DRY FARMING CONGRESS. 



195 



growing of crops, but with the knowledge of the conditions which de- 

 termine maximum yields at our command,, we proceed logically and in- 

 telligently to the production and maintenance of satisfactory yields. 



In the case of uncontrollable factors, a knowledge of the influence 

 of each factor is of no less importance. With this knowledge we are in 

 a position to obtain an intelligent view of the situation, to make the most 

 of existing conditions. We know what the conditions have been in the 

 past. According to the thoroughness with which we know of these past 

 conditions, we are able to forecast with intelligence what we may rea- 

 sonably expect in the future. We are in a position, not to guess blindly, 

 but to make a reasonable estimate based upon facts, regarding our 

 chances of success — how many seasons out of ten we may expect profita- 

 ble returns. 



The writer, is in charge of the investigation of the influence of pliysical 

 conditions on crop yields in these experimental farms in the Great Plains. 

 This includes the influence of climatic factors, such as rainfall, temperature, 

 the dryness of the air, evaporation, etc. It includes also factors peculiar 

 to the soil alone, such as the moisture content of the soil, its porosity, 

 its temperature, its humus content and the nature and amount of the 

 mineral substances in solution in the soil moisture. This part of the work 

 then resolves itself into the answering of the following questions: 



1. What are the physical conditions in the Great Plains, and to what 

 extent is crop production in different parts of the area dependent upon 

 the local conditions? 



2. How can these conditions be modified so as to insure larger and 

 surer returns? 



3. In the case of adverse conditions not under our control, what 

 S3^stems of farming will give the best returns for a long term of years? 



The agricultural productivity of any region is primarily determined 

 by climatic and soil conditions. For example, the rainfall may be so 

 scanty or the growing season so short, or the occurrence of frosts so 

 frequent as to make agriculture on a productive soil impracticable. On 

 the other hand, no matter how favorable the climatic conditions, if the 

 soil is so compact as to prevent the free movement of air and water, or 

 if it lacks one or more of the essential elements of plant food, crops can- 

 not be successfully grown. 



The climatic factors w^hich are most important in determining crop 

 production are temperature, rainfall, and evaporation. Now I am intro- 

 ducing there a matter which has not been given very much consideration, 

 but one which I think — and I shall try to make you agree with me before 

 I am through — that we must give consideration throughout these investi- 

 gations in arid farming, namely, the influence of evaporation as it varies 

 from place to place through the Trans-]\Iissouri states. In considering 

 these factors which I mentioned as applied to an}' given region, we have 

 to consider also the nature of the crops grown. Thus, wheat and oats 

 will stand much lower temperature than corn or the sorghums. On the 



