CULTIVATION. 169 



Since, as already remarked, the bine and leaves of the 

 hop plant generally remain on the farm, it follows that the 

 major part of the plant food they contain is sooner or later 

 returned to the land. 



To maintain the fertility of the soil in equilibrium it is 

 therefore principally necessary to devote attention to the 

 amount of plant constituents that actually goes- off the land 

 in the form of hop cones, the chief of these constituents being 

 nitrogen and potash, an ample provision of which in the soil 

 has been proved by numerous experiments to be of prime 

 importance to the well-being of the hop plant. Of course, 

 also, according to the nature of the soil, neither lime nor 

 phosphoric acid should be forgotten. 



Usually there is no need for any special addition of sul- 

 phuric acid, magnesia, or iron to the soil, plants in general, 

 and hops in particular, requiring such small proportions 

 of these bodies that there is no fear of the ground becom- 

 ing exhausted in this respect. Furthermore, sufficient 

 amounts of these last-named bodies, to some extent in a 

 dormant condition, are added to the soil in stall manure, 

 in compost, and also in some artificial manures, e.g., potash 

 salts, etc. 



Inter alia, the method of gathering the hop crop exercises 

 a certain influence on the amount of plant food required. 

 Thus, if the bine is cut off at picking time the transmigratory 

 substances present in the leaves and stems are lost to the 

 rootstock, and consequently an increased manuring is neces- 

 sitated. 



Hanamann's researches {Allgemeine Brauer- tmd Hopfenzeit- 

 ung, 1887) show that when the cutting of the bine is delayed 

 until the plant has died down after harvest, 28'3 per cent, of 

 the phosphoric acid present in the stem and leaves at gather- 

 ing time will have returned to the rootstock, together with 



