LIMESTONE 



165 



use of burned lime and ground limestone in comparative tests is 

 reported by the Pennsylvania Experiment Station (Report 1902). 

 Four plots were treated with burned lime (slacked before being 

 spread) at the rate of two tons per acre once in four years. Four 

 other plots were treated with ground limestone at the rate of two 

 tons per acre every two years. A four-year rotation was practiced, 

 consisting of corn, oats, wheat, and hay, the hay being mixed 

 timothy and clover, seeded on the wheat land in the spring. By 

 having four sets of plots, each crop was grown every year. Seven 

 products were obtained and weighed each year; namely, corn, 

 corn stover, oats, oat straw, wheat, wheat straw, and hay. 



TABLE 25. PENNSYLVANIA EXPERIMENTS WITH BURNED LIME AND GROUND 



LIMESTONE 



Twenty Years' Produce per Acre 



Thus, after twenty years' results had been obtained (1882 to 

 1901), the Pennsylvania Station reports data showing that with 

 every product a greater total yield had been obtained from the 

 plots treated with limestone than from those treated with caustic 

 lime. Furthermore, with every product whose total yield for the 

 last eight years was greater than the total yield of the first eight 

 years, the limestone produced a greater increase than the caustic 

 lime; and with every product whose total yield for the last eight 

 years was less than the total yield of the first eight years, the 

 decrease was less where limestone w r as used than where caustic 

 lime was applied (oat straw alone excepted). This is significant, 

 in that it demonstrates the tendency of caustic lime with continued 

 use to exhaust or destroy the fertility of the soil. In discussing 

 these investigations, Doctor Frear of the Pennsylvania Station 

 says: 



