WI WWW HUM i ’UlWlHlHH‘Uw’l '—1 IS: (I (D—sco ACID TOLERANCE OF STRAWBERRY PLANTS Thesis for Degree of M. S. Laval Sidney Moms I 9 Z 6 I .lt.vV1 1 23.15.! J“ 9.3.. .. h'.u.v. 37:... . I V . . -JJ 1: . do. u . p . .¢ .. o ,......££.:.... .,.. . . , . .\.4 V . J‘.IAI‘.J~...,.. . , . . ~w . . . . i 1 .1. . ... . ... . .1». 1 V \ .. .o, THESIS . Z r!" .W“ o . 1. I... ...z.4..4\.‘.¢1.~,41zq_1 «11.31.14 .11 I . .‘j A) r . . . , , . .r. aggg EQL§§g§CE OF STBAWBEBBY PLAETS BY Laval Sidney Norris M -00000- A Thesis Submitted to the Faculty of the Michigan State College of Agriculture and.Applied Science in partial ful- fillment of the requirements for the degree of Master of Science. - ooOoo - Department of Horticulture \ East Lansing, Michigan 1926 TfiESIS AC \TCE OF ST WBERRY LANTS Etroduction Strawberries rank first in importance among the small fruits. Due to their high quality as a fruit and their wide adaptability both to climte and soil conditions they are grown extensively in many parts of the United States. The fourteenth census of the United states-«1920, v. 5-- gives the area of strawberries in 1919 as 119,395 acres, and the value of the crop as $36,004,245.00. It has been frequently stated in horticultural literature that strawberries require an acid soil. This belief has been based upon the fact that my wild strawberry beds are found growing on acid soils. geview of Literature In 1912 Wright (24) sent out a circular letter to prominent growers asking for the results of any experience that they may have had with liming strawberries. Replies were received from twenty—nine growers who had made observations. Of this number six had secured favorable re- sults from liming; twenty-three reported unfavorable results. Wright states, "Of 100 or more tests of soils in New York, Michigan, and Pennsylvania where wild strawberries, blackberries and black raspberries were growing, luxuriantly, practically all gave an acid reaction with litmus and none gave an alkaline reaction." His experiments showed that in most cases liming an acid soil was harmful to strawberries. However, twice out of a series of pot culture experiments the limed plants pro- duced more fruit, though the difference fell within the bounds of ex- perimental error. Hartwell and Damon (ll) sunmarise the results of liming experi- 1013993?) -4- ments with about 280 different kinds and varieties of plants at the Rhode Island Experiment Station. Some of those worked with, which were supposed to be acid-loving, were actually benefited by liming. Wheeler and Tilling- hast (23) of the same station give a detailed account of the work on strawberries, subsequently summarized by Hartwell and Damon (11). In 1897 and 1898 Wheeler and Tillinghast grew three varieties of strawberries under four treatments: (A) Sulfate of ammonia, limed; (B) Sulfate of Annonia, unlimed; (c) Nitrate of soda, limed; (D) Nitrate of soda, un- limed. In all but one instance the limed out-yielded the unlimed plots. They sake the statement, "It is probable thAt on a soil but slightly acid lime would prove of little or no value to the strawberry and upon an alkaline soil one would reasonably expect it, if used in considerable quantity, to exert even a slightly injurious action. 011 very acid soils lime is never- theless beneficial and particularly so if sulfate of amnia and possibly other manures leaving acid residues are employed.” Beatty (2) cites experience in various states of the central West, which shows that moderate liming of acid soils is somewhat bene- ficial to strawberry plants. Darrow (7) states that, "Experiments show that lime has a harm- ful effect upon the roots of strawberries. Lime nay improve a poor physical condition but it should be added considerably in advance of planting. There are a number of such general statements suggesting that lime is harmful to strawberries, current in horticultural literature, yet there is about as much evidence for lime as against it. Common sense would indicate that the liming of an extremely acid soil should prove beneficial to strawberries, though the opposite might prove true if the soil were neutral or only slightly acid. although data on the reaction best suited to other plants may have no direct application to the strawberry, the results of certain recent in- vestigations with cultural solutions of known H-ion concentration are not without interest. A knowledge of the general behavior of certain plants growing in nutrient solutions is helpful in knowing what to expect from strawberry plants. Due to the many variables of soil cultures, physiologists have developed a recent practice to determine the acid requirements and acid tolerance of various plants in nutrient solutions. By varying the H-ion concentration of nutrient solutions it is a simple nutter to deter- mine the emact range of acidity plants tolerate under given conditions. The following are some of the findings of various physiologists on plants grown in nutrient solutions. Alstine (1) using Shive's solution at different PH values found that soybeans died in nutrient media ranging from PH 3.2 to PH 3.6 and that buckwheat showed root injury in solutions ranging from PH 3.2 to PH 4.0. Soybeans growing in solutions tint were only slightly acid soon showed chlorosis and died. Hoagland (12) showed that barley seedlings did best in a solution with a PH 5.1 and that a concentration of PH 3.5 on the one extreme and PH 8.2 on tha‘other were toxic. Reed (17) found that the roots of walnut seedlings were injured in two of Hoagland's solutions, i.e., PH 7.3? and PH 10.85, after 24 to 36 hours' exposure. When the seedlings were placed in a nutrient solution of PH 5.2 the roots recovered and grew well. He states, "It seems that injury is due to calcium starvation rather than high hydroxyl concentration." Tarr and Noble (20) used three of Whittier's solutions, one Shreiner and Skinner solution, one Hartwell and Wheeler solution, one Knop solution, one Pefeffer, one Tottingham, one Shiva and one McCall -4- solution. Reaction values ranging from PH 3 to PH 9 were established by the addition of H3PO4 and neon. Seedlings of wheat, soybeans and corn 'were grown. A reaction of PHSiwas prohibitive to growth in all cases. Wheat seedlings grew best in a solution with.PH4, soybeans at approximately PBS, and corn behaved practically the same as soybeans. "Chlorosis was due to the insolubility of iron at all concentrations less than PH 6." Grist (6) growing lettuce seedlings in Theron's solution obtained best growth at PH 5. McCall and Hagg (16) grew wheat in sand cultures in which the reaction was varied by adding HZSO4 and KéSO4 or KDH. PH 3.06 to PH 3.56 solutions produced normally green plants. Plants growing in cultures with a lower concentration than PH 4.02 became chlorotio. Salter and McIlvaine (18) found that best growth was obtained from seedlings of wheat, soybeans and alfalfa, when the reaction of-the nutrient solution adjusted with H3P04 and NaOH was PH 5.94. Corn did best at a reaction of PH 5.16. Duggar (9) using a number of nutrient solutions in which were grown wheat, cone and field peas, found results similar to those already enumerated. Chlorosis took place in all cases where plants were grown in a solution above PH 6. From the literature so far reviewed it will be observed that all the plants grown in nutrient solutions require an acid reaction of PH 3.06 to PR 5.94 for best deve10pment. It will also be noted that all the plants used are not supposedly "acid-loving." When plants refuse to grow in a nutrient solution with a reaction below PH4 it might be concluded that Halon concentration per se is the direct limiting factor. However, under soil conditions there may be various -5- other limiting factors of growth, which accompany acidity, rendering it impossible to attribute the cause to any one factor. for instance Burgess and Pember (5) show that aluminum is responsible for toxicity in certain acid soils, and that less aluminum is taxen in by plants when lime is added. They also present evidence showing that many plants which are sole to grow normally in fairly high concentrations of H-ions in water - and sand-cultures, are unable to subsist in certain soils of similar or even lower H-ion concentrations. Hoffer and Carr (16) found that aluminum and iron were the limiting factors of growth in certain acid soils in Illinois. 10 check with their soil observations they injected solutions of iron and aluminum salts and also a number of dilute acids into n althy corn plants. host of the.aluminum injections proved fatal, some iron injections were injurious, while only formic acid, out of seven acids, was harmful. They also present numerous data from other work to show that in certain soils aluminum compounds associated with soil acidity are more limiting to growth of some plants than acidity per so. However what might prove toxic to some plants may be beneficial to others. Coville (5) treated Rhododendron catawbiense seedlings with aluminum sulfate as a substitute for an acid growing medium and obtained beneficial results. The plants grew practically as well in their natural habitat. Thus it is seen that this problem of acid ‘ requirements and coil tolerance of plants is hijhmcomplex. The Problem Stated As shown by the review of literature, former wor? ti l2tcrnine the soil reaction tolerance of the strawberry has bee; of a cunaéry nature, the results of which are nerely suggestive. The purpose of this investigation was to study the behavior of strawberry plants grown in media with various lime requirements and PH values. *Kore Specifically, the primary purposes were -5- (l) to determine whether or not strawberry plants require an acid medium, (2) to determine the acid and alkaline range (if there is an alkaline range) in which strawberriescwill grow, and (5) to determine the Optimum PH value of certain growing media, for the plants, under given conditions. It was a secondary aim to observe every peculiarity of behavior of strawberry plants subjected to various acid and alkaline conditions. The first eXperiment was started in the autumn of 1933 and later ones were performed during the summers of 1924 and 1925. General observa- tions concerning natural habitats and soil reaction in numerous cultivated plantations in hichigan, Utah and a few in Colorado were made at various times. There are three experiments and general observations discussed in this paper. The first experiment deals with soils to which were added various amounts of lime. The'other two eXperiments have to do with strawberry plants grown in nutrient solutions, with various concentrations of H—and Cd-ions. Experimental Work Experinent I: The purpose of this experiment was to study the inf uence on the growth of strawberry slants of lining certain soils known to be very acid. This work.was started September 1, 1923. I. DEL-JGRIBI‘IUNQQG Two acid soils, a sandy soil and a muck, were employed. The sandy soil, with a lime requirement (Jones method) of 1864 pounds of Ca(OH)2: per acre was supporting a fairly dense growmh of so-called acid soil plants. The muck had a lime requirement of 39,826 pounds per acre,. and was supporting no vegetation]. It was evidently too acid for even very acid-tolerant plants. waever, blackberries, strawberries and other acid soil plants were growing at the edge of this area where presumably acidity was less extreme. t The term lime in this paper refers to Ga(OH)z. -7- A certain.annunt of each soil was divided into five lots and lime added to give a gradation in acidity from the original to a theoretical alkaline condition. Table 1 shows the. amounts. of lime added to the various lots to produce different theoretical degrees of acidity and alkalinity. The soil was kept moist to facilitate bacterial action, and thoroughly mixed to break up all particles of lime. In order to allow the soil and lime to come to a fair degree of equilibrium, before setting the plants, it was allowed to stand, with an occasional mixing, for six weeks. These soils were then employed as media for growing straWberry'plants. Twenty-feur five-inch pots each supporting one plant were used for each treatment. The plants were left exposed to outside conditions for six weeks after potting to become rooted and also that they might undergo at least a short rest period to insure growth, before being transferred to the greenhouse. Upon introduction to the greenp houee, one-half of the pots of both sand and muck‘were each fertilized with .5 gm. ammonium sulfate,'.5 gm. potassium chloride and 1.5 gm” acid phosphate. This was for the purpose of determining'whether the plane of nutrition materially influences the harmful or beneficial influence of certain degrees of acidity. The plants were watered uniformly as possible whenever it was needed. Notes'were taken from time to time on the condition of the plants during the course of the experiment; and final records including soil reaction ‘were made at the conclusion of this experiment, June 28, 1924. 2- was: The results of this experiment are summarized in Table l. The follovb ing notes are explanatory. -8- Table 1. Influence of lime and fertilizer applications to two acid soils on initial and subsequent lime requirements and on plant growth. H Soil Initial lime Theoritical Lime Lime Line Total 3 requirements degree of added requirements requirements green m (lbs.per acre) satisfying per Nov. 15,1923. July 2, 1924. wts. lime acre (lbs. per acre) (lbs. per acre) (gms) 1'th (1st rd 3:: Muck 59 , 826 0 0 52560 19240 55 , g g: 1/5 15,275 19240 8995 72.2 +3 2/5 26,550 15520 2551 80,2 3 5/5 59,826 5920 1998 53.1 g 4/5 55,100 2568 666 53.5 H g o 0 52560 —-—- Plants dead :3 Muck 59,826 1/5 15,275 19240 8658 100.9 :1 2/5 26,550 15520 4985 59.0 +; 5/5 59,826 5920 1525 80.1 g 4/5 55.100 2568 666 64.5 “a? o 0 2664 0 i - .5. Band 1864 1/5 621 1552 0 1 .. 2 2/5 1242 552 o i _ 2 5/5 1864 552 o ‘ _ 33 4/5 2485 666 0 r _ a :2) H o 0 2664 0 _ 3 Band 1864 1/5 621 1552 o - 5, 2/5 1242 552 0 _ '3 5/5 1864 552 0 — 3; 4/5 2485 666 0 - a: \ ll 1. The fertilizer treatment consisted of .5 gm. ammonium sulfate, 1.5 gm. acid phosphate and .5 gm. potassium chloride added to each pot. the first Practically no growth took place by any of the plants during four weeks after being transferred to the greenhouse. All the plaEts in the unlimed, fertilized muck soil died during the first ten Weeks. Th plants in the unlimed, unfertilized muck were very sickly during the first eight weeks but gradually developed new leaves. The plants in the limed muck and sand started to grow before those in the unlimed soil. During the early -9- part of the expenment the plants which received heavy applications of lime did the best, while towards the end there was very little difference in the general appearance of the plants in plots which had received various amounts of lime. However, table 1 suggests very strongly that liming the unfertilized muck had a decided influence upon the weights of the plants. It will be observed that the twenty-four plants produced in the unlimed unfertilized muck weighed 56.2 gms. As compared with 72.2 gms. and 80.2 gms. the weights of plants grown in muck'whose lime requirements were onsthird and two-thirds satisfied, respectively. Thus the applications of lime were beneficial up to 26,550 lbs per acre. Where the applications of lime were 39,826 lbs and 53,100 lbs per acre the plants were no better than where no lime was added. This difference is due apparently to applications of lime which were too heavy. The only conclusion to be drawn from the results on the muck soil which received fertilizer is that the fertilizer without line was very harmful. The plants grown in the sand were not weighfled because all th; sand tested neutra ”a fact that all of the soil beCamc less acid is interesting. The sand, regardless of previous treatment was entirely neutral, perhaps due to only a slight initial degree of acidity. This decrease in acidity may have been due to at least three causes: (A) The water used was highly charged ‘with Ca CO3 which to some extent would be deposited in the soil. (B) Liming and aeration would make possible the propagation of a soil flora which destroy certain organic acids (10). This statement verifies the popular assumption that it is well to apply lime to soil sometime previous to planting the cr0p. (C) Leaching would wash out some of the acid content in spite of caution to avoid excessive watering. -10- There seemed to be a correlation in the rate of growth of the plants and decrease in acidity of the soil up to a certain point. This experiment shows that strawberries were actually benefited by liming an extremely acid muck, and that lime did not seem to interfere with growth of the plants grown in a moderately acid sand. Experiment II. Since soil acidity is so complex and the factors involved are so difficult to deal with satisfactorily, either individually or en masse, in work of this kind, it was decided to grow strawberry plants in nutrient solutions maintained at different 3 H concentrations. 1. Descriotion and neth:ds.-- A modification of Koafland'e soluti. , presented in table 2 was used. Table 2.--Composition of Nutrient Solutions Used in Experiment 2. £2 HPO4 KH2 P04 mg 8 04 Ca (N05) 2 Na Cl P H 7.0 cc —--~ .3cc 1.0cc .3cc 7.5 3.0 cc 6.0cc .3cc 1.0cc .3cc ‘ 6.4 1.0 cc 8.0cc .3cc 1.0cc .3cc 5.7 ----- 9.0cc .3cc 1.0cc .3cc 4.4 3.ccl% H5 PO4 4.0cc .3cc 1.0cc .3cc 3.6 Note: The above amounts refer to molecular solutions and were added to one liter of water. The table shows that four degrees of acidity and one of alkalimity were employed. Quart mason Jars, fitted with cork-stappers (Figures 1 to 5) each containing two holes to support strawberry plants were employed. Sixteen plants were used in each solution. -11- Young plants selected for uniformity of size and vigor, and which.were still attached to the mother plants were used. The plants were severed from the ones to which they were attached by runners, carefully lifted, so as not to injure the roots, and washed in tap water. The plant roots were then placed in tap water and allowed to stand over night that they might adjust themselVes gradually to a somewhat abnormal growing medium. After rinsing the roots in distilled.water, the plants were weighted individually, set in the cultural solutions and numbered. It was the original plan to'change the solutions every third or fourth day; however, the PH values remaining practically constant longer than was expected, changes were made only once a week. The PH values were tested at . the beginning with a type K Leeds and Northrup potentiometer, and afterwards at definite intervals, colormetrically. I The plants were set in the cultural solutions August 2, 1924 and grown four weeks and five days. 2. gesults.-- The data obtained from this experiment are given in table 3. Figures 1 to 5 inclusive show the condition of the roots three weeks after. the plants were set in the solutions -12- Table 3. Gain in wt., gain in leaf area and condition of plants in Experiment 3. PH Total gain Average Total Average Reaction lbrtality in green gain in gain gain in of (percent) wt.(gms.) green wt. in leaf area Remarks. sol (gms.) leaf (sq.Cm). area (sq.Cm) 7.5 37.5 13.26 1.33 l13.48 11.35 Plants sickly, young leaves chlorotio. roots brown, declin— ing at and of the experiment. 6.4 18.7 29.27 2.25 419.76 32.29 Young leaves slightly Chlorotic, but fairly vigorous; roots white, healthy, medium length. 5.7 O 39.76 2.48 782.5 48.9 Plants normally green, vigorous; roots well ' developed, laterals longer than any others. 4.4 18.7 6.42 .49 453.19 34.86 Plants normally green, not vigorous; roots white, short laterals poorly developed. 3.5 31.2 2.96 ‘ lost --— 34.17 3.11 Plants sickly, lost in weight, a few small leaves develop- ed; roots dies under the solution, short roots developed at crown. Note; Sixteen plants, in each degree of acidity were used. 3. Discussion.-- The data presented in table 3 together with figures 1 to 5 show conclusively that the plants grew best in PH 5.7 solution. All the plants lived in this particular lot and the largest average gain in weight took place here. The Second best solutiOn was apparently PH 6.4 where the mortality -13... was 18.7 per cent, and the average gain in weight per plant was 2.25 gun. The plants grown in the solution with a reaction of PH4.4 were decidedly inferior to those grown in the PHB.4 solution. Singularly the average gain per plant in the PH7.5 solution was relatively higher than was eXpected; however, the plants were sickly and seemed to be declining rapidly at the end of the experiment. EXperiment III This experiment, set up July 1, and concluded July 29, 1925, was for the purpose of again checking on the results of the solution cultures already described. I. Descripti n engagethods Young Premier strawoerry plants, of the current season's growth, were secured from the field as soon as roots had become one or two inches long. The plants were first set in clean sand for four days to promote greater root developnent and make possible more uniform selection. Six- teen plants to each degree of acidity were use‘. The plants receiving the same treatment were grown in a siafle three—gallon crock, fitted with suitable supports and set on a rotating table (figure 6) to provide uniform insolation. Theron's (21) solution and titration curve were employed though the distilled Water used (J4 it was necesssrv to modify his titration qfigve at f‘x r. ' '3 3 ' ""0 ‘. »‘. 1"“ 1 2‘ 7 1' fit. (1. " 1‘1“ “ ° ‘ 3 ‘ C. " ‘ ‘ i i'“ r.“ " contained diiierent amoants oi vU at aiiierent tines. chcI (CLIdeE 01 -- ._oq ' I' ' L . \‘I. "" . *, A; a ' "y n ‘L' ' I reectuxiiangnggirwnirbato :59,zi definite intervals of one, were employed. The reactions of the solutions were kept practically coratant by adjusting the desired EH value with normal solutiOns of 101 and HaOH . a . . . 0 . tWice daily. All testing was done coldhetrically. -14.. harsh and Shive (15) found that iron could best be supplied by adding small anounts to the cultural solutions to meet the apparent re— , .. A. a ., - .. r, ~ . nu . - 4.‘ ,- .r‘ ”“irements of the plavts. Consequentll loo 0. a .5 percent solution oi 19.1 V n ’ !'-- . J- "3 - , -v' - «L'v ; ~-~;- 7 -- - -~‘.‘-.;" .- -,-;-'.‘-‘, 1'”. - .. Lerro“ c.wrwte .nr litnd‘ti. solution, an.. use; alternatciul.nitn .ne 83x; 1 anount of ferric tartrate at the oeginning of each change of solution; and.sxa11 additional amounts (a few drOps) were added alternately each day. It has recently been demonstrated by Trelease and Livingston (22) that climatic conditions have an influence on the salt proportion require- ment. Consequently for the sake of completeness of record, tegperature and humidity were recorded with a Tries hygrotheruofraph, regulated once a in; cr' ' r'-”. .v . . r,:' ".-r 7s ‘, ,~ -- :3 .- - r‘ W ' ~ "r ~‘ 1 v v A r ,. 4c“ . .. r~ ultd a Stcgue-e therroneter and sling :QJCJrOfletSP; eVapozation was - - .. n. ‘ V. T ' . ,C - . ,7,‘ ' . ' ,r. ‘ ~.— , . ‘ rm. ‘. t :u _' _ ’. a o r“. meanled by a n1v1ngston white oulb-atnnnetez, and ini dense 01 light calculated by comparing the evaporation from a radio—atmometer and the ~~',’\. '1 .-- , "4% "1 ,,' ‘—~ I. . r“ ‘rvr. 1 ‘3 ‘v‘x‘L' ." «3“. "' wulte bulo‘atiometer. Ja.1e 4 51Vcb data on enviIOnnental conuitions. Table 4. Environmental Factors in Experiment 4. Factors July 1 July 5 Jul? 10 July 15' July 20 July 25 to July a to n 10 to n 15 to u 20 to n 25 to n 29 Temp.(av night in 3°) 70 70 55 63 so 66 Temp.(av day in F0) 83 84 83 79 77 72 Rel. Humidity(av night in %) 81 81 _ 82 83 83 82 R61. Humidity(av day in %) 45 4s 51 50 49 59 W. Atmometer (av night in cc) 86.67 92.34 102.6 102.8 96.39 58.32 B. Atmometer (av day , . in cc) 106.4 114.4 124.8 125.6 122.4 72.8 ""—-——A—_—-e _ -15- The plants were weighed at the end of the experiment to determine the amount of growth made. Ash, calcium, iron and aluminum contents of the plants were determined by A.O.A.C. methods. 2. Results Gains in weight and general conditions of the plants are given in table 5. \ Table 5. '73ijhts anl gzncral ooniition of plants in Experinent 4. PH "ortalitv “0t"l rr' A , ~ ->‘ " -1 d ‘ i a éalh verase gain Dry Jt. Value Green wt. Green wt. Tops Roots Remarks (gms.) (gas) 5'0 15 All died during first 12 days. 4-0 0 28.1 1.76 14.9 2.9 Plants normally green, apparently more varia- ble than others; roots mostly vigorous, short laterals, some white, ‘ . a few bluish. 5 to 15 cm lone. 5-0 0 30.4 1.90 12.5 5.0 2 lants normally green, vigorous; roots well deve10ped, many short laterals, 10 to 15.5 . . cm. long. 6'0 1 32-6 2.17 14.5 2.? A few young leaves slightly chlorotic, plants vigorous; roots have longer laterals than in PH4 or 5,slightly brownish, 10 to 15 cm. long. - 7-0 1 25.5 1.71 12.6 2.1 Young leaves chlorotic, plants fairly vigorous; roots grew faster at first then turned brownish, 7.5 to 15 cm. long. 8’0 9 8-7 1.45 5.2 .7 Plants very sickly,groumh was made early then tendency was to go back- 9.0 15 wards- roots dark brownish. Plants lived longer than those in PH 5 solution, all were dead July 29; roots dark brown, slimy. , . 1 ‘ 4L -15- After five days the plants in PHS solution had become sickly, the leaves were somewhat flaccid and the roots slightly darkened. Twelve days after the experiment had been set up all the plants in PB? solution ‘woro dead. The roots had turned dark bluish'black and were gelatinized. Figure 6 shows the dead plants in the P35 solution July 12. The plants in solutions P34, P35, P98 and PH? appeared to be very similar in dovoIOpment during most of the time. Table six shows that the differences in behavior between these four lots were not great. There was a gradual weakening of the plants in PBS solution, with very little growth taking place. The plants in PH9 solution started to die six days after being set in the nutrient solutions. Table 6 gives the percentages, dry weight basis, of ash, calcium, and iron and aluminum. Table 6.--.Ash, calcium, and Iron and Aluminum.content of Plants, Dry wt. Basis. P H s c ron and luminum rcent. Ialuo 292: nogts Top§_ figots. 3.0 -- -— -- - 4.0 13.660 1.376 .577 1.959 5.0 -- "‘ 1.269 -‘ 1.701 6.0 14.050 1.339 .549 1.649 7.0 12.700 21.350 1.574 2.129 .474 1.357 8.0 12.790 17.590 1.207 2.178 .569 1.240 9.0 ‘ ample was lost. There was a change in reaction in all solutions except the extremely acid one. The following data give. the total amounts of HCL and NaOH required to keep the solutions at the desired PH values. -17.. We Amount added 00 3 -------------- '-0 4 ............... 5.0 HCL 5 ............... 8.5 HCL 5 ............... 38.0 HCL 7 ............... 23.5 HCL 8 ............... 29.0 NaOH 9 ............... 60.0 NaOH 3. Discussion: The two extreme limits of acid and alkaline tolerance of straw- beny plants were reached. Although six of the plants in the PHB solution survived the duration of the experiment, it seems certain that if the period of growth had been continued a little longer, this solution would have appeared in the record as the alkaline limit instead of the PH9 solution. The demarcation in behavior of the plants grown in PH4 and Phrasolutions is sharp. At first it was thought that a mistake had been made in the reaction of the PH3 solution but upon carefully checking the PH values this was not found to be the case. The plants grew well in a fflgrly acid solution -- P114 -- but refused to grow and soon died when the concentration was any higher. Best results were obtained in the PBS solution; however, there was not a striking difference between the plants grown in the four solutions from.PH$ to PR? inclusive. Some data will be presented under "General Observations" to substantiate these data showing that acid tolerance is not limited to a narrow range. -18- The last column in table 7 shows that the roots absorbed iron in proportion to the degree of acidity of the solution. This was also apparent from the color of the young leaves. However not enough growth was made by the plants in PHB solution for much chlorosis t0 deve10p. (Chlorosis did not show in the old leaves of any of the plants.) The reason for a higher percentage of iron and aluminum in the plant teps produced in PPS solution, may'be explained as being due to the very small amount of growth made by the teps, hence the original amounts would tend to remain constant. There is no direct relationship between the calcium content of either the roots or the tons and the reaction of the nutrient solution or the tendency to become chlorotio. Growth, in this case, did not seem to be contingent on the amount of calcium within the plant. general Observatiggg During the course of the laboratory experiments observations were made on the acid tolerance of both wild and cultivated strawberry plants growing in the field. Numerous tests were made on the reaction of soils, where indigenous strawberry plants were growing. "Soiltex" (19) a solution of bromthymal blue dye, saturated to the neutral point with calcium hydroxide, was used for all testing. .At the beginning the J0ne@®:method for lime requirement determina- tion was used to obtain a quaneétive test, but later abandoned due to a lack of sensitivity. In some cases the JoneWfi method indicated a lime requirement of over 300 pounds per acre, which is of course a very light application, while 'soiltex' a very sensitive and accurate indicator, as far as quality is concerned, gave an alkaline reaction. -19- Practically all of the Michigan soils supporting a growth of wild strawberry plants gave an acid reaction with "soiltex." Over forty-five samples were tested in various parts of the state. In some cases the plants showed a very high degree of acid tolerance. One particular lot of strawberry plants were observed growing with blackberries at the edge of a muck area, the main part of which was so extrexely acid (with a lime requirement of 23 tons per acre) that no vegetation could grow. The lime requirement of the soil where strawberries were growing, was eight tons per acre. It was found, however, that '! in many places the soil was only slightly acid. These observations support Wright's (24) findings. However in two cases the soil was found to be slightly alkalini. Possibly some 0‘7 "L‘l plaster had been dumped in these two particular places as they were in close proximity to recently constructed houses. A few tests were made of soils supporting wild strawberry plants in the mountains of Colorado; all of which tested slightly acid. a few of the Utah soils, supporting wild strawberry plants, tested slightly