254 SOILS AND PLANT LIFE 



In making a litmus paper test to ascertain whether 

 clover will probably grow in a given field, we do not 

 usually follow the above method since it is necessary to 

 make many tests in different parts of the field. This 

 is due to the fact that the soil may be acid in some places 

 but not so in others. 



The test of an entire field may be made in this manner : 



Go into the field after a rather light rain while the 

 soil is in the form of a stiff mud about like putty. If 

 the test is made after a heavy rain, some of the acids 

 may have been washed out of the soil, and this will in- 

 terfere temporarily with the test. 



Beginning at some point in one corner of the field, cut 

 a slit in the soil with a knife blade and insert a slip of 

 blue litmus paper to a depth of from one to three inches, 

 pressing the wet soil firmly against it. Repeat this 

 process at other points about ten rods apart each way 

 all over the field, marking each place by a stake. 



After an hour or more, go over the field again, carry- 

 ing a small pail of soft water, in which to rinse the slips 

 of paper as they are dug from the ground. 



Since some parts of the field are liable to be more 

 strongly acid than others, it is better to carry a plat of 

 the field, showing the location of each test, and to record 

 the results on it as the slips are dug up and examined. 

 It is important to have this information when we get 

 ready to correct this acidity in the soil by the method 

 which we shall shortly learn. 



It should be understood that soil acidity may or may 

 not extend to the subsoil below. 



189. How a Lack of Phosphorus affects Clovers. — 

 In many parts of the eastern states, as well as in some 

 sections of the Middle West, the soil is deficient in phos- 



