382 
Field Experiments on Root- Crops. 
4. Common salt, in quantities of 4 cwts. per acre or more, 
added to superpliosphate, apparently does more harm than good 
to potatoes in a dry season. Practically speaking, the yield of 
potatoes on plot No. 6, upon which 4 cwts. of common salt were 
used, together with 4 cwts. of superphosphate, gave no more 
potatoes than the average produce of the two unmanured plots, 
No. 1 and No. 5, and somewhat less than the third unmanured 
plot. No. 10. Superphosphate alone, I do not doubt, would have 
given a better crop than the mixture of 4 cwts. of superphosphate 
and 4 cwts. of common salt. 
5. A striking difference will be noticed in the effects of com- 
mon salt and of potash-salts, when each is used in combination 
with mineral superphosphate. 
On plot No. 4, where 4 cwts. of superphosphate and 4 cwts, 
of potash-salts were used, the produce per acre was 8 tons 10 cwts. 
60 lbs., or an increase, by that mixture, was obtained over the 
unmanured plots, amounting to 4 tons 7 cwts. 26 lbs. ; whereas 
4 cwts. of superphosphate, mixed with 4 cwts. of common salt on 
plot No. 8, gave only 4 tons 8 cwts. 24 lbs., or, practically speak- 
ing, no increase at all over the unmanured portions of the field. 
6. It follows clearly from the results of the experiments on 
potatoes here recorded, and of those previously published by 
me, that potash-salts materially increase the produce of potatoes ; 
that they are very useful constituents in a potato-manure, at all 
events upon light land ; and that they cannot be replaced with 
advantage by soda-salts in such a manure. 
Experiments on Mangolds made, in 1870, at Escricli Home Farm, 
York, hu Messrs. Coleman and Hull. 
The field on which the following experiments were tried was 
of a light sandy character. It was divided into 12 equal plots 
of ttV^Ii of ^cre each, which were treated as regards manures, 
as on the following page. 
The dry summer greatly influenced the produce, which was 
but small on the unmanured plots, and not nearly so large on the 
manured portions of the field as it might reasonably have been 
expected on at least some of the plots in a more propitious 
season. The mangolds, topped and cleaned, were carefully 
weighed ; and in the Table given on p. 384, the results of these 
weighings are given, together with the produce of each plot, 
calculated per acre, and the increase over the average produce 
per acre of the three unmanured plots. 
The average" produce of the three unmanured plots per acre, 
was 15 tons 10 cwts. 
Although the dry weather spoiled to some extent the experi- 
