168 BOARD OF AGRICULTURE. 



manure exists in a form or in forms such that much of it 

 cannot be taken up by the plant at once, if at all. It must 

 undergo an alteration to become of use, and much of it, in- 

 stead of passing into an available condition, doubtless becomes 

 permanently inert. 



Mr. S. L. Goodale, of Saco, Maine. What are the cir- 

 cumstances under which the nitrogen of manure is converted 

 mto ammonia, which is retained in the soil, and what the 

 circumstances in which it is converted into nitrates, which 

 may pass out of the soil ? 



Prof. Johnson. So far as can be judged from our imper- 

 fect knowledge, a rapid decay of nitrogenous matter which 

 goes on with comparative exclusion of air, generates ammo- 

 nia ; on the other hand, where there is a large access of air, 

 there we have nitrates 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 be- 

 comes lost as a fertilizer. 



Mr. Gould. Before the current of questions drifts away 

 from the main subject of the lecture, I am desirous of asking 

 the Professor a question as matter of explanation. He has 

 stated a distinction among plants — plants which exhaust the 

 nitrogen and plants which accumulate 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 practi- 

 cal farming, than it ever has done in the past. The state- 

 ment which he made would justify the inference, although 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 proportion between the amount of accumulation and the 

 length of time. I desire to know whether the Professor 

 #ishes to be understood in that way ? 



