508 MISCELLANEOUS FARM SUBJECTS 



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

 crops and by leaching. Often some carbonate remains, but it is too 

 much 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 re- 

 quirements 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 1 to 2^2 tons per 

 acre (40 pounds per plat would be approximately 2M> 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 of 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 be- 

 lieved 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 alu- 

 mina of the soil to form compounds which are not readily utilized 

 'by plants. If, however, 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 be- 

 comes 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 there- 

 fore 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 cer- 

 tain soils, which plants would otherwise be unable to use. 



Hilgard has abundantly demonstrated the great value of gyp- 

 snm (land plaster) in renovating alkali soils in the arid portions of 

 the United States. Wherever too much sodium carbonate (black al- 

 kali) is the cause of the unproductive condition of the soil the gyp- 

 sum reacts with it, producing sodium sulphate and carbonate of 

 lime, whereby the alkalinity may be sufficiently reduced to render 

 possible the profitable production of crops. In case protosulphate of 

 iron and certain other poisonous compounds are present in soils, 

 liming so changes them as to render them harmless to plants. 



When the remains of plants undergo decay upon soils deficient 

 in carbonates of lime and magnesia, aoid or sour humus is liable to 



