Field ETperiments on Root-Crops. 503 



The chloride of sodium (common salt), which enters so largely 

 into the composition of these salts, has in itself a decidedly- 

 beneficial effect upon root-crops grown on light sandy soils ; it is 

 therefore further necessary to eliminate, if possible, the effects 

 likely to be produced by its action. To this end one portion of 

 the experimental field was manured with common salt, and 

 another portion with crude German potash-salts. After a good 

 deal of consideration, I laid down the following scheme, having 

 special reference to light soils : — 



No. 



1. Farmyard-maniu-e, at the rate of 20 tons per acre. 



2. Farmyard-manure, at the rate of 10 tons per acre, and 4 cwts. of dissolved 



bone-ash. 



3. Dissolved bone-ash, at the rate of 4 cwts. per acre. 



4. Unmanured. 



5. Crude potash-salts, at the rate of 4 cwts. per acre. 



6. Common salt, at the rate of 4 cwts. per acre. 



7. Dissolved bone-ash, at the rate of 4 cwts., and crude potash-salts, at the 



rate of 4 cwts. per acre. 



8. Dissolved bone-ash and common salt, each at the rate of 4 cwts. per acre. 



Each experimental plot was exactly one-twentieth of an acre. 



For root-crops this is a convenient and sufficiently large piece 

 of ground for each experiment. Smaller plots I do not recom- 

 mend, and patches of land measuring only the 100th part of an 

 acre or less, in my opinion, are decidedly objectionable for 

 field trials upon roots. 



It is to be regretted that in the preceding scheme only one 

 plot was left unmanured. In more recent field trials three plots 

 are left without any manure ; in this way an insight is obtained 

 into the variations of the natural productive powers of different 

 parts of the experimental field. The unmanured plots are best 

 placed one right in the middle, and two at the ends of the 

 experimental field. 



It will hardly be necessary to remind the reader that farmyard- 

 manure contains all the mineral elements which are found in the 

 ashes of swedes, and besides these mineral constituents, supplies 

 ammoniacal salts, nitrogenous and carbonaceous matters to the 

 land. 



Good farmyard-manure, that is to say, manure in which the 

 urine of animals and the soluble matters of the excrements have 

 been well preserved from being washed out by rain, &c., contains 

 about a half per cent, of potash. The dressing of 20 tons per 

 acre thus added to the land considerably more potash than the 

 crude German potash, which contained only 24 per cent, of 

 sulphate of potash. Even half that dressing of yard-manure, 

 which in No. 2 was applied to the land in conjunction with 



2 L 2 



