116 SUCCESSFUL FARMING 



the rate of underground drainage. The fact that drainage waters and 

 well waters in all regions where lime is abundant in the soil are highly 

 charged with it is an indication of the readiness with which lime is lost 

 from the soil in this way. 



In limestone soil regions the water generally finds its way into under- 

 ground drainage channels, and few surface streams occur. Very little 

 of it passes over the surface. This explains why limestone soils become 

 deficient in lime. The presence of an abundance of humus in the soil may 

 retain lime in the form of humates, and reduce its loss. 



Lime is also removed in farm crops. The amount of removal in this 

 way depends on the yield and character of crops removed, together with 

 the amount that is returned in manures and other by-products. Legumes 

 contain much more lime than non-legumes, and, therefore, cause a more 

 rapid reduction in the lime of the soil. 



Lime Requirements of Soils. — The character of vegetation is a good 

 index to the lime requirement of soils. When red clover fails or when 

 alsike clover does better than red clover, it indicates a sour soil. The 

 presence of redtop, plantain and sorrel also indicates a sour soil. In 

 traveling over the country from the Missouri River to the Atlantic sea- 

 coast, the acidity of the soil is indicated by the presence of these weeds. 



Farmers who are troubled with failure of clover and by the encroach- 

 ment of the above-mentioned weeds, may feel reasonably sure that their 

 soils need lime. If these signs leave doubt in the mind of the farmer, he 

 can further test his soil by the use of neutral litmus paper. Five cents 

 worth of neutral litmus paper purchased at the drug store will enable him 

 to make tests of many samples of soil. This is conveniently done by 

 collecting small samples of soil to the usual depth of plowing at a number 

 of points in the field in question. The soils should be made thoroughly 

 wet, preferably with rain water or water that is not charged with lime. 

 A strip of the litmus paper brought in contact with the soil and allowed 

 to remain for fifteen or thirty minutes will turn red if the soil is sour. 

 The intensity of the change of color will in a measure indicate the degree 

 of sourness. 



Upon request, most of the state experiment stations will test repre- 

 sentative samples of soil and advise concerning their lime requirements. 

 The laboratory method determines approximately the amount of lime 

 required to neutralize the soil to the usual depth of plowing. 



Crops Require Lime. — Some crops are more tolerant of soil acidity 

 than others. Of our staple farm crops, common red clover is about the 

 least tolerant of such a condition. The staple crops that draw most 

 heavily on the soil for a supply of lime are those first affected by soil 

 acidity. They are also the least tolerant of soil acidity, and are usually 

 most responsive to applications of lime. The clovers contain much more 

 lime and magnesia than the cereals and grasses. The following table 

 gives the average lime and magnesia content as carbonates in a ton of 



