Scientific Agriculture. 



186 



From the preceding statements regarding the different kinds of lime used for 

 agricultural purposes, it is evident that it is impossible to state definitely for all 

 locations and conditions which kind is most economical to employ. This is still 

 more evident when one considers that the character of the soil and of the crop 

 to be grown, as well as the market prices, must be taken into account. Caustic or 

 quick lime is the most concentrated, and consequently the most economical to 

 handle. Its caustic properties, however, render it more vigorous in its action than 

 the milder sulphate (gypsum) or carbonates (limestone, chalk, wood ashes, marl, 

 etc.), and thus better suited for application to soils which are rich in organic matter 

 than to light soils deficient in this substance. It is also specially suited to correct- 

 ing acidity in sour soils. There may be special reasons in particular cases why 

 some of the other compounds of lime are preferable to quicklime. Gypsum has 

 been used in agriculture to a considerable extent with very satisfactory results, 

 On account of its peculiar composition it has been found especially valuable for 

 neutralizing sodium carbonate (black alkali) in alkali soils. Wood ashes are used 

 extensively in some localities, in many cases as much for the lime as for the potash 

 Avhich they contain. It is very doubtful, however, whether it would not be more 

 economical at the present prices of wood ashes and caustic lime to employ the 

 latter in many cases, supplementing the lime with potash salts and other fertilizing 

 materials if the latter are required by the soil.* The item of transportation is 

 also decidedly in favor of the use of lime and agricultural chemicals as substitutes 

 for ashes. 



SUMMARY. 



The use of lime as a soil improver is very ancient, and its value for this 

 purpose is generally recognized. Its action as a fertilizer is both direct and indirect. 



There are many soils in which lime is deficient, notably such as are derived 

 from granite, mica-schist, and certain sandstones, slates, and shales. On such soils 

 lime is often of direct value in supplying a necessary element of plant food. 



The indirect value of lime is perhaps more important than its direct action, 

 because probably the majority of cultivated soils contain sufficient lime to meet 

 the direct demands of plants for food. Lime is of indirect value in unlocking the 

 unavailable potash, phosphoric acid, and nitrogen in the soil. 



Lime exerts a decided influence on the mechanical condition of soils, render- 

 ing heavy compact soils looser in texture and tending to bind particles of loose 

 leachy soils. 



Lime is also beneficial in furnishing conditions in the soil favorable to the 

 activity of the micro-organisms which convert the nitrogen of organic matter into 

 nitrates which are readily assimilated by plants, which decompose organic matter, 

 and which assist certain leguminous plants to assimilate the free nitrogen of the air. 



Lime is also beneficial in furnishing conditions in the soil favourable to the 

 activity of the micro-organisms which convert the nitrogen of organic matter into 

 nitrates which are readily assimilated by plants, which decompose organic matter, 

 and which assist certain leguminous plants to assimilate the free nitrogen of the air. 



One form of lime, gypsum, has been shown to be a most effective corrective 

 of black alkali, found in some of the soils of the arid portions of the United States. 



The continued use of lime unaccompanied by other fertilizers may prove 

 injurious, especially on poor soils, since it converts the insoluble nitrogen, potash, 

 and phosphoric-acid compounds of the soil into such as can be rapidly taken up by 

 plants or washed out in the drainage, thus hastening the exhaustion of the supply 

 of these substances in the soil. As the German adage states, "The use of lime 

 without manure makes both farm and farmer poor.*' If the soil is not abundantly 



* U.S. Dept. Agr., Farmers' Bui, 65, p. 24. 



