4 



JOURNAL OF THE ROYAL HORTICULTURAL SOOll'VPy. 



phosphates nnd potash forms n coniph^io iiuuuive for siicli planls, 

 whereas it is hicking in llic nit lo.i^cii wliich t1u> grassi^s specially 

 require. The manure, in consequence, f:n()in-s Icguuunous plants 

 growing in competition with the grasses, until they hecome the domi- 

 nant species of the plot. Similarly we can understand why certain 

 shallow-rooting grasses like ' sheep's fescue,' ' hent grass,' and ' sweet 

 vernal ' become dominant on the plots receiving ammonium salts. 

 They are all grasses possessing a shallow I'oot-system, and it is 



Fig. 3. — Turf from the Plot receiving only Nitrogen in the form 

 OF Ammonium Salts. 



Vegetation wholly grasses, among which Festuca ovina is the most 

 prominent. 



characteristic of the ammoniacal manures to be caught up and retained 

 by the surface layer of the soil. Such plants as have their roots in 

 this surface layer are therefore most benefited by the manure and get 

 an advantage in the competition that is always going on in the piece of 

 grass land. On the other hand, when nitrate of soda is a source of 

 nitrogen, the manure washes deep into the subsoil, with the result 

 that such grasses and other plants which possess a deep tap-root 

 derive the chief benefit from the manure. We can see reasons for one 



