10 Report of the Department of Agronomy of the 



acidity and promoting the growth of clover as equivalent amounts 

 of slaked or caustic lime." (Rep't Penn. State College, 1911.) 



Top dressing meadow lands. — Four years' experiments in England 

 comparing ground lime and ground limestone for top dressing 

 meadow lands have shown an average annual increase in hay per 

 acre of 1650 for ground lime and 2525 pounds for ground lime- 

 stone. (Experiment Station Record 25:33.) 



limestone vs. caustic lime. 



The results of these experiments discredit the theory that burned 

 lime is any more effective for soil improvement than chemical equiv- 

 alents of ground limestone. They further show that ground lime- 

 stone is likely to produce better results on the average than burned 

 lime. Ground limestone is safer to use, since applied in almost 

 any quantity at any time it can have no injurious effect upon the 

 succeeding crop nor upon the organic matter of the soil. Many 

 instances are on record of positive injury to crops from the use of 

 caustic lime. 



Burned lime is offered to the agricultural trade in three con- 

 ditions: (1) hydrated lime in sacks, (2) ground quicklime in sacks, 

 (3) lump lime in bulk or barrels. Lime in the first two forms is 

 usually too expensive to be considered, and it is only the bulk lump 

 lime that comes in competition with ground limestone to any extent. 

 The lump lime sold for $4 to $6 per ton is usually run-of-kiln and 

 cannot be considered high grade. It must be slaked before being 

 applied to the soil, and in practice it is very difficult to get it applied 

 uniformly. In comparative experiments it has usually been the 

 hydrated or ground quicklime that has been used, so as to insure 

 the lime being applied as uniformly and as thoroughly incorporated 

 with the soil as the ground limestone. Ground limestone is so much 

 more agreeable to handle than caustic lime that this fact alone will 

 usually lead the farmer to decide in its favor after he has once had 

 experience in applying both forms. 



Limestone is a neutral material and does not exert a distinct 

 alkaline reaction excepting when in contact with an acid. Even the 

 weakest acids easily decompose the limestone, setting free carbon 

 dioxide and allowing the calcium or magnesium to combine with the 

 acid, thus neutralizing it. There is thus no difficulty about the 

 " availability " of ground limestone; if any acid is present in the 

 soil it is easily neutralized by the limestone. 



There should be no hesitancy about the use of limestone on potato 

 land that is acid. Potato scab is favored by the absence of acid 

 in the soil yet ground limestone does not set up the alkaline reaction 

 that we get with burned lime. It has been shown that the potato 

 crop is directly benefited by the use of lime carbonate where needed 

 to correct acidity. Besides it is not profitable to require the other 



