48 



THE ROTHAMSTED EXPERIMENTS. 



carbohydrates are so largely formed, was much higher than 

 in that of the root ; though, as Tables 10 and 12 show, by 

 far the greater part of the total potash of the crop was found 

 in the root, where is the great accumulation of sugar. 



Before leaving the subject of the experiments with sugar- 



manurt ** beet > {t wil1 be wel1 to refer brie % to the amount of the 

 nitrogen supplied in manure which is recovered in the in- 

 crease of crop. Below are shown the amounts recovered in 

 the increased produce of the roots only, taking the mean of 

 plots 6 and 4, with potash as well as superphosphate as the 

 mineral manure. The results are given for the three years 

 of the direct supply of the nitrogenous manures, and for five 

 years, three with and two without, the direct supply ; and 

 the figures show the amounts of nitrogen recovered in the 

 increased produce of roots for 100 supplied in manure : — 



Nitrogen 



manure 

 and re- 

 gained in 

 crop. 



As the leaves are annually returned to the land as manure, 

 it will be obvious that, taking the average over a number of 

 years, it is only the amount in the roots that can be credited 

 as immediate return from the manure employed. It is seen 

 that the highest amount recovered is from nitrate of soda — 

 namely, 61.3 per cent over the 3 years, and 66.9 per cent 

 over the 5 years ; next we have 49.6 per cent over the 3 

 years, and 57.4 per cent over the 5 years, with ammonium- 

 salts and rape-cake ; then 45 per cent over the 3 years, and 

 52.7 per cent over the 5 years, with rape-cake ; and lastly, 

 only 42.9 per cent over the 3 years, and only 49.0 per cent 

 over the 5 years, with ammonium-salts. These amounts are, 

 however, higher than those obtained with wheat or barley — 

 a result no doubt chiefly due to the period of accumulation 

 and growth extending much later in the season than in the 

 case of those grain crops ; and hence also, no doubt, is to be 

 explained the much greater accumulation of nitrogen under 

 equal conditions of soil by maize than by either wheat or 

 barley. We shall recur to this subject further on. 



Plan of ex~ 

 periments 

 with man- 

 gel-wurzel. 



4. Experiments with Mangel- Wurzel. 



We have now to consider the results of experiments with 

 manzel- wurzel, a variety of beet largely used in some districts 

 of our own country for feeding purposes. The experiments 

 were made in the same field, and on the same plots as those 



