THE ROTHAMSTED EXPERIMENTS 359 



1330 pounds on the unfertilized land, 2633 pounds where minerals 

 alone are used, and 718 where both minerals and nitrogen are 

 applied. These figures relate only to the fallow plots. On the 

 legume plots there was very much less trefoil. Director Hall 

 states that the amounts that grew on the fallow plots in 1907 are 

 rather exceptional, but that in every crop of wheat or barley there 

 is some of this wild legume, " which must have some influence 

 upon the nitrogen content of the soil." 



(6) The effect of feeding off the turnips by pasturing with sheep 

 is a distinct benefit to succeeding crops wherever the yield of tur- 

 nips amounts to much. This effect is most marked, of course, on 

 the mineral plots, where nitrogen is very deficient, and it is also 

 most marked on the barley crop, which follows immediately after 

 the turnips, although the influence can usually be seen on the 

 legumes and wheat, and even on the following turnip crop. 



Before leaving Agdell field we may well try to view these results 

 from the financial standpoint, particularly during the last twenty 

 years, because the world affords no other data from crop-rotation 

 experiments in which can be studied 2o-year averages secured after 

 a preliminary period of forty years. (See also page 419.) 



In Table 59 the turnips are valued at $1.40 per ton, the clover 

 hay at $6 per ton, the barley at 50 cents a bushel, the beans at 

 $1.25 a bushel, and the wheat at 70 cents a bushel. At these prices, 

 the turnips and beans were more valuable per acre than the wheat. 

 Nitrogen is figured at 15 cents a pound, phosphorus at 12 cents, 

 and potassium at 6 cents; and it is assumed that the magnesium 

 and sodium salts cost the same as the extra salts in kainit at $15 

 a ton. These various prices may be modified and the results re- 

 calculated to fit different local conditions. 



No values are allowed for the straw of barley, beans, or wheat, 

 or for turnip leaves; but in computing the value of increases it is 

 assumed the increase in these by-products would be worth as much 

 as the extra cost of harvesting, threshing, etc. 



At the prices used in Table 59, the use of minerals in the legume 

 system has more than doubled the value of the crops produced 

 during the last 20 years, the average of which really represents the 

 condition just fifty years from the beginning, in 1848. While the 

 effect upon turnips is to change a practical failure into a crop which 



