manure 

 alone, 



172 THE EOTHAMSTED EXPERIMENTS. 



Average In conclusion, it is seen that the average produce of the - 



produce. ^0 years by farmyard manure was nearly 35 bushels ; which 

 is about 7 bushels more than the average of the United 

 Kingdom under ordinary cultivation ; and it is not far short 

 of 3 times as much as the average of the United States, or of 

 the whole world ! 



Various Artificial Manures. 



The next question is, Which constituents of farmyard 

 manure are the most effective for wheat in this agricul- 

 turally exhausted rather heavy soil, with a raw clay subsoil ? 

 The first illustrations on this point will be drawn from 

 Table 48. 

 Mineral The average of the 40 years by mineral manure alone 



shows an increase of only 2 bushels over that of the un- 

 manured plot, though during the preceding 8 years (1844-51) 

 it had received mineral and nitrogenous manures, whilst the 

 unmanured plot had, during the same period, grown eight 

 Addition unmanured wheat crops. The addition to the mineral 

 of nitrogen. manure f the first 43 lb. of nitrogen (plot 6) gives an 

 average annual increase of 9| bushels ; the second 43 lb. 

 (plot 7) an increase of 9, and the third 43 lb. (plot 8) only 

 3f bushels increase. This result affords an illustration of 

 the inapplicability of conclusions from manure experiments 

 when the condition of the land is too high already, or when 

 Nitrate v. an excess of manure is applied. A given quantity of nitrogen 

 in the form of nitrate, yielded more produce than an equal 

 quantity in the form of ammonia. The nitrate, being always 

 applied in the spring, was not subject to winter drainage. It 

 is, however, very soluble, and becomes rapidly distributed 

 and available ; but it is at the same time very subject to 

 Loss of drainage after sowing, if heavy rains follow. Prior to 1878, 

 nitrogen bij tne ammonium-salts were applied in the autumn, and a great 

 loss of nitrogen by winter drainage, chiefly as nitrates, was 

 proved. To the loss of nitrogen by drainage reference will 

 be made further on. 

 increase Thus, minerals not being deficient, the increase was in 



^imat'eto P ro P or ti° n to the available nitrogen, when it was not applied 



available in excess. 

 nitrogen. 



influence of It will be of interest here to refer to the influence of 

 mtrogen- nitrogenous manures in increasing the production of the 



OUS l)XCt7b~ O A 



ures on non-nitrogenous constituents of our crops, as illustrated in 

 non-nitro- Table 34 (p. 107). It shows the estimated amounts of carbon 



qenous con- vjr ' t • ■* 



stituent of per acre per annum m various crops grown by mineral 

 crops. manure without nitrogen, and by the same mineral manure 



ammonia. 



