126 The Rothamsted Barley Experiments. 



the third column actually received ammonia-salts equal to 861b. 

 nitrogen the first six years, equal to 431b. nitrogen the next 

 ten years, and nitrate of soda equal to 431b. nitrogen the 

 last sixteen years. The increase here, brought about by use 

 of the nitrate, is seen to be greater still, and is again by far 

 the greater where the superphosphate is used. As the rape- 

 cake itself contains phosphates, the construction to be placed 

 upon the results in the fourth column is that the phosphate 

 of the rape-cake was effective when none was otherwise 

 supplied ; but when it was so applied in addition, there was 

 more effect with the nitrate, with its more rapidly available 

 nitrogen, than with the rape-cake, with its greater actual 

 amount of nitrogen, but in a less rapidly available condition. 



Since nitrogenous manures alone had much more effect than 

 mineral manures alone, it is obvious that the exhaustion 

 induced by the continuous growth of the crops is character- 

 istically that of nitrogen. 



Both with and without nitrogenous supply, phosphates 

 were more effective than potash salts, showing that the avail- 

 able store of phosphoric acid in the soil became deficient 

 sooner than that of potash. With the, shorter period of 

 growth of barley than of wheat, and its greatei propor- 

 tion of surface-rooting, both nitrogenous and mineral 

 exhaustion are sooner developed ; and, so far as mineral 

 exhaustion is concerned, the available supply of phosphoric 

 acid was sooner exhausted than was that of potash. In deed 9 

 in ordinary agricultural practice, it is clearly established that 

 superphosphate is more effective with the spring-sown than 

 with the autumn-sown cereals. 



CHAEACTEEISTICS OF THE BEST AND WOKST 

 SEASONS OP THE THIETY-TWO YEAES. 



Eespecting the influence of season on the amounts of 

 produce, the best seasons of the thirty-two were 1854 and 

 1857 ; the best season for wheat 1863 was also a very good 



