VALUE OP ANIMAL MANURE. 141 



manurial value, when compared on the basis of their dry 

 substance. Wheat-straw takes the lowest place when 

 foods are compared on the basis of their dry substance. 

 Bean and pea straw are far more valuable than the 

 straw of the cereals. 



To obtain the amount of nitrogen, potash, and phos- 

 phoric acid voided as manure, we have simply to subtract 

 from the amounts of these constituents contained in the 

 food the quantity retained by the animal. The manure 

 resulting from nitrogenous foods, as decorticated cotton- 

 cake, is frequently the cheapest form of nitrogen which 

 a farmer can obtain. This is especially the case when 

 the food is skilfully used, and gives a good return in 

 animal increase, as well as furnishing a supply of 

 manure. 



The ash constituents present in animal manure have 

 probably the full money value of the same constituents in 

 artificial manures, but the nitrogen has a lower value 

 than the nitrogen of ammonium salts or nitrate of sodium. 

 The nitrogenous matter of the urine (urea) is rapidly 

 converted into carbonate of ammonium by the action of 

 certain bacteria present both in the atmosphere and in 

 the soil; the carbonate of ammonium may afterwards 

 be converted into nitrates in the soil. If these changes 

 occurred without loss, the nitrogen of the urine would have 

 an equal money value with the nitrogen of ammonium 

 salts, or nitrate of sodium ; owing, however, to the vola- 

 tility of carbonate of ammonium, considerable losses are 

 apt to occur during the decomposition of urine. 



The nitrogen of the solid excrements is not in a form 

 suitable for plant food, and will be only slowly converted 

 into nitrates in the soil. Taking into consideration both 



