46 THE KOTHAMSTED EXPERIMENTS. 



further show that where ammonium-salts, ammonium-salts 

 and rape-cake, or rape-cake alone, was employed, there was 

 considerably more sugar produced on plots 4 and 6, where 

 potash was supplied, than on plot 5, where superphosphate 

 was the only mineral manure. Doubtless with the continued 

 supply of superphosphate alone as the mineral manure, and 

 the growth forced by nitrogenous supply, the amount of pot- 

 ash available within the range of the roots had become more 

 or less exhausted. Where the nitrogen was applied as nitrate, 

 however, there was no deficiency of sugar -production with 

 superphosphate only as the mineral manure ; a result prob- 

 ably due, as already observed, to the greater range of the 

 roots induced under the influence of the soluble and more 

 rapidly distributed nitrate, thus securing a better command 

 of the potash of the soil and subsoil. 

 Sugar-pro- The bottom division of the table illustrates very strikingly 

 and, 1 ™ iv ^ ne interesting fact of the dependence of the amount of the 

 of nitrogen, non-nitrogenous substance — sugar — produced on the amount 

 of nitrogen available within the soil. Thus, taking the results 

 for plots 6 and 4, with full mineral supply including potash, 

 there is over the three years — for 1 lb. of nitrogen supplied 

 — when as nitrate 34.1 lb., as ammonium-salts 27.4 lb., as 

 rape-cake 31.5 lb., and when applied in excessive amount in 

 ammonium -salts and rape-cake together 19.4 lb., of sugar 

 produced. Taking the results for the five years, three with 

 direct supply and two with residue only, the increased pro- 

 duction of sugar for 1 lb. of nitrogen supplied is somewhat 

 greater — namely, with the nitrate 38.1 lb., with the ammo- 

 nium-salts 31.4 lb., with the rape-cake 36.4 lb., and with the 

 ammonium-salts and rape-cake together 24.1 lb. It will be 

 seen, however, that when superphosphate without potash 

 was used as the mineral manure, the produce of sugar for 

 a given amount of nitrogen in manure was, excepting in the 

 case of the nitrate, distinctly less. 

 Cariohy- It is not only in the case of sugar-beet that the amount 

 drates of produced of the special carbohydrate of the plant is largely 

 supply of influenced by the supply of nitrogen. It is so in the case of 

 nitrogen, root-crops generally, which may be fitly called sugar-crops. 

 As we shall see further on, the result is very similar in the 

 case of grain crops, the produce of which is greatly increased 

 by nitrogenous manures ; and in their case it is the carbo- 

 hydrates — starch and cellulose — that are chiefly produced. 

 It is also much the same with potatoes, the increased pro- 

 Nitrogen- duction of starch being then the characteristic result. In 

 ousman- f ac £ j t w jjj ^ e f oun( j that nitrogenous manures are chiefly 

 crops poor used for crops poor in nitrogen, the increased produce of 

 innitro- which is characteristically that of non-nitrogenous bodies. 

 Without attempting to give a physiological explanation of 



