MANURE FOR BARLEY. 247 



poor manure into rich manure. There is manure in our soil, but 

 it is poor. There is manure in our barn-yard, but it is 

 poor also. Nitrogen and phosphoric acid will make these 

 manures rich. This is the reason why a few pounds of a good 

 artificial manure will produce as great an effect a"s tons of common 

 manure. Depend upon it, the coming farmer will avail himself of 

 the discoveries of science, and will use more artificial fertilizers. 



But whether we use artificial fertilizers or farm-yard manure, we 

 shall not get the full effect of the manures unless we adopt a 

 judicious rotation of crops. 



When we sow wheat after wheat, or barley after barley, or oats 

 after oats, we certainly do not get the full effect of the manures 

 used. Mr. Lawes' experiments afford conclusive evidence on this 

 point. You will recollect that in 1846, one of the plots of wheat 

 (105), which had received a liberal dressing of salts of ammonia 

 the year previous, was left without manure, and the yield of wheat 

 on this plot was no greater than on the plot which was continu- 

 ously unmanured. In other words, the ammonia which was left in 

 the soil from the previous year, had no effect on the wheat. 



The following table shows the amount of nitrogen furnished by 

 the manure, and the amount recovered in the crop, when wheat is 

 grown after wheat for a series of years, and also when barley is 

 grown after barley, and oats after oats. 



