206 SCIENTIFIC AGRICULTURE. 



be used for any crop on land which is already disposed to 

 produce too much straw. They are exceedingly soluble, and 

 are for this reason not so beneficial on loose, light soils, because 

 more easily washed away than on close, compact soils : for the 

 same reason they produce little effect after the first year. 

 They furnish a large amount of nitrogen, and are most bene- 

 ficial to poor soils which are deficient in organic matters. 



Chloride of sodium, or common salt, has been used with 

 yarious results as a fertilizer. Plants require for their growth 

 both of the elements of common salt, viz, chlorine and soda ; 

 and in soils which are deficient in one or both of these ele- 

 ments, there can be no doubt as to its efficacy ; but in a soil 

 which contains them in sufficient quantity in a soluble state, it 

 cannot be expected that this salt will be of any service. It is 

 most likely to prove beneficial on lands lying remote from the 

 sea, and which, consequently, would be more apt to require it. 

 This salt is of more benefit to green crops than cereals; and 

 also to hasten and increase the growth of the herbage of plants 

 than the seeds. 



The chlorides of lime and magnesia contained among the 

 refuse of chemical manufactories, are also used as manures 

 with good effects. The chlorides are destructive to both ani- 

 mal and vegetable life, when used in large quantity; they 

 have consequently been used to destroy weeds, worms and 

 insects in the soil. 



The silicate of potash and soda, and the various salts of 

 ammonia, are, without question, powerful fertilizers, particu- 

 larly on the grasses; but they are not in general use, on 

 account of their high price, as well as doubtful reputation 

 among those practical men who have not tested them. 



EARTHY MANURES. 



Wood ashes. The ashes of wood and all other vegetable 

 matter, contain various proportions of several different salts, all 

 of which are necessary to the growth of plants. The following 



