SOME PROBLEMS IN CONSERVATION 41 



tention of the farmers and suggesting corrective measures. The 

 Iowa Station has made a careful inventory of the leading ele- 

 ments which determine soil fertility in Iowa, of which nitrogen, 

 phosphorus, potassium, carbon, lime, and sulphur are the most 

 important. According to the Station authorities : "The Missouri 

 loess, which is richest in phosphorus and potassium on which corn 

 makes the heaviest draft of all grain crops, contains in its surface 

 soil enough phosphorus for 90 crops of corn and enough potassium 

 for 1,782 crops, if only the grain is removed. If the stover also is 

 removed, there is enough phosphorus for only 66 crops and potas- 

 sium for only 477 crops. ... In the lowan drift, the poorest 

 soil in both phosphorus and potassium, there is enough phospho- 

 rus in the surface soil for only 75 crops of corn and potassium for 

 1,170 crops if the stover is returned to the soil. If the stalks are 

 removed, the phosphorus would supply only 56 crops and the po- 

 tassium 313 crops." These elements have required hundreds of 

 years in their accumulation, and in farming, as ordinarily prac- 

 ticed, are being rapidly withdrawn. In fact the average farmer 

 is overdrawing his account in terms of soil fertility and the prac- 

 tice if persisted in must ultimately lead to bankruptcy. 



The most important of all of the ingredients of the soil, and the 

 medium through which plants take the so-called essential foods 

 is water. It is a truism that the habitability of any continent de- 

 pends on its water supply. Mr. McGee's epigram is "no water, no 

 plants; no plants, no people." In the arid and semi-arid regions 

 the chief problem was and is to put water on the land and for a 

 time putting on water was considered to be the only problem. 

 After expensive and sometimes ruinous experience it was discov- 

 ered that drainage was quite as important as irrigation in these 

 regions. 



Up to this time the prompt removal of the water is the prob- 

 lem receiving most attention in the humid regions, while every 

 intelligent farmer knows that crop production could be increased 

 if the rainfall in humid areas was more equally distributed 

 throughout the growing season, and in a relatively few instances 

 some effort has been made to supplement this deficiency by irriga- 

 tion. In our inland states, Iowa and its immediate neighbors, ir- 

 rigation is applied in a very limited way to gardens only. In or- 

 der to extend the service to general farming operations the availa- 

 ble water supply must be conserved. All of the water available 

 for this purpose is meteoric in origin, that is, comes as rain and 



