BENEFICIAL ACTION OF SALT. 421 



mined by the "minimum" proportion of the ingredients 

 necessary for the crop under cultivation (see p. 290). In 

 the mangold the percentage of chloride of sodium is so large, 

 as compared with the other necessary substances, that 

 unless this is present in the soil in equivalent proportions, 

 the other valuable fertilizing matters, phosphates, ammo- 

 nia, and potash, no matter how liberally they have been 

 applied, can only be rendered partially available to the 

 growing crop. Common salt, therefore, should always 

 form a portion of the manure used for the mangold crop, 

 the quantity per acre being regulated by the locality, or 

 by the known composition of the soil. It may be mixed 

 with the farmyard manure intended for the crop at the 

 time of forming the heap, or it may be broadcasted at the 

 time of ploughing it in, or, if left until the spring, it may 

 be advantageously mixed with the guano, and distributed 

 with it over the surface previous to sowing. As it is not 

 a very costly article, and acts very beneficially on most 

 soils, especially those of a dry character, it is desirable to 

 give a good dressing of it, say from 5 to 10 cwts. to the 

 acre to the mangold, and also to the turnip crop ; this is 

 not more than sufficient for the interval between their 

 recurrence in the rotation on the same field. 



The beneficial action of salt upon the growth of the 

 mangold is clearly shown by the results of Mr. Caird's 

 experiments. 1 In order to satisfy himself as to the best 

 manure for the crop, he directed certain portions of a field 

 of uniform soil to be manured with different substances 

 farmyard dung, Peruvian guano, superphosphate, and 

 nitrophosphate by themselves, and mixed together in 

 certain proportions. In every case when salt was added 

 to either of these, an increased yield was obtained. The 

 following tabulated statement of the results of the experi- 

 ments gives the various manures used, with their respec- 



1 Roy. Agri. Soc. Jour.) vol. xvii. p. 400. 



29 



