232 Transactions. — Chemistry. 



phosphate, and No. 136 had received 200 lb. sulphate of 

 potash, 100 lb. sulphate of soda, and 100 lb. sulphate of 

 magnesia. 



We have already referred to the three classes into which 

 the constituents of a soil may be divided, namely : (1) Non- 

 available mineral material for plant-nutrition ; (2) latent 

 mineral material for plant-nutrition ; (3) available mineral 

 material for plant-nutrition. These divisions are shown in the 

 following tables, the first class being represented in Tables I. 

 and II. — that is, those constituents insoluble in boiling hydro- 

 chloric acid; the second class in Tables III. and IV. — i.e., 

 those constituents soluble in hydrochloric acid excluding the 

 amount soluble in citric acid ; and the third class in Tables V. 

 and VI. — i.e., those constituents soluble in citric acid. Whilst 

 the results in the first and second class are of considerable 

 interest, as showing the composition of the soils and the stores 

 of latent plant-food contained in them, we may pass at once to 

 the consideration of Class III., since in this we have a mea- 

 sure of the present fertility of the soils. 



For the sake of clearness we repeat the most important 

 results in Tables VII. and VIII. Before considering these 

 results let us determine by what standard of fertility w^e shall 

 judge them. Dr. Dyer's investigations led him to consider 

 that a soil containing as little as 0-005 per cent, of available 

 potash is not in immediate need of potash manures, whilst 

 one containing more than O'Ol per cent, of available phos- 

 phoric acid does not require special phosphatic manuring. If 

 we adopt these standards it is at once evident that the Taupo 

 soils are, on the whole, in a fertile condition. In potash they 

 are all above Dr. Dyer's limit, and, with the exception of 

 Nos. 4 and 6, very much above that limit. In phosphoric 

 acid the first three soils are from two to four times the limit, 

 and are higher than the Mount Eden basic soils, which are 

 noted for their fertility. Of the remaining three Taupo soils 

 No. 5 is very little under the limit. No. 6 is about half that 

 quantity, and No. 4 is very poor. It will be remembered that 

 No. 6 is pure pumice, and not a sample of the Taupo soil, and 

 as such may be left out of consideration. That being so, No. 4 

 is the only sample that is decidedly deficient in phosphoric 

 acid. It is evident from the foregoing that all the require- 

 ments other than nitrogen are well represented, but if we refer 

 to Table VIII. we shall see that, without exception, the 

 results under the Taupo soils are very low, and there is not 

 the slightest doubt that they are altogether too low to give 

 luxuriant plant-growth. 



