294 ACTIONS OF ARTIFICIAL MANURES 



bacteria which normally people the soil and require a neutral 

 medium for their growth are largely pushed out. The fungi 

 in question compete with the higher plants like the grass for 

 the manure applied to the soil, and being active and abundant, 

 they take so much that the crop suffers. At the same time, 

 the higher plants are doubtless injuriously affected by the 

 suppression of many kinds of bacteria which are useful in 

 preparing food for the crop. For example, the nitrifying 

 bacteria, which change ammonia in the soil first into nitrites 

 and then into nitrates, are wholly inhibited by a very slightly 

 acid medium. A number of experiments were made to 

 ascertain if nitrification was still going on in these acid 



TABLE XCVIII. Effect of Lime upon Eothamsted Grass Plots. 



Rothamsted soils, both by testing for the organisms which 

 cause nitrification, and by putting large samples of the soil 

 under conditions favourable to nitrification and seeing if any 

 nitrates were found. Small fragments of the acid soils rarely 

 showed the presence of the organisms, but the bulk samples 

 in all cases but one did gain some nitrates during the course of 

 the experiment, showing that the process of nitrification was 

 not entirely suspended. Extracts from the soil, however, 

 refused to form nitrates even when fresh active organisms were 

 introduced. On the whole, the evidence points to the fact 

 that a little nitrification is going on in the soils, because a few 

 tiny fragments of carbonate of lime exist here and there, and 

 maintain a neutral condition in the soil with which they are 

 in immediate contact. These nuclei serve to keep a limited 



