EXPERIMENTS AT ROTHAMSTED 105 



an average increase of over 9 tons of roots when superphos- 

 phate and potash were also applied. When the potash is omit- 

 ted (plot 5-\) the increase by ammonia salts is only 7-6 tons. 



The percentages of sugar found at Rothamsted are not so 

 high as would be obtained at the present day in a good season. 

 During the last 25 years a considerable improvement has been 

 effected both in the sugar-producing character of the beetroot, 

 and in the mode of its cultivation. 



The very small crops yielded by the purely cinereal manures 

 are seen to have contained the highest percentage of sugar. 

 \Yhen ammonia salts are used with superphosphate and potash 

 the percentage of sugar is but little diminished, while the 

 quantity produced per acre is more than doubled. The profit- 

 able use of the ammonia salts is, however, plainly dependent 

 on-t^esupply of a potash manure, when that is omitted the 

 return of sugar per unit of ammonia is considerably decreased. 

 The addition of ammonia salts to farmyard manure increases 

 the weight of the crop rather than the production of sugar ; 

 Plot i A is indeed an example of the inferior quality of roots 

 always obtained by over-manuring. 



In the Rothamsted experiments nitrate of soda gave a 

 larger produce per acre than a corresponding quantity of am- 

 monia salts, but the roots grown with nitrate of soda contained, 

 a smaller percentage of sugar. Thus while the average per- 

 centages of sugar in the roots grown on plots 4.* and 6A, and 

 5A, were 12-2 and 11-9, the percentages in the roots on the 

 corresponding plots witl^ nitrate of soda were n-o and 10-7. 



In France the beetroots cultivated for sugar are grown in 

 a three-course rotation of beets, wheat, oats. The land in- 

 tended for beetroot receives farmyard manure at the rate of 14 

 tons per acre in September. The manure is ploughed in thus 

 early to ensure its thorough decomposition in the soil. Next 

 spring the land receives 3 to jj cwts. of superphosphate, and if 

 potash is needed i- cwt. of chloride of potassium, with either 

 2 to 3 cwts. of nitrate of soda, or 2 to 2^ cwts. of sulphate of 

 ammonia. The seed is planted in rows 16 inches apart, and 

 one plant is allowed to grow in each 10 or 12 inches in 

 the row. 



