ENGLISH AGEICULTURE. 171 



on with the fullest possible vigour ; and the growth of turnips 

 is carried on through the months of May, June, and onward 

 to October, a period during which the temperature of the 

 soil is suitable for the development of nitric acid. Therefore 

 it appears as if the turnip received its nitrogen from the 

 soil in sufficient quantities, and that the tables are turned ; 

 and whereas in the case of corn crops the tension is for 

 nitrogen, in the case of root crops the condition of tension is 

 with reference to mineral matter. I think that partly 

 explains the fact, because turnips require nitrogen. If you 

 look into the composition of a turnip crop you will find it 

 takes up a great deal of nitrogen, but still the application 

 of superphosphates to the soil seems to be especially requisite. 

 Bear in mind also the words used by Dr. Gilbert, that the 

 turnip and root crops are essentially sugar crops, and phos- 

 phoric acid seems to be needed where you have crops of this 

 description. 



How is it then with the application of these lesser im- 

 portant substances, sulphate of potash, sulphate of soda, and 

 sulphate of magnesia to our turnip crops ? The effect is very 

 small. Whereas you get with superphosphate alone 7J tons, 

 you obtain 8 tons 8 cwt. with the mixture of superphos- 

 phate and these other mammal substances. In another 

 case we notice an increase of from 6 tons 1 cwt. to 6 tons 

 16 cwt. In another case, the third season you get an increase 

 from 4 tons 14 cwt, to 5 tons 9 cwt. only. In another case 

 an increase from 1 ton 18 cwt. to 2 tons 2 cwt., a very slight 

 increase. Superphosphate produces a great effect, but the 

 addition of these other substances gives a small and inade- 

 quate but apparently constant effect. The effect of ammonia 

 on the turnip crop is small. For instance, on an unmanured 

 plot I have before me a result of 2 tons 6 cwt., but dressed 

 or crossed with ammonia salts, I see only 3 tons 7 cwt. The 

 effect is not satisfactory, the effect of superphosphate is very 



