114 A YEAR IN AGRICULTURE 



limestone or calcium carbonate, the burned lime or calcium 

 oxide, and the hydrated lime or calcium hydroxide. Recent 

 practices have justified the conclusion that ground limestone 

 may be applied in any amount with no injurious results, 

 while caustic lime destroys the organic matter, dissipates the 

 soil nitrogen, is disagreeable to handle, and may injure the 

 crop. If dolomitic limestone is used, magnesium as well as 

 calcium is thus added to the soil. Limestone need not be 

 very finely pulverized. If ground so that it will pass through 

 a ten-mesh sieve, it is fine enough, and the coarser and finer 

 material may be profitably mixed together in the application. 



Limestone is easily soluble in soil water carrying carbonic 

 acid. It is thus readily available, and in humid sections the 

 loss by leaching is great. About two tons an acre of ground 

 limestone should be applied every four years when necessary 

 in economic systems of farming. There are now on the mar- 

 ket special spreaders to use in the application of fine ground 

 raw rock phosphate and the pulverized limestone. 



The following record of a crop rotation and the applica- 

 tion of rock phosphate and limestone in a system of per- 

 manent agriculture is an account of an actual farm in south- 

 ern Illinois which had been agriculturally abandoned for five 

 years previous because of its inability to produce profitable 

 crops with ordinary methods of farming. This outline care- 

 fully studied will give the student and the practical farmer 

 the correct idea of permanent systems of soil fertility, and 

 what is meant by conservation of soil resources. 



The farm under consideration consisted of about 300 acres 

 of poor, gray prairie land and was purchased in November, 



