■254 THE SHEEP OP GREAT BRITAIN. 



nitrogen and 3001b. of mineral matter. The latter is composed 

 as follows : 



PerAcfe. Percent. 



ID. 



110-94 Potash 36'98 



20-28 Soda 6-76 



1-77 Chloride of potassium -59 



23-55 Common Salt 7*85 



10-83 Magnesia 3-61 



33-42 Lime 11-14 



29-22 Phosphoric Acid 9-74 



37-29 Sulphuric Acid 12-43 



10-29 Silica 3-43 



3-27 Iron 1*09 



19-14 Carbonic Acid 638 



300-00 100-00 



Supposing that the ewes consume at the rate of 201b. a day 

 when fed on turnips alone, and that we reduce the turnips by 

 •one-half and substitute l|lb. of straw, it follows that with each 

 acre of turnips 2 tons 4 cwt. of straw will be eaten. Straw, on 

 an average, yields | per cent, of nitrogen ; therefore we have 

 24"61b. of nitrogen, of which probably 21*61b. is left in the land 

 as manure, the remaining one-eighth bemg exhaled from the 

 animal's skin, &c. The same quantity of straw will yield 2211b. 

 of mineral matter, of which about 48 per cent, is silica; the 

 remainder contains minerals which are valuable as plant food. 

 The addition to the soil of this large amount of silica — viz., 

 about 1071b. — in a condition available for plant food would act 

 beneficially on the barley crop, which requires for grain and 

 straw more silica than any of the other cereals. The following 

 table shows the composition of oat straw, and the quantity 

 returned per acre if used as above described : 



An Analysis of Quantity 



the Ash of returned per 

 Oat Straw. acre as Manure. 



Per Cwt, lb. 



Potash 19-14 42-29 



Soda 9-69 2141 



Magnesia 3-78 8-35 



Lime 8-07 17-83 



Phosphoric Acid 2*56 5-68 



Sulphuric Acid 3*26 7-20 



Silica 48-42 107-00 



Peroxide of Iron ' 1-83 4-04 



Common Salt 3-25 7-18 



100-00 220-95 



