Field Experiments on Root-Cropa. 



519 



The average produce of tlie unmanured plots tlius amounted 

 to nearly 4 tons, and the dung, on an average, gave an increase 

 of rather more than li ton per acre. 



Taking the exact average produce of the unmanured plots as 

 a basis for calculation, we obtain the following increase or de- 

 crease in each experiment : — 



Table 5. — Showing the Increase or Decrease in Potatoes on each Plot, 

 calculated to the Acre, and Average of Increase or Decrease. 



On looking over the results of these potatoe experiments, the 

 following points cannot fail to arrest the reader's attention : — 



1. Foremost, he will notice that the heaviest crop was obtained 

 by the use of good rotten dung. 



2. But superphosphate and crude potash-salts, a purely mineral 

 manuring, also gave a nearly equal increase. The mixture of 

 superphosphate and crude potash-salts appeals to be specially 

 useful for root-crops on light land. 



3. The efficacy of superphosphate as a manure for potatoes on 

 light land is not only enhanced by potash-salts, but also, though 

 to a minor extent, by common salt. 



4. It is remarkable that whilst the addition of salt to super- 

 phosphate had a very beneficial effect, common salt alone slightly 

 diminished the crop. 



5. Potash-salts applied alone, though by no means the most 

 desirable manure for potatoes, nevertheless had a better effect 

 than common salt ; for whilst crude potash-salts gave an increase 

 of nearly 8 cwts. per acre, common salt produced 7 cwts. and 

 44 lbs. less than the unmanured plots on an average. 



Perhaps it may appear strange that there were many more 

 diseased potatoes on the first four plots than on the remaining 

 six. This, however, I am informed, may be accounted for by 

 the fact, that a small portion of the end of the first four plots 

 was old land. On this old land, constituting about l-30th 



2 M 2 



