FOURTEENTH ANNUAL YEAR BOOK— PART X. 713 



soil treatment, but there are some tests of particular soils which the 

 farmer can very readily make for himself. 



Acidity.— In the first place the soil should be tested for acidity. Most 

 crops will grow satisfactorily in acid soils, and many maKe no growth 

 whatever. 



There is a wide range in the sensitiveness of different crops to acid 

 conditions, the legumes, such as clover and alfalfa, being most readily 

 affected. Beneficial bacterial activities are also inhibited by acidity 

 and the change of insoluble plant food into a soluble form is restricted 

 or absolutely prevented. 



There are certain outward indications of soil activity which are quite 

 evident to any farmer. For instance, if clover or timothy refuse to 

 grow and red top and sorrel appears instead, the soil is usually in 

 need of lime. The presence of moss, or the growth of red sorrel bluets, 

 horsetails or other similar weeds is evidence of a lack of lime in the soil. 



There is, however, a definite test for soil acidity which may be made 

 on any farm. It is known as the litmus paper test and is based on the 

 power of acids to change blue litmus paper to red. 



In order to make the test a small sample of soil, free from roots and 

 grass, is put into a clear glass container like a water glass. Two or 

 three strips of blue litmus paper are inserted in the soil so that they 

 are half covered, care being taken that the portion in contact with the 

 soil is not touched with the fingers. Pure water is then added carefully 

 until the soil is thoroughly wet. The test is allowed to stand for several 

 minutes and the paper removed and rinsed thoroughly. If the portion of 

 it which was in contact with the soil has become red, the soil is acid 

 and would be benefited by liming. The litmus paper for this test may 

 be bought at any drug store. 



That a thorough test for acidity may be made, samples of the sur- 

 face soil and the subsoil should be taken from several different places in 

 the field. If the soil is shown to be acid by this litmus paper test, then 

 ground limestone should be applied. An application of 2,000 to 3,000 

 pounds per acre should be sufficient to remedy a moderate degree of 

 acidity for most crops, but if the soil is shown to be strongly acid, and 

 alfalfa or clover are to be seeded, 3,000 to 4,000 pounds per acre should 

 be used. 



By application of ground limestone not only is the acidity of some 

 soils corrected, but heavy clay soils which are too wet and improperly 

 aerated are opened up and made more fertile. Light sandy soils, also, 

 which tend to lose valuable plant food by "burning out" and leaching 

 and are apt to dry out too quickly are made more compact and thus 

 more retentive of moisture and plant food. 



The physical character of such soils therefore is improved and they 

 are made more favorable for the growth of bacteria and indirectly for 

 the growth of plants. 



Finally the lime may remedy an actual deficiency in plant food, cal- 

 cium. Alfalfa, for example, removes a large amount of calcium from 

 the soil and the aucceeding crop may suffer for lack of calcium. 



