THE MANAGEMENT OF MANURES. 95 



manure, we add nothing to it ; there is no more actual nitrogen, 

 or phosphoric acid, or potash, or any other ingredient after fer- 

 mentation than there was before, but these ingredients are rendered 

 more soluble, and can be more rapidly taken up by the plants. In 

 this sense, therefore, there is a great gain. 



One thing is certain, we do not, in many cases, get anything 

 like as much benefit from our manure as the ingredients it con- 

 tains would lead us to expect. 



Mr. Lawes, on his clayey soil at Rothamsted, England, has 

 grown over thirty crops of wheat, year after year, on the same 

 land. One plot has received 14 tons of barn-yard manure per 

 acre every year, and yet the produce from this plot is no larger, 

 and, in fact, is frequently much less, than from a few hundred 

 pounds of artificial manure containing far less nitrogen. 



For nineteen years, 1852 to 1870, some of the plots have received 

 the same manure year after year. The following shows the aver- 

 age yield for the nineteen years : 



Wheat Straw 



per acre. per acre. 



Plot 5. Mixed mineral manure, alone 17 bus. 15 cwt. 



u 6. Mixed mineral manure, and 200 Ibs. ummo- 



niacal salts 27 bus. 25 cwt. 



" 7. Mixed mineral manure, and 400 Ibs. ammo- 



niacal salts S6 bus. 30 cwt. 



" 9. Mixed mineral manure, and 550 Ibs. nitrate 



of soda 37 bus. 41 cwt. 



" 2. 14 tons farm-yard Jung 86 bus. 84 cwt. 



The 14 tons (31,360 Ibs.) of farm-yard manure contained about 

 8,540 Ibs. organic matter, 868 Ibs. mineral matter, and 200 Ibs. ni- 

 trogen. The 400 Ibs. of aminoniacal salts, and the 550 Ibs. nitrate 

 of soda, each contained 82 Ibs. of nitrogen; and it will be seen 

 that this 82 Ibs. of nitrogen produced as great an effect as the 200 

 Ibs. of nitrogen in barn-yard manure. 



Similar experiments have been made on barley, with even more 

 striking results. The plot dressed with 300 Ibs. superphosphate of 

 lime, and 200 Ibs. ammoniacal salts per acre, produced as large a 

 crop as 14 tons of farm-yard manure. The average yield of barley 

 for nineteen crops grown on the same land each year was 48 bus. and 

 28 cwt. of straw per acre on both plots. In other words, 41 Ibs. of 

 nitrogen, in ammoniacal salts, produced as great an effect as 200 

 Ibs. of nitrogen in farm-yard manure ! During the nineteen years, 

 one plot had received 162,260 Ibs. of organic matter, 16,492 Ibs. of 

 mineral matter, and 3,800 Ibs. of nitrogen ; while the other had 

 received only 5,700 Ibs. mineral matter, and 779 Ibs. of nitrogen 

 and yet one has produced as large a crop as the other. 



