May 26, 1921 



The Florists' Review 



21 



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TEST YOUR OWN SOIL 



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ACID SOILS. 



How to Know Them. 



Inquiries are sent to us at the ex- 

 periment station at the University of 

 Illinois from time to time by growers 

 in regard to acid soil. They tell us 

 that they have applied manures and 

 other fertilizers to the soil, but, never- 

 theless, the plants are not growing as 

 they should. This is followed by the 

 inference that the soil is acid and the 

 question is raised, "Do you think that 

 my soil is acid?" or "How can I tell 

 if my soil is acid?" 



It is true that many soils are acid in 

 reaction. Probably the majority of the 

 soils in the eastern and southern states 

 are of this nature and, in addition, some 

 sections of the middle western states 

 are usually considered as acid soils. 

 Acid soils also are of frequent occur- 

 rence in greenhouses. It is probable 

 that they are even more common in 

 greenhouses, for there the conditions for 

 the development of acidity are usually 

 more favorable. 



Some Plants Prefer Acid Soil. 



The fact that a soil is slightly acid in 

 reaction does not mean that plants will 

 not grow in it. There are many forms 

 of plants that can tolerate soil acidity; 

 in fact, there are some which prefer an 

 acid soil. Lupines, for instance, grow 

 well in a soil which is slightly or me- 

 dium acid arid some investigators have 

 even found that liming the soil is in- 

 jurious to these plants. The common 

 sheep sorrel also thrives well on soil 

 which is distinctly acid. There are 

 other plants which, though they are 

 well adapted to acid soils, grow better 

 in soils which liave received lime. Many 

 plants, on the other hand, do not tolerate 

 an acid soil, but demand for growth a 

 soil which is non-acid. Clover and al- 

 falfa belong to .this group. The usual 

 greenhouse crops of the florist have not 

 been onrcfully studied in this respect, 

 altliough it is generally assumed that 

 all respond hotter in a soil which is not 

 acid. 



How Soils Become Acid. 



The exact cause of soil aciditv is not 

 completely understood. A number of 

 factors unquestionably are contributory, 

 and the conditions which bring about 

 acidity are somewhat variable in the 

 different types of soils. We find state- 

 ments to the effect that some plants 

 exude small quantities of acid from 

 their roots during growth and an ac- 

 cumulation of this acid secretion will 

 eventually j.roduce a sour soil. The 

 statement, too. is occasionally made that 

 heavy watering of the benches will pro- 

 duce n sonr soil. Tliis is not neces- 

 sarily true, though it is quite true that 

 soils which ;iio kept wet and become 

 water loggPfl tend to become more acid, 

 while soils which are well drained tend 

 to become less acid. It is not neces- 

 sarily true that low, wet soils are sour 

 soils, though this is occasionallv the 

 case. 



Soils become sour when tliev lose 



By DR. P. A. LEHENBAUER. 



their lime or other substances which 

 are similar, chemically speaking. In 

 the language of the soil chemist, soils 

 become acid when there is a deficiency 

 of bases. This deficiency is brought 

 about by several conditions. The most 

 important is the loss of the bases by 

 means of the drainage water. The lime, 

 or, to be more exact, the calcium, and 

 other bases are leached out of the soil 

 by means of water. This is the most im- 

 portant factor. The bases also are lost 

 from the soil because growing plants 

 remove them by absorbing them through 

 the roots. There is one other factor. Or- 

 ganic matter, such as manures and dead 

 plant material decaying in the soil, is 

 acid in character and this acid neutral- 

 izes the bases; that is, it combines with 

 the bases and this, we may say, re- 



Soil requirements are often 

 perplexing problems to growers 

 who have not gained familiarity 

 with them by long experience. 

 Some of the problems, however, 

 are not difficult for growers to 

 solve. Every grower, for 

 instance, can learn for himself 

 whether his soil is acid or not 

 by applying certain simple tests, 

 described on this page. Cor- 

 rective methods will be given 

 in a later article. 



moves the influence of the bases in 

 keeping the soil non-acid. As organic 

 matter continues to decay, more acid is 

 produced and thus there is an accumu- 

 lation of it after the lime, or other 

 bases, have disappeared. 



As is well kuown, in order to correct 

 acidity lime is used. In a later article 

 I shall discuss the different forms of 

 lime compounds and the use of each. 

 The point under discussion at present 

 is how to tell if the soil needs lime. 



Some Plants Indicate Acidity. 



For outdoor soils, a good index of so- 

 called acidity is the vegetation found 

 growing on the soil. As said above, 

 some plants are more sensitive to an 

 acid condition than others. As a rule, 

 the greater the acidity the smaller the 

 number of plants. Therefore, as the 

 acidity increases certain forms of plants 

 disappear while others continue to thrive 

 and multiply. Clover and alfalfa dis- 

 appear quite early, while the common 

 plantain and the sheep sorrel continue 

 to grow and spread in an acid soil. 

 Inspection of the kinds of plants on a 



soil, therefore, affords an indication of 

 acidity. However, this method must be 

 used judiciously. We must remember 

 that the presence of sheep sorrel alone 

 does not prove acidity, for this plant 

 will grow quite well on soil which is 

 not acid; it is the presence of the sorrel 

 together with the absence or poor growth 

 of clover or alfalfa which is indicative 

 of acidity. 



By growing these different forms of 

 plants, alfalfa and sorrel, in the green- 

 house benches in a similar way their 

 relative growth will serve as an index 

 to the reaction of the soil. If the soil 

 is unfavorable to the growth of alfalfa, 

 but supports a good growth of sorrel, 

 there is reasonable assurance that the 

 soil is in need of lime. 



The Litmus Paper- Test. 



Another method which is fairly satis- 

 factory from the qualitative standpoint 

 is the litmus paper test. In order to 

 be reliable, however, the test must bo 

 properly made and its shortcomings must 

 be appreciated. Litmus paper is either 

 red or blue or "neutral" in color. When 

 a strip of blue or neutral paper comes 

 in contact with an acid it is changed in 

 color from blue to pink or red, the in- 

 tensity of color and the quickness of 

 the change depending on the concentra- 

 tion of the acid. An alkali, as for in- 

 stance lime, on the other hand, turns 

 either the red or neutral paper to a 

 blue color. Therefore, when either the 

 blue or the neutral litmus paper is turned 

 red when in contact with moist soil, the 

 usual indication is that the soil is acid 

 and that it does not contain much, if 

 any, lime. 



Litmus paper may be purchased from 

 the druggist in the form of small strips. 

 It comes in small vials and the paper 

 should be kept in these containers, 

 tightly corked, and preferably in the 

 dark when not making a test. The 

 moist hand must not come in contact 

 with the paper, for perspiration is acid 

 in character. It is best to use a pair 

 of forceps in handling litmus pajiers. 



How to Use Litmus Paper. 



A number of slightly different 

 methods have been recommended in 

 making the test for acidity by means 

 of litmus paper. Any nietliod will do, 

 provided certain precautions, given be- 

 low, are carefully observed. If the soil 

 is dry, a small amount may be placed 

 in a clean tumbler and moistened with 

 boiled, soft water so as to get the soil 

 in a good, moist condition. By making 

 two openings in this soil with a stick, 

 a red paper should be placed in one and 

 a blue in the other opening. A slightly 

 different procedure is to place the two 

 pieces of litmus on a piece of clean win- 

 dow glass, make a ball of the wet soil, 

 break it into two parts, ]>lace i>uo of the 

 ])arts, flat siile (lown, on the pajiers, 

 press down firmly and allow to stand 

 about ten minutes. By looking through 

 the glass any change of culor may be 

 observed. If the soil is acid, the blue 

 litmus should turn to a ])ink or red color. 

 If there is an abundance of lime in the 

 soil, tlie red }>a]ier will tuiii at tiist to 



