130 EXPERIMENTS UPON ROOT-CKOPS 



considerably higher where the mineral manures were used than 

 where farmyard manure was employed, whether alone or with 

 the cross-dressings. With the mineral manures used alone, 

 and less than 6 tons of roots produced, there was in one case 

 rather over, and in the other very nearly, 13 per cent, of sugar 

 in the roots ; and in several other cases there was nearly, or 

 over, 12 per cent. 



The lowest percentage of sugar comes where the very 

 excessive cross-dressing of 184 lb. of nitrogen was employed ; 

 the nitrate of soda produces almost as bad a result, and in both 

 cases the sugar is lowest where potash is omitted and only 

 superphosphate is supplied with the nitrogenous manure. The 

 l)est results, as to proportion of sugar, come where rape cake 

 or ammonium -salts are used as sources of nitrogen and where 

 potash is also supplied. The amount of nitrogen and of 

 mineral matter in the roots was found to vary in the opposite 

 sense, being at the highest where the sugar was lowest, and 

 vice versa. 



It is quite evident from these results, that the amount of 

 crop grown depends very largely upon the amount of nitrogen 

 available within the soil ; but that with crops forced beyond a 

 certain moderate limit of produce, the proportion of leaf is 

 unduly large, the percentages of nitrogen and of mineral 

 matter in the root are relatively high, and the percentage of 

 sugar is objectionably low ; all these conditions indicating 

 too much luxuriance and defective maturity at the time of 

 taking up the crop. 



B. Second Series, 1898-1901. 



The conditions under which the sugar-beet was grown in 

 the first series were so different from those which prevail when 

 the crop is grown for sugar-making that a second series was 

 begun in 1898, when much smaller amounts of nitrogen were 

 employed and the plants were grown more closely together. 



The land was a portion of the mangel field which had 

 previously been receiving dung. It was subsoiled and well 



