16 REPORT OF THE AGRICULTURAL RESEARCH 



IV. — Soil Problems. 



Drainage. — The records of drainage are maintained 

 and it is probable that another collection of data will be 

 published early next year. 



Lime and Magnesia. — The relationship between the 

 amount of gaseous carbonic acid in soils and the amounts 

 of lime and magnesia in solution has been the subject of an 

 investigation which has been conducted by Mr. Sen and 

 myself. The first section of the work was published in 

 1909 and dealt with the relation between calcium carbonate 

 and gaseous carbonic acid. The second section dealt with 

 the corresponding relationship of magnesium carbonate 

 and carbonic acid. Following this we ascertained the 

 solubility of the two carbonates when present together and 

 also of dolomite under like conditions. It then transpired 

 that if magnesium carbonate is present in anything more 

 than quite small quantities, calcium carbonate becomes 

 practically insoluble. Dolomite was found to dissolve as 

 a double salt in carbonic acid, but the maximum concen- 

 tration which we could obtain was smaller than was anti- 

 cipated from a consideration of the other work. The pre 

 sence of either calcium carbonate or magnesium carbonate 

 was found to protect dolomite from the action of carbonic 

 acid. Magnesium carbonate protects it practically en- 

 tirely, because it rapidly forms a solution of bicarbonate 

 so concentrated that no appreciable amount of calcium car- 

 bonate can dissolve in it and hence the dolomite cannot 

 dissolve. Calcium carbonate does not protect it quite so 

 perfectly, but this salt rapidly forms, in contact with 

 carbonic acid and water, a solution of bicarbonate so strong 

 that little or no more calcium carbonate can dissolve in it 

 and hence the dolomite can only dissolve to a limited degree. 



This work has shown that no fertile soil can contain 

 material proportions of magnesium carbonate, for if it did, 

 the lime would become practically insoluble and the plant 

 would die of lime starvation. This is probably the reason 

 why in so many of the experiments which have been made 

 in Europe and America on Loew's lime-magnesia ratio in 



