70 Maine Agricultural Experiment Station. 1920. 



can be ascertained by subtracting the mineral nitrogen from the 

 total nitrogen. For instance in sample A above one finds the 

 mineral nitrogen by adding the nitrate nitrogen (1.76 per cent) 

 and the ammonia nitrogen (1.38 per cent) together. Subtract- 

 ing this sum (3.14 per cent) from the total nitrogen as found 

 (4.10 per cent) the difference shows the organic nitrogen in the 

 sample to be .96 per cent. 



And if one wishes to know the amount of inactive organic 

 nitrogen a fertilizer contains it is readily found by subtracting 

 the active from the total found. Thus in A this inactive or- 

 ganic nitrogen is (4.10 less 3.78) .32 per cent. 



It has also been found in vegetation experiments that in 

 good grade organic nitrogen more than one-half of the nitro- 

 gen is available (active) for plant use. In A above the organic 

 nitrogen is .96, the inactive is .32 per cent or less than one-third 

 the total. This shows the organic nitrogen in A to have been 

 from good sources. In like manner B-i with its high (3.63 

 per cent) total nitrogen has 1.56 per cent organic (3.63 per 

 cent less the mineral nitrogen 2.07 per cent). But of this 1.56 

 per cent total organic .86 per cent (3.63 less 2.76) is inactive. 

 That is much less than half of the organic nitrogen is in the ac- 

 tive (available) form and the organic nitrogen used is of poor 

 quality. But the story with B-2 is quite different though it is an- 

 other sample from another lot of the same brand. In this case 

 there is .yj per cent organic (2.85 total found less 2.08 mineral 

 nitrogen) of which only .13 per cent (2.85 total less 2.72 active) 

 is inactive. That is about five-sixths of the organic nitrogen is 

 available showing the organic nitrogen to be of high quality. 

 By the total nitrogen B-i would look far superior to B-2 but 

 the active nitrogen is about alike in both. B-i seems so far as 

 total nitrogen is concerned to be above the guaranty and B-2 

 below. In fact from the standpoint of the Maine law which 

 calls for a guaranty of available nitrogen they are both below 

 the 3.29 per cent guaranty. 



The column headed Active Nitrogen gives the information 

 at a glance as to the relation between the nitrogen guaranteed 

 and that which plants will make use of in the first year. But 

 it is important for the grower of crops to consider the mineral 

 nitrogen and the character of the organic nitrogen as outlined 

 in the preceding paragraphs. Fertilizer tables are not like a 



