316 STATE BOARD OP AGRICULTURE. 



should not be depended upon, however, as a means of supplying the 

 crops with available potash to the exclusion of artificial fertilizers, for 

 unless the soil contains an almost unlimited supply of potash, we are 

 only hastening the time when the soil will be depleted of this form of 

 plant food. Whether or not lime affects the availability of the insoluble 

 phosphoric acid compounds is a disputed question. 



The most important chemical action of lime upon soils is to "correct 

 acidity." Soils that have been cultivated for a great many yeare may 

 become acid due to the accumulation of organic acids produced by the 

 decomposition of organic matter. Many crops are affected by an acid 

 condition of the soil and in such cases are greatly benefited by the addi- 

 tion of some form of lime or material containing lime such as marl or 

 hardwood ashes. 



Physical Action. — Heavy clay soils that puddle and bake after a rain 

 are benefited by the addition of lime. It acts beneficially upon a soil 

 in this condition by binding the fine particles together in ''crumbs," thus 

 making the soil more friable and easy of cultivation. It also makes it 

 more open and porous thus facilitating the movement of air and water 

 in the soil. The action of lime on sandy soils is quite the reverse of 

 that on clay soils since it binds together the loose particles of sand and 

 makes the soil more retentive of moisture. 



Biological Action. — The decomposition of organic matter added to the 

 soil in the form of barayard manure, green manure, stubble, etc., is 

 brought about by the action of the numberless bacteria that live in the 

 soil. Certain of the soil bacteria living in connection with the roots 

 of legumes, such as the clovers, vetches, alfalfas, beans and peas are 

 able to take nitrogen from the air and change it into a form that is 

 available to j^lants. In order for these bacteria to accomplish the most 

 good, the soil conditions must be favorable for their best development, 

 and this condition may sometimes be improved by the addition of some 

 form of lime. 



There are several forms of lime that may be used for agricultural 

 purposes and the choice of the form should depend upon the purpose for 

 which it is to be used and also upon the price. 



Ground Limestone. — The word lime as ordinarily used, refers to burned 

 lime or calcium oxide, but it is very often used to designate any form 

 of lime without regard to its composition. Limestone in its natural 

 state consists of lime or calcium oxide in combination with carbon-dioxide 

 and is known as carbonate of lime. It usually contains more or less 

 of magnesium carbonate together with some iron, aluminum and sand. 

 It was originally supposed that magnesium limestone was injurious, 

 especially if used on the same soil for several years, but later researches 

 have proven that this belief is untrue and that it is equally valuable as 

 the i)ure calcium limestone, for use on soils. Good limestone should 

 conlaiu at least UU per cent calcium and magnesium carbonate. 



The availability of the ground limestone depends upon its fineness. It 

 should all pass through a sieve of 80 meshes to the inch. Material 

 coarser than that may remain in the soil for several seasons before be- 

 coming available. This form of lime may be applied (o the soil in almost 

 any (quantity without danger, although it is generally recommended at 

 the rate of 2,000 2,500 pounds per acre. 



Burned Lime. — This is also known as "stone lime," "lump lime," 



