2X6 BOARD OP AGRICULTURE. 



Prof. Johnson. So far as can be judged from our imperfect 

 knowledge, a rapid decay of nitrogenous matter which goes on 

 with comparative exclusion of air, generates ammonia ; on the 

 other hand, where there is a large access of air, there we have ni- 

 trates formed. But we do not know minutely the conditions 

 under which nitrates are produced. Another fact to be noticed is 

 this : that in the decay of animal matters with access of air, there 

 is invariably a quantity, and often a large quantity, of nitrogen 

 liberated in the state of free, gaseous nitrogen, such as exists in 

 the air about us, and which does not assume the form either of 

 ammonia or nitrates, and thus becomes lost as a fertilizer. 



Mr. Gould. The Professor has stated a distinction among 

 plants — plants which exhaust the nitrogen and plants which ac- 

 cumulate nitrogen, in the soil. This is a subject of immense 

 practical importance, and I think it will play a much greater part 

 in questions of practical farming, than it ever has done in the past. 

 The statement which he made would justify the inference, al- 

 though he did not state it himself, that plants accumulate nitrogen 

 in the soil in proportion to the surface of their foliage extended to 

 the air, and to the length of time during which that foliage is in 

 actual growth. The inference would be that there was a propor- 

 tion between the amount of accumulation and the length of time. 

 I desire to know whether the Professor wishes to be understood 

 in that way ? 



Prof. Johnson. I would not assert that to be the fact, abso- 

 lutely or unqualifiedly, but the indications very strongly favor 

 that general conclusion. 



Mr. Gould. That is my own impression. 



Prof. Johnson. I was about to say how much nitrogen was 

 needed in the soil. 



. A wheat crop of thirty-three bushels, with straw and chaff, con- 

 tains fifty-six pounds of nitrogen. If we allow for stubble and 

 roots one-fifth this quantity, we have for the total nitrogen 

 required in the vegetation of an acn* of wheat, say sixty-eight 

 pounds.* Ilellriegel found, by actual trial, seventy pounds of 

 nitrogen to be sufficient to produce his maximum wheat crop. 



Mr. Lawes' soil furnished enough nitrogen to yield seventeen 

 bushels of wheat. Addition of forty-one pounds of nitrogen, in 



* On examination of wheat roots collected by Schubart, June Sth, 1855, Stockbardt 

 found that the roots composed a little more than one-Cfth of the entire plant, or twenty- 



