1905.] 



On the Retention of Bases by the Soil. 



9 



average weight of 2,500,000 lbs. for the fine dry earth in the top 9 inches of 

 soil, thus leaving out of account both the changing weights of the upper slice 

 and the contents of the subsoils. The two sets of figures lead to much the 

 same comparative results, but the lower table is to be preferred as free 

 from any speculative corrections, bearing in mind, however, that the rate of 

 loss is probably over-estimated on most of the plots and under-estimated 

 on the plot receiving farmyard manure. Fig. 1 shows these percentages of 

 calcium carbonate in the upper soil plotted against the time. 



5% 



4% 



3Z 



z% 



5 



3 



9 

 2 

 IO 



\ 



\ 



N 







7 



















- J^N. 



















3 



3&2 



5 



8 



1865 1881 1893 1304 



Fig. 1. — Percentage of Calcium Carbonate. Broadbalk Field. First 9 inches. 



A cursory examination of the figures and curves shows that if it may be 

 assumed that the calcium carbonate was equally distributed over the whole 

 field initially, then the greatest losses have occurred on the plots manured 

 with ammonium salts, the loss increasing with each addition of ammonium 

 salts ; sodium nitrate, on the contrary, would seem to have exercised some 

 preservative influence on the calcium carbonate, which is now at its maximum 

 on the plot where that manure is used. 



Table VI gives the weights of calcium carbonate per acre in soils from the 

 Hoos field as calculated from the percentages in Table V and from the average 

 weights of soil in Table II, without any attempt at correction ; the results 

 being also thrown into a graphic form in fig. 2. 



