56 GENERAL CONSIDERATIONS 



never be employed in any country without making 

 full provision in some way for the carrying off of the 

 surplus water. 



Improving the Soil Chemically. — In the previous 

 paragraphs various means have been discussed for 

 improving the physical condition of the soil. It 

 now remains to consider how its chemical condition 

 may be improved. 



Liming. — When soils are lacking in lime, the 

 transformation of vegetable matter does not proceed 

 properly and an acid condition of the soil is induced 

 that is very detrimental to certain crops, especially 

 to clover and many other of the legumes. Corn and 

 potatoes, on the other hand, do not mind a slightly 

 acid soil. In fact it is an advantage for the latter 

 crop, since it partially prevents the growth of the 

 scab fungus, and the potatoes are smoother. Whether 

 or not a given soil will be benefited by the application 

 of lime can usually be easily determined by mixing 

 a little of it to a thin paste with water and inserting 

 bits of blue litmus paper. If after standing a few 

 minutes the paper turns red or reddish, an acid con- 

 dition and the need of lime is indicated. As a rule, 

 sandy lands are more likely to be deficient in lime 

 than clays. In the case of very stiff, refractor}^ clays, 

 however, applications of lime are sometimes useful, 

 even if there is no acid reaction, since the lime tends 

 to make them more friable and to render the mineral 

 food elements more soluble and available. Recently 

 drained muck and swamp lands too are usually sour 

 and are much benefited by lime. On sandy lands, 

 where a large amount of vegetation is plowed under as 



