186 



THE ROTHAMSTED EXPERIMENTS. 



Phosphoric 

 acid. 



Effect 

 of bad 

 seasons. 



much shorter period of collection, in the case of the spring- 

 sown crop. In both crops, by far the greater proportion of 

 the soda is found in the straw ; but there is more in the 

 grain of barley than in that of wheat, due doubtless to the 

 palcce or chaff being adherent and included with the grain in 

 the case of the barley, but not in that of the wheat. 



"With regard to the phosphoric acid results, as superphos- 

 phate was applied equally to all four plots, the difference in 

 the amounts taken up and retained are obviously not due to 

 differences of available supply, but are connected with the 

 differences in the amounts of produce due to the supply or 

 deficiency of other constituents. As in the case of the barley, 

 by far the greater part of the phosphoric acid of the whole 

 plant is accumulated in the grain, but the proportion remain- 

 ing in the straw is greater in the wheat than in the barley. 



Keference to the details in the Table (52) will show that 

 generally, and even where there was full supply, there was 

 less of both potash and phosphoric acid in the crops over the 

 third than over the fourth period of 10 years — a result doubt- 

 less due to the third period including a more than average 

 proportion of unfavourable seasons, as already referred to 

 when considering the amounts of produce. 



Table 53 

 explained. 



We have thus traced the effects of exhaustion and of full 

 manuring, of nitrogenous and of non-nitrogenous manures, 

 on one particular soil. It has been seen how very different 

 was the effect of one and the same manuring in different 

 seasons ; but the real extent of this variation is more clearly 

 brought out in Table 53, which shows the amounts of pro- 

 duce in the best and in the worst seasons of the 40 years, 

 and the average produce over the whole period, under very 

 opposite conditions as to manuring. 



TABLE 53. — Wheat year after year on the same Land. Pro- 

 duce of the best Season, 1863 ; of the worst Season, 1879 ; and 

 the Average of 40 years, 1852-91. 



Plot. 



Description of manures— quantities per acre. 



Dressed grain per acre — bushels. 



Best 

 season, 

 1863. 



Worst 

 season, 

 1879. 



Differ- 

 ence. 



Average 

 40 years, 

 1852-91. 



Unmanured 



Farmyard manure 



Mixed mineral manure alone . 



Mix. min. man. and 200 lb. am.-salts = 43 lb. N 



Do. and 400 lb. am. -salts =86 lb. N. . 



Do. and 550 lb.i nitrate soda =86 lb. N. 



Do. and 600 lb. am.-salts = 129 lb. N. . 



17i 



44 



19f 



39f 



53f 



55f 



55} 



10J 

 16J 

 22 



12J 



28 



14 



35J 



13 



34| 



15 



24* 



33£ 



35| 



36£ 



1 275 lb. nitrate soda =43 lb. nitrogen, 1885 and since. 



