EXPERIMENTS ON' WIIKAT. 185 



the land for sevrral months, ami liarrowiii:; it occasionally, will 

 do niiRii to rcniKr its constituents availal)lc. But let us return to 

 Mr. Lawes' wonderful exiKTiincnts." 



"On eight plots," said 1, "300 lbs. of ammonia-salts were used 

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

 plots was nearly 20 bushels per acre, or an average increase of 9 

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

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

 per acre. 400 lbs. ammonia salt.s, with superphosphate of lime, 

 gave an increia.. of nearly Ki bushels per acre, or throe bushels 

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

 i\sed 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." 



" 1 see," said the Deacon, " that ground r!ee was used this year 

 for manure ; and in 184o, tupioca was also used as a manure. The 

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

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



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

 Lawos wanted to ascertain whether cirfx)naceo"8 matter was needed 

 hj the growing wheat-plants, or whether they could get ad 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 lbs. 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, lt^7-8. 



