DEPENDENT UPON NITROGENOUS MANURES 99 



A. Effect of Nitrogenous Manures. The mangold, being 

 a plant with a large leaf development, was at one time to 

 a certain extent regarded as one of the restorative crops, 

 capable, with its large area of leaf, of drawing upon the 

 atmospheric nitrogen and thus rendering itself independent of 

 nitrogenous manures. Though it was obvious that nitrogenous 

 manures had a powerful effect even upon leafy crops, it was 

 urged that the benefit consisted in starting the crops, which, 

 as soon as they had attained their proper development of leaf, 

 would continue to feed themselves by drawing upon the 

 nitrogen of the atmosphere. It was with the view of testing 

 the truth of this opinion that the manuring on Plots 7 was 

 arranged. They receive superphosphate and sulphate of 

 potash as mineral manures, together with a small quantity of 

 nitrogen, 36 J Ib. per acre of ammonium-salts containing 7 '8 Ib. 

 of nitrogen per acre, i.e., about one-eleventh of the amount 

 applied to the plots in Series A. 



On the hypothesis indicated above, the small quantity of 

 nitrogen would act as a starter, and establish the plant, which 

 should then be able to maintain itself upon atmospheric nitrogen. 



The results, however, yielded by Plots 7 as compared with 

 Plots 6 showed this opinion to be mistaken ; the small addition 

 of 7 '8 Ib. of nitrogen per acre produced an increase of crop of 

 1*4 ton per acre only, whereas a further 86 Ib. of nitrogen 

 raised the crop by 87 tons per acre. This experiment was 

 discontinued 1902. 



Thus the opinion may be dismissed that the mangold plant 

 when once started can become independent of the nitrogen in 

 the soil and manure. 



We may next pass on to a consideration of the effects of 

 the varying forms and amounts of nitrogen when used with- 

 out any mineral manuring, i.e., on Plots 8, where no standard 

 manures are applied. The entirely unmanured plot (8 O) 

 has produced an average crop of 3 '69 tons of roots only, 

 which is increased by the application of 86 Ib. nitrogen in the 

 ammonium-salts to 5'61 tons, and by 98 Ib. of nitrogen in the 



