1 88 THE CHEMICAL ANALYSIS OF SOILS [chap. 



Valuable as these determinations may become in 

 judging a soil, a sufficient body of data do not as yet 

 exist to enable them to be interpreted with precision. 



In the analysis of a soil, without doubt the most 

 important figure is the proportion of calcium carbonate, 

 for on that must be based the decision not only of 

 whether liming is necessary, but what class of artificial 

 manures should be employed. Where the calcium 

 carbonate is scanty, manures like superphosphate and 

 sulphate of ammonia should never be employed, but basic 

 slag or some neutral phosphate on the one hand, and 

 nitrate of soda as a source of rapidly acting nitrogen on 

 the other. The texture of the soil, the rapidity with 

 which decay and nitrification of organic matter take 

 place, freedom from fungoid diseases, all depend on an 

 adequate proportion of calcium carbonate in the soil, 

 say from half to one per cent. ; so that of all the 

 determinations this is the most important. 



The determinations of the loss on ignition, the 

 nitrogen, and possibly the humus, give the analyst an 

 idea of the reserves of organic matter in the soil ; 

 judged in conjunction with the mechanical analysis and 

 the proportion of calcium carbonate, an opinion can be 

 formed as to the condition of the soil and how far these 

 reserves are likely to be brought into play by cultiva- 

 tion. An opinion may, again, be formed as to the need 

 for organic manures to increase the humus content of 

 the soil, or whether fertility is likely to be maintained 

 with purely mineral manures. 



A consideration of the available phosphoric acid and 

 potash will give the analyst an idea of the immediate 

 need or otherwise of mineral manuring ; the proportions 

 these bear to the " total " phosphoric acid and potash 

 give him grounds for deciding whether the lack is only 

 temporary or real. In the former case measures may 



