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DRY FARMING CONGRESS. 



on the several plats we would find much less difficulty in reconciling our 

 results. Looked at, then, from this point, our experiments instead of 

 establishing too many facts, have, so far as this table shows, established 

 too few. If we had even the additional facts which have been established 

 by the physical investigations carried on by Dr. Briggs upon these plats we 

 could come much nearer to an explanation of the seemingly incongruous 

 results obtained. But even these facts would not be sufficient to enable 

 us to draw any definite conclusions. We must not only know something 

 of the chemical conditions and changes in the soil, but we must also learn 

 much more than we now know concerning the bacterial life of the soil, 

 before we can venture to draw any definite conclusions, and the work 

 must, as has already been repeatedly stated, be carried on for a long term 

 of years at many different stations before we can reach that degree of 

 certainty concerning many of the problems involved, that will warrant us 

 in formulating our knowledge into any definite system. As I stated at the 

 beginning of the discussion of results from the North Platte Station, all of 

 the theories which have been formulated and all of the systems, the estab- 

 lishment of which has been attempted, either by theorists or practical 

 farmers, have been based solely upon differences in crop yields obtained 

 from different fields, receiving different methods of tillage, often without 

 any precautions whatever being taken to see that the two fi,elds in ques- 

 tion were of uniform condition at the time the experiment was undertaken. 

 If there were the same opportunity to analyze the facts upon which the 

 attempt has been made to establish these theories and systems that there 

 is to analyze the results of last season's work at North Platte, there is 

 no doubt that the number of unclassified facts would be even greater in 

 this instance. 



I here submit the conclusions at which I have arrived from a study 

 of the two years' work at the North Platte Station. 



1. — The problems involved in crop rotation and cultivation methods 

 are exceedingly complex and are made up of many factors, such as 

 seasonal soil and air temperature, evaporation, humidity, wind velocities, 

 sunshine, altitude, topography, exposure or lay of the land, chemical 

 composition, physical composition, structure and tilth of the soil, effect 

 of previous cropping and tillage, crop sequence, varietal and physiological 

 peculiarities of crops grown, and probably many other factors even more 

 obscure and difficult to deal with. 



2. — From the standpoint of the practical farmer the above mentioned 

 factors may be divided into two groups: the modifiable and the unmodi- 

 fiable. The modifiable factors are those which are more or less under 

 the control of men, such as the chemical composition and physical structure, 

 tilth and moisture of the soil, crop sequence, seed selection, etc. The 

 unmodifiable group includes by far the greater number of these factors, 

 which can be controlled by man to only a very limited extent or not at 

 all, such as general climatic conditions, topography, physical composition 

 of the soil, etc. If these unmodifiable factors were constant in their 

 occurrence, and in their relations to each other, the problem would be 



