356 VALUATION AND PURCHASE [chap. 



In the somewhat analogous case of the compensa- 

 tion to be paid to the outgoing tenant for the fertiUty 

 he leaves on the farm from foodstuffs purchased and 

 consumed during the last years of his tenancy, it is 

 possible to draw up a fairly satisfactory scale. The 

 custom in many parts of the country was, and still is, to 

 allow the outgoing tenant one-half of the cost of the food- 

 stuffs he had brought on to the farm during the last 

 year of his tenancy, but such a system has obviously no 

 scientific basis. The price of a given feeding stuff is 

 determined by its value as food, not as manure ; oil or 

 fat, for example, is one of the most costly constituents 

 of a feeding stuff and yet leaves no fertilising residue 

 behind. Many foods, e.g. maize and rice, consist mainly 

 of carbohydrates and contain an unusually small pro- 

 portion of nitrogen and ash which would wholly or in 

 part add to the fertility of the farm. The proper basis 

 is to begin by ascertaining the nitrogen, phosphoric 

 acid, and potash contained in each class of feeding 

 stuff; an estimate can then be formed of how much of 

 each of these is likely to reach the manure, and a 

 valuation made of these latter quantities at the current 

 rates. The difficulty lies in estimating the proportion 

 in which the fertilising constituents will reach the 

 manure ; for example, it has already been shown 

 (p. 199) that of the nitrogen fed to an animal anything 

 up to 15 per cent, will be retained by the animal, and 

 of the rest that is excreted as much as one-half may be 

 lost in making the dung. Taking a general average 

 from the experiments quoted, it will be seen that about 

 one-half of the nitrogen in the food is likely to find its 

 way to the land in the dung produced under ordinary 

 conditions of farming. If the manure is carelessly 

 managed the losses will be greater ; on the other 

 hand, if the food is consumed directly on the land 



