3i8 SYSTEMS OF MANURING CROPS [chap. 



farmyard manure rich in potash is also used. The 

 beneficial effect of potash salts is, however, less apparent 

 when nitrate of soda is employed as a source of nitrogen, 

 because the soda attacks and renders soluble some of 

 the reserves of potash in the soil. Potash thus becomes 

 more necessary when ammonium salts or rape cake 

 form the source of nitrogen ; but in any case it is 

 desirable to use some sodium salt, such as common salt 

 itself, as an economiser of the more valuable potash. 



(4) That with proper manuring mangolds can be 

 grown year after year on the same land without any 

 falling-off in yield or any accumulation of disease. It 

 is sometimes convenient to keep a little piece of land near 

 the homestead always in mangolds, this can be done 

 for a long time in perfect safety if organic manures are 

 employed to maintain the texture of the soil. 



Coming now to the requirements of the crop in 

 practice, not much variation will be required because of 

 its position in the rotation, since mangolds are practically 

 always grown on a stubble with the land in compara- 

 tively poor condition. The basis of a manure for man- 

 golds should be dung ; probably there is no crop in the 

 rotation to which farmyard manure can be better applied 

 than to mangolds. When, therefore, the mangolds are 

 grown on a portion of the root breadth, the dung should 

 be concentrated on this part of the field. On light 

 soils and in dry climates it is better to plough in the 

 dung in the autumn and grow the mangolds on the 

 flat, lest the fresh manure should leave the soil too open 

 and let in the drought, but on heavier land and where 

 the rainfall is greater the land will generally be laid up 

 in ridges. The dung should be spread in the furrows ; 

 the artificial manure, other than nitrate of soda or other 

 active nitrogenous manure, should be sown on the 

 dung and the ridges then split back on to the dung. 



