494 STATE BOARD OF AGRICULTURE. 



4. Effect upon the availability of minerals. 



5. Increase the rate of decay of vegetable matter. 



6. Increase the efficiency of fertilizers and manures. 



7. Supply needed lime to plants. 



Improvement of the Physical Condition of the Soil. It was formerly 

 assumed that the chief reason for adding lime to the soil was to improve 

 its physical condition or tilth diie to its granulating effect upon the 

 fine particles. It is recognized that heavy, compacted soils may be some- 

 what improved in this respect by liming, but this action is less general in 

 occurrence and also less important than others. 



NcntraUzation of Acids and Other Sudstanccs Injurious' to Plants. 

 S(»in(' poorly drained soils as well as some that contain very large 

 ([vuuilitics of vegetable matter such as peats and mucks carry acids in 

 their soil moisture. These may be injurious to plants, the extent of 

 the inhibitive effect depending upon the amount present. Although 

 adecpiate drainage may improve many such soils liming is effective 

 inasmuch as lime neutralizes these acids. Moreover, other injurious 

 substances which occur in some soils may be counteracted by adequate 

 applications of lime. 



Meeting the Silicate Requirements. One of the chief effects to be 

 gained from liming the majority of mineral soils is to supply the silicates 

 with lime. It is known that the loss of lime from the soil leaves the 

 silicate compounds, which compose the major portion of the mineral 

 constituents of the soil, deficient in lime. This condition is detrimental 

 to plants and is popularly spoken of as soil acidity or sourness of soils. 



Effect Upon the Atmilahility of Minerals. Lime may increase the 

 availability of mineral plant food in some soils. This action of lime 

 has long been held to be a very general and also a very important one, 

 special emphasis having been placed upon the liberation of phosphorus 

 and potash to the plants, but recent investigations indicate that undue 

 emphasis has been placed upon this action, it being negligible with 

 some soils. 



Increase the Rate of Decay of Vegetahle Matter. It is well known 

 that the presence of sufficient amounts of lime in the soil results in a 

 more rapid decay of vegetable matter as evidenced by the dark green 

 color of various crops growing on limed land as well as the slightly 

 delayed maturity in some cases. Moreover, the amount of nitrogen in 

 the roots, tops and seeds of crops may be increased by the addition of 

 lime to the soil. Such changes in the composition of the crops of course 

 sliow that the available nitrogen in the soil is increased by lime and 

 involve the soil bacteria. It is obvious that the free use of lime on the 

 soil without suitable crop rotation and constant renewal of the vegetable 

 matter content by means of stable manure, crop residues, and catch 

 crops will result disastrously. On the other hand, if these precautions are 

 taken the lime will be instrumental" in maintaining tlie vegetable content 

 due to the increased crop production. In some soils, more frequently 

 in muck than others, the root development of crops is retarded, being 



