15 



experiments ? The question clearly admits of an answer, as 

 we know exactly what crops the incoming tenant would have 

 obtained from the residues of manure remaining in the land. 

 In order to deal with this question in a practical manner, I 

 have sought to ascertain, in the first place, what was the 

 natural produce of the land before the farmyard manure was 

 applied ; I have taken this as representing the fertility of the 

 land when it was entered upon by the improving tenant. The 

 improving tenant applies farmyard manure every year for a 

 number of years, and then leaves the farm. He is followed 

 by one who employs no manure on the land in question. What 

 is the money value to him of the unexhausted improvements of 

 his predecessor ? It appears to me that the second tenant is 

 deriving substantial benefit so long as the produce of the land 

 remains above what it was before the farmyard manure was 

 applied, and that as soon as the crop falls to what it originally 

 was without farmyard manure all practical benefit has ceased. 

 The money value to the second tenant of the previous manuring 

 is shown by the value of the excess of crop which this manuring 

 produces, this excess being reckoned by subtracting from each 

 crop the produce obtained before the application of manure 

 commenced. 



The produce of the unmanured plot 6 1 , in the first year of 

 the experiment, 1852, was 29 bushels of barley and 17 cwts. 

 of straw ; in the first five years of the experiment the average 

 produce of the same plot was 28 J bushels, and 16| cwts. of 

 straw. As it is impossible to say that the first season was 

 one of average produce, I adopt the mean of the first five 

 years as indicating the producing power of the soil when the 

 first tenant commenced his operations. In adopting this mean 

 of five years we have more probably put the original fertility 

 of the soil too low than too high. During twenty years, 

 1852-71, plot 7 1 received annually 14 tons of farmyard 

 manure, ploughed in in spring before sowing the barley ; the 

 average produce during this period was 48 bushels of barley, 

 and 28J cwts. of straw. 



We assume that the second tenant now enters on the 

 land, and leaves the field unmanured. The average pro- 

 duce of barley during the first five years without manure 



