ACTUAL VALUE OF MANURE 221 



them. The cereal grains and the roots contain about 

 the same proportion of nitrogen in their dry substance ; 

 the roots, however, supply much more potash. Potatoes 

 stand below roots in manurial value when compared 

 on the basis of their dry substance. Wheat straw 

 takes the lowest place of all when foods are compared 

 on the basis of their dry substance. 



(2) Actual Value. — The nitrogen, phosphoric acid 

 and potash in one ton of decorticated cotton cake, if 

 reckoned at the market values of these substances in 

 active manures already quoted, will have a total value 

 of i65 12s. Id. ; the actual value to the farmer is, how- 

 ever, far below this. The actual value of the manure 

 from a food depends partly, as we have already seen, 

 on the amount of nitrogenous mr.ttcr, phosphates and 

 potash appropriated by the animal ; these have in 

 every case to be deducted from the constituents of the 

 food before we can estimate its value as manure. The 

 actual manure value depends also partly on the con- 

 dition of the nitrogen, phosphates and potash present 

 in the manure. It depends, finally, to a very con- 

 siderable extent, on the changes which the manure 

 undergoes before it reaches the land. 



The potash in fresh manure is mostly in a readily 

 soluble form, and may be reckoned as having a money 

 value equal to the potash in commercial potash salts. 

 The phosphates in manure can hardly be reckoned as 

 equal in availability to the soluble phosphate of super- 

 phosphates, but it may probably be considered as 

 similar in value to the phosphates in bone dust. The 

 nitrogenous matter in fresh urine (chiefly urea) is 

 perfectly soluble, and diffuses are readily in the soil as 

 a nitrate ; is is rapidly converted into carbonate of 



