71 



Scientific A gricy. I hire . 



if any one of the essential elements of plant; food is lacking, As already stated, 

 lime has been found to be especially deficient in soils derived from granite. It is 

 also often true of soils derived from mica-schist, sandstone, and from certain 

 conglomerates, slates, and shales. Fortunately, however, many soils are well 

 provided with lime by nature, and it is seldom or never necessary for those who 

 cultivate them to resort to liming. It would be just as irrational to apply lime 

 where it is not needed as to omit it where it is required, and hence arises the 

 necessity of ascertaining the needs of particular soils in this respect. The 

 method usually resorted to for ascertaining the amount of lime in soils is to treat 

 them with some strong mineral acid (usually hydrochloric) and determine the 

 amount of lime which is thus dissolved. Some writers state that if only one-half 

 of one per cent is thus shown to be present, immediate resort to liming is desirable ; 

 others set the amount higher, and some seem to prefer to have present as much as 

 one per cent. It is possible that a soil may contain considerable quantities of lime 

 thus removable by acid, and yet in actual practice show much benefit from liming. 

 As a matter of fact, soils of limestone origin sometimes show benefit from 

 liming because sufficient carbonate of lime is not present in the soil. 



This is due to the continual removal of carbonate of lime by crops and 

 by leaching. Often some carbonate remains, but it is too mnch inclosed by 

 other materials to be sufficiently active to prevent acidity and to insure the 

 proper changes in the organic matter. The fact that beets of all kinds make 

 a ready response to liming on soils which are deficient in carbonate of lime 

 may be utilized as the basis for a practical and reliable method of testing the 

 lime requirements of the soil. For this purpose lay out two plats of land, each 

 about 12 by 30 feet, manure each of the plats with like amounts of a fertilizer 

 containing potash, phosphoric acid, and nitrogen, and apply lime to one of the 

 plats at the rate of from I to 2h tons per acre (40 pounds per plat would be 

 approximately 2h tons per acre). A comparison of the growth and yields on 

 the two plats will furnish a safe means of judging whether the soil will respond 

 profitably to applications of lime. If the crop is helped but slightly by liming, 

 most varieties of plants will not be in immediate need of lime. If the crop is 

 greatly helped or is increased several times, it is likely that the soil is too 

 much in need of lime to make complete success with most varieties of plants 

 possible, 



CHEMICAL ACTION OP LIME ON SOILS. 



Lime is said to take the place of potash in certain chemical compounds 

 which exist in soils, thus liberating the potash and placing it at the disposal 

 of plants. In this particular, gypsum (land plaster or calcium sulphate) is 

 believed to act more energetically than carbonate of lime, air-slaked or water- 

 slaked (hydrated) lime. When soluble phosphates are applied to soils deficient in 

 lime and magnesia the phosphoric acid combines with the iron and alumina of 

 the soil to form compounds which are not readily utilized by plants. If, how- 

 ever, the soil is fairly well supplied with lime and magnesia this transformation 

 is retarded, so that the plant is afforded an opportunity to utilize much of the 

 phosphoric acid before it becomes unassimilable. If a soil containing a certain 

 inert phosphate of iron is heavily limed, it is believed that this phosphate 

 will be changed into a form which the plant can utilize. Lime may therefore 

 not only aid in keeping recent applications of phosphoric acid in assimilable 

 condition for a long time, but it may, if applied in sufficient quantity, help 

 to unlock stores of phosphoric acid, in certain soils, which plants would other- 

 wise be unable to use- 



