EXPERIMENTS ON WHEAT. 185 



the land for several months, and harrowing it occasionally, will 

 do much to render its constituents available. But let us return to 

 Mr. Lawes"' wonderful experiments.'" 



"On eight plots," said I, " 300 Ibs. of ammonia-salts were used 

 without any other manures, and the average yield on these eight 

 plots was nearly 26 bushels per acre, or an average increase of 9 

 bushels per acre. The same amount of ammonia-salts, with the 

 addition of superphosphate of lime, gave an increase of 13 bushels 

 per acre. 400 Ibs. ammonia-salts, with superphosphate of lime, 

 gave an increase of nearly 16 bushels per acre, or three bushels 

 per acre more than where 14 tons of barn-yard manure had been 

 used four years in succession. 



" I hope, after this, the Deacon will forgive me for dwelling on 

 the value of available nitrogen or ammonia as a manure for 

 wheat." 



" I see," said the Deacon, " that ground rice was used this year 

 for manure ; and in 1845, tapioca was also used as a manure. The 

 Connecticut Tobacco growers a few years since used corn-meal for 

 manure, and you thought it a great waste of good food." 



I think so still. But we will not discuss the matter now. Mr. 

 Lawes wanted to ascertain whether carbonaceous matter was needed 

 by the growing wheat-plants, or whether they could get all they 

 needed from the soil and the atmosphere. The enormous quanti- 

 ties of carbonaceous matter supplied by the barn-yard manure, it 

 is quite evident, are of little value as a manure for wheat. And 

 the rice seems to have done very little more good than we should 

 expect from the 22 Ibs. of nitrogen which it contained. The large 

 quantity of carbonaceous matter evidently did little good. Avail- 

 able carbonaceous matter, such as starch, sugar, and oil, was in- 

 tended as food for man and beast not as food for wheat or 

 tobacco. 



The following table gives the results of the experiments the 

 fifth year, 1847-8. 



