—v ‘ SELECED MOESTURE RELATEONSHIPS AND IRRIGATEON OF CONTAINER-GROWN NURSERY STOCK Thesis {Ear flue Degree of M. 5. MECEEGAN STATE UNIVERSITY Jack Stank'ey Wilde- 1960 L I B R A R Y Michigan Stats University SELECTED MOISTURE RELATIOJSKIPS AED IRRIGATION OF COHTAINER—GROUN NURSERY STOCK By Jack Stanley Wikle AN ABSTRACT Submitted to the College of Agriculture Michigan State University of Agriculture and Applied Science in partial fulfillment of the requirements for the degree of MASTER OF SCIENCE Department of Horticulture 1960 ‘ 4 E 4 I. ‘ ’4 I Approvege;;zgé;fidj§;7 ,A:E>::49G3LA:::/7 Jack Stanley Wikle ABSTRACT water retaining characteristics of five growing media were determined by pressure plate and pressure membrane ap- paratus. The five media were; sand, clay loam, sand-peat mixture and sand-peat-clay loam mixture. Phaseolus vulgaris plants were grown in the five media under five moisture regimes as follows: regime l, irrigation at a moisture stress midway between waterholding capacity .and 0.1 atm. stress; regime 2, irrigation at 0.1 atm. mois- ture stress; regime 3, irrigation at 1 atm. moisture stress; regime h, irrigation at 5 atm. moisture stress; and regime 5, irrigation at 15 atm. moisture stress. Other 2, vulgaris plants were grown in the sand-peat-clay loam mixture and subjected to sub v.5. surface irrigation treatments and polyethylene contrasted with no polyethylene around the growing media. Forsythia intermedia plants were grown under similar treatments with the exception that sand, peat and clay loam were not used. Evaluations of oven dry weights of roots and shoots gave the following results: Under equivalent moisture regimes, growth of 2, 22;? gggis roots and shoots was significantly less in sand me- dium than in sand-peat or in sand-peat-clay loam mixtures. Root and shoot growth of 2, vulgaris and E. intermedia plants Jack Stanley Wikle grown in sand-peat and sand-peat-clay loam mixtures was not significantly different. beimum root and shoot growth of the E, zulga2;§_and E. intermedia plants resulted under moisture regime 2. Growth of 2. vulgaris roots and shoots under moisture regime l was equal to that under moisture regime 2, how- ever growth of E, intermedia roots and shoots was signifi- cantly reduced under moisture regime l. Mbisture regime 3 resulted in 2, vulgaris root and shoot growth and E. intermedia shoot growth equal to that under regime 2, however, E. intermedia root growth was significantly reduced. under moisture regime %, E, vulgaris shoot growth and E} intermedia root growth were significantlyless than un- der regime 3. 2, vulgaris root growth and E. intermedia shoot growth were not limited significantly although values approached significance.. Moisture regime 5 resulted in growth of 2. vulgaris roots equal to that under regime H, and significantly re- duced growth of E. vulgaris shoots and E, intermedia roots and shoots. E, intermedia plants subjected to sub and surface ir- rigation treatments and to polyethylene and no-polyethylene treatments exhibited their maximum growth under moisture regimes 3 and h. Growth was reduced by regimes l, 2 and 5. Jack Stanley Wikle Sub irrigation reduced root growth of EL iaiezmggig in contrast to surface irrigation, however, shoot growth was not affected. The polyethylene treatment in contrast to the no-poly-— ethylene treatment significantly reduced both root and shoot growth of E. intermedia. The text is augmented by 12 tables and 2 figures. Data on frequency of irrigation necessary under various moisture regimes and treatments is included. SELECTED MOISTURE RELATIONSHIPS AND IRRIGATION OF CONTAINERpGROWU NURSERY STOCK By Jack Stanley Wikle A THESIS Submitted to the College of Agriculture Michigan State University of Agriculture and Applied Science in partial fulfillment of the requirements for the degree of MASTER OF SCIENCE Department of Horticulture 1960 ACKI‘IOEVIEDGT“ vfill‘TT The author wishes to express his deep indebtedness to Dr. Harold Davidson under whose guidance this research was conducted and whose time and resources were given un- stintingly when help was needed most. The author is al- so indebted to Dr. 3.3. Erickson for his valuable coun- sel. Finally, the author must reaffirm the importance of Jeannine Wikle whose help with tedious details, un- derstanding and sacrifices made completion of the work possible. a) TABLE OF CONTENTS Page Introduction ........................................1 Review of Literature ................................2 Procedure ......................................... 17 Results and Discussion ...........................a 32 Significance of Results and Conclusions for Contain- er Growing of Nursery Stock ........................56 Literature Cited 00000000000000.0000...000000000000059 tuna. Ono-00 009.....9"'..A°Q.. FfinIIOOflQBCOQGOUQ‘VOICO noonooaleioooa. l. 2. 3. 5. 6. 7. 9. LIST OF TABLES Page Percent Moisture Retention by 5 Media at Satu- ration, Waterholdine Capacity and at Equili- brium.with various ressures on the Pressure Plate and the Pressure Membrane..................2O Percent Moisture on Oven Dry Basis Retained and the Moisture Stress DevelOped under 5 Mois- tue Regimes...OOOOOOOOOOOOOOOOOOOOOIOOOOOOOOOOO025 Influence of 3 Media on Growth of Phasedlus' vulgaris while Under 5 Moisture Regimes..........38 Influence of 2 Media on Growth of Fors thia EEEEEEEQ;§.While under 5 Moisture Regimes........39 Influence of 5 MoiSture Regimes on Growth~of ‘ EllaseOlus Vulgaris Grow in 3 I'I'edia.....o..oo..oo)+2 Influence of,5 Meisture Regimes on Growth of Forsythia intermedia Grown in 2 nedia............’+1l- Influence of 5 Moisture Regimes on Growth of Fors thia i termedia while subject to Polyethy- Iene and NoPonethylene and Sub and Surface Irrigation Treatments............................#5 Influence of Polyethylene and NoPolyethylene Treatments on Growth of Forsythia intermedia while under 5 Moisture Regimes and subject to Sub and Surface Irrigation Treatmentsx...........48 Influence of 2 Irrigation Treatments on Growth of Fgrsythia intermedia while under 5 Moisture Regimes.and subject to Polyethylene and No Polyethylene Treatments ........................1#9 7‘ ~ .QAOI‘IQO‘OO.QP00 coo-\t-nsanqno-De-vono cannon-99- ‘0’”! «(cano‘iaQ'Ql-lo 1....‘OI. a-oaanaq ‘a-aoca-uvoaoe IORGCQIOOO‘) Q‘IQ?QO.RCOQ.QIOI‘. neat! Q Qr‘QQI-GQQQDOd.‘ noon 10. Influence of Poly-No Poly. Treatments Sub-Sur- face Irrigation Treatments and 5 Mois ure Re- gimes:on Intervals between Irrigation of Forsy- thia intermedia oooooooooooooooooooooooo.coco-0051 ll. Influence of 3 Media and 5 Moisture Regimes on Intervals between Irrigation of Phaseolus vulgaris.......o................................52 '12. Influence of 2.Media and 5 Moisture Regimes on ‘ Intervals between Irrigation of Forsythia inter- m Qiaovoooocoooooqooooooooooooooooooocoo-00.0.0053 0.9.0.9....QIOCIPQ.Q.QQO COCOOOO. Q . . C . D \ ._ - ‘- ‘ ... ' r _- ., .4 , ', . . ' - a. -. ... 'lrvv- n. -'-..'.-.-—— ‘ ‘- 0 D O C O O I 4 I H O C O . O I . 0 Q C Q C . C C 0 C 9 Q ‘. LIST OF FIGURES Page 1. Curve of Moisture Retention for 5 Media (Oven Dry BaISiS)-.C..0................0......0-00......2l 2. Curve of Moisture Retention for 5 Media (Volume B8313 OOOOOOOOOOOOOOOOOOOOOOOOOCOOOOOOOOOOOO0.022 v 0....400..OII0....9! O...I‘.OIQQQIOQIDOQCQ QC... Q C . I Q Q 0 l i . . \ 0 C \onol¢0 INTRODUCTION Growing of nursery stock in containers is an estab— lished practice in California (Baker 1957) and is rapid- ly increasing in importance in many other areas of the United States (Reisch 1959). Container production has several advantages over field culture. Since growing conditions for container plants are more uniform and more readily controlled by the grower, it is possible to increase standardization and mechanization of cultural procedures. Another advan- tage is that container production makes possible extend- ing the marketing period from the spring planting season through the summer . Furthermore some plants can be sold when they are in bloom and most appealing, and the con- tainer can be a more attractive package than the usual burlap wrap used for field stock. Maintenance of adequate moisture levels for opti- mum.growth of container plants has been a major problem. Since soil in containers dries more rapidly than sail finder field conditions, plants must be irrigated frequent- ly. This irrigation often requires much expensive hand labor. Little literature directly concerned with mois- ture relationships and problems in irrigation of contain- er plants is available (Baker 1957 and ReiSch 1959). The following study was initiated to obtain infor- mation for establishing irrigation practices for contain- er grown nursery stock. REVIEW OF LITERATURE Pioneers in biological research and more recent workers; have compiled an impressive mass of literature in the field of soil water and plant growth relationships. It has long been recognized that the water holding capa- city of fine textured soils is generally greater than that of coarse textured soils. The common method of evaluating amounts of water held by soils has been oven drying of the soils to determine the percentage of mois- ture held on an oven dry weight basis. Egg Avgilgble Moisture fiéflfifih - - - Research by Briggs and McLane (1907) and Briggs and Shanta (1912a) has become classic and is frequentTy cited in current, literature. Briggs and McLane (1907) established that the moisture equivalent, which is the percentage of moisture held by a saturated soil after being subjected to a force of 1000 times that of gravity in a centrifuge, is ancharacteristic moisture retaining value for a given soil. The moisture equivalent was found to closely ap- proximate field capacity for many soils particularly those offine texture (Veihmeyer and Hendrickson 1931). Briggs and Shantz; (1912a) studied many plants to determine variations in ability of plants to reduce the moisture content of a soil before the plants exhibited permanent wilting (wilted lower leaves do not regain f’a \ I 1' I .-r .§~ . .. l n . 1 g, -o y n u v w I. a 'L . I I .. ...-' _‘.. u 6- -.——-u r n I I n 0 u c . . - .‘_ w . ‘\ . . .9. _ al' . . \ u . . u u - ‘. u “. e 1' - ‘ I , .. .\ C . l - l ' n . I . r J 9 - . . ., . ~ - -w— . 4.- ' ,af) .II' . | . \ -- I, n C l ' I : . v . g . v' ' r r . . u _ I . o I’ I 7 ‘ , 4 \ g f '. r ' . . I' o" I V . . «I ' fl .~ C's". I. .1 O >- ,. 5 u ' . -~ \. ~ . . _ ‘ r . . — - . ~ . ~ . . 1 . .‘ 1 - . , v , .. . . '. - a I ‘ | . . w . l . - r , , ' A . i . . . a \ . . v a q . , 7 t u ‘ . n‘ h . .. ’ rv o . n . . - 0 . v \ ' V r — n _ j r 7 I O 1 ' ‘ ' - \ . . - ._ . . . _ a" 1‘ . 1 U I I — I C \ . . . a ‘J turgor when exposed to humid atmosphere), and concluded that variations in abilities of different plants to ex- tract the moisture content of a soil before permanent wilting takes place were insignificant. They designated the percentage of water held at permanent wilting as the wilting coefficient below which plant growth would not take place. They noted also that plants native to dry regions demonstrated no greater ability to reduce soil moisture content prior to permanent wilting than other plants. Thus the moisture equivalent as a value for the moisture content of a soil at field capacity and the wilting coefficient as a value for the moisture content of a.$oil at cessation of plant growth, were established as constants which have been increasingly utilized as li- mits of the range of moisture available to plants in a soil. Briggs and Shantz (1912b) also determined that the percentage of moisture held by a soil at the wilting co- efficient could be calculated from the moisture equiva-' lent by dividing it by 1.8%. However, Veihmeyer and Hendrickson (1928) demonstrated that the moisture con- tent at permanent wilting could not be calculated reliably from the moisture equivalent. Veihmeyer and Hendrickson also noted at that time that plants are able to reduce the percent moisture content of different soils to dif- ferent stages of dryness before permanent wilting results. Veihmeyer and Hendrickson (1931) have preferred tor use field capacity instead of moisture equivalent in their work as being most representative of the upper limit of moisture generally utilized by plants. They feel that field capacity is an acceptably definite soil moisture content at which drainage is reduced to a constant level if there are no discontinuities in structure or texture and no water table. Veihmeyer and Hendrickson (1934) concluded that the simplest and most accurate method of determining the permanent wilting percentage (term in current usage for the wilting coefficient of Briggs and Shantz) was growing and wilting plants in the soil. They also noted that the importance of surface forces in soils in causing wilting of plants is indicated by experiments showing that the permanent wilting point for a given soil does not vary with kind of plant or climatic conditions. Methods of measuring field capacity, the permanent wilt- ing perCentage of soils and the importance of these mea- surements have been reviewed by Veihmeyer and Hendrick- son(l9%9). Breazele and McGeorge (l9h9) have proposed another method of determining the wilting percentage of soils. This method involves the jacketing of small amounts of soil on tomato plant stems. They found that the adven- titious roots which developed in the soil would bring the moisture content of the soil to a constant level by either reducing the moisture content of moist soils or increasing the moisture content of dry soils. The au- thors feel that this moisture.level can be taken as the wilting percentage on the basis of comparisons with the wilting percentage computed by dividing the moisture equivalent by 1.8%. Fgllacy 1f _Ma_intaip_i_pg Mgisture 14231.3 M field Qgpacipz.- - - Shantz (192%) pointed out that practical- ly all experimentson plant growth at differing moisture levels, which had been conducted previously, had been designed without adequate knowledge of soil moisture conditions and the difficulties of controlling soil mois- ture.’ Two common errors were comparing unlike soils at the same percentages of saturation and trying to bring dry soil to a certain percentage of moisture below field capacity by adding water to the surface. Veihmeyer and Hendrickson (1927) and Hendrickson and Veihmeyer (1933) reiterated the point made by Shanta, that achieving any uniform moisture level between field capacity and the permanent wilting percentage by appli- cation of water to soils on Which plants are growing is impossible. Veihmeyer and Hendrickson (1927) also in- 4 I \‘I ~~ c. . - n . \ D I . .2 . v. ' ' a“ .- - . . . . .' \ . . I .. . .' ’- v . >.\ . . . \' . a f _. IV ‘ v " ‘ ‘ ,. .. . . . . k, .. \ o I ’ '. . u. .. _ .. a. I I A. .c‘ . a . . . r . ‘ f ‘ r,\ _. V. . . . ' ’v u - -' .. . . n \. . . 4 . .4“ -‘ — -_. . . . r .v n _ .~. . v ‘ ’ ' .‘ c . , . - U I ‘ ‘ ‘ A ‘ , . . . . . . . ‘ . ‘ . I ' I ' 'l . . " . r l ._ ‘ , » V. c ~ . I I ' s “v“ a .u— > - l- ‘4' b -‘ u o . I v .. fi. « , L _. t' ' . '_ '. . . . . . _ .. ) .~. ~ .I . —-\ o l ‘l ‘. ' t I ‘ r .. ' ‘ .. .1.) ._,. I L ’ ' - ‘ -‘d 4' l i A . ... . I . _ . . ‘ r V -<‘ ‘ a ’~ <4 .. . . “ f I — .v 't x. - u .A . -. .J ..--. J —.... .‘ . - . . . b .' - l o\ ,u.’ - .- - . . ‘. .. r ‘, ‘t' ‘ . -L. I . .\ . . ._ ‘-‘ \ , ‘ .. ., .' p ‘ .. ‘ .. ‘ 1-. ' \ . ~ ' v " . ' ‘ .- ..~ . . -‘ x . -. ‘o' ,_ . ‘- ' .3. .1. .4 1 Q ' ‘- . 0 I 1 I I r r - . f - . . - I .. ”A ' - ‘y - l I .’ J - ' ,. K‘ .A \.' tJ , c- . ‘c 4 - n - v r ‘ - y ‘ 1 ~ . - - .»-. '- _ J x. \4 . , . I \‘A . , _ - _ -.. . __7 ‘ M ' . u n ‘ \ , ‘.( ‘ . t ' g I A ‘ J .. ' . ‘ . s . \ z _. _, _ _ A , u ‘ - , I . I . ’ v I ‘ . . . . - , ‘. r . - ' - . ,. .4 n - n I ~ ‘ a ,- 1 . u a . . , ,‘ 1 . . , « . u .1 « .... A. A \v . ~- ,\.' . . _... ._. ,‘u _ .'J a . o o -\ o \ 1 ~' - . ‘ “ '- '7‘ - A > - ‘ r , ' - . ‘0 ‘- .1- » , \ ‘ . - ‘ _ , .~ I ‘ . ' “ ‘ - o 4- - ' ‘ . . - v ‘ I - r I . _ _ , . . ~V. -. . l _ -xa .. - r ‘ ' l ‘ a . , , . ; ‘. .. . . ,.. . ‘ ' _ _. . I .vo J . . . .I.. . I - - ’ O ‘ - o o v ‘- . _ . . . . ,.v . , t .. _ _ . . - . . ' - up .. .‘ ‘ a a a . . —-& -—-I -. g- - -w - w A. C Q ‘a ea-I. - o. O..- -a... ‘v - ~. , o - . . t ‘. ' ' ‘ ' in O. I. '- ¢ y - " If ' . \ ‘ ' 4 .. .—o - <.o -._.‘ may 0 o . . I... .— - , .. . » A - A .. - _.. . . - 4 . I . , \. “ »-. .4 . . -' ' J ’ —-o - ) ~ ‘ c o n o- r v v\ ‘ ‘ ‘ .. ‘ . 7 ‘1. , ‘ - ‘ - '4 ' ‘ '- . . t .u u “ 4 .w . - . n ‘ , o - I ~' » ' ' r > v y -. r , , . a I ' | ' V . . i r. b 3! . ' w ’ L) ‘ ~ _ A _ g‘ . D . , . . n u . r . | * i. - .r - - . .. I . t - .‘-4 -a. ~ \ ‘-‘ v" ' ‘ u _ . ‘7' ',- . . ' ' - - - A h .. . ’ ~r , .o. . ~ I_ . 1‘ ' . 0 . A 7 V . A ‘ a - , . ,A A . _ ‘1' , ‘ )r r .. . k , . ~ \ ~ _ s. . . ‘4 -. - d \_. . - . ‘v > . k v , . o’ ‘ r‘ ‘ " ‘Y r A I t ' ‘ _ ‘9 u q . . pr A l , . v '- - c 4 1 ~ ‘. .- . . . ‘ f —, - ii . ‘ ‘s . s . ' .. ‘ | -, ‘ w .. ' a ' J ’ . C _ . “ f. ' . ~ I ' .. _ _ v -‘ - .-. . ' . - J .." . x , .. ' . I I {I (\ . ‘ \ - g o — r .— A . . I \ ‘ ' ' ' .. . I . , «- r' - l -' N ' . ‘ . .-. ,‘ r ‘ ‘_ ' i- ... . .-‘ . ' \ L' ’ ' I .A ‘V . ~ - . ,_ "‘i . ._ A) .‘ n ‘v‘ Iv .’ 'v _ .U I. - ‘ \o . _, s A _ g . ,1 ‘ _ r 3 , \l . . 1 . \a ‘J u I , ' .. ‘ a p I ' " o— “ a n , ._ I . i . , . . -‘ ‘ , . . ...J u . ‘ -.‘.' - -_,.‘ _ .,_ .1 ,‘ dicated.that contrary to the then papular belief, that water movesawith considerable Speed by capillarity from moist to dryer soils, their results.showed that movement is slow in rate and slight in both amount and extent. Moistggg ggime Experiments and Availability 9;: - water withip the Available Bapge, - - - Recognition of the impossibility of maintaining moisture levels between field capacity and.the permanent wilting percentage re- sulted in.what are commonly called moisture regime e39 periments in which soils are allowed to dry to various moisture levels and then irrigated sufficiently to bring the total volume of soil to field capacity. 0n the basis of their moisture regime axperiments with fruit;trees and container plants; Veihmeyer and Hendrickson (1927) and Hendrickson and Veihmeyer (1933) statedithat results indicated soil moisture is.eoually available to plants at all soil moisture contents from field capacity to about the permanent wilting point; and that there is no relationship between.moisture con, tent and either use of water or growth in length of‘ plantSiwithin this range. Since that time; conflicting evidence has been pre- .sented for and against water being equally available to plantssthroughout the available moisture range (field capacity to permanent wilting percentage). to ,\.l u '_ - s.) 9- .f p a I . s I C ' . . .' I. a A . l ' ' 0 I. . -' ‘ ‘l v‘ A .V . \4 V‘ \l ’ ,. . ‘. ‘l . . . . , - « . . l _ -IA- , ‘c " .- a . u w l O l y‘ 0 V , ‘ _ .. . ‘u .. ., - - a - . i J C - r A V ‘i . F g . - . . .- - - A. \r -. - ‘ - ‘ | . . ‘ ‘ 4 A.’ i \ ,Z... - - I 4 . x n l . a . 4r . I ’ ‘ . ‘ ' ' a . ' ' ‘ - . . . . . . - ,, . -- g - . . .m- .- . - - - .- 0-. u - « - . -9 - a q u I | u- a o a n v 1 1 v \ . ‘ ‘ v . _ I. ~ .9 . , ' i — ~ — 3 CD ~ - . I - ' I I- I. ' - ' . . a . , l l - ‘ V r .. “ . .. ‘ ‘- J - - - . n . o a v - .7 . . ‘ ‘ ,, .. "3 'I - . - » .. . .' A ‘4 . ‘A ~ - u ‘vj . - a, -l I , . p -a a o u - a l-A A - . . , ' , - . » . ‘ ‘ . “ . , a , , q t, . 4 ' 5-. . - ’. a . - ‘ a .- ‘ '-‘ ‘ ! . " ’ ' -.‘" A _ c .. . . A .~ . _ A I . - ‘ . A O t " I . -' ’- . -.‘ . , m I n ( , A ~ ‘ .3 - c , f - v ‘ . ~ . a ’ J - .‘ . . . - s .. . _. a, - - . a ‘ . c I a - . v. ‘ I - ‘ o r] ' ' I ' ' ( I l . ..- . . _ ..'. ' , . »8 .. .- s. 1 .' - . v i ' i‘ , , . - _ -, , ‘ r l , .. ‘. , . '3 Al. ‘, -. . . . _ . I. - .. .o ‘.. ‘ ' s: ' . ‘ E. _ ._ i 1' ‘ ._. . .' , . y. _ _- ~ - ' ' \ ' ' ' v f. ‘ . _ ‘4 " - o ,' ' 7.. J. . ”f /. ,‘ " - .- .- ~ 0... I ."‘-‘ " .'\ . .A. l .A . - -. . , .Au . - _»¢ . _ \ ‘_ , -.- I -' a i. V ,., s .- . . .. o a , ‘ . _ t ‘, - ,‘Y i .> . - . v . , , .-. .‘ .' ,3 , r‘ '5' -.. _ r. 3‘ ,. I ' .. \4 ~ . -44 a . n . — -i .N a) ,.- <\ . < ' _ i \A _ ‘ . t ,. i r‘ . o .- , ’ ‘ . . - I. . ,—. r . _‘ .. ‘ ‘ . . ‘ r. , ~ f\‘ . , ,. . u ‘h 3.. \ - '_ .. \’ \ ._ \J . .1 '4 h. .- -., \' k - ’\l — , < . . . - . I‘ I . . u , I o - . . A . . . . -pr -‘ --,.. 7i '7 .A .‘ , v - r- . r A . ‘ "'2' 'i’ .. t\..-.A . ,,,. ...-.._ 1' , \‘J k-...\- ' 1' . o I l - c . I l r‘ c ‘p . I - , _ \~ r - '. i.— ‘7 q - . . . ‘ I .\ f"- . ,. .- _ \‘_.;n f ‘ . .L- g, -- -v . -_ .1 . _ ‘ __..\ .-. ' - A. c in . : _~ I . ‘ o. . A | A . . § - f \ - ~ ' V " . . ' . ' _ \vl . N , i. \ . ) ‘ I « I \ ' ' . . r . ’A;i .. ~ . — .. . . . . ‘ - _\. -v v n g . a o o - c . . _ . .‘ \ ‘. . . .. . ., ‘ . . .- . a. . , A- .. , A K- ' ‘ ' - -;' - » ‘ . - .v <‘- '7 ‘ Q h - ‘1 '- - ‘ . - .c - - ' u I . . ‘ r 1" ' ‘n‘ ‘ ‘ . ‘ - ' " fl - v"‘ ' ' ’o ' ' ' ‘ ' 0‘ a . v . , .' . \,. . b - . . . - . .I -. . x. . . - ,- ~. ~ A . o , \ | o r- r" o _l 7 A I . - 3,“. ’ , i “p . e . _ - A. - ‘ a '1'. ‘. ’ . -_ j i. .l— v- ~. _- I a A -'-‘l. V'.‘ . . .g- u I si J - .J ' o v Q ' I l i 4 ‘ i , , r" . _ i . , ‘H , .- - x . i. ._ . 'fi . . 0\ ' - -m. ‘4. .- \, ‘v In more current work; Hendrickson and Veihmeyer (1950) subjected walnut trees to two moisture regimes, a wet treatment and a.dry treatment. With both treatments; moisture levels dropped to the wilting percentage on occa- sions; but the moisture percentages for.the dry treatment were reduced lower and for longer durations. Moisture ' determinations were made by the soil sampling technique and growth was recorded by measuring increase in the trunk diameter. In this instance; less growth of wet treatment trees than dry treatment trees was attributed to a difference in nitrogen levels between treatments; However, the authors took issue with evidence by Allemen- dinger et; a1. (l9h3), Kenworthy (1949) and others who found that moisture was not equally available in the available range.. Citing the results of the above walnut tree experiment; Hendrickson and Veihmeyer state that their belief in.water being equally available is further Juwtified and that greatest growth does not result from maintaining soil moisture high in the available range. The most plausible reason of those advanced by other workers; for Hendricksonis and Veihmeyer 's.find- ings is that most of their work was done with sandy soils which hold nearly the entire amount of water in the avail- able range at very low tensions. I In the research mentioned.above, Allemendinger et.al. l. (I .0 ‘ - a q ‘. W . .. l-' ‘ l . F ‘ . E . o "4 . l. ‘ . . n ‘ ‘ , . V ' ' . ll 0 . ‘ - r . | ' - D I u . ‘ ‘. \"l A l ..' I» f .4 ‘ . J A. I \ . ‘ ‘7 v‘ I \. - - U ‘ ‘ - . r. . l._ 7‘ (J.- - . _ . n ‘ h ' . .. K A: ‘ r .0 _. . ‘ - A I - ‘ I .4 ‘4 J - -— _ . \ ”I D 5 J g - : ,-- . d ' . I l . l v‘; F. V. .. n- ‘l )2 I .,I v _‘ n _ I . - . q. I o . l \ ‘ o . r 1 ,.- l .' 4. _,\a .. , A‘ ' , .. , iI ‘ \A‘ Q . I .1 ~ -(, .I‘ .§. ',- I . .ad ‘ \ U r o g-» , 5 r . ‘. .. ' .- : __ r. 5- .- ‘5 . ' .- v" > 1 r. . . .~ "' 9 w. .. . _\—‘ \‘1 -. x ,- ~ I a t I U ‘ l I l .* ' . I-.. - x a -V o ' V ‘sl '1 \‘1 r J . ‘, V I w a . . (u , 1 i 4‘ ' 4' ‘ - n. I I . . - I“ ' “ a. ' ! ‘ U "- W \D V O o“. ‘ I . . . .u -. u . ‘~-- U (1943) and Kenworthy (1949) conducted similar experiments in.which apple trees were grown in containers and times for irrigation were determined by tensiometer readings for the wetter levels and by wilting of leaves at the lower levels. Treatments were irrigation when 20,40 60,80 and 100 percent of the available water was removed. In both cases allowing 80 percent of the available mois- ture to be removed before irrigation, resulted in signi- ficant reductions in tree growth indicating that water was not equally available throughout the available range. Working with beans, Ayers et. a1. (1943) studied the relationships of salt concentration and moisture ten- sions with bean growth and yield. The beans were irri- gated when water was reduced to the point that it was held by the following tensions: 250 cm. of water, 750 cm. of water, and approaching 15 atm. (plants appreciably wilted by mid morning). They found that bean growth and yield were reduced as the soil moisture tension at the time of irrigation was increased, even though beans in the first two treatments were always above the wilting points. Blair et. a1. (1950) grew sunflowers in containers of soil for which weights had been calculated at various moisture levels. The containers were weighed daily. The time rate of elongation of sunflower stems was mea- . . .. .. -- 9 L; O I I . A .V k 0 .. -. - d' 0 . . k .' . I _ . n 1‘ . A . v .. 4 .-v . .. ,- .v .— . . -‘ \z .w‘ . 'r g. - L ; I l _ x o . .K- A r ' I I, ‘ .. t \. O a ‘ --’ a ‘ F \ l .‘ , I -. . . ,. . _ . v _ ' . - f . I ‘ n _ u ‘ . V _ , . \._“ . . 4 _- c I n ' ‘ f . . . I " I l ‘ ‘ . 1| . .. .7 . I‘ ._ s ‘ I _ I \ a . l’ A . 7‘ | . . . J .. , ‘ ..§ r ~ 1 l I . . r ' ' ' 1 . v ' - ' . v ‘ - ° a >\ r 7‘ - $ - , ‘~ . ‘. - » i l I “ . . K V ‘— . . . o . r ‘ t . . _ . . . . < . H ‘ .H ' . . . . . - . .- r O ‘ 1 . r. - '1 . . ‘ _A . I _ —' -, r - v r ‘ ‘ . ‘ . , A _, a . . I -" o ' \ n ' ' ‘ ’ . 1‘. _ . . . r- ‘- ‘ ‘ , . u I v ‘ I .. . 0 ‘¢ \ r, ' . '- I ‘ x V . , , ' ' "" I O s ' ’ ' v . -, , l . .-\ ’ ‘ - ' 7 l ‘ - ‘ . r , . A v ' . . . . '. .. - r‘v'A ' " , v I w A . I . ._ U —Q ‘ ) J - . _ - v" ' . I 9-. ‘ surediin relation to soil moisture depletion following the final irrigation. They found that the time rate of stem elongation of the sunflowers was markedly reduced before half of the available water was depleted, and that the rate of stem elongation dropped to zero during the extraction of the last quarter of the available soil water and before the permanent wilting percentage was attained. . wenger (1952) used the weighing technique to main- tain three moisture levels on sweet gum and pine seed- lings grown in containers in the greenhouse. The seed- lings were grown on three soils: clay, silty clay loam and sand. Treatments were moisture level maintained at. the moisture equivalent, irrigation.when moisture level dropped to 60% of the available moisture and irrigation when moisture level dropped to 20% of the available mois- ture.. Significant differences_in growth in length and increase in fresh weight were found between maintaining the moisture level at the moisture equivalent and irrigat4 ing when 20% of the available moisture remained. Stanhill (1957) reviewed and analyzed the previous water regime experiments (soil allowed to dry to definite point and water is applied to bring it back to field ca- pacity). More than eighty percent of the papers revieWB ed indicated that growth was affected by differences in I. 10 available water before the soil was rewetted. No papers were included in which soil moisture was reduced to the wilting percentage for more than a short period of time. In all papers reporting significant results except one (carrot seed crop), greatest yields were recorded at highest moisture levels. The ratio of positive to negative re— sults was significantly greater in experiments with an- nual plants than in experiments with perennial plants. The ratio was significantly smaller in field experiments than in experiments with plants in containers, and signi- ficantly greater when vegetative growth was measured than when reproductive characteristics were evaluated. .There was no significance in the ratios when an avail- able water scale was used contrasted to a soil moisture tension scale, or when positive and negative results ra- tios were compared in respect to date of publication. Gingrich and Russell (1957) compared growth res-l ponses of corn roots to seven soil moisture tensions and corresponding osmotic stresses. They found that growth of the corn roots showed a linear response to osmotic stress throughout the 1/3 to 12 atm. range used. 0n the other hand, growth responses to changes in mois- ture tension were linear except in the l to 3 atm. range. The authors believed that the effect of water transmis- sion characteristics of the soil must be most pronounced I' in the 1 to 3 atm. range. lanes:and Johnson (1958) used tensiometers and gyp- sum.moisture blocks to measure available moisture in field plots of onions and potatoes. Both crops respond- ed to irrigation at .3 atm. tension (80% of the available, water remaining), while delaying irrigation until 1.2 atm. tension (HO% of the available water remaining) had a very detrimental effect on both crops. Hbodhams and Kozlowski (195%) have studied the ef- fects of soil moisture stress on carbohydrate develOp- ment in bean and tomato plants.» The plants were grown under three moisture regimes and analyzed for starch and sugars. Results indicated that appreciable moisture stress is imposed on roots before moisture is depleted to the permanent wilting percentage and that each deve- loped stress effects changes in the metabolic status of the plants as indicated by differences in carbohydrate reserves. _ Percent g1.&yailable Moisture fiange,2;§. figil Moisture Stress.- - - It should be noted that in the preceeding review of moisture regime emperiments, some workers have measured moisture as percent of the avail- able range, while others have recorded moisture avail- able in terms of the soil moisture stress develOped, usually in atmospheres or centimeters of water. l2 Livingston and Koketsu (1920) advocated a dynamic approach to measuring the water supplyingpower of soils by use of porous porcelain absorbing cones. Using these cones they found that the water supplying power of sev- eral soil combinations was the same at permanent wilting. Later work has developed the-feeling among research work- ers in soil water and plant relations (Kramer 1949, Rich- ards and.wadleigh 1952) that the tension with which wa- ter is held by the soil (Soil moisture stress) is more significant for use in comparing plant responses to dif- fering moisture levels and different soils than is per- cent moisture within the available range. Moisture retention curves obtained by plotting mois- ture stress against percentage of water held by a soil indicate not only percent moisture available but the tensions which must be applied by plants to take up the water. Iota that coarse soils hold most of their avail- able water at low tensions while fine textured soils with wider ranges of available moisture hold much water at the higher tensions. ‘ Richards and Weaver who have done extensive research on moisture stress and methods of measuring it, have de- veloped the pressure plate and the pressure membrane. These devices have been accepted as the most convenient means for measuring the soil moisture stress and the per- I71 5‘ cent moisture content as they interact within the avail- able moisture range (Richards and Wadleigh 1952). Richards and weaver (19#3) have compared permanent wilting percentages and moisture equivalent values deter- mined with sunflower seedlings and centrifuge, with 1/3 atm. and 15 atm. percentages determined with the suction plate and the pressure membrane. They found that the 1/3 atm. percentage corresponds closely to the moisture equivalent for coarse textured soils, and that for 102 of the 119 soils tested the permanent wilting percentage is in the range between the 15 atm. percentage and 1.5% of the moisture above that figure. Richards and weaver (l9kh) reported that for 6% of 71 soils, the 15 atm. percentage was found to be between the first permanent wilting percentage (permanent wilt- ing of lower leaves) and the ultimate wilting percentage (permanent wilting of all leaves). Also on the average for the soils studied, the 1/3 atm. percentage correspond- ed closely to the moisture equivalent. They concluded that tensiometers, suction plate, preSsure plate, pressure membrane or centrifuge may be used for determining equiva- lent negative pressure or soil moisture tension but can- not be used for determining free energy without disregard- ing osmotic effects. Soil Amepdmente gpd Effect gp_Available Mgistuze Capacity. - - — Another aspect of concern in considering P) 1’. ’\ ‘, ». x. . l '1 0 ”fi- \. . \ .— . . .. ..- y . \ .. . l .-. . - ~.. . 1 . . -..§. . .4 . -. r‘ , ‘i L . ‘ I o a \ A ‘\. ..: 1% the available moisture capacities of soils is the effect of soil amendments that are sometimes added to change water holding characteristics or structure. Mchol (1932) reported that adding peat and fertie lizer salts to sand soils resulted in satisfactory grout ing media. He noted that Optimum ratios of sand to peat were low while optimum ratios of finer textured soils to peat were higher. ‘ ' Feustel and'Byers.(1936) found that no moisture economy resulted from adding peat up to equal parts by volume to clay loam soil. Mixtures.of peat with a clay loam were capable of absorbing #0 to 50 percent more moisture (on volume basis) than clay loam alone, but an increased evaporation rate and higher moisture cons tent.at the wilting point were said to counteract the initially higher moisture holding capacity. However, they did find that improved moisture conditions may be obtained by incorporating peat with sand or sandy soils. Tukey and Erase (1938) grewrapple trees in boxes of soil and in boxes with soil and peat mixtures. wa. ter was added as necessary to maintain the boxes at several predetermined weights ( not a moisture regime experiment as not enough water was added to bring boxes to field capacity or moisture equivalent). They found that addition of peat to soil (50% by volume) increased \ ’ I L . r - I , . . .. _ . w ' ‘ J I . a I , . I t i ’Q I Q - ‘ us) ~ . . I“ ' ' ‘ . . . ,7 . ‘<0- ‘- , . - ' o . - A t “ I r 4 ‘ ' 9..“ .3- . . . .‘ ‘ _ v' ’ " I '-v ‘ V . 1' w t. 'l c 7' ‘ - < . . — -' * I I r ,_ I 'I ‘ . ‘ - - r- 1 p. - ‘ . L. ‘ I V a. .- . ,x ' -- . . d ,' - . . . ‘ - \ . .- . --. ‘ A , , . . l a - . . l ' ‘ ' r ' o “ o " J I I 1 . h ‘ t .. \ ' ‘ ‘ u . I r ( , . , J . _‘ J o I- '0 . . f D ' Y I - ’ ’\ . 7 , “' .‘. | ‘ A «I . . ' 0-. . , 0 \n m n . . , . . . .. , _ A .. o -- . . I ), )1 . . ~ , , ~ . , 1 A . . ‘ . - .. , '- . . , - . .‘ .‘ ' | 1 ‘ . .—‘ ' '. . 1 - (I ’ / . . | - t -- . ‘ v | .. .. 1 4 v ._ A - . - . , v . . . ‘ - ‘1 .—1 ' !~ s v - . ,. . . I ‘ I . . x A . . - ‘ . i I . . . , . . \ - . . « . 1~ , - . r ' .c _ I . . _ , .-.. . r . - . , , L . . . ‘ , \I 1‘ _, . A - . ' i I 1 ‘- _ , . .. . .fi ‘ . 5. ~. x. \ ~ . I . . 7 , .. _ . . .a . - ,- . — . ‘ . a - — r V ‘ - , o ‘ r . . . .. \ I . \ - e ‘ V w 4 I u .- a v , , \ . v . 15 growth of roots in all cases and of shoots in most cases. The effect of the peat was attributed to better contact of soil with roots, improved aeration, easier penetration of rainfall and less runoff, and easier penetration of. roots because of decreased density. . Havis (l9h3) reported that differences in organic matter content of Chenango loam resulting from additions of manure over a-twenty-seven year period did not resu1t in a statistically significant increase in available moisture, while with a Chenango fine sandy loam, there was a significant increase in percentage of available water in the manured plots. Jamison (1953) reached the following conclusions by use of moisture tension determinations: for most fine textured soils with unrestricted drainage, in-~ creases;in total porosity through tillage, granulation or addition of organic matter results in increased air capacity and unavailable water capacity along with at decrease in available water capacity; apparent increases in available water capacity stated on a percent basis are the result of diluting the medium with a lighter material; addition of peat to a sandy soil is in effect adding a fair water holder to a very poor water holder; only with coarse textured soils will increases in organ- ic matter result in available water capacity increases I ( , ‘ - . . ' l‘ i M ‘ . ‘ . | ’ ' _ h . ‘ n N : ~ ‘ . I - I- no A, ' ‘ h I l ‘ . ‘ v - r7 - . I ‘ u _ . ,M _ . A L ‘ I \ . . . [F J ‘ l ‘ Y . A . ~ . ~ H ‘ I , . ' t - . . H v . . ., . x A _ , ‘ —. I . . . ’_ . . ' ‘ — . . i . . - .‘ ~ A . . fl ‘ . . . ‘ r ’ c - u ‘ I ‘ I I ‘ A ~ .. .. I. . , — ' V. . u I . r . E f " .. x‘ . » L i I H 4 .. I . h u ‘ I . ‘ , ' J . , - . v - . '- ’ . . w ’ ‘ I ' | ' ‘ .A r — I l I - ' . . a r . ' 6 ‘¢ —’ > » l - . I _,p . ~ ‘ a. . ‘ ~ . ' . .., - ~ . ‘— . . . ' . H I < I. p . . . i _ u ‘ - w I . v C , . F . -. . _ . . A 1 > __ v - ‘ - ) I . .‘ . I ‘ A . . \A . __ ‘ r r . ' V A . .. ‘ A. - ‘ - I I . t ‘7 . . ‘ ‘ ‘ i _ ‘ . ., ‘ . ' ' r).‘ - . “‘ - h “' I “ I , >_ i , , n . w . .A L 16 and good structure improves field water relationships because of increased water infiltration, Moistuge ngngeductiog by Elastic. - - -.In rele- vant work, Letey and Peters (1957) “used plastic material to cover corn plots. The purpose of the plastic was to prevent the wetting of low moisture treatment plots by rainfall. The authors found that efficiency of water= use was much greater in covered than in uncovered plots. Later; Shaw (1959) grew corn on plots covered with plastic material which intercepted rainfall and reduced evaporation. Soil moisture loss frOm plastic covered plots averaged #6 percent of the total water loss from an uncovered plot. Corn yield from the uncovered plot was 129 bushels per acre; while yield from the plastic covered plot was 121 bushels where the profile was not "recharged"!with water in the spring and 10% bushels where the profile was ”recharged”. The reduction in yield where the profile was 'recharged" was believed to be due tothe condensation of moisture under the plastic; resulting in excess water in the surface soil early in the season and to very favorable weather giv- ing high yields under the natural conditions. L. 1 \ _. II ‘ I ‘1 v 'i v .. n ‘ 4. \. ,— “I A 1- ‘0 . o w o I '. w 1 . ~_, 7 d 4‘ ' l . - 1? PROCEDURE. EMring the spring and summer of 1959, determinations on moisture.relationships and irrigation of container grown nursery stock were carried out on the campus of Michigan State University at East Lansing, Michigan. The purpose of this research was to determine the effects-on growth of container grown nursery stock of the following variables: five moisture regimes. five growing media. sub irrigation contrasted with surface irrigation and a,polyethylene.covering around the soil mass contrasted with no polyethylene covering. Five growing media which are representative of me- dia used for container plant production and readily avail- able at Michigan State University were selected for usem One medium was Canadian peat which was used as it came from the bale with the exception that a few large fiber masses were discarded. The second medium was a coarse sand of the type used in greenhouse potting mixtures at M.S.U. The third medium was a clay loam which was sifted through a% inch mesh screen to remove larger clods and debris. The fourth medium was a mix- ture of 50% of the sand and 50% of the peat, and the fifth medium was composed of 1/3 sand, 1/3 peat and 1/3 claybloam (mixture on volume basis). ’4 \ 18 The two mixtures (sand-peat and sand-peat-clay loam) were mixed to the point of presenting a fairly homogeneous appearance. The media were steam sterilized (180°C. for 30 minutes), samples.to be used in laboratory determina- tions were taken and the media stored in the containers to be used in the experiments ("plantainers," number 10 cans crimped to somewhat less than the usual volume and punched with drainage holes). The samples of the sterilized media were placed in soil sampling cores (metal cylinders, 3 inches in dia. and 3 inches in depth, inside dimensions). The media were retained in these cores by filter paper and cheese cloth which were fixed in position at the lower end by a rubber band. Five cores of the sand-peat-clay loam mixture and four cores of each of the other media were used. The cores were saturated by immersion and weighed (all weighing was done on a balance tared to read weight of the media and water). The amounts of water the media retained against various tensions were then determined by use of pressure plate apparatus as described by Richards(l9h9). The cores of media were subjected in turn to pressures of 0.1 atm., 1/3 atm., 0.5 atm. 2/3 atm. 1 atm., and 2 atm. for #8 hour periods. Weights were taken prior to each pressure change, after which l9 the;samples:were oven dried for 48 hours and the percent moisture (on oven dry basis) retained at each tension was computed by the following formula: 7: Moisture Retained ’_-_-‘ Five samples of the sand-peat—clay loam mixture and four'samples-each of the other media were then placed 0n the pressure membrane described by Richards (19%9), and allowed to come to equilibrium with a pressure of 10 atm. Anetherset‘ofpsampleswas allowed to come to an equilibrium with a pressure of 15 atm. on the pressure membrane. After coming to equilibrium on the pressure membrane the samples were weighed. oven dried, and re- WEighed, and the percentages of moisture held at 10 and 15 atmospheres.were computed. The mean percentages of water held by the five.me- dia at the various tensionS' are given in table 1. Hois- ture retention curves.(Figs. l and 2) were plotted to illustrate graphically the relationships between soil moisture tension and moisture retention for the five me- dia» Upon evaluation of these curves and related litera» ture, itgwas decided that the moisture levels at which the containers would be irrigated should be as follows: I. A moisture percentage midway between water hold- 4. (I 20. .m_mmn __0m do oE:_o> m :o ovum—3u_mu.ohm m_mucpcohma c_ tome—ecu mommucoohoa .__0m mo u;m_oz >Ln cm>o one we m_mmn 0;“ co ovum—:o_mu ohm m_mo:ucohma c_ memo—0cm u0c mommucmohom.uouoz# . Ewe; >m_u AON.hV AN_.N_V Aho.a_v Ahh.a_v Ah:.w_v Awo.o~v Amm.o~V Amm.-v A_.:mV Amm._mv -emma :a.h :N.N :m.w_ ow.m_ ho.ow ha._m ~_.~N am.m~ . __.Nm ma.mm -ecmm A_~.Nv Amm.av Amm.m_v Amm.o~v Awh._Nv Aom.N~v Amm.m~V Ama.m~v Am.mmV Aum.mmv mm.a mm.“ mm.o~ mm._~ :o.- mm.m~ ho.m~ mm.o~ m_.mm mm._: Emon >m_u Ase.mv Ame.ev ANN.~_V Ame.m_v Aeo.e_v ANm.e_V Amm.e_v Ame.n_v Aa.emV Ahe.mmv have _~.w m:.a .m.w_ mm.m_ mm.o~ :_._N mm.m~ ma.m~ ~:.mm :m.:w -ecmm A_N.hv Am_.hv Amm.~_v Aoo.mev : Aho.:_v Am_.a_v Ao:.o~v Amm._mv Am.mmV Aoo.hhv mm.mo_ mm.mm :N.ao~ mm.m_~ .N.h- mh.hau oo.m~m w:._mm .o.hmh Nm.:ho_ seem Ahh.v Amm.v Awe._v Aem._v. Aom.~v Ama.~v Aam.~v Ame.mV A_.N~v enem.emv ah. ah. N... :4... ma._ No.~ m_.~ ha.~ wa.h_ .. «oo.o~ new” a, a .Eum m. .Eum 0— .Eum N .Eum _ .Eum m\~ .Eum m.o .Eum M\_ .Eum _.o “WWW—M“ cowumnaumm E:_oox mohammohm uncumz wz IF.) 23—mm_4.3dm h< oz< >h_om zo_FZMhmxtm¢=hm_oz hzmuxmm _ m4mlllnlo.3010..|-..|.Oilylu.t."lx-l l-nCsILtllnlluall‘l..¢l.l|"‘dn..0‘00lollInsuli‘llli'I‘acvlll..tl.nu|.uolt.lll‘llivna . v . on. . . l _' u I - .- I .' I I 0 D I I - - I- t- I III I..- ".‘.-lr‘ll a .lluIIlIIU.‘ '1‘ 8|... -i,‘ I -ll . If- -".‘u‘l\l. O I...) I. ICIIIII-II .Il’llv!‘ | .vlll -II '1’} '.I.l. A. v I l 1 .) .. . . . u g . . t . n - l ». h . . I l . . a . . . . o . I n I — 0 K .O o I o o .1 . u . _ I , ..\ .nre - .‘I‘ I, Inn: I ' I Ill-“ '- «il' . ‘rl .lg’l | I u-.l‘ I . -t 'l' ".1 [I’ll' . -\ I lul“-it I” .1 II-‘ 7' I -U‘. ' - a. ill. l ‘I ' I'i ll ‘. - ' ’1‘, -.I‘.v- but ‘ ‘ cl . ‘lr r I! U ‘1‘ ' ' t.“‘ [I I‘».‘~l ' I ‘II' o ‘ . Ir a 2 1 e . I u a m ,7 _ I . I v . c y 0 . o a I I z. I . y c . u .r o n . . . I . a a 1 . x . , .la . x _' , . '5 m n . . ~¢ . o o . . I o o e o . I . o x x a . 4 . r . . . I r c 4 A . I . .. c . v \ _ I u I . u .. c o A c 0 ~ C . a, v . I z \ . x J . . \ r x . \ J x ‘ o I . . e . x J u . . . o ' o . n _ I n . L. . o . .1 o w .I \ v .. o I o o , f .. .. .v . e . r v , .. r . z. a ,_ o . s I 0 e» f e u N r . c o - a .. . a .. . \i , I I w W o. u . a . a 4 o . o . . u .. t J , a a .. a n . o r ., o , . . o r A n ..a I s. n _ o .. u _ v ' O . . o p a c . I r — e z u ._ o a c _ - o . . o I I s a . e .. I ‘ I e {a \ 1 N 1 _ i _ . . o . . . h u _ o ., o o . f O . u x . . . . e a .. \ ,1 o z x o s. . . . f x r \ t..- . I’ll I'lv‘lil‘.‘ {II-Ill lull-ii It Q ‘Kloil'ut. .III. A . I ill‘ ll, ‘l‘lil‘ il \Iyll. ob ll..||-I.Ol£. 0 ‘l... I ,1? ‘Il I. .I inrl‘l‘ I.» a. .3... iii)! 1! 3:1.‘211'19 I. I I. - 3. .9 la 1 iii.- .ll. ,l .l e e u I . n I . . H . .I. p _ n _ . . . . I . v 1.. _ I . . . 1 l » I. _ — . ’ f I . . .I . . I : l I . I. I l v . . a . : nu. . .- _ . e x u A I . . i . I _ . l n u ; . t. . I f .... v I! l I t; l‘ Ana-an PB capo. 1.30: m .3.“ deduce»... 95:3: no 09.50 .H 0.9m! .0qu 55.83: to ngmo-fli ma 2 m a a 8. m. an. ad .93 in; , 3-0!00‘00-00L0-3-oo'oo-oo- o 0.-., 9“”..-oo'oo. BamIOI‘qogooooooo 00 a ‘O|O-O!!'O’O OOH 'O'O’O'O' o’o'o'o-o-o'o-o-o -o'o’o’o 08 'o-i'o'o'o'o-o'o .0-.-) of. L 8.: ’0’. I. 'o” l 08 .11 l 08H (SISVH MIG MEMO) aauvuu summon mousa a w . . :28 also: .3.- m...8 339»... 9523. «a 3.5... .m 9:82 noun-E. ES- uo gnofi< MA S m u H 09m... 2. 4.: u. o fl-foo-oiuioo-oo!i00hoo-IIHIIIMD . d d go. - 00"- hilmonhm_u :m.o m.~_ om.m_ mm.mu :m.mm numoduncmm mm.m m.m_ am._~ mm.m~ mo.~m amen >m_u .N.w 3.2 3.9 m5m~ mmdm ummauucmm No. o._ :J.. w~.~ mm.m vcmm mm.wo_ odi: mmd: msgmm ‘ flaw: “mom mmouum .Eum _.o ocm >u_umamu mmodum mmocum mmoeum mmoeum mc_n_ozcoum3 .Eum m. .Eum m .Eum _ .Eum _.o coozuom >m3n_: E:_voz m .02 J .02 m 002 N .02 — .02 : oE_mmm ousum_oz mmz_wmm mmzhm_oz w>_m amoz: ammoam>mo mmmmhm manhm_oz m1» oz< cuz_mo zm>o zo maakm.oz hzmoxmm N m4m o -- - .. — .0 o - -- .’-*— or. .- .. ‘ a. c" o a. o -- -- . - c - ~ a... o n---- O 1“- ‘3' '. ‘~' "h' ’ an o -. o- .- oao> - 1w.) ‘9 -n ._.._... --|.'-\'-' .4.-—- O -- no ”-01. .10-.. '0‘ .09. ~--- Q. n» “0*“... ”*9 TABLE 7 Influence of 5 Moisture Regimes on Growth of Forsythia intermedia while subject to Polyethylene and No Poly- 45 ethylene and Sub and Surface Irrigation Treatments. Moisture Regime Mean Shoot Gpowth Me Root Growth (Grams of Oven 8%? weight) 1. (Irr. below 0.1 atm. stress) 2.59 2.91 2. (Irra at 0.1 atm. stress) 2.62 2.77 3. (Irr. at 1 atm. stress) 3.13 '3.73 ‘h.~(Irr. at 5 atm. stress) 3.21 3.87 5. (Irr. at 15 atm. stress) 1.62 2.53 .05 0.51 Ool+3 LSD .01 0.69 0.58 1+6 cepted as a value for the wilting point and as a point where no growth takes place. Moisture regime # (irrigation at 5 atm. tension) is apparently a critical regime. It has generally resulted in reduced growth of both shoots and roots except in the experiment in which plants were subject to the poly.- no poly. and the sub-surface irrigation treatments. In this experiment regime H was one of those found to be optimum and regime 2 which was an optimum regime in other experiments was found to reduce both shoot and root grow- th. These results, which contradicted results of the other experiments, were very likely caused by insufficient aeration due to poor drainage resulting from the poly- ethylene covering of the media in some containers. Ap- parently insufficient aeration in these containers was more limiting than the moisture stresses applied with exception of the 15 atm. stress. Moisture regime 3 (irrigation at 1 atm. tension) was generally conducive to maximum root and shoot grow- th except that it limited the growth of forsythia roots. Moisture regime 2 (irrigation at 0.1 atm. tension) was also conducive to maximum growth except in the case of poly.-no poly., sub-surface irrigation treatment con- tainers as stated above. Moisture regime l (irrigation at a tension midway - . ' . . - > v f 1 . r L ‘ I . . . - ‘ . { / I ‘ ‘ J; . . ‘ r . ‘1 7 . ’ x ‘ . s . x I - r fl - I . . . . I I . . I ‘ [A . -. . v Q . o A . . . . r . I . . 1‘ ‘ r A . . a r u - z ' ‘ . . } V . _ a ‘ \ _ ‘ I O I . ’ ‘ ' ‘ . . . . AI I - ‘ - ‘ - J v , . . ‘ v ' ‘ . ' - . ' ~ I ‘ I . V ~ - v H - U ‘ I V. 1 l H I ‘ . o . ' ' i ‘ . r I .‘ I V ' - ‘ . r" 7 . 5 .. _ . - ., x . \ , n o . ‘ ‘ . n l- W . ' ‘> .v . ‘ I ) I . ‘ . s .. . v . 1 \— .e ~ . ' ,- _. . . . .5 . ‘ \ ' 7 I : ' u . A. I . . ‘ r J. 7 ~ — n_ ‘ L . | . a ' : 7 h . c " ' - 7 / ‘ ‘ r - . I... b I l l I . I . 4 - 1 - ‘ ' ‘ ‘1 I . . I I . > h‘ ‘ \ - . . > _ Q ~ \ h V r ’ - 1 47 between waterholding capacity and 0.1 atm.) was satisfac- tory for good growth of bean plants but was limiting to the growth of forsythia roots and shoots. Evidently for- sythia plants were more sensitive to poor aeration of the media than bean plants. ‘ EifllhsmoePOlX’ Ineagnent Resultn, - - - Root and shoot growth of forsythia were both reduced by a poly- ethylene covering around the growing media as contrasted with no polyethylene (Table 8). Again the explanation is insufficient aeration of the growing media due to insufficient drainage and the polyethylene covering. Sngface Irgigation Contrasted ninn,§nn_lrrigation Results. 2." - Shoot growth of forsythia plants was not affegted by the irrigation treatments (Table 9). How- ever, root growth of the forsythia plants was signifi- cantly increased by surface irrigation as compared with sub irrigation. It is felt that this may have been the result of no poly. treatment plants receiving more water when surface irrigated than when sub irrigated and poly. treatment plants receiving less water when sur- face irrigated than when sub irrigated. Freguency n; Innigation_Results. - - - As would be predicted, the frequency of irrigation of the non-poly treated containers was much greater than that for the containers with a polyethylene covering around the growa .- . .- \ ' .. ..... #8 TABLE 8 Influence of Polyethylene and No Polyethylene Treatments on Growth of Forszthia intermedia while under 5 Moisture Regimes and subject to Sub and Surface Irrigation Treat- ments Treatment Mea Shoot Growth Mean Root Growth (Grams of OvenDry weight) Polyethylene 2.23 2.#6 No Polyethylene 3.0% 3.86 LSD significant at the .05 level. , -, I I ~ - > r l . ,A. r ; \ ‘ l ' I V . ‘ I . .. i . . .....l- " - ‘- I f. ‘ I ’ r O ‘ _ V I - _ r I : - _- . a .. . y ‘. .4 V A I A > h l \ . o -- -. m. .. -- v . .- . A -. . h‘ m . “~- .. a o . .a as. -. ¢ . . o o-‘. .., . .- n— .-. . .40.“...v— 4-..V‘M- .m...—._. ---.u c-. «.a.~¢.u« v .90... . . . - v w v atm.-.- o *. n“ i . -- ~~g M or . up. 0 . . v- . ~ 1 ‘ v ' ‘ r- . . - 7 v- I ‘ . - r‘ ‘ ,, , . 1 - . , , .. - . .. e .‘ u- i s. r . v 1V or. - 7A .A«--‘ I ‘ -- fl‘ . --‘. A. . ' 1' I A b . ‘ . O . A I - r A . , . .- _ - a . . A -. ~ - -~ 1.7 . a -- up n, — o. - _,. «I I o H . ‘ I l v . . r . 1 ' ‘7 . r J . V - . - . . . ~ 7. , -. my - « u o . ~ ,. 1-. . .- . .. q - - 'a .. "”‘V O ' _ . ...-- ..--. -“‘ . I. --'“ "A" H #9 TABLE 9 Influence of 2 Irrigation Treatments on Growth of Forsy- ' thia intermedia while under 5 Moisture Regimes and sub- ject to Polyethylene and No Polyethylene Treatments. _ —— Irrigation Treatment Mean Shoot Growth dean Root Growtg (Grams of Oven Dry Heightyfi Sub Irrigation 2.36 2.56 Surface Irrigation 2.90 3.76 #4 LSD .05 N.S. 1.13 50 ing media (Table 10), since the polyethylene covering reduced the rate of evaporation from the media. There was little difference in frequency of irriga- tion for sub irrigated plants as contrasted with surface irrigated plants (Table 10). Plants under moisture regimes where irrigation was to be applied at low tension were irrigated much more. frequently than those that were irrigated at high ten- sions (Tables 11 and 12). On the other hand, contrary to what might be expected, plants growing in media.with low water holding capacities were not irrigated as often as plants growing in media with high water holding oa- pacities. This result can be explained by the fact that plants grew better in media of high water holding capa- city (probably due to suffering less moisture deficit prior to irrigation than plants in low moisture holding media prior to the time that roots permeated the entire amount of media). Larger plants with larger root systems will tranSpire more water and be more efficient in re- ducing the water level of the media than will smaller plants. Thus even though they are growing in media of high waterholding capacity, they will be irrigated more often than small plants growing in media of low water holding capacity. TABLE IQ Influence of Poly-Ho Poly Treatments, Sub-Surface Irri- gation Treatments and 5 Moisture Regimes on Intervals between Irrigation of Forsythianintermedia: _‘_‘ Treatment ' Number of Plants Mean Number of Days Included in hean between Irrigations Poly.-Na; Poly. Pol ethylene 30 . nee olyethylene 30 18:3 Irrigation Sub Irrigation 30 6.4 Surface rrigation 30 5.8 Moisture Regime. 1 12 2.2 2. 12 .6 a 12 7.0 . 12 906 5- 12 21.3 aaaaaaaaaaaaa . , A . . . - t u A 0‘ - V L . ' ' ‘ A ,—_ ‘. Pl . I v ' , f - . . _. L - ~ - a- . '.‘ ) . . - - . - . . o I -7 i A , . --v- n n - - A.- . .. -- . . . . . I . 3.. .. p . .. ,. -. - , - , - -0 no - . I ‘ W "—HOU - é'I ' - a - A .w <~—‘ - n u. ‘ a - —~ I'.‘ .v‘l'- fi-‘ 0- r 9 I . u. - .. c- -’ ‘0» - ' ' ‘ ’ , . I l . s . ' , ' - , ‘ ‘ I ‘ ‘ v pa ‘l- \' g ‘ a - o '- e . . -‘ _ ‘ - V x . ‘ a ' . . -. , n. ‘J . , , - V . I .I‘ . . ' i . . -A , . y ‘, Au. .. --r , c.“ -777- n <- *7. .7 -. .., . n u o» a. .7 ~ - .c e. rn— o- q- . » .i. - - -... ”um. .~ :- , . .9 Cp‘l I-.A -e . .g n L7 -_ . ~-.. -...-.. n Is . . y | . z ‘ >- ‘ '. -‘ ..... . - t - v '- 0 . \- —- v o ‘ ('5 , - ‘ U I . . ‘ .' . ‘ , . I . . . -. . C . . . . ‘ ‘ H ‘ 1“ V" I ‘ . > . VA. .‘ t t ~‘ 0 I ~ 0 . v. y. I '. - I I V . Q l p. l 7'! . O . .' ‘ , r l . . . v . . Q ~_ ‘ . v . Q . ' I ‘ ' u . t ' I I e _ .. . . 'J ~. I. -.- ‘v"---~-'-- -1 p n - ~ 0. t4 , «... ‘ me, -u- -- _. - -7- _...-. .4 I . ‘r. 7‘ -7- ...e. -o.e‘. .. . 7‘1. -I‘.\. .. .... .1.‘ .. . u - -.-..-— --._- ...-'. TABLE 11 Influence of 3 Media and 5 Moisture Regimes on Intervals between Irrigation of'Ehaseolus vulgaris Treatment Number of Plants Mean Number of Days Included in Mean between Irrigations Sand Medium. Moisture Regimes 1 4 11.3 2 4 5.0 t 4 3.5 5 t 3.5 Sand-Peat Medium Moisture Regimes l 2 3 13:? E t 2:3 5 4 3.0 sand-Peat-Clay Loam Medium Moisture Regimes mrwmw :r::: V O O 52 V I ' . ' ‘ ‘ < \ , I ~ . . A o ’ H h I I - u ' , ' v . - . .m- . - - . a . . . ~ .. _ .« . . _. .. ~ .- -. . n - . .-u .. ..1 — . ..- - .... m . .. . . .,; ..<.. -... A.‘ .-, ~. - - —.. . , .- . A » - -» — ... . o v I'vhv’4; . u. a - H-~~v -.H,A.'- w 4- . - 7-- ' r .- " ‘ o r». I‘ , k . __i v , , -., _‘. H . , . _ ._ _ ._ ‘ _ -‘ . . -. .7 .-..-.- .l i a -. --.. - _._-. ~... - . - ._. ”1. ., . ,_.. i .. -. v V , I i, ' r _ 7 7 , v - . . < v Q . .“ ‘ O ‘ I . . 1 . v - - ' — . , _, 7 ~ ,, A . . P r ‘J ‘ . J - . . Q' .. I ~ . d r “ ‘ . . , - ‘ u... 6 an. ‘ . ‘ . . - . . ~ , . . u ‘ . .- _e - . ‘ a - .... . . .- ,--« ,,‘ 'g..... . , .a... I . ,. - - o.-o-»~ --.-.‘-- _- ,. r .‘ - -. . _ . a ...- TABLE,12 Influence of 2 Media and 5 Moisture Regimes on Intervals .between Irrigation of Forsythia intermedia Treatment Number of Plants Mean Number of Days Included in Mean between Irrigations Sand-Peat’Medium Moisture Regimes 1 H &# g t: 93 5' E 132a Sand-Peat-Clay Loam Medium Moisture Regimes \J‘l-F‘UUNH errrr U1 O C) ....... .A ‘r . I u I. _ - , . I“ - ,v ‘ . ‘ ‘ L ‘ , . ' ' J ~. 7' ' . , .-)o . ‘ I . I ‘ z - P . — . . . - < . . , § . . . .- . I . .o . ‘- - ,— ~c \ v a- n - - ‘- o > .. . .. . . 4 .— o - .. .- .n .c ~41. -. s .3 A A - - - __ A - .- -. _,. - o - -- N - - .- - v r. q a- a u- - --.o----- -‘u-_ ~ m- 0.... my.-. - e no — p ,, ,- a .. .a A c .- , - — ----.. u .— a a u u..---'- '— --—-¢—.--..- -m‘c-‘M ~.*-*AQ’-‘ - - A t ' ‘ ' , . _ , 7 _ ‘. ' : . ‘ , , . . ‘ e - . . - .- 1 .. - ' . _ . . _ _ l I O o I . , , , .. . . . . , . , _ ' ‘ ' , -. A - " p. o ‘ --.. - a - a - r 4 I .. - . --.-.~~ In 4. .- -‘w‘n—ua. --“ -u-~~v“-‘vn‘- - - u- -- ’ v on *.r A.-- m.-. o... .u- . ¢-o‘—. ‘ a " n r i — . , , ~ I . O ' .5. - -, e , s -. . . . . ,_ . _ . Y I ,- r - a : O .l. .o . g ‘ C ' o -‘ v C ' . , . . 1 I I ‘ . . r' \ . o ' c . W. Q ~ \ ‘ -' - -- . . 1 _ _ . l v , .u - , ‘ '~ ”x; - - "" ’- \f o v . I " . , _ g - . . .- - . , . 7. 1‘ n. .J..' , - V .- J \ , w . .‘ . . . ' i o . -- 4‘ ‘. u . . .1 O ' ~' ‘ ' v- - .u " . -c ' , y - tr a. c u. -— L- a . < . v. . o- —-‘ - —-4 g . 7- u ‘ r a.- 0 ti -‘c-n- -‘ ~- Dr .w ".. —-‘..- .0..- qui- ve-V " .v".’ -‘1... A g - - ,. . - ~ — c s. an — v .— .~ - o . v .- - w-o - n- -‘—r A u. "M‘. vfl- .' ‘0‘-.-“ ~- _- - v s --4 nun-Gr” 54 Cone usions: 1. Moisture retention curves.with percent moisture on a volume basis are of more value in evaluating water supplying characteristics of a growing medium.than mois- ture retention curves with percent moisture on an oven dry basis. 2. Plants do not necessarily grow equally well unp der equal moisture regimes if the media are varied. 3. Sand alone is a medium that retains little water for plant growth. h. Sand-peat and sand-peat-clay loam are approxi- mately equal in their water supplying “’power'' as indicat- ed by plant growth. 5..(a) Moisture regime 2 (irrigation at 0.1 atm. tension) resulted in maximum growth of been and forsythia plants. (b) Moisture regime l (irrigation at a tension midway between waterholding capacity and 0.1 atm.) re- sulted in bean plant growth equal to that under regime 2 and limited the growth of forsythia p1ants.. (c) Moisture regime 3 (irrigation at 1 atm. tension) resulted in growth of bean plants and of for- sythia shoots equal to that under regime 2 and inhibit- ed growth of forsythia roots. 55 (d) Moisture regime H (irrigation at 5 atm. ten- sion)" limited'growth of both been and forsythia plants. (e) Moisture regime 5 (irrigation at 15 atm. ten- sion) resulted in minimum growth of both bean and forsy- thiahplants. 6. A.polyethylene covering of the growing medium reduced the growth of forsythia and caused limited growa th under moisture regimes that called for irrigation at low tensions. 7. Shoot growth of forsythia plants was little ef- fected by surface as contrasted with sub irrigation. However, on plants subjected to poly.-no poly. treat- ‘ ment, surface irrigation increased root growth. 8. A polyethylene covering of the growing media re- sulted in a large decrease in the frequency of irriga- tions needed under a given moisture regime as compared with media not covered with polyethylene. 56 SIGNIFICAECE OF RESULTS AND CONCLUSIONS FOB COHTAINEB GROWING.OF NURSERY STOCK Growing Medium (Sgil_flig). --- - Sand proved to be a poor medium for holding water for plant growth. The other media studied did not exhibit differences in wa- ter holding capacity that‘Were great enough to cause any one medium to be recommended over another. Therefore, choice of a media (Other than sand) for container pro- duction, should be made on the basis of considerations other than water holding capacity. It was noted that clay loam was the only medium used that had a tendency to crust or harden and shrink away from the walls of the container. Amount and_E;eguency gglIrrigation. - - - The necessi- ty of applying enough water to raise the moisture level of the entire volume of media to waterholding capacity (field capacity) it the media in the bottom of the con- tainer is to be wetted, was pointed out by the literature reviewed. Drainage of water from a container of media with uniform composition is usually a good indication that enough water has been applied to wet the medium to capacity. Only with special situations such as soluble salt concentrations that require leaching would applying appreciably more or less than enough water to wet the entire amount of medium.be recommended. 56 SIGNIFICANCE OF RESULTS AND CONCLUSIONS FOR CONTAINER GROWING.OF NURSERY STOCK Growing Men—dig (§_g_i_l_ fling). - - - Sand proved to be a poor medium for holding water for plant growth. The other media studied did not eXhibit differences in wa- ter holding capacity that were great enough to cause any one medium to be recommended over another. Therefore, choice of a media (other than sand) for container pro- duction, should be made on the basis of considerations other than water holding capacity. It was noted that clay loam.was the only medium used that had a tendency to crust or harden and shrink away from the walls of the container. Amnnnt nnghfineguency n§_Irrigation. - - - The necessi- ty of applying enough water to raise the moisture level of the entire volume of media to waterholding capacity (field capacity) if the media in the bottom of the con- tainer is to be wetted, was pointed out by the literature reviewed. Drainage of water from a container of media with uniform composition is usually a good indication that enough water has been applied to wet the medium to capacity. Only with special situations such as soluble salt concentrations that require leaching would applying appreciably more or less than enough water to wet the entire amount of medium be recommended. 57 Evidence indicates that media may be allowed to dry until about 1 atm.of moisture stress is developed and should definitely be irrigated before stress increases to 5 atm. Although some commercial devices for measur- ing moisture stress (tnnsiometers, resistance blocks) are available, their value in container-growing media has not been established. Observations of the autior indicate that in growing established plants media may be allowed to dry until the surface material is un- questionably dry and should then be irrigated within 12 to 24 hours depending on the intensity of evaporat- ing conditions. Drainage. - — - Good drainage has been shown to be very important as excessive moisture retention pre- vents adequate aeration of the media which in turn in- hibits root activity. Possibilities of over irrigation are greatly reduced by good drainage. Polzennylene Covering 9;,Growing Medium.(§nil Mass}. --k- The polyethylene covering of the growing media which greatly reduced water loss by evaporation, also limited growth because of poor aeration due to li- mited drainage. The author suggests that instead of co- vering the entire amount of media with polyethylene, the polyethylene might be cut to cover the eXposed upper ' surface. This polyethylene could be perforated as ne- . ., . .1. .\ a Q. ‘ . .. . . . . . l A A .. . w . c ‘ 1 . O x x . I . . u 1 a . . . 4 r . .- 58 cessary to provide adequate aeration. finb lEEigéilQBa.- - — Flooding a tray or basin-like structure in which the containers remain permanently should prove to be an economical method of irrigating large num- bers of container plants. 59 LITERATURE CITED Allemendinger, D.F.. A.L. Kenworthy and E.L. Overholser. l9k3. The car on dioxide intake of apple leaves as affected by reducing the available soil water to different levels. Proc. Am. Soc. Hort. Sci. #2: l33-1h0. Ayers A.D., C.H. wadleigh and 0.0. Magistad. 1943. The interrelationships of salt concentration and soil moisture content with the growth of beans. J.Am. Soc. Agron. 35:‘786-810. Baker Kenneth F. 1957. The U.C. system for producing healthy container-grown plants. Calif. Ag. Exp. Sta. Ext. Ser. Manual 23. Baver L.D.. 1956. 8011 Physics. Third Ed. John Wiley & Sons. Chapman & Hall. Beneke, E.S. 1960. Personal Communication. Blair, G.Y.. L.A. Richards and R.B. Campbell, 1950. The rate of elongation of sunflower plants and the freez- ing point of soil moisture in relation to permanent wilt. Soil Sci. 70: h3l-fl39. Breazeale J.F. and W.T. McGeorge. 1949. A new technic for determining wilting percentage of the soil. Soil Sci. 68: 371-374. Briggs, L.J. and J.W. McLane. 1907. The moisture equiva- lent of soils. U.S.D.A. Bur. 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Value of peats for mineral soil imp p§gvement. Boyce Thompson Inst. Contrib. h: 245- 2 . ' . Reisch, K.w. 1959. Growing of nursery stock in contain- ers. Publication of American Association of Nursery- men. .V . a D . a - 9 o " f ‘ J g , O c Q n ‘ , o ‘ .0. O O I 4 9 c 0 CI" 0‘ c" n . t c o . b. n o o r" r‘ 61 Richards, L.A. 19%9. Methods of measuring soil moisture tenSiono SOil 8C1. 68: 95-112. Richards, L.A. and C.H. wadleigh. 1952. Soil water and plant growth. Soil physical conditions and plant growth. (Byron T. Shaw). Academic Press. Richards, L.A..and L.R. Weaver. 1943. Fifteen-atmosphere- percentage as related to the permanent wilting per- centage. Soil Sci. 56: 331-339. and ‘ . 19H4. Moisture retention by some irrigated soils as related to soil-moisture tension. J..Agr. Research 69: 215-235. Shantz, H. L. 1925. Soil moisture in relation to the grow; th Of plantS. J. Am. SOC. Agrono 17: 705-711. Shaw, R.H. 1959. water use from plastic-covered and un- covered corn plots. Agron. J. 51: 172-173. Stanhill, G. 1957. The effect of differences in soil- moisture status on plant growth: a review and ana- lysis of soil moisture regime experiments. Soil Sci. 8%:205-21h. ’ Tukey, H.B. and K.D. Brase. 1938. Studies of top and root growth of young apple trees in soil and peat- soil mixtures of varying moisture content. Proc. Am. Soc. Hort. Sci. 36: 18-27. Veihmeyer F.J. and A.E. HendricksOn. 1927. Soil moisture conditions in relation to plant growth. Plant Phy- SiOlo 2:71-820 ' and . 1928. Soil moisture at per- manent wilting of plants. Plant Physiol. 3: 355- 357. . and . 1931. The moisture equiva- Tlent as a measure of the field capacity of soils. Soil Sci. 32: 181-193. and . l93#. Some plant and soil mgistgrg FElations. Rep. Am. Soil Survey Assoc. 3.7—0. and . 19H9. Methods of measuring field capacity and permanent wilting percentage of 30115. Soil Sci. 68: 75-9H. l‘l 62 Wenger, K.F. 1952. Effect of moisture supply and soil texture on the growth of sweet gum and pine seed- lings. J. Forestry 50: 862-864. Woodhams, D.H. and T.T. Kozlowski. 195#. Effects of soil moisture stress on carbohydrate development and growth of plants. Am. J. Bot. #1: 316-320. .. .4. MIC AN will: ”11111111111!flifiillflllflflfllfl/Wfl] RIES H - _........- A___._~. ._— 4 -.__—.