128 SOILS 



A striking peculiarity of the nitrobacter is this : they 

 need no organic food. So far as now known, they com- 

 prise the only living form that is able to live in an envi- 

 ronment wholly devoid of organic matter. Decomposi- 

 tion bacteria cease their labors when the organic matter 

 is used up, but these, the nitrobacteria, only begin their 

 work when such becomes the case, and so this is proved : 

 nitrifying bacteria are inactive in the presence of organic 

 matter for they labor only when it has been completely 

 destroyed. 



Nitrogen-starved soils may contain much nitrogen. 

 All agricultural soils contain some nitrogen. Some may 

 show considerable quantities and others but little. And 

 often the latter class produce the best crops. A question 

 naturally arises: why is this so? In the first place, other 

 conditions being secured, crops are dependent upon a 

 plentiful supply of nitrates in the soil. These, as has 

 been shown, pass through various changes before reach- 

 ing the final usable state. Nitrogen compounds may be 

 present in the soil in great abundance, but until these 

 are changed to nitrates, they are useless to plants. Hence, 

 nitrification is essential. The bacteria must be stimulated 

 in this work. It may be, decomposition of the organic 

 supplies is slow; if so, decomposition bacteria must be 

 induced to work with more energy. Tillage may help ; 

 lime may help. But the fault may be elsewhere : the 

 decomposition bacteria may have completed their effort; 

 they may have done every bit of work possible to do. 

 Maybe the nitrobacteria the nitrifying agents are at 

 fault. They must be induced to greater effort. If the 

 soil is acid, the explanation is at hand, for these bacteria 

 never work in sour lands. Liming the land may answer 

 the question. And then tillage will help. It will admit 

 the air, which certainly can do no harm, for air is just 



