1062 EXPERIMENT STATION RECORD. 



essential factors of crop production, namely, heat, light, moisture, physical condition 

 of the soil, and seed. 



The results of studies made hy the station of the plant food in typical Illinois soils 

 and the crop yields and fertilizer requirements of these soils are summarized, with 

 suggestions as to the best methods of improving these soils and permanently main- 

 taining their fertility. 



The following system of farming to insure high productive capacity of the soil is 

 outlined: 



"(1) Thorough underdrainage wherever needed. 



"(2) Applications of ground natural limestone whenever necessary to correct and 

 prevent soil acidity. 



"(3) Continued use of large quantities of fine ground natural rock phosphate (or 

 some other form of phosphorus) in connection with decaying organic matter by 

 which the phosphorus is made available, and by this means gradually increasing the 

 total phosphorus content of the soil, even though maximum crops are removed. 



"(4) Liberal use of clover and other legumes in rotation and as catch crops, by 

 which nitrogen and organic matter will be added to the soil. 



"(5) Feeding of all crops excepting some of the most valuable grains or other 

 high-priced products and returning all manure to the land, by which means the 

 supply of potassium, the most abundant plant-food element in our common soils, 

 will be practically maintained. The manure together with the legume crop residues 

 will effect an increase or permanent maintenance of the supply of nitrogen and 

 organic matter in the soil. 



"With the use of sufficient limestone to keep the soil sweet and abundant use of 

 legume crops and catch crops, and the addition to the soil of a ton of ground rock 

 phosphate or its equivalent every six or eight years, in connection with all of the 

 farm manure which can be made, the ordinary lands of the Central West can be 

 made to grow large crops indefinitely." 



Soil treatment for the lower Illinois glaciation, C. G. Hopkins and J. E. 

 Readhimer (Illinois Sta. Bui. 99, pp. 561-599, figs. 12). — The methods of treatment 

 described in this bulletin are based upon the results of chemical soil analysis 

 (E. S. R., 15, p. 23), and of several years' field experiments on four soil-experiment 

 fields located in different parts of southern Illinois, especially on the common 

 prairie soil in the lower Illinois glaciation, the oldest glaciated area in the State. 



"This great area of agricultural land of depleted fertility includes the counties of 

 Fayette, Effingham, Jasper, Marion, Clay, Richland, Washington, Jefferson, Wayne, 

 Edwards, Perry, Franklin, and Hamilton, and parts of as many more surrounding 

 counties. The principal type of soil in this area is a gray silt loam. It is not 

 strictly a clay soil, although it is quite commonly spoken of as 'clay,' sometimes as 

 'white clay.' Silt consists of soil particles smaller than sand, and impalpable, but 

 it is not sticky, plastic clay." 



The different fields are described and the results of experiments with various 

 crops and crop rotations and fertilizers are summarized. The principal results and 

 recommendations are in brief as follows: 



" (1 ) It is possible to adopt a profitable system of farming that will make the soils 

 of southern Illinois permanently productive. 



"(2) Chemical analyses show these soils to be quite deficient in nitrogen and 

 organic matter, very deficient in phosphorus, only moderately well supplied with 

 potassium, and markedly acid. 



"(3) The effects of tile drainage upon these soils under certain conditions of 

 season and treatment are very suggestive. 



" (4) Very beneficial results with legumes are obtained from the use of lime. 



"(5) The results obtained from experiments strongly confirm the universal 

 experience as to the very great value of farm manure upon this type of soil. 



