172 THE PRINCIPLES OF 



great; but the effect of crossing it with ammonia salts in 

 the case of the turnip crop is only to raise the yield from 

 8 tons l(j cwt. to 9 tons 18 cwt. per acre. 



In examining into the effects of various manures upon 

 mangel wurzel we must be prepared for different results. In 

 the first place, we are dealing with a crop belonging to an 

 entirely different order (Chenopodiaceae), and therefore pre- 

 sumably with a different habit of growth, and selecting its 

 food in a different manner. The striking effect of chloride 

 of sodium upon this crop has been already mentioned, and 

 must be borne in mind in examining the effects of various 

 fertilizers at Rothamsted. 



First of all we see brought out strongly in the case of both 

 turnips and mangel wurzel the superiority of farmyard 

 manure. This I have already drawn attention to as in a 

 great measure accounting for the high estimation in which 

 this fertilizer is held. Repetition only confirms the result of 

 previous experiments, and a large number of plots support 

 the conclusion that as far as the root crop is concerned there 

 is nothing like farmyard dung. 



Secondly, the need of mangel wurzel for nitrates is 

 abundantly shown. The effect of superphosphate alone is 

 less marked than in the case of turnips, and it evidently 

 requires to be aided by a source of nitric acid, the best being 

 nitrate of soda. It is curious and not easy to explain, that 

 ammonia salts produce a poor effect compared with nitrate 

 of soda except when used upon plots dressed with farmyard 

 manure, when the ammonia salts give equally excellent 

 results. Five hundred and fifty pounds of nitrate of soda, at 

 once send up the yield of mangel wurzel many tons per acre, 

 in many cases trebling and sometimes quadrupling the crop. 

 The effect of superphosphate without nitrate of soda is not 

 nearly so marked as in the case of turnips. The increase 

 over umnanured plots is not striking, but when nitrate of 



