96 TALKS ON MANURES. 



Why this difference ? It will not do to say that more nitrogen 

 was applied in the farm-yard manure than was needed. Mr. 

 Lawes says : " For some years, an amount of ammonia-salts, con- 

 taining 82 Ibs. of nitrogen, was applied to one series of plots (on 

 barley), but this was found to be too much, the crop generally 

 being too heavy and laid. Yet probably about 200 Ibs. of nitrogen 

 was annually supplied in the dung, but with it there was no over- 

 luxuriance, and DO more crop, than where 41 Ibs. of nitrogen was 

 supplied in the form of ammonia or nitric acid." 



It would seem that there can be but one explanation of these 

 accurately-ascertained facts. The nitrogenous matter in the ma- 

 nure is not in an available condition. It is in the manure, but the 

 plants can not take it up until it is decomposed and rendered sol- 

 uble. Dr. Vo3lcker analyzed " perfectly fresh horse-dung," and 

 found that of free ammonia there was not more than one pound 

 in 15 tons ! And yet these 15 tons contained nitrogen enough to 

 furnish 140 Ibs. of ammonia. 



" But," it may be asked, " will not this fresh manure decompose 

 in the soil, and furnish ammonia ? " In light, sandy soil, I pre- 

 sume it will do so to a considerable extent. We know that clay 

 mixed with manure retards fermentation, but sand mixed with 

 manure accelerates fermentation. This, at any rate, is the case 

 when sand is added in small quantities to a heap of fermenting 

 manure. But I do not suppose it would have the same effect when 

 a small quantity of manure is mixed with a large amount of sand, 

 as is the case when manure is applied to land, and plowed under. 

 At any rate, practical farmers, with almost entire unanimity, think 

 well-rotted manure is better for sandy land than fresh manure. 



As to how rapidly, or rather how slowly, manure decomposes 

 in a rather heavy loamy soil, the above experiments of Mr. Lawes 

 afford very conclusive, but at the same time very discouraging 

 evidence. During the 19 years, 3,800 Ibs. of nitrogen, and 16,492 

 Ibs. of mineral matter, in the form of farm-yard manure, were ap- 

 plied to an acre of land, and the 19 crops of barley in grain and 

 straw removed only 3,724 Ibs. of mineral matter, and 1,064 Ibs. of 

 nitrogen. The soil now contains, unless it has drained away, 

 1,736 Ibs. more nitrogen per acre than it did when the experiments 

 commenced. And yet 41 Ibs. of nitrogen in an available condit'on 

 is sufficient to produce a good large crop of barley, and 82 Ibs. per 

 acre furnished more than the plants could organize. 



" Those are very interesting experiments," said the Doctor, " an1 

 show why it is that our farmers can afford to pay a higher price 

 for nitrogen and phosphoric acid in superphosphate, and other ar- 



