THE PEINCIPLES OF MANUEING 



199 



nitrogenous manures and potash salts may also be used 

 with advantage. 



Nearly all recipes for garden manures include a cer- 

 tain amount of gypsum and ferrous sulphate (copperas), 

 but for the reasons previously mentioned, these sub- 

 stances cannot be expected to produce any great effect. 

 Practical men appear to think that ferrous sulphate is 

 really beneficial on calcareous soils, and even on ordinary 

 soils, for certain crops, e.g., spinach. Gypsum, again, 

 can only be useful on non-calcareous soils and its effects 

 under any circumstances are more than doubtful. As 

 a matter of fact some of the best informed French gar- 

 deners have ceased to employ either of these substances. 



From the point of view of their manurial requirements, 

 the vegetable crops may be grouped as follows : 



The characteristic requirements of these various groups 

 are as follows : - 



I. Principally phosphate with a liberal supply of 

 potash and small amount of nitrogen. 



II. Principally potash with moderate amount of phos- 

 phates and small amount of nitrogen. 



III. Principally nitrogen with liberal quantity of phos- 

 phates and small amount of potash. For the more 

 delicate plants of this group celery, asparagus, etc., 



