CONTRIBUTIONS FROM THE WISLEY LABORATORY. 



239 



This difference in the depth of the soil was not to be found on the 

 cultivated land, for there the crops the land carried had effectually 

 prevented the washing. 



As has been repeatedly pointed out in the literature of the subject, the 

 amount of available nitrogen (i.e. nitrogen combined in the form of 

 nitrates and salts of ammonia) has a marked influence upon the extent to 

 which leguminous plants avail themselves, so to speak, of the work of the 

 nodule-forming bacteria. When a soil is rich in nitrates, as Nobbe showed, 

 the nodule production is markedly lessened, but becomes greater as the 

 quantity of nitrate is less. In a soil such as that of the Wisley Garden, 

 nitrates are never present in great quantity, for it is so unretentive that 

 water passes through very freely, and carries with it the soluble nitrates. 



The quantity of organic matter present in the soil will give some 

 indication of its nature, especially as the organic matter is the source of 

 most of the nitrogen which, after it has been acted upon by bacteria, other 

 plants are able to make use of. 



The " cultivated " soil gave the following results : 



Air-dry soil 100 



Loss on ignition * . 3*61 



Loss on drying at 100° ( = water) . 1-00 



2-61 per cent.* 



and the fallowed soil : 



Air- dry soil 100 



Loss on ignition * . 2*65 

 Loss on drying at 100° (= water) . 1*32 



1-33 per cent.* 



* These figures represent organic matter, water of combination, salts of ammonia, 

 &c, and it will be seen from them that the amount of organic matter in the cultivated 

 land as well as in the fallowed land is very small indeed. 



Professor Bottomley states in his pamphlet (I.e. p. 10) : " Inoculation 

 is useless when the legumes usually grown are producing high yields and 

 the roots show nodules in abundance." It is worthy of note, therefore, 

 that in the Wisley Garden peas and beans have not as a rule produced 

 high yields, so that in this direction also the garden offered a well-suited 

 place for the experiment. Further, no leguminous crop has been grown 

 on the site on which the experiment was conducted since the garden came 

 into the p ssession of the Society, and probably not for some years before 

 that. Nor have leguminous weeds been allowed to grow, since the land is 

 continually hoed, and no weeds succeed in maintaining their existence for 

 any length of time. 



On the other hand, however, many leguminous plants occur spon- 

 taneously in remarkable numbers in the uncultivated parts of the garden ; 

 in one part, for instance, both the furze (Ulex europacus) and the br^om 

 (Cytisus scoparius) grow well, and, in addition, the ground in some parts 

 is carpeted with the bird's-foot (Ornithopus perpitsillus), the bird's-f, ot 

 trefoil (Lotus comiculatus), vetches of various kinds (Vicia sepium, 

 V. angustifolia, V. sativa, V. hirsttta, and V. tetraspcrma), clovers 

 (Trifolium repens, T. hybridum, T. pratense, T. procumbens, and T. 



