — enter into very fixed compounds with the soil, and 

 are only recovered over long periods of time. In confirma- 

 tion of this fact, I may say, that, at Rothamsted, we are at 

 the present moment taking up in our wheat-crop phosphoric 

 acid and potash which were applied thirty years ago. Some 

 considerable addition, therefore, in the shape of interest, 

 must be charged on the cost-price of these substances by the 

 farmer who employs them as a manure. With regard to 

 nitrogen the case is different. It appears probable that 

 nitrogen, applied either as ammonia or nitric acid, does not 

 permanently enter into any fixed combination in the soil, 

 unless it has become a part of living vegetation. 



And it may be considered an established fact, that, wher- 

 ever nitrogen is used as a manure, there will be a consider- 

 able loss of the amount aj)plied, although the amount of such 



