.^22 The Wohiirn Pot-Cvlture Ex})€rimenfs, \^10-\\A'L 



A review of these figures shows that one may divide the 

 lots roughly into two sets, first, the more soluble salts (chloride, 

 sulphate and nitrate) which all show a certain stimulating 

 action, this ;' being far the most marked with the nitrate, 

 secondly, the more insoluble salts, where the influence is 

 neutral or nearly so. Setting aside the one case of the phos- 

 phate (which will be dealt with later), there would appear to 

 1)6 no instance of any toxic effect from the use of zinc salts 

 when used so as to give not more that '02 per cent, of zinc in 

 the soil. Further, that, when so used, the influence is a 

 slightly stimulating one, more especially with the more soluble 

 salts, and, in particular, the nitrate. The increased tillering 

 from the use of nitrate has been already noted, and, though the 

 straw was shortened, its total weight was, as set out in the table, 

 increased. Moreover, it was noticed that the grain from this 

 lot was essentially of glutinous nature. 



2. Zinc Phosphate and Zinc Nitrate, 1911. 



The above led to a repetition of the experiments in 11) 11 

 with special reference to the phosphate and nitrate of zinc. At 

 the same time, as the results of the 1910 work were not then 

 available, it was not possible to devise the new experiment in 

 accordance with these, and the quantities used followed the 

 lines of the corresponding experiment with lithium phosphate 

 and lithium nitrate. 8o the quantities used were respectively 

 •025 per cent, zinc, '05 per cent., '075 per cent., and "10 per 

 cent. On this experiment it is unnecessary to dwell long, for 

 it resulted in showing that practically all the applications 

 exercised a toxic influence, the higher amounts, more especially 

 with the nitrate, entirely destroying the germination of the 

 seed and so preventing any crop resulting. The zinc phosphate 

 applications did not seem to affect the germination of the seed, 

 Irut the nitrate undoubtedly .did. While the smallest dressing 

 (•025 per cent, zinc) prolonged the period of incubation, and 

 the next one ("05 per cent.) still more so, the higher quantities 

 nearly or quite killed the seed. Plate 2 shows the action of the 

 phosphate and Plate 4 that of the nitrate on the wheat crop of 

 1911. The untreated set to compare with these is (a) of Plate 1. 

 On weighing the produce the lowest dressing ("025 per cent.) 

 of zinc phosphate gave 70 per cent, of the corn of the untreated 

 soil, but all the other dressings showed much heavier losses. 

 Even the ^025 per cent, application of zinc nitrate showed 

 marked toxic action, although the previous year's experiment 

 had shown that "02 per cent, exerted a stimulating action. It 

 is hard to think that this could have been purelj' the result of 

 season. It might be pointed out, however, when comparing the 

 two seasons 1910 and 1911, that these were of very different 



