LIME AND ITS ACTION ON SOIL 



ELMER O. FIPPIN 



Formerly of Cornell University 



The Kinds of Lime That Are Available, How, and How 

 Much to Use, And How to Judge Your Soil's Requirements 



|T TOO often transpires that the last phase of soil 

 management to be stressed is its treatment with 

 a[ '' lime; yet lime occupies a place in crop economy 

 O^ comparable with moisture and fertilizers. Its 

 functions are those of a plant food as well as a conditioner of 

 the soil — by which latter term is meant the regulation of all 

 those processes and materials that contribute to make a fer- 

 tile soil. Like humus, its effects on the soil and on vegetation 

 are multiple. Chief among these is the regulation of the 

 balance in the soil between acid and alkaline constituents. 



Action of Lime 



THE first and primary function of liming material is to 

 swing the soil balance away from the acid condition — in 

 other words, to sweeten the soil. The microscopic plants 

 in the soil — the bacteria — are quite as much affected by 

 the presence of lime as are the higher crops, and of these the 

 useful forms are benefited. The function of some is to bring 

 about the decomposition of organic matter into the form of 

 humus, thereby liberating nitrogen and mineral plant con- 

 stituents, while others have to do with the fixation of nitrogen 

 from the air in forms that plants may use. Lime holds the 

 phosphorus of the soil in favorable forms, and it seems to 

 economize the potash needs of the plant also, though it prob- 

 ably does not unlock potash from the minerals in the soil in 

 any direct way. Further, it improves the tilth of the soil, 

 helping to regulate the growth of some disease organisms. 



The detection of an acid soil may be accomplished in 

 several ways. The kind of plants that thrive is one good in- 

 dication. Scab in potatoes is a pretty good indication of a 

 non-acid soil, also the growth of beets as well as alfalfa. The 

 canteloupe thrives on a fairly sweet soil. On the other hand, 

 when sorrel is the dominant vegetation, when potatoes are 

 free from scab, where watermelons thrive [or where Laurel 

 and Rhododendron grow luxuriantly], the chances are that 

 the soil is acid. As a matter of fact, there is very little land 

 in the country, especially the eastern United States, that is 

 not in need of lime to some extent. 



Kinds of Lime 



THERE are two general classes of liming material suitable 

 for use on the soil. These are the carbonate form, which 

 includes pulverized limestone, marl, and mussel shells; and 

 the burnt forms of lime. The carbonate is the natural form 

 in which free lime occurs in the soil, but it is important to 

 remember that such material must be very fine to be effective 

 within any reasonable time. Carbonate forms of lime should 

 be reduced to grains below one twenty-fifth of an inch in size 

 to be effective within an ordinary rotation of four or five 

 years. While material coarser than this size has some value 

 it must be remembered that particles as coarse as a wheat 



grain will persist in an acid soil for a great many years; there- 

 fore, insist on having it finely pulverized. 



The other class is derived primarily from limestone by 

 burning it to produce either lump lime or hydrated lime; both 

 are commonly called caustic or burnt lime and are from 30 

 to 50 per cent, stronger in essential material. They further 

 have the advantage in concentration. 



Caustic Lime and Humus 



THE mention of caustic lime is much like a red flag be- 

 fore a bull to the minds of some because it has been so 

 many times said that caustic lime burns out humus in the 

 soil. The repetition of this does not make it true; and at- 

 tention is directed to the careful investigations of Dr. Mcintire 

 at Cornell University, and of Dr. Mooers of the Tennessee 

 Agricultural Station. Their work has demonstrated beyond 

 question that there is no possible destruction of organic 

 substance by caustic lime even in a very strong solution. 

 On the other hand, it must be recognized that any material 

 that sweetens the soil favors the growth of the bacteria in 

 the soil and hastens the destruction of organic matter. This 

 applies to carbonate forms as well as to caustic forms, and 

 is a perfectly legitimate process; and if any further argument 

 were needed concerning the innocent character of caustic 

 lime it is found in the fact that caustic lime applied to the 

 soil quickly changes into the carbonate form. 



The carbonate and caustic forms should be rated upon 

 the basis of the cost of available oxides delivered upon the 

 land. This method takes account of three factors — (1) the 

 purity in the oxides of lime, (2), the fineness, and (3), the 

 handling cost. Special emphasis is put upon this matter 

 of the comparative value of carbonate and caustic forms 

 of lime because of the many loose and incorrect statements 

 that are given to the public bearing on this point. 



Quantity to Use 



THE amount of lime to apply varies according to the 

 acidity of the soil, and the sensitiveness of the crop to an 

 acid soil. A very acid soil coupled with a very sensitive crop 

 would require a large application of lime, a tolerant plant on 

 a very acid soil might respond to a light application of lime. 

 Small applications frequently are likely to be better than 

 large applications at long intervals. Three to five hundred 

 pounds of burnt lime to the acre (or 20 to 30 lbs. to 50 x 50 

 ft.) twice that quantity of finely ground limestone, or three 

 to four times that quantity of coarsely ground limestone, 

 once in every year or two, would be a fair application, and 

 correspondingly larger amounts at longer intervals. The 

 lime should be thoroughly incorporated with the soil; there- 

 fore, it is usually best to apply after plowing but before 

 cultivating. 



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