338 SALT, NITKATE OF SODA, SALTS OF AMMONIA, ETC. 



The experiments are remarkable, in so far as they 

 appear to indicate the cases in which the nitrates alone, 

 or in combination with common salt, exert a favourable 

 influence upon the increase of the crops. 



The land in Weihenstephan is peculiarly suited for the 

 cultivation of barley. Field A, after a manuring of the or- 

 dinary kind, about 600 cwt. per hectare, had borne turnips 

 in 1854, peas in 1855, and wheat in 1856 ; it was then 

 intended to let it he faUow for one year, and to dress it at 

 the end of the year for a new crop. On the other hand, 

 Field B,before the experiment was made, had abeady borne 

 four crops, namely, rape, wheat, clover grass, and oats ; 

 and was, in comparison with the first field, more exhausted, 

 and by means of the oats and clover made much poorer 

 in nutritive substances for the following cereal crop. 



This seems to afford an explanation of the striking fact, 

 tliat in 1857 the nitrates exercised upon the field a far 

 more favourable influence than guano, although the soil 

 had received as much nitrogen in the guano as in the 

 nitrates, with the addition of phosphoric acid and potash. 

 The field was still rich enough in nutritive substances for 

 a good barley crop, and merely required theu" more uni- 

 form distribution (which was effected by the nitrates and 

 the common salt), in order to make available to the roots 



