28 



THE ROTHAMSTED EXPERIMENTS. 



Accumula- 

 tion from 

 rape-cake. 



Further 

 trials with 

 Swedes. 



fully ripe will be the roots ; and within limits it is desirable, 

 with a view to the storing qualities of the root, that it should 

 not be too ripe. 



After the four crops of Swedish turnips had been taken 

 from the land, barley was grown for three years in succession 

 without any manure, in order as far as possible to equalise 

 the condition of the various plots, as affected by the previous 

 manuring. It will suffice to say that the results clearly 

 showed that there had been accumulation where rape-cake 

 had been applied. 



Then for five years in succession (1856-60) Swedish turnips 

 were again grown on the comparatively exhausted plots, 

 much on the same plan as before, but with smaller amounts 

 of nitrogen supplied. No special interest attaches to the 

 results over these five years for our present purpose. 



Table 7 shows the average produce per acre over the next 

 ten years, 1861-70, again with Swedish turnips. 



During this period larger quantities of nitrogen were 

 again applied, but for mineral manure superphosphate of 

 lime was used alone — that is, without any further addition of 

 either potash, soda, or magnesia. 



TABLE 7. — Swedish Turnips. Results showing the effects of ex- 

 haustion and manures. Mean of ten seasons, 1861-70. Manures 

 and produce per acre per annum. 



Series 1. 

 No nitro- 

 genous 

 manure. 



Series 2. 

 Sodium 

 nitrate 



= 82 lb. 



nitrogen. 



Series 3. 

 Ammonium- 

 salts = 

 82 lb. 

 nitrogen. 



Series 4. 

 Ammonium- 

 salts and 

 rape-cake 

 = 180 lb. 

 nitrogen. 



Series 5. 



Rape-cake 



= 08 lb. 



nitrogen. 



WITHOUT MINERAL MANURE. 



firmed. 



The results of these experiments are little more than con- 

 ™Jw c<m ~ firmatory of those which have gone before, but the amounts 

 of produce are throughout on a lower level. This can only in 

 part be attributed to the exclusion of potash from the man- 

 ures. It is doubtless mainly due to the incidental circum- 

 stance that in growing the same description of crop, with the 



