COMMERCIAL FERTILISERS 401 



Hungarian grass, red-top, blackberries, and the 

 lupines, do poorly on a sour soil; these seem to 

 prefer it. Indian corn and rye stand it much 

 better than the other cereals. Clover, alfalfa, 

 beets, and timothy are almost sure to fail on sour 

 soils. 



TESTS FOR SOUR SOILS 



A simple and fairly reliable method of deter- 

 mining whether a soil is sour, is to test it with blue 

 litmus paper. This can be bought at a drug- 

 store for a few cents. Get several samples of 

 moist soil from different parts of the field, mix them 

 into a paste with water, and insert one end of the 

 litmus. At the end of an hour, if the blue paper 

 has turned red where it came in contact with the 

 paste, probably the soil is sour. 



The litmus test will usually show with con- 

 siderable accuracy whether a soil is badly in need of 

 lime, but soils which are not actually sour may need 

 it. The best way is to apply lime to a strip 

 of soil and compare the growth of crops on this 

 strip with their growth on unlimed parts of the 

 field. In the fertiliser test previously described, 

 use about 200 pounds of lime on the uV-acre plot. 



HOW TO SWEETEN SOUR SOILS 



A sour soil should be limed at the rate of 1,000 

 to 4,000 pounds per acre; two tons per acre is 

 about the maximum of application. The lime 

 should be applied broadcast in late fall or early 

 spring. The oest form of lime to use is the water- 

 slaked. Put stone lime in heaps on the ground 

 and cover it with moist soil. In a few days the 



