ANALYZING AND TESTING SOILS 571 



sium sulfate, for each year. One half of each plot may be treated 

 with limestone, applied at the rate of 1000 pounds per acre, and 

 for some soils magnesian limestone is undoubtedly preferable to 

 the more common limestone, which contains only calcium car- 

 bonate. 



Some rotation of crops should be practiced, such as corn, oats, 

 wheat, and timothy. To introduce legumes in this system, largely 

 destroys the value of the test with nitrogen, and the plan is designed 

 to discover as quickly as possible what the soil fails to furnish 

 to the crop. 



When definite information has been secured, the materials 

 which need to be added should as a rule be applied in larger 

 amounts at longer intervals. Thus initial applications of 10 tons 

 of ground limestone and even 3 or 4 tons per acre of fine ground 

 rock phosphate are not unreasonable for land valued at $10 to 

 $50 per acre which the owner desires to improve until it shall 

 yield as much as is produced on $150 or $200 land. 



