184 



DRY FARMING CONGRESS. 



We' assume, therefore, that unless bacteria and the proper kind of bac- 

 teria are present in the soil that it is not going to be a productive soil. 

 In the east — to a less extent here — but in the east, where the soil is of 

 comparatively a thin layer, we can take a deep subsoil, top it up with 

 organic matter, and have the same organic elements present that would 

 be present in the fertile soil. There are very few bacteria in the lower 

 soil, however, and until bacteria assemble that soil remains a poor soil. 

 That will show you some of the necessity for having bacteria in large 

 numbers present. Then, as I said, this bacteria ought to be there in cer- 

 tain definite kinds. There is one point which has been investigated per- 

 haps more than any of the others, and as that one point is of greatest 

 interest to anyone who is growing crops, that is the one to which I shall 

 confine myself. That is the question of nitrogen in the soil, and the re- 

 lation that bacteria play to this nitrogen. The nitrogen cycle is some- 

 thing like this: The seed sprouts, or, of course, many seeds; the crop 

 sprouts and begins to grow, and as it begins to form complex compounds 

 especially such compounds as the protein of wheat, nitrogen must be 

 used. This nitrogen can be used only when it is in the form of nitrates. 

 The plant grows, matures, is harvested, and the stubble is turned under. 

 At least we will suppose it is turned under for purposes of illutsartion 

 here. That decays. That decaj^ is brought about by bacteria. These 

 highly organized compounds — for there are protein contents even in 

 wheat stems — will be changed into simple compounds, and by different 

 bacteria, through different grades of decomposition until ammonia and ni- 

 trates finally result again, and then the material is again in shape so that 

 it is available for subsequent plants. That will show you, in a skeleton way, 

 what nitrogen does in the soil. 



Now all bacteria don't change these compounds back into nitrates. 

 Some bacteria — and these are the undesirable ones — will change nitrates 

 back into compounds, which plants cannot use. You can appreciate what 

 would happen to a field if you got the wrong kind of bacteria growing 

 in large numbers; you would destroy its fertility. This will happen when 

 the conditions for the favorable bacteria are wanting, and when the condi- 

 tions which are favorable only to the undesirable bacteria are brought 

 about. This may be by bad cultural conditions, insufficient air supply, and 

 sometimes — I don't suppose,' however, you will be troubled here with that, 

 although you may be by over irrigation — by having too much moisture. 

 That, really, would be about the same thing as not having sufficient air 

 supply. If you have too much moisture on your land of course there will 

 be water in places where the air might be, down in the soil. 



Yesterday, in Prof. Scofield's paper, you will remember he spoke 

 about the necessity or desirability of cultivating at different depths in 

 order to break up the hard-pan whch might form a few inches below 

 the surface, and spoke briefly there of the necessity of getting air into the 

 lower layers on account of aiding nitrofication in the soil. This is the 

 explanation for that. 



