82 A UYPTIA N A GRIC UL TURE. 



be applied which will return the largest nett profit and 

 not necessarily the largest crop. There is no satisfactory 

 method of testing the soil in its relation to the production 

 of the best yield except by applying to the crop itself. 

 In other words the condition of the soil for plant growth 

 can only be ascertained experimentally. Manures are 

 fully dealt with in a later chapter but considering the 

 importance of the question the following few notes may 

 not be out of place. The soil of Egypt is usually deficient 

 in nitrogen and phosphoric acid, and very occasionally in 

 potash, hence those are the substances which require to be 

 applied to the soil in manures. Those plant foods occur 

 in manures either in an easily soluble, slightly soluble or 

 insoluble state. The plant food in an easily soluble state 

 is most valuable since it is most quickly absorbed by the 

 crop. Insoluble plant food in manure is of much less value, 

 because manures containing only such plant food but 

 poorly fulfil the object of manuring which is the supplying 

 of available plant food to the crop. Easily soluble plant 

 food is contained in nitrate of soda, sulphate of ammonia, 

 tafia, sebach coufri, superphosphate, dissolved bones, kainit 

 and sulphate of potash. Slightly soluble plant food or 

 partly soluble and partly insoluble is contained in farm- 

 yard manure, and sewage. The plant focd in bones and 

 natural mineral phosphate is insoluble. 



Crops which have a long period of growth cotton, sugar 

 cane and certain vegetables, as Jerusalem artichoke, globe 

 artichoke, asparagus, etc., should be manured with ma- 

 nures which contain the plant food in all the three stages 

 of solubility or at least in the first two. Crops which 

 receive very much water and crops on sandy soil should 



