" ’"s—v -— v‘ww. fi‘ f (ww— ‘— IHE EFFECT OF CONDITIONING AND PHYSICAL ENVERGNMEW ON 'E-‘I‘IE E-‘EELS‘ IRVING GI: ANNA Thesis for Ike Degree of M. S. MICHIGAN STATE UNIVERSITY Thomas Tougaard Pederaen 195.9 THEGII LIBRARY § Michigan State University x. :22 NDITIONING AND PHYSICAL ENVIRONEENT I—EI fr: h [1] Fri *1 L‘J C) *3 0 {TI 0 0 ON THE FIE'D DRYING OF ALFALFA C \‘7 DJ THCMAS TOUGAARD PEDERSEN ‘_ . .' "C’TIF‘ A hm I’M“ A Do .L “Jib J. Submitted to the Michigan State University of Agriculture and Applied ScienCe in partial fulfillment of the requirement for the degree of MASTER OF SCIENCE Department of Agricultural Engineering 1959 Approved: ,;Z%Eékézéé;§r/%r:;<£3;27§%é:;é:e ABSTRACT s of years, alfalfa has been an important C). Eor hundre animal feed. Today alfalfa is one of the most important for- age crops in tne United States. There are, however, large losses durine the production of hay both in quantity and quality. Approximately 21 percent of the feeding value of the day crop is lost due to weather damage during field cur- ing. It is t ,re-ore important to fird the best possible method of curiné the hay -- drying to 20 percent moistur) 5 content in the alertest possible time. The object of this research was to develop a quick method for field curing of ha”. The problem was approached by studying the anatomy and physiology of tne greenzilfalfa plant and considering the field environments while the hay is dry'nd. The experiments were conducted during the summer of ~-~ en - n r a: t n ‘ ~ 173( and 133;. It is a well krown fact that the leaves cry “3 18; there ore, part of the hay swath was e tne stems shade the leaves. (L . : .. ° V ‘ . m-w . drneo ops1ae down. inis ma H (‘I fie *‘5 here was, however, no d ence in dryin; rates between this turned swath and the conventional drying method of + a 1‘ O ‘ \ ‘ crusni.%; ale Haj 41* toe SNath. iii stems. Hard crushing and penetrating the cuticle of the stems several places per inch length orave the highest dry- ing rates. Smashing the stem every two inches for a length of half an inch, and twisting the stems resulted in slightly higher drying rates than uncrushed alfalfa plants. While crushing of the plant increased the drying rate for the stem asxwell as leaves, the gain in rates was much greater for the stems. When crushing was severe, the stems dried faster than the leaves. For some time after a rain the relative humidity of the air near the ground is nearly 100 percent. Such conditions have often existed during the first cutting of alfalfa. After mowing, the hay lies on the ground for drying for a consider- able time. Water vapor lost from the wet soil by evaporation to the atmosphere moves continuously through the swath and reduces the drying process. This influence of evaporation from the soil was elimi- nated by placing a vapor barrier in the form of a polyethylene sheet between the soil and the hay. This considerably increased the drying rate. It was found that black polyethylene was the best suitable, because it, besides being a vapor barrier, also absorbed radiation energy, and thereby was able to raise the temperature of the hay sample as much as 67 degrees F. This increased the drying rate of the hay. The plastic served as a sheet for collecting leaves lost during drying. iv If the alfalfa was out before 10 a.m. and crushed (clear- ance of less than 0.015 inches between the crushing rollers) it was possible with the black polyethylene-vapor~barrier method to dry the hay to a 20 percent moisture content during the same day it was cut. This was possible when the calcu— lated yield did not exceed four to five tons of 20 percent moisture content hay per acre. i This research study has shown the possibilities of her- vesting field cured hay the day it was cut. Because one day weather forecasts are more reliable than two to four day fore- casts, weather damage, and furthermore, dew damage to hay, are reduced to a minimum. vvfl ‘I‘ 11*] Far-‘rr A 7 Pr‘Y’.‘ r —:—-.—_"5- :‘7n. . ‘wfi ngyx'fi *l‘. v -..~.YI~“(‘y-n.fi-7T , I t I ‘. t .. ‘ . " x.‘ 4‘ , | , . Th3; :Jbt‘ :J.’ l V- ‘- ‘. "J.-’L A...\/l\ -,..J -&.u-) I ll- de‘V'rAJJ Lk‘ V J.“ -'.I \uQcI L ’ T"t‘ 1-. ‘PT '\ T‘ 1" ’v "T 7‘ " ,3 :7. 1' 2-!" CL: ‘51... E. IL._JUIJ .41"... .LL“J 'J.‘ liqursLJl It '.““.." 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H }...I \,N r- F1 .\:] LIST OF WIrURES The distribution of water in green alfalfa - Drying curves for alfalfa hay, where part oi trie hay swath was turned upside ”Uta — - - - - Drying curves for alfalfa slant: treated in different ways - — - - Drying curves for alfalfa plants treated in different ways - - - - - - - — - - - - - - - - Drying curves for normal alfalfa plants, when r t s are dried senarately- - -’- - Drying curves for crushed alfalfa, when leaves a stems are dried separately - - - - - - — - Dryin5 curves for chopped alfalfa (2 inches) wnen leaves and stems are dried separately - - Dryin n5 curves for chopped alfalfa (0 inches) When leaves and stems are dried separately - - 'or chopr ed alfalfa (10 inches) stems ar dried separate]y _ - Dryin5 curv'es for "penetrated" alfalfa when leaves and ste s are dried senarately- - - - - Dryin5c Ceres for alfalfa th 3 ms snashe d .i te every 4 inches wzien leaJe s a-d stems are dried seoarately - - - - - - - - - - - - - - - Drying curves for normal alfalfa plant - - - - Drying curves for crushed alfalfa- — — - - - - Dryin5 curves for alfalfa chopped in lei5ths Drying curves fo alfalfa crwop Ie‘ iu len5tns 4.4-. \O \n O K! 3. 3.. 2/ raj _ S _ m t _ :0 E . m. .11. . m“ . ._J _ flay 0 _ {r AL». — O H . 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Q wait. 5 3.; e V .1 r t C «.1 ago if.” 3 01,. «WV 0: A .... r. v.1 ...J. an; LIST OF TABLE UJ Table P859 I Avera .5e consecutive days Without rainfall, Central Michigan, 1918 - 19L} - - - - - - - - \ )J II Leaf contents after d ifferent mechanical treatments at different oisture contents- - - 6 III The relative feeding values of normal hay and of hay that has ‘ceen lmeat d in stack - - - C IV Gross weight and amount of water to be re- moved for different initial moisture at storage- - - - - - - - - - - - - - - - - - - - 10 V Losses of dry Ina th er and protein by field curin5 and barn fi ”1 nin5- - - - - - - - - - - ll VI Chan n5es in carotene content of alfalfa har vested y field curin5 and barn finish ing- - - 12 VII Rate of natural drying alfalfa hay cut from VIII Tile mdist-ire content in leaves and needs of alfalfa-- - ~ - - - - - - - - - - ~ - - — - - 25 IX b’oisblre content of different treated alfalfa hay durin5 drying in th field - - - - - - - 29 X Time required to reduce the moisture content of hay to 20 percent - - - - - - - - - - - - - 55 XI Time required for separated leaves and stens to reach 20 percent moisture content - - - - - L7 XII The moisture content in different sections of the alfalfa plant through at the dryin5 time - 56 XIII The moisture content (w.b.) in the different samples after 8 and 22% hours of drying- - - - 61 XIV Required time for the different treatments to reach a moisture content of 20 percent (w.b.)- 66 Table .‘T A \J ‘5 XVI XVII ‘4 [-0. I» J. Tne temperature of hay sarples, surface of polyethylene, air, and relativ humidity of polyetnylene, air, and relative humidity in J""L\ Dir- - - - .- cn - — - u- - - - u- - - - .- - - 0‘54 J- The temperatures of hay samples, surface of The temperature of hay samples, surface of black polyethylene, air, and relative humidity intheair---------""‘"'"'"" LIST CE ICIURES Picture 1 Hay cut and the snath turned upside down 2 Ha: cut and left to dry in the swath - - 5 Plant cut in pieces of 2 inches- - - - - h Plant cut in pieces of 6 inches- - - - - 5 Twisted stems of alfalfa - - - - - - ~ - 6 "Penetrated" stems of alfalfa— - - - - - 7 Uncrushed alfalfa- - - - - - - - - - - - h Smashed alfalfa- - — - — - - - - - - - - 9 Alfalfa crushed at clearance less than . lO Alfalfa crushed at clearance 0.0125 in - ll Alfalfa crushed at clearance 0.025 in- - l2 Alfalfa crushed at clearance 0.050 in- - O (D \J l H. t’xPliEIIEIX a , ..‘-' 1".CQSQUIX 5 . 1 .: .-, .z ,. 8 applied to clyin5 a fahay-----------' ‘ INTRODUCTION For hundreds of years alfalfa has been an important crop in providing food year round for livestock. Since an- cient times hay has been made largely from legumes and grasses. The observations of the Greeks and Romans are as true today as they were when Columella wrote in A.D. 60: "...But of all legumes, alfalfa is the best, because, when once it's sown it lasts ten years; because it can be mowed four times, and even six times a year; because it is a remedy for sick beasts; because a jugerum ( = two-thirds of an acre) will feed three horses plentifully for a year. " Today alfalfa is the leading forage crop in the United States. It accounts for about one-third of the annual hay crop of 100 million tons and is grown on approximately 15 million acres. The alfalfa growing areas are located princi- pal 1y in the Midwest and the Farm West. Michigan and Cali- fornia have more than one million acres each. Nebraska, Minnesota, Kansas, Wisconsin, Idaho, Montana and Iowa each grows about 700,000 acres (USDA 19148). The value of the alfalfa hay produced by these 15 mil- 1101'1 acres represents approximately two billion dollars. The P8 are, however, larger losses during the production of alfalfa hay, both in quantity and quality, than in any other farm crop (fruit and vegetables excepted). About 21 percent of the alfalfa crop is lost during harvesting and curing, and another 7 percent loss occurs during storage, making an annual total loss of 28 percent or more than one-half bil- lion dollars (15). The object of research on hay-harvesting methOds is to find ways of reducing these nutrient losses and harvest hay of good quality. With today's method of field curing of good alfalfa hay the farmer must depend upon good weather for several days after cutting. It is difficult to predict the weather two or more days in advance. The result is that. the farmer cannot always complete harvesting before the hay is damaged by rain while curing in the field. If a method of fast drying of the hay in the field Could be developed, i.e., hay could be harvested in opera- tions not covering more than one day, a great step would have been taken toward better quality hay and smaller losses of nutrients. The object of this study and series of experiments was to develop such a method by studying the anatomy and phys- 1010337 of the plant and the atmoSphere under which hay is Cured in the field. REVIEW OF LITERATURE The farming operations required to produce a good seed- ing and to grow an alfalfa crOp are well established. The difficult part of alfalfa production occurs in harvesting the forage so as to save the maximum feeding value. These difficulties in hay harvesting are found throughout the humid regions of the world. They are due in part to the fact that the period of time between rains is less than the time required to cure the hay and transport it to the barn. The average number of consecutive days without rainfall in Central Michigan during June and early July are shown in Table I. . TABLE I AVERAGE CONSECUTIVE DAYS WITHOUT RAINFALL, CENTRAL MICHIGAN, 1918-19119 (Vary, 19511) ‘ Czazzuiiizfzas IWirst week in June 2 - 3 Second week‘in June 2 - 3 Third week in June 1 - 2 Fourth week in June 1 - 2 First week in July 5 plus \ \ 11 Using the best equipment available for the conventional method of hay harvesting - cutting the forage followed by' a crushing or crimping of the stems -- a minimum of two days under good drying conditions is required to dry the condi- tioned hay to 20 percent moisture content. The above table shows that the possibility for harvest- ing high quality first cutting hay in Central Michigan is low. This is especially true during the third and fourth weeks of June, when most of the first cutting of hay is har- vested. In July the possibility for two or more consecutive days with no rainfall are considerably better, but over- matured hay has a low feeding value. During the month of August, when the second cutting of hay is made, the average rainfall is 0.69 inches less than the normal rainfall for June. With the less rainfall during the second cutting, the possibilities of obtaining benefits from the use of hay crushers are greater. The reason for this was showed by Hopkins (195)“, who found that there was little difference between drying rates of the crushed and the uncrushed hay after a rain. He found strong evidence that the climate in the vicinity of the hay was altered by rains. The evaporation of moisture from the ground would lower the air temperature and raise the relative humidity, and conditions would arise in which the capacity of the air to absorb moisture was reduced and even though there was adequate heat available to evaporate moisture from the hay, 'the rate of drying would be limited by atmospheric condi- tions. In this case Hopkins found that the ability of crushed hay to evaporate water more rapidly was of little 'use until the atmospheric conditions had improved. From the above it appears that the conditions are sel- dom ideal for drying when the farmer has forage ready to be harvested; this accounts for great losses in dry matter and feeding value while drying the forage. Rain damage causes leaching of nutrients, bleaching, and makes it necessary to give the hay several mechanical treatments. ‘Windrowing and raking of the hay several times causes loss of leaves, especially when these operations are carried out at moisture contents below ks percent. Hepkins (1955) published a table, which is reproduced in Table II. This table shows the influence of mechanical treatments on the leaf content in the hay, when the operations are carried out at different moisture contents. From Table II it is evident that the hay contains the {greatest percentage of leaves when the mechanical treatments, :in this case raking and baling, are carried out at as high Inoisture content as possible. The leaves are the most valuable part of the hay crop. llpproximately 70 percent of the total protein and 90 percent <3f the carotene are located in the leaves (USDA l9h8). The Ileaves of green alfalfa contain from ho to 50 percent of the (iry matter when the hay is harvested in the one-tenth bloom stage. The second cutting normally has a higher leaf con- tent than the first; the 50 percent refers to the second cutting.and the lower figure to the first cutting. With to- day's methods of curing hay in the field at least 20 percent of the leaves are lost, and this figure is often much larger when the hay receives one or more showers while remaining in the field. This means that even under optimum conditions 1h percent of the protein and 18 percent of the carotene are left in the field in the form of lost leaves. TABLE II LEAF CONTENTS AFTER DIFFERENT MECHANICAL TREATMENTS AT DIFFERENT MOISTURE CONTENTS (HOpkins, 1955) Average leaf content-percent Average moisture Treatment Before After After content raking raking baling when baled, __¥ percent Uncrushed 147 .14. 118 . 9 ’42 .9 51 raked at 57% 115.2 25 hl.7 25 Crushed, was 118.8 No.5 50 raked at 117% 110.5 20 59-5 17 Crushed, .2 1.2 110.9 25 raked at 51% 1+7 LL 112.6 20 58.1 16 IJncrushed, h5.5 h5.h 59-8 55 raked at 55% 56.0 22 5u.8 20 Some of the losses in quality generally are obvious enough; among these are the loss of leaves, color, aroma, changes in physical condition, and the palatability of the feed. The latter characteristic, which constitutes what is called quality in hay, reflects other losses such as losses of dry matter, total digestible nutrients, and carotene. The losses in nutrients are not as easily recognized as the losses in leaves, color, and aroma; from the feeding standpoint of view, however, they are of great significance. During the interval from cutting until the forage is dry enough to store, a progression of events promotes,losses and deterioration of the quality and feeding value of the forage. Freshly cut forage is a living material. The plant cells continue to respire, and the plant enzymes continue active for some time after the crop is cut. In addition mi- croorganism naturally contained in the forage remain active as long as air is present and there is sufficient moisture. These fermentation processes affect principally the soluble carbohydrate fractions and the carotene. If the drying is prolonged, however, important losses in dry matter may also occur. Losses amounting to 5 to 15 percent of the total crop have been found to occur from so -called field- fermentation losses (USDA, 19118). This means that the method of handling the hay in the field should be designed to promote the most rapid evaporation of moisture so that the fermentation losses can be kept to a minimum. Field cured hay will generally sweat after it is stored, and if it is undercured, it will heat in the barn (USDA, 19MB). This heating process causes losses in both dry matter and feed- ing value. Frequently such hay will loss from 5 to 15 percent of the dry matter and nutrients while in storage. If the heating is excessive, brown and black areas of charred and burned hay may develop. Brown or black hay appear to be palatable for livestock. This type of hay, however, has a decidedly lower feeding val- ue. An analysis of the loss in feeding value caused by heat- ing to different degrees is shown in Table' III (USDA, 19118). TABLE III CREE RELATIVE FEEDING VALUES OF NORMAL HAY AND OF HAY THAT HAS BEEN HEATED IN STACK (USDA, 19A8) ‘- I tem Normal Brown Black hay hay hay D1 gestibility percentages: Dry matter 60 L11 27 Protein 67 16- 5 faiber A1 56 1A Ether extract L15 55 112 lqitrogen-free extract 72 59 55 Calculated digestible nutrients: Protein 1AM; 5.11 .6 T°tal digestible nutrients 55.8 57.7 25m P"allatability’: Lbs eaten for 1,000 lbs weight 20 15 10 \ This analysis shows that hay damaged by heating has lost almost all its content of protein, and in the case where the heating has progressed so far that black hay has developed, more than half of the total digestible nutrients are lost. The leaf loss can be reduced and the quality of the hay improved by removing the alfalfa crop from the field before it is fully dried. The leaves of alfalfa hay generally do not shatter when the forage contains 55 to [5 percent or more moisture. When partly cured the hay is placed on a barn hay finisher for removing as much moisture as necessary for safe storage. The amount of moisture that has to be removed de- pends upon the initial moisture content when the crop is Placed on the finisher. Table IV shows the amount of water to be removed by the drier (McCurdy). 10 TABLE IV GROSS WEIGHT AND AMOUNT OF WATER TO BE REMOVED FOR DIFFERENT INITIAL MOISTURE AT STORAGE (McCurdy) Initial moisture Gross weight to Water to be removed at storage make 1 ton at to make 1 ton (wet basis) 20% M.C. at 20% M.C. percent lbs lbs 20 2,000 -—- 50 2,286 286 35 2.1160 A60 to 2,667 667 AS 2.910 910 50 5,200 1,200 60 h,000 2,000 80 8,000 6,000 When the crop is put on the drier at moisture contents between 55' and 110 percent, most of the water has been evapo- rataed.during the curing time in the field, but even then the had’ is still wet enough to allow rapid fermentation and mold dewelopment to take place. To avoid this and thereby losses in ITutrients it is important that the material be dried as quixlkly as possible. Table V (USDA, l9h8) shows the losses or ciry matter and protein by field curing and barn finishing. 11 TABLE v LOSSES OF DRY MATTER AND PROTEIN BY FIELD CURING AND BARN FINISHING (USDA, 19A8) Field curing Barn finishing Field Storage TEtal Field StoragetTotal Item losses losses losses losses losses losses % % 76 % % % Dry matter: lat-cutting alfalfa 19A5 21 5 26 16 1*) 17 2nd-cutting alfalfa l9LI5 17 h. 21 15 8 21 Protein: let-cutting alfalfa 19115 51 2 55 26 1*) 27 2nd-cuttin alfalfa 19E5 29 1 50 16 1O 26 '3‘“) Heated air was used in this installation to complete drying. This table shows that the total losses are considerably lower when the method of barn finishing has been used; espe- Cially this is the case for frst cutting alfalfa and is, in part, due to less favorable drying conditions in the field. Another important advantage of the finishing method is that the crop is removed from the field more quickly in the 0336 of threatening weather and in that way large amounts of feecling value are saved that would be lost by normal field 12 By using ordinary sun curing methods the carotene in the hay is destroyed to an extent of 50 to 80 percent. This loss can be reduced considerably by using the barn finishing method. This is indicated in the following table (USDA, 19h8). TABLE VI CHANGES IN CAROTENE CONTENT OF ALFALFA HARVESTED BY FIELD CURING AND EARN FINISHING (USDA, 1‘9LI8) Carotene content (dry basis) When sample was taken Field curing Barn finishing mcg. per gram mcg. per gram When out 297 508 When put on drier --- 122 When dry (15 days later) --- 29 When stored 119 --- When stored 50 days 26 --- When fed 12 22 The only way this carotene loss is prevented today is by dehydrating at air temperatures running as high as 1,700 degrees F. When dehydrating alfalfa for alfalfa leaf meal, the green material is chopped and brought to the dehydrator at a moisture content of about 75 percent and is dried down t0 a moisture content of 8 percent. The high drying costs, $25 to $55 per ton, however, have limited the use of this metSl'lod to about 2 percent of the total production. It is 13 only economical to feed the artificially dried product to animals, who for fast growth, require food with a high con- tent of provitamin A. Furthermore, carotene, even though preserved during the drying process, is continually being destroyed during stor- age and as much as 50 percent may be lost in six months. To prevent this storage. loss, the material may be sealed in oxygen-free gas, or with anti-oxidants such as 2,5-di- tertiary-butyl-hydroquinon, 6-ethoxy-2,2,I'l-trimetyl-l, 2- d1 hydroqyinolini and diphenyl-p-phenylene-diamine must be applied at levels of 0.5 and 2.0 lbs per ton of dried alfal- This last method. has been shown to reduce the carotene fa. destruction to one-half to one-fourth of the usual amount. The Anatomy And Physiology 0f Alfalfa While this is not the place for a detailed description of the anatomy and physiology of the leaf of alfalfa, the meczhanics of transpiration from leaves of living plants must be studied to determine how plants lose moisture. The leaves of alfalfa are composed of a thin-walled Parenchyma tissue through which numerous finely divided vas- culam bundles permeate and end free so that there are thou- 3aride of these veins in a square inch of the leaf. The en- tire leaf is covered by a single layer of cells. This layer is generally called the epidermis and is somewhat cutinized and for that reason more or less impervious to water vapor. u The epidermis of the leaf, however, is not completely intact, but perforated by numerous microscopic pores, which are called stomata. They are intercellular openings between two special formed epidermal cells -- guard cells. The pa- renchyma tissue of 'the leaf is very loosely constructed so that there are many air spaces between the cells. These in- tercellular spaces join with one another and finally unite with one of the large air spaces directly beneath each stoma. In the guard cells the wall of the cell is much thinner where it borders on the epidermal cell than on the opposite side next to the stoma. When the turgor pressure of the cell is increased this thinner wall is stretched out mrther than the other and pulls the thicker wall bordering the stoma. This increases the size of the pore. The Number Of Stomata The number of stomata developed per unit area depends on different weather factors such as the relative humidity, the intensity of light and probably some other factors. Mariana (19112) studied the effect of the humidity in the air. upon the development of stomata. He came to the conclu- 810m that the humidity favors the development of the superfi- c18.1 areas of the leaves, but it does not increase the abso- lute number of stomata. Reed and Hirano (1951) found that the density of stomata was decreased when the intensity of l ight was reduced. 15 Miller (1928) has studied the number of stomata per square inch of various agricultural plants and found the av- erage number for the upper leaf surface of alfalfa leaf to- be 680,000 and for the lower surface 555,000 per square inch. Thus, the total number of stomata per square inch is some 1,255,000. The ratio of stomata on the lower surface to upper surface is 0.816. unit area, the area of the stomata is only one to three per- In Spite of the high number per cent of the leaf surface. Opening And Closing 0f Stomata The stomata on the upper surface may behave differently from those on the lower. That is, those on the lower surface Open more slowly and close earlier than those on the upper. On all leaves there are a certain number of stomata that are functionless, while others are more or less inactive. Different factors such as light, temperature, humidity and moisture cause the opening and closing of the stomata. The drying rate in hay may be increased by keeping the sto- ma t9. open. For alfalfa, there is a daily cycle of opening and closing of these stomata. Loftfield (1921) found that the stomata of alfalfa under favorable conditions are open all day and closed all night. They open two to six hours after daybreak and remain open three to six hours and then gradually close over a period about twice as long as that required for opening. When the I 1 6 conditions become less favorable for moisture, the stomata close partially for a time during the middle of the day; this period of midday closure increases to complete closure as the conditions become more unfavorable. With the appearance of midday closing, night opening develops and increases with the increase of day closure, until finally there is partial open- ing, of the stomata all night and a complete closure all day. This means that the opening and closure of the stomata is controlled by so many factors that it hardly can be relied upon for selection of the optimum time of day for mowing. The Transpiration From Living Plants It is generally known that all living plants require Water for their existence and development, and that the Plants use it in considerable amounts. Most of the water ab- SOI‘bed from the soil, however, takes no permanent part in the deVelopment of the plant or the metabolic process. Far the greatest part of the water escapes from the plant in form of Water vapor. This form of water loss is called transpiration. The greatest part of the transpiration takes place through the stomata, and is called stomatal transpiration. A far smaller amount, less than 10 percent of the water vapor, is lost from the leaves and stems by direct evaporation from thfi cuticle. All of the living cells within the leaves are filled with liquid water, and evaporation takes place from the wet cel'l 17 into the intercellular spaces which constitute a connected system, ramifying throughout the leaf and finally joining the air space just beneath each stoma. If the stomata are closed, the evaporation from the cell wall will stop when the entire volume of air of the inter- cellular spaces reaches 100 percent relative humidity. When the stomata are open, diffusion of water vapor may occur through them into the atmosphere outside the stoma, unless the atmOSphere has a vapor pressure equal to, or greater than, that in the intercellular spaces. Factors That Affect The Rate Of Transpiration Such weather factors as temperature, relative humidity and wind affect the transpiration rate. As the temperature rises, in general, the rate of tran- sPiration increases. Briggs and Shantz (1916) concluded in the case of alfalfa that the transpiration graph rose in ad- Vance of the temperature in the forenoon; however, in the aI'ternoon the transpiration always fell off more rapidly than the temperature. When the transpiration had reached its night level, the temperature was still above the minimum by 8‘bOut one-third the daily range. Thomas and Hill (1957) found that the rate of transpira- tion from a six foot square plot of alfalfa in grams per hour Panéged from 200 grams to 500 grams during the night to maxi- 11112111 5,000 grams about 2 p.m.; the rate of transpiration starts 18 to rise from night time low at 6 a.m., and it reaches nearly the same level between seven and eight in the evening. In general it is known that a decrease in the relative humidity causes a higher transpiration rate. Darwin (1911;) found that the relation between relative humidity and the transpiration rate is linear. In some cases, however, the graph was actually a curve instead of a straight line. This happened when the change in the rateof transpiration lagged behind the change in relative humidity. He also discovered that the transpiration rate is not zero in saturated air, ‘wh. ich means that the vapor tension in the leaf is higher than that of saturated air. The effect of wind depends upon the wind velocity. In the first place, the wind tends to remove the blanket of more or less saturated air surrounding the leaves. This tends to decrease the distance the water vapor must travel to find free air conditions. On the other hand, if the wind Velocity is too high, some of the stomata may close, and the rate of transpiration stops increasing and may begin decreas- ing, The conclusion of all the experiments conducted con- cerning the influence of wind on the transpiration can be Stated as follows: the water loss from most living plants (1033 not increase as the wind velocity increases above a gent 18 breeze . 19 The effect of relative humidity and temperature upon stomatal behavior is reflected in the results obtained from methods of drying hay. (Table VII) TABLE VII RATE OF NATURAL DRYING ALFALFA HAY CUT FROM 8 TO 9 a.m. (Jones and Palmer, 1952) As 2 hrs 11 hrs 8 hrs 20 hrs 25 hrs Method or out after after after after after handling cut cut cut cut out Moisture content in percent Swath 70 60 L16 26 14.6 25 Single windrow as cut 70 62 58 21 58 22 Double windrow as cut 70 6h 5L1 26 58 27 Single windrow 2 hr after cut 70 60 no 22 57 22 Double windrow 2 hr after out 70 6O 52 18.5 50 17 Single windrow hr after cut 70 58 L5 21 25 21 Double windrow hr after cut 70 58 Ml 20 50 20.5 ——_._ Jones and Palmer (1932) found that a double windrow of a‘lfal fa two hours after cutting produced hay with a more de- 811‘able color and a lower moisture content than the hay that was Cured in the swath. At the end of two hours in the swath, the stomata were nearly all closed, and plasmolysis of the 20 cells had occurred. At the end of the same period, the sto- mata of the windrowed hay were partially closed and some had begun to reopen. This reopening was followed by an increased rate of water loss. The temperature inside the windrow three hours after cutting was 5 to 8 degrees Centigrade lower than :i n the swath while the relative humidity of the windrow was 10 percent higher than in the swath. In the subdued light of the windrow, the chlorophyl was better preserved and thus made brighter hay. The rate of natural drying alfalfa hay is shown in Table VII. This experiment was carried out by Jones at Mississippi Agricultural Experiment Station (1959). From this table it may be concluded that in Mississippi double windrowing from two to three hours after cutting 231 ves hay with the lowest moisture content at the end of the day . Translocation Of Water In The Plant Besides the loss of water through transpiration from the leaves, much smaller amounts are utilized in photosynthesis and growth. A still smaller amount is lost in cuticular tran- Spil‘ation from the stems. The water enters the plant mainly through the epidermal 0f the root hairs at or near the tips of the roots. After CI:‘0-‘-"~31ng the cortex, endodermis and a part of the pericycle, th° Water finally enters the lumina of the vessels of the P001: Sy stem. When in the vessels the water moves upward 21 through the stem and out in the leaves. In the mesophyl it nzoves from cell to cell. From this point, however, most of the water is lost from the cells by evaporation into inter- cellular spaces. As much as 98 to 99 percent of the water obtained from the soil is lost from the plants by transpira- tion, and has no other function than just keeping the plant wet. INVESTIGATIONS OF THE SUMMER OF 1957 The Distribution Of Water In Green Alfalfa From research in plant physiology, it is well known that axztively growing sections of the plant, such as growing stems, zrcust-ends, flowers, and leaves, utilize a considerable amount (31’ water. It has not been possible, however, to find any exact figures concerningthe distribution of water throughout the entire plant of alfalfa. The first experiment was conducted, concerning the basic :Faxztors involved in field drying bay, to determine how water is loot and percent of total loss from various parts of the plant. The distribution of water in the plant was determined I'OZII‘ alfalfa plants of different ages. The alfalfa plants Were divided into three groups: 1) Young alfalfa plants in pre-bloom stage 2) Alfalfa in l/lO bloom stage (normal maturity for bay) 5) Old alfalfa plants past full bloom (l/h seed pods) Immediately after cutting, the heads and leaves were Separated from the stems. The water content of heads (flow- erg plus flowerbuds) and leaves was determined separately. StaI‘ting at the top end of the stem, these were cut in two irlcfi lengths. The stem pieces from the different sections 25 of'the plant were collected and the moisture content was ld alfalfa plants the moisture content at the same place was something lower -- about 76 percent. The further away the sample was taken from the growing zfioint, the lower the moisture content. From the curves, it appears that the decrease per unit length was considerably ilarger near the top end than in the lower stem part. The lowest moisture content of all plants was near the root. It \was 60 percent in old plants, while in middle-age and young alfalfa at the same place, it was 12 - 15 percent higher, Inamely in both cases 72 percent.) The average moisture con? tent for old, middle-age and young alfalfa was 65.5, 75.7, and 77.5 percent, respectively. Table VIII indicates that the moisture contents in heads as well as leaves decreased with the age of the alfalfa plant. This seems reasonable -- the younger the plant, the more un- an 535:: turn .6 ozu n6» :9: 32355 on a e d .mowo msoanm> mo macaw whawhaw no pnoucoo endpmaoz H .waa ta on 1 J — 4 (mugs—.3 0.5 I .l I <56: e28» . I I . l/ . £44.34 ua< Baez [/ /. w m w mu (mm) was use NI mamas gunman m \n ciexmflopmd leaves and heads; the results in Table VIII thus (ccprresponded with those found in the analysis of the stems, \Nlaere it also was found that the growing parts have the high- e s t mois ture content . TABLE VIII VIHE MOISTURE CONTENT IN LEAVES AND HEADS OF ALFALFA Moisture Content ‘A86 Leaves 'Heads percent (w.b.) C)ld alfalfa 6h.h 61.2 hdiddle-age alfalfa 70.8 80.2 lfoung alfalfa 77.1 ---- Turning Of The Swath Of Alfalfa Bay In Order To Increase The Drying Rates Of The Stems It is a well observed fact that the alfalfa leaves dry faster than the stems. In order to decrease this difference -111 drying rate, an experiment was initiated in which part (>1' the hay swath was turned upside down. Such an inversion C>f‘ the swath caused most of the stems to be placed on the ‘lrrper side of the swath, where they were exposed to sun and Wind, and the leaves were shaded by the stems. This experiment was conducted on crushed and uncrushed alfalfa hay. The four treatments were as follows: ,y:-,.,¢~,‘§. 1...; .' n13, if “A“fii ft 4' r ., . '.~ 17,]! "£37" kit the" ,sa‘v'J -‘ ”Wx\§.:§'~é Q“ J- _ (AV-k“ 37"" .. "5&3“? .' ' ' . 7. ‘ ‘ ' " I.'l..i. :V ‘D— .' I‘. . f ‘ . - E“ ‘ 3t ' ' 9:9,. ;_ 3 'mm; 'aJH‘I \“ ‘ ’4 k p. far. :Ln'zT-o’ 2:. 3N2 ' .- ut and swath turned upside down. : T'? v \ ‘. fi‘ . . . :‘Zr‘::\’ ’ \ ‘ fi.~.“\ \\ at. . " . . _‘v‘ . a g ' 5.- . '3‘. ‘a' ‘ ‘ ’. ~‘ ‘ «5 ‘- 9“. ‘ F Picture 2. The hay cut and left to dry in swath. 27 l) The hay cut and left to dry in the swath. 2) The hay cut and the swath turned upside down imme- diately after cutting. 5) The hay out, crushed and left to dry in the swath. h) The hay out, crushed, and the crushed swath turned upside down immediately after crushing. The research was first carried out July 5 and 6, 1957. It was repeated July 16 and 17, 1957. All the treatments from the first experiment were repeated and two additional treatments were added. Those were as follows: 5) The hay cut and left to dry in the swath for four hours; after four hours of drying the swath turned upside down. 6) The hay cut, crushed and left to dry in the swath for four hours; after four hours of drying the swath turned upside down. In each of the experiments, there were three replica- tions. Discussion of Results The results of the first experiment are shown in Figure 2. The data indicated that crushing of hay increased the dry- ing rate, whereas turning of the swath did not influence the drying rate. The irregularity of the curves between 8:50 and noon on July 6 was due to the fact that some of the samples were collected before the rain started (indicated on the dia- gram), and some collected during the first ten minutes of the rain. All the samples from the plots containing crushed hay were taken before the rain started. This was the reason for EK)_. ' SHOWER 7o - \'\ '\ 6{)b ‘\. ‘\“‘i a \ 5 \ a! u _z_ 50 L- \ p. 2! “I p. 2! g 40 — . causn-Iso AND TURNED 0 ORUSHED 33 - CHECK AND TURNED E’ 0 CHECK 95’ 30%- 2 EILE; l 1 1 l I .J 8 NOON 4 8 8 NOON 4 JULY 5 JULY 6 Figure 2. Drying curves for alfalfa hay, where part of the hay swath was turned upside down. 29 ‘the increase in moisture content of the crushed samples be- tween 8:50 and noon. The uncrushed samples were already Isartly wetted by the rain when they were bagged, hence, there vvas little or no increase in moisture content in these sam- ples. TABLE IX MOISTURE CONTENT OF DIFFERENT TREATED ALFALFA HAY DURING DRYING IN THE FIELD Date July 16 July 17 9:50 1:00 u:00 7:00 9:00 h:00 Hour acme pom. pom. p.111. acme noon pom. Treatment Percent moisture (w.b.) Crushed 76.7 55.2 h1.5 57.5 51.6 27.8' 16.5 Crushed p turned at 50 77.8 57.8 L5.u 55.7 55.0 27.9 19.5 Crushed plu turned at 1 50 77.2 56.1 A2.6 55.2 52.7 19.5 1u.5 Cut plus turned at 9:50 75.7 60.2 h5.7 no.7 59.8 29.1 29.5 Cut at 9:50 plus , turned at 1:50 7b.? 58.u h5.b A2.S u5.7 55.2 2u.9 Check 7L.9 5u.1 hL-S t1.6 h2.9 50.9 25.8 Temperature(°F) 75 80 77 77 75 78 82 Relative humidity (%> 51 A6 52 72 68 52 AL ¥ 2 50 Table IX shows the results of the second experiment. . An analysis of the above two experiments showed that no in- crease in drying rate could be secured by inverting the swath. This was the case when the hay was turned immediately after the conventional treatments as well as when the hay was left to dry four hours before turning. Different Treatments Of Alfalfa Hay In Order To Get Quicker Evaporation. After turning of the swath had failed to give any in- crease in evaporation, and taking into consideration the ana- tomy and physiology of alfalfa, it was evident that the only way to increase the rate of evaporation from alfalfa lay in breaking the cuticle. As previously mentioned this layer covers stems as well as leaves, and consists of cutinized cells impervious to water vapor. It is more important, how- ever, to break that on the stems than that on the leaves which has the stomata as natural openings for transpiration. An attempt was made to find the most efficient way of breaking the stem. The following treatments were applied to alfalfa plants: 1) Alfalfa plants cut in pieces of 2 inches length. 2) Alfalfa plants cut in pieces of 6 inches length. 5) Alfalfa plants cut in pieces of 10 inches length. h) Crushing of the plant (This crushing was more se- ’ vere than that normally carried out by commercial hay-crushers.) 31 \ ( ' 1 ’r .‘l‘ “\-A(/ - Picture 5. Plant cut in pieces of 2 inches. ‘ _ .6 ,1: “‘55, ‘§=!![.‘ ' lrt LI] d , Ill ‘2 350, TWISTED u. \, O m .3. Z 8 95 cMot SMASHED ' EVERY 2" 20!- l j n _|_ I O 8 |6 24 : 32 (.0 HOURS AFTER CUTTING Figure 11. Drying curves. for alfalfa plants treated in di fferen t ways .‘ 8h degrees F and a relative humidity of 68 percent. On a good haying day the drying conditions are better and should result in a shorter drying time. Differences In The Evaporation Rate From Leaves And Stems. As mentioned before, under normal curing conditions leaves always dry much faster than the stems (USDA, l9h8). Research has shown that when the crop has dried to an average moisture content of 25 percent, the/leaves will be at approxi- mately 15 percent and the stems at approximately 55 percent moisture. This differential in drying rate is oneof the factors that causes a considerable loss of leaves and even a greater'decrease in feeding value of the hay. In order to determine the influence of the different treatments on the rate of evaporation from leaves and stems separately, an experiment similar to the previous one was conducted. In this case, due leaves were separated from the stems immediately after the treatments were finished. The treatments were the same as in the previous research. O Discussion of Results The curves of evaporation obtained from this research are shown in Figure 5 through 11. They indicate that only when the stem surface was nearly disintegrated (hard crushed or "penetrated"), the rate of evaporation from the stems approached that of the leaves. 39 The drying rate curves for leaves showed high evapora- tion during the first and second hour after cutting. In the third hour of drying the evaporation was lower but still of considerable amount. An average h5.6 percent of the total moisture was evaporated during the first three hours after Cutting. Between three hours after cutting and equilibrium moisture the evaporation rate (slope of curve) was nearly constant and considerably less than during the first hours of drying. The constant decrease in drying rate in leaves from one and one-half hours to three hours after cutting may be the result of the loss of surface openings caused by the progres- sive closing of stomata. On account of a decreasing turgor pressure in the guard cells most of the stomata may be closed after three hours of drying. After that the evaporation takes place only through the cuticle and possible wounds caused by mechanical treatments. On account of this and the fact that alfalfa leaves are very thin, it seems reasonable that the rate of evaporation is nearly constant until the moisture con- tent reaches the point of equilibrium.) Table XI shows the number of hours required to dry the leaves and stems to 20 percent moisture. The leaves, the hard crushed and the "penetrated" stems dried to 20 percent in 18 to 21 hours. The alfalfa stems chopped in 2 inches length dried in 57 hours. All other treatments required more than L8 hours to reach this moisture content. to war NORMAL a ALFALFA 5 LEAVES PLANT m 80 "‘ \ \s E E: II In E I... 50 ' STEM. C) «r/ in 3 p. 2 In L) SE Q"O# o s u} 24. 32 40 Figure 5. HOURS AFTER CUTTING Drying curves for normal alfalfa plants, when leaves and stems are dried separately. loo r LEAVES \ CRUSHED ALFALF'A \ JRUSHED STEM i3 PERCENTAGE OF WATER EVAPORATED. 8 [ 1 L I l J O 8 I6 24 32. 40 HOURS AFTER CUTTING Figure 6. Drying curves for crushed alfalfa when leaves and stems are dried separately. 142 IOO 7 LEAVES x. E} .. CHOPPED g 80% ALFALFA I o 2 ‘-' o. 3‘ U CHOPPED 5 , STEM 2 '— 4: . 3 so ll. (3 m 0 u: I: m. '3 3 407» u. (D U] ‘3 p. 2! h] 8 “1:2. 0. O 1 l I I 1 _ - O 8 IS 24 32 40 48 HOURS AFTER CUTTING Figure 8. Drying curves for chopped alfalfa (6 inches) when leaves and stems are dried separately. PERCENTAGE OF WATER EVAPORATED I00 '- LEAVES \ 3° - CHOPPED ALFALFA IO' \- CHOPPED 60 P «n—/ STEM IO“ w b 20 1 1 1 J 1 o 8 l6 24- 32 40 HOURS AFTER CUTTING Figure 9. Drying curves for chopped alfalfa (10 inches) when leaves and stems are dried separately. 1+5 IOO r 'PENETRATED 'PENETRATED STEEL. ALFALFA" ao _ £3 5’50; LEAVES I! E >' h] I! .“J 4 4O 3 F’ u I (D “I ‘3 '5 o 20" I! “I O. l 1 1 l 1 o 8 IS 24 32 40 HOURS AFTER CUTTING Figure 10. Drying curves for "penetrated" alfalfa when stems and leaves are dried separately. I46 IOOr LEAVES N ‘ STEM SMASHED EVERY 2 i3 L . PERCENTAGE OF WATER EVAPORATED O l l l 1 I O 8 I6 24 32 40 HOURS AFTER CUTTING Figure 110 Drying curves for alfalfa with stems smashed every 2 inches when leaves and stems dried separately. 1+7 TABLE XI TIME REQUIRED FOR SEPARAZED LEAVES AND STEMS TO REACH 20 PERCENT MOIST” E CONTENT . Pene- 2 6 10 rm. 3 Item ”“CC‘ trated Smashed Crushed in. in.. in. Hours Leaves 19 15 21 18 21 21 18 ’~ more Stems over ha 16 26 19 57 than hB prying Time For Alfalfa When The Leaves Are Separated From The Stem Versus Drying Time When The St ms And Leaves Are Dried As A Unit. From the results of the previous experiments, the eva- poration of leaves plis stems was computed. These were com- pared with those obtained from alfalfa plants dried as a The results are shown in Figure 12 through 17. In these figures the dashed curve represents the treatment -- leaves and stems dried separately. The full curve shows the results of leaves and stems drying as a normal plant. These curves indicate that the drying time was the same for alfalfa hay, whether the leaves were dried together with the stems or they were dried separately. The assumptions or theories stated by different scientists (Palmer and Jones, 1952 and 1959) that the main portion of the water in the hay AB leaves the plant through the stomata of the leaves, are in— valid. An analysis of the above data indicates that water was not translocated in the severed plant. Water located in the stem when the plant was mowed did not move to the leaf for evaporation but remained in the stem wall and was lost by evaporation through the stem. It should be remembered that by separating the leaves from the stems, open wounds were created at each place where a leaf was cut from the stan. This would naturally favor the evaporation rate of the stems as well as that of the leaves. Sectional Drying Rates Of Alfalfa When Different Degrees Of Crushing Are Applied. .An experiment was conducted to determine the path of water movement in the alfalfa stem during the drying process. The research conducted by Jones and Palmer (1952) on windrow- ing of alfalfa hay two hours after cutting does not answer the question, "Does the water move radial to the surface of the stem during the drying, or does the main part of the wa- ter move longitudinal in the stem, following the natural ways for transporting water in the green alfalfa plant?". Following degrees of crushing were applied to the al- falfa plant: 1) Uncrushed alfalfa. 2) Crushed alfalfa (similar to that done by a commer- cial hay crusher). OD 5L 0) q PERCENTAGE OF WATER EVAPORATED 8 8 ' 1 1+9 -- LEAVES AND STEM DRIED SEPARATELY -- ALFALFA DRIED AS A WHOLE PLANT NORMAL. ALFALFA PLANT 1 1 i1 1 1 0 3 '6 24 32 40 , I-DURS AFTER CUTTING Figure 12. Drying curves for normal alfalfa plant. IOO r 50 8 0’ C) PERCENTAfl OF WATER EVAPORATED a a -- LEAVES AND STEM DRIED SEPARATELY -- ALFALFA DRIED AS A WHOLE PLANT caveat-:0 ALFALFTA 0 it 1 1 1 J 8 IS 24 32 40 HOURS AFTER CUTTING Figure 15. Drying curves for crushed alfalfa. Imr 51 I ’ ’ / / / / _ /' 80 / / / / / §°°i , g / In I a: I I'.’ I “ I 3 4O ' I u. ° I 3 I g , --LEAVES AND STEM DRIED SEPARATELY 5 I --ALFALFA DRIED AS A \VHOLE PLANT s i “2 O. CHOPPED ALFALFA 2" I l I I 1 0 8 I6 _ 24 32 40 HOURS AFTER CUTTING IFigure 1h. Drying curves for alfalfa chopped in lengths of 2 inches. 10c:r 52 O O 1 § . -- LEAVES AND STEM DRIED SEPARATELY '— ALFALFA DRIED AS A WHOLE PLANT PERCENTAGE OF WATER EVAPORATED CHOPPED ALFALFA 6" 1 1 l 1 O 8 I6 24 32 4'0 HOURS AFTER currme Figure 15. Drying curves for alfalfa chopped in lengths of 6 inches. ICKD L J} a, fig 9 P T PERCENTAGE OF WATER EVAPORIATED IO (3 r 55 -- LEAVES AND STEM DRIED SEPARATELY -- ALFALFA DRIED AS A WHOLE PLANT CHOPPED ALFALFA 10" l I I 5— T5 24 32 i6— HOURS AFTER CUTTING Figure 16. Drying curves for alfalfa chopped in lengths of 10 1 “Che S o I00 9 a CD PERCENTAGE OF WATER EVAPORATED 3 T 0’ C) l O -"- LEAVES AND STEM DRIED SEPARATELY — ALFALFA DRIED AS A WHOLE 'PLANT SMASHED ALFALFA 1 1 1 l 8 I6 24 32 40 HOURS AFTER CUTTNG Figure 17. Drying curves for alfalfa "smashed" every 2 111011380 5) Hard crushed alfalfa (considerable amounts of juice appearing on the stem surface). To get uniform drying conditions throughout the whole re- search period the experiment was conducted in the research laboratory at a constant temperature of BL degrees F and a relative humidity of 59 percent. The moisture content was determined after 0, 2, 7, 12, 25, 28, DB and lhh hours of dry- ing. Immediately before each moisture determination the leaves were separated from the stem, and the remaining stems were divided into four groups according to the distance from the top end of the stem. The stem pieces from the different groups were collected and the moisture content was determined separately for each stem section. The alfalfa plants used in the OXperiment were all of the same maturity and had a uniform length of 22 inches. Discussion of Results Table XII shows the results of the experiment. The data indicate that both degrees of crushing applied in the experi- ment increased the drying rates of stems as well as leaves. The drying rates of the stems was, however, increased consi- derably more than that of the leaves. This was especially true for the hard crushed alfalfa; here the stems dried out quicker than the leaves. The experiment shows that the moisture movement in the stem was mainly radial; only in the case of the uncrushed alfalfa did a small longitudinal movement take place. For 56 TABLE XII THE MOISTURE CONTENT IN DIFFERENT SECTIONS OF THE ALFALFA PLANT THROUGHOUT THE DRYING TIME. Hggrs Treatment Section of plant (inches from top) drying Leaves 0-6 6-12 12-18 18-22 Percent moisture (w.b.) 0 Uncrushed 70.2 72.2 70.7 69.5 66.8 Uncrushed 67.1 67.7 67.5 66.1 57.6 2 Crushed 67.6 67.2 65.1 60.5 60.1 Hard crushed 66.1 57.8 57.h 52.7 55.h Uncrushed 65.7 66.5 65.8 62.0 55.1 7 Crushed 59.1 61.6 60.1 59.6 56.I Hard crushed h7.h 57.h 5h.9 22.0 25.9 Uncrushed 61.7 65.5 62.0 61.5 5L.o 12 Crushed 19.0 50.1 A5.2 59.6 57.2 Hard crushed 52.9 25.1 17.0 10.9 9.7 Uncrushed 57 8 E9.8 h9.6 L6.9 t6.6 25 Crushed 51.7 50.1 25.6 16.9 15.1 Hard crushed 18.5 16.5 11.7 10.1 9.9 Uncrushed 25.5 16.0 TE5.9 59.2 52.1 28 Crushed 26.5 50.6 25.1 11.2 11.6 Hard crushed 11.L 11.0 10.2 10.1 9.7 Uncrushed 12.9 57.5 59.7 55.1 22.6 L8 (hushed 9.2 lidi 11.0 10.9 8.7 Hard crushed 8.h 8.7 8.h 7.5 7.2 lhh Uncrushed 7.7 7.8 7.6 7.6 7.7 57 this treatment the difference in moisture content between the upper and lower part of the stem was 9.5 percent at the time of cutting, while the same difference was 1h.9 percent after L8 hours of drying; and, furthermore, at the latter time the highest moisture content occurs in the middle sec- tion of the plant. A comparison of the moisture content of uncrushed alfalfa at 0 and NS hours of drying also indicated that the greatest longitudinal water movement took place in the lower stem portions. INVESTIGATIONS OF THE SUMMER OF 1958 Evaporation From The Soil And Its Influence On The Drying Rate Of Alfalfa. An analysis of the results of the experiments previously described indicated that the most effective method of decreas- ing the drying time mechanically was obtained by crushing the plant to such a degree that the outer cell layer was nearly completely destroyed. This method in itself, however, did not increase the drying rate to the extent that hay can be cut, conditioned and field dried in one day under Michigan conditions. Evan when "complete" crushing was applied, the hay would still have to be left in the field overnight and thereby exposed to the damage of dew, or it would have to be artificially dried. It therefore seemed natural next to ana— lyze the surroundings in which alfalfa is dried in the field. After cutting, the hay lies on the ground for drying. The soil contains moisture which is continually being lost to the atmosphere by evaporation. This moisture raises the relative humidity of the soil surface air, and tends to slow down the drying rate. During parts of the day and night the hay may gain moisture from the high humidity air. When the hay is placed in the swath for curing, the water vapor gen- erated from the soil can escape only through the layer of hay, 59 and thereby cause a decrease in vapor pressure differential between the hay and the air surrounding it. In Michigan, the soil is often near field capacity when the first cutting of alfalfa is harvested. An experiment was conducted in which hay was placed on soils with two different moisture contents; air dry soil con- taining h.5 percent moisture, and soil with a moisture con- tent of 15.0 percent. Half the area of both these soils was covered with transparent pcgyethylene, impermeable to water vapor. Uncrushed and hard crushed alfalfa were dried on these soils. The research was carried out in the research labora- tory in order to get uniform drying conditions throughout the whole drying period. The results from the experiment are given in the curves of Figure 18 and Table XIII. T.e curves in Figure 18 repre- sent the percentages of total water in the green plant eva- porated at a given time. They indicate that there was little or no difference in the drying rates of hay when it was dried on air dry soil, air dry soil and wet soil covered with poly- ethylene. The air dry soil under the hay seemed to have in- creased the drying rate a small amount. The difference be- tween the three treatments, however, was so small that it would not have any practical influence on the drying time. For this reason the curve drawn, is the average line for the three; the maximum deviation from this did not exceed two percent. PERCENTAGE OF TOTAL HATER EVAPORATED IOOF ”"1... ,v riaure l I) V. / ’ f ., 2; ”H- A /’ / :6 “/ /# I / / ’ I I I u/' so ~ / . / r / / ./ / / . / go_. 1’ ./ f / / / a PLASTIC cow-men AIR DRY son. 3 / A DRYSOIL 20- / / x pusnc COVERED.WET son. ‘7 a \VEW'SOH. —- caususo ' cl — — uucnusueo l l I ' I o as 24 32 no HOURS AFTER C077!" 6 The influence of evaporation from the soil 1 the drviné rate of alfalfa. V The difference between these treatments and that of dry- ing the hay directly on the soil containing 15 percent mois- ture was considerable. After 22 hours of drying, 80 percent of the water was evaporated from the hard crushed alfalfa on wet soil, while the corresponding number was 9h percent for hay placed on dry soil or polyethylene covered soil. For the uncrushed samples the difference was even greater, although not nearly as much water had been evaporated. TABLE XIII TLE HOISTUIE cCNTEN (V.B.) IN THE DIFFERENT SAMPLES AFTER 8 AND 22% HOUPS or DRYING. Hours of drying 8 22% Moisture content in percent (w.b.) Treatment Crushed 4 dry soil - polyethylene h5.h 16.7 Crushed + dry soil h5.h lh.l Crushed 4 wet soil - polyethylene h5.2 15.2 Crushed 4 wet soil 58.1 h0.5 Uncrushed + dry soil - polyethylene 68.6 52.5 Uncrushed + dry soil 67.u 50.6 Uncrushed + wet soil - polyethylene 67.0 52.h Uncrushed + wet soil 71.5 65.7 Comparison of the figures in Table XIII (22% hours of drying) shows that covering wet soil with a sheet, impermeable to water vapor, caused the hay to dry to approximately 15 percent in 22% hours, When it was hard crushed, while the uncrushed hay had reached a moisture content of only 52 per- cent. The corresponding figures for hay on wet soil were LO.5 and 63.7, respectively. The experiment clearly indicates that it was possible to reduce the drying time in the field by eliminating the influence of a moist dryingloed. When studying these data it should be remembered that it was a laboratory experiment. The drying time in the field can be expected to be consider- ably shorter on account of the influence of solar radiation and greater air movement through the sample. Effect Of Vapor Barriers Upon Field Drying Rates. The experiments presented above have shown that hard crushed hay dried quickest when the influence of evaporation from wet soil was eliminated. In order to take advantage of the solar energy, this experiment was conducted in the field. The alfalfa was out at 8:50 a.m. The crushing of the alfalfa in this and the re- maining experiments was conducted on a model hay crusher con- structed by Dr. James L. Butler (1958). The crushing unit consists of two cylindrical rollers with a smooth surface. Contrary to the conventional hay crushers, where the rollers are spring loaded, this model crusher was constructed in such a way that the clearance between the rollers is variable nd can be fixed at any chosen clearance. The following treatments were applied to the alfalfa: 1) Hard crushed (a severe crushing where the distance between the rollers was fixed with a clearance of less than 0.010 inch), and placed on black poly- ethylene. 2) Hard crushed and placed on transparent polyethylene. 5) Crushed (this cruShing approximately equal to that of a commercial hay cruSher) and placed on black polyethylene. h) Crushed and placed on transparent polyethylene. 5) Crushed and placed on the ground. 6) Uncrushed and placed on black polyethylene. 7) Uncrushed and placed on transparent polyethylene. (I) ) Uncrushed and placed on the ground. All the treatments were applied less than half an hour after cutting. The alfalfa was placed on the different dry- ing beds in such a way that 200 grwns of green material cov- ered one square foot. Moisture content determinations were carried out after 1, 2, 5.5, 5, 6.5, 8, 9.5, 25, 2h, 27, 50, 52, h7, h9, 51 and 55 hours of drying. At the same time that the moisture contents were determined, measurements were taken of the sample temperature, the surface temperature of the po- lyethylene, the temperature of the air, and the relative hu- midity of the air. The temperature of the air and the rela- tive humidity was measured 6 inches above the around. 0\ Discussion of Resalts The results of this experiment are shown in Figure 19, Table XIV, and Table XV. In Figure 19, moisture content in percent (dry basis) is plotted versus drying time on semi-log paper. An analysis of the graph for hard crushed alfalfa shows that the drying rate is nearly constant to 25 percent moisture ( = 20 percent wet basis). When artificial drying is applied to material, this is usually not the case. It should, however, be remembered that when drying is conducted in the field, the relative humidity in the air decreases from sunrise to mid-afternoon. If the drying of the product can be completed during the time of decreasing relative humidity, the vapor pressure differential between the hay and the sur- rounding air will continually increase. his is the reason for obtaining a more constant drying rate, than if the rela- tive humidity of the drying air was held constant throughout the entire drying time. Only in the case of hard crushed alfalfa on black and transparent polye hylene was it possible to obtain a moisture content of 20 percent (w.b.) Within the period of decreasing vapor pressure of the air. In Table K V is shown the number of hours required to reach a moisture content of 20 percent (w.b.). None of the checks on the ground reached a moisture con- tent of 20 percent (w.b.) within three days of drying. At :50 p.m. of the third day the crushed sample showed a mois- MOISTURE CONTENT (0.8) x l HARD CRUSl-ED O WRMAL CR USHED A UNTREATED ALFALFA _— BLACK PLASTIC -.—- WHITE PLASTIC ---cuecn< ON GROUND x8 I I /,’ ‘\\ z ’/ \‘ I / \ I / ‘4 ‘A’ / \ / o‘ \ / “\ ./°. ,\ / A /r . \. \ \\ \ ./ // \A :3\ \A . \ ‘ \\./” ‘ \o \ \ \ ‘ o o\ A\ ;r o \ \ \ i ;‘ \° .. \ IO 5 I I i 1 1 J g I NOON 6PM 6AM NOON 6PM 6AM NOON 6PM O IO 20 30 40 fl GO HOURS AFTER CUT Figure 19. The effect of vapor barriers upon field drying rates. 66 ture content of 21.6 percent (w.b.), that of the uncrushed 2h.5 percent {W.b.). TABLE XIV REQUIRED TIME FOR THE DIEFERENT TREATMENTS TO REACHIR MCISTURE CONTENT or 20 PERCENT (w.s.) Treatment Time Hours Hard crushed alfalfa on black polyethylene h.0 Hard crushed alfalfa on transparent polyethylene 6.5 Crushed alfalfa on black polyethvlene 25.5 Crushed alfalfa on transparent polyethylene 28.5 Uncrushed alfalfa on black polyethylene h9.5 Uncrushed alfalfa on transparent polyethylene 51.5 Crushed alfalfa on ground more than Uncrushed alfalfa on ground 56.0 Table XV sets forth the variation in temperature of the different hay samples, the surface temperature of the poly- ethylene, the tmnperature of the air, and the relative humi— dity of the air. During the first day of the experiment, when the sun was shining, the energy received by the polyethylene by radiation was able to raise the surface temperature of the black and transparent plastic an average of no.5 and 21.2 degrees F, respectively. The maximum temperature of the polyethylene I 67 TABLE XV THE TaxPsRATURE OF HAY SAMPLES, SURFACE OF POLYETHYLENE, AIR, AND RELATIVE HUMIDITY OF THE AIR. Temper ture in Degrees Fahrenheit R.H. 6 Re- Time Hay Sample Plastic Air in- ~— — 1 above marks 330* BC* Bhefficarce TNa "0% CN* 8* Ta soil % 103; S5 86 95 81 S9 90 79 75 111 98 77 51 lla; 85 1'6 136 85 98 105 85 80 122 99 77 85 0:50pm 96 108 105 86 98 100 86 85 122 102 77 80 2pm 98 11; 118 97 105 108 95 89 122 99 77 59 5:50pm 118 115 110 96 106 110 90 88 125 108 79 at 5pm 100 101 88 98 96 88 85 108 95 79 5h 6:50pm 82 82 80 79 75 75 7h 75 76 56 P.C. - - - q ............... - - - . _ - - - 1 - - 86 79 80 78 78 72 72 85 78 7h 65 0.0. lOas 88 86 82 85 79 78 95 87 76 59 0.0. 12am 99 100 98 9h 8 86 117 99 78 52 0.0. 5.m 101 101 95 96 88 88 118 108 80 57 H. 5pm 98 9h 90 90 88 85 102 90 76 59 H. 8am 87 88 75 75 88 82 75 61 10am 106 102 90 88 150 111 78 52 12am 150 125 99 100 150 150 85 87 L:50pm 98 89 88 96 81 u? a B = Black polyethylene T = Transparent polyethylene EC = Hard crushed alfalfa sample C = Crushed alfalfa sample N = Uncrushed alfalfa sample .C. = Partly cloudy 0.0. = Overcast : Haze 68 was obtained on the third day. The maximum temperature of the black polyetiylene reached 150 degrees F and that of the transparent, 150 degrees P, which corresponded to an increase above the air temperature of 67 degrees F and h? degrees F, respectively. Even on the second day of the experiment, when it was partly cloudy or overcast the main part of the day, the in- crease in temperature was considerable. As an average it amounted to 2h.2 degrees F and 16.; degrees F for black and transparent polyethylene, respectively. The radiation energy caused the temperature in the hay to rise above the temperature of the surrounding air. As it appears from Table XV this increase was largest for the hay placed on black polyethylene. It was somewhat lower for the sample on the transparent polyethylene, and lowest for the sample placed on the ground. No averages can be taken here because the rise in temperature depends on the amount of eva— poration from the sample. When the evaporation from the hay was high, as it was in the case of the hard crushed sample on black and tranSparent polyethylene during the first two hours of drying, the increase in the sample temperature was rela- tively small. In this case most of the absorbed energy was apparently used for evaporation of water from the sample. As soon as the amount of water evaporated per unit time de- creased, the sample temperature increased. 69' The Influence Of Swath Thickness On Drying Rate Of Hay Placed On Polyethylene. The quantity of alfalfa, or the thickness of the layer of alfalfa, placed on the polyethylene sheet will obviously affect the drying rate. To determine the maximum amount of hay that could be placed per square foot of polyethylene and still be able to reach 20 percent moisture conte.t within the same day as the hay was cut, the following initial weights of alfalfa were placed on black polyethylene: l) 100 gram per sq. ft. (emial to 1.2 tons of 20 per- cent hay per acre) 2) 203 gram per sq. ft. (equal to 2.h tons of 20 per- cent hay per acre) 5) LOO gram per sq . c ft. (equal to h.8 tons of 20 per- cent hay per a ) h) 600 gram per sq c ft. (equal to 7.2 tons of 20 per- cent hay per a ) 5) 300 gram per sq. ft. (equal to 9.6 tons of 20 per- cent hay per acre) These samples were all crushed with a clearance less than 0.010 inches between the rollers on the modelcrusher. Discussion of Results The result of this experiment is shown in Figure 20. The graphs indicate that all the samples reached a storable mois- ture content the same day as the hay was cut. This moisture p .L 2) el' H° (I l (- level of 20 percent (w.b.) was obtained after .rying the following number of hours: 70 3 8 MOISTURE CONTENT (0.8.) $ 8 zoo IOO G/Ffl. . 3/": 60° L4 '0 l I l I O 2 4 o 0 .0 HOURS AFTER CUTTING Figure 20. Drying curves for alfalfa when different initial amounts per sq. ft. are placed on black polyethylene. ”\3 H 100 gram sample after 2.8 hours 200 gram sample after 5.9 hours LOO gram sample after 5.0 hours 600 gram sample after 6.1 hours 800 gram sample after 7.7 hours It is important to notice that evenwwith an amount of hay equal to 7.2 tons of 20 percent hay per acre it was possi- ble on a good drying day to store hay 6 hours after cutting. The results indicate that it would not be necessary to cover the whole field with polyethylene to dry the hay. A swath can be placed on a strip of polyethylene 1/5 to l/2 the w dth of the mower cutterbar -- depending upon the yield of alfalfa. In Table XVI is shown the climatical data which corre- sponds to the above discussed experiment. TABLE XVI THE TEMPERATURES OF HAY SAMPLES, SURFaCE OF POLYETHYLEHE, AIR, AND RELATIVE HUMIDITY OF THE AIR. Temperature in Degrees Fahrenheit R-H- Time Hay sample of lOOgr ZOOgr hOOgr Ebogr EOOgr PlaStic Air Air % 10am 90 91 82 80 75 122 5 53 llam 100 87 82 So 76 156 77 A? 12am 105 10h 90 g; 75 156 79 MA 2pm 118 120 110 96 86 130 82 33 tpm 99 130 90 88 122 81 ac 6pm 36 8h 82 96 80 h2 The Influ exp of crushing ne content the same day as it is cut. a.m. All the following clea 1) Less eriment ence Of Degree Of Crushing On The Drying Rate Of Alfalfa. 'fi CA w s enducted to determine the deéree eded to field dry alfalfa to storable moisture The hay was cut at 8:5 c '13s is ill cl k 0 ye h e 0. he sam ‘ ~ w re dried on b ac 1 t yl ne T rances between the crushing rollers were used: than 0.005 inch 2) 0.0129 inch 3) 0.02 50 inch h) 0.0500 inch 5) (3.lt{“‘ incl} 6) Check (uncrusr ed sample) Moisture def enninati one were made after 1, 2, 3.5, 5.5, and 6.5 hours 01 drjin n5. The amount of initial *reen m r rial placed on the polyttnyteie for drying was 300 prams per square foot, which corresponds to~3.5 mo 3 per acre of hay with a moisture content of 20 pe crcent (w.b.). Discussion of nesalts Figure 21 indicates the results of this experiment. Only With clearances of less than deployinitely 0.01511nc h bctve en fwd re lers was it possible to dry the he; to a moisture con- text of 20 percent (w.b.) Within the same day a: it was cut. This moisture level vas reached after 5.5 hours of dryino *UP the hardest crushed sample, and after 8 hears for the ,emple a“ ‘ 9 we . cw " a! _ sung £2.00 ‘, a! 3 I00 5 a) I: '2 s m o 5- a! o 50-- m o t z “1 50. a: a: E E Q g u E C) 85 - o a: p. I'M! 22 ' CI c»0 0‘? I l 1 I l I I n 4 l 2 4 O 0 HOURS AFTER CUTTING Figure 2l. Drying curves for alfalfa crushed at different degrees. .—~.‘ ) V ‘ ‘3 hi "4.! .T' ’ Alfalfa crushed at clearance less than 0.005 inches. Alfalfa crushed at clearance 0.0125 inches. Alfalfa crushed at clearance 0.050 inches. x A-. I - 1 9. , - . he udj on \"nih this experts“ ent was conducted - ' I' \.'- ‘Q . . :V 0" q ;"-' 7 -- ~ : the weather was partly clot“; t; Cloudj. This ex;lains the relatively low dryin5 rates. "f&1fi Cut At Vazicus Times Of The Day. The purpose of this en:eriment was to determine how late ; hay ceuii be cat and still be field dried to stor— Samples with _. _. .. .- ,. a rat ”5,,“ . “'1 _ s 7 “r, . an in-t1a1 fieloht o- QQJ a.m.s were leased un blacx polyevuyl- ELQ. A hard crushi15 (clearance less thar C.013 inch) was appli:i. The senples h—.e out d! “laced on drvin 5 trays at -. V '7 ~«\ 5". .I‘ \ \v I r >' a 5". I , 1L 'a ..|? . , l r} 0.1». Q , ) }-'..n. , and ) p.rn. Ttis experiment was cenductee for tw; hays. Durin5 th: first ea" the weather vas part1? cloady, the temperature of 1e sun sl“i= vapor pressure differential between air and hay (psi) V 1: Velocity of air (ft/hr) T = Hours of dry ing 1: = Initial thickness of Stem (in) l. 2 Thickness of stem after crushing (in) 9 = Density of hay on basis of dry matter (lb/ftg) h Thickness of swath (in) Solving the problem with 4p, V, and h as incompatible variables gives: I11: g ($2,413, V9 h) 3 15(2- (1) II« a g (T,AO, V, n) : T ,X V ‘ (2) 0‘) -J 1 - , w ‘ X 7'2 1*; ' $5 (994?: ‘19 h! = P X h (5) L . , L ‘ IIL = a if ,Ap, v, A) = I (4) , ___ n’ / ,‘\ { ’ 1:: CI. 11, y .11 x .115, x h) (,) OP I"o T x v xv2 L / W- : g ( n ) £0 x h) < T ) (O) O - Enteriment" shoald be carried out varying 115 and holding plot of Ill against 115, he relationship :,~L 1 z 2, II‘LL) ( b '\J V where the .ars denote constant values, could be determined. From a second set of experiments with 112 and I15 held constant and II varied, the relatidnship of | 4 (*1 ‘— — - d (II II II \ (“ *T/ZK-V’) “1"" 7’ V) ""91 g ‘f 2 ) conld be deter'i*ed from a plot of Ill versas Ila. ) (i) ,0 can as deterrined from a plot o. II1 verSLS F-i F4 3‘») ll. REFERENCES Bri55s, L. J. and H. L. Shantz, 1916. Hourly transpira- tion rate on clear days as deterri ed by cyclic environmental factors, J. A5r. Res., 5:585-651. _ ant , 1910. Daily transpiration during tne normal 5rovth period and its correlation with weather, J. Agr. Res , 7:155-215. Butler, J wwes L., 1958. Factors afi‘e cting the pell etir5 of hay. Unpjc blished thesis for Pn.D., Michi5an ‘- Darwin, F., 191h. The effect of light on t tion 0: leaves, Pr cc. R05. 300., B, “7:2:1-23(. Hopkins, B. R., 1955. Some effects of chemical ar d ecrianiczl treat..ents in haymakin5. Unpublished tnesis for Pn.D., Michigan State University. James, T. N. nd L. O. Palmer, 1952. Field curing of hay as influerced by plant physiology reactions, A51". Eng., 157:1)?" ECHO. and , 19j9. Hay curing; III. Re- lation of ertineering principles and physiolO5 ical factors, Agr. En5., 20:115- -116. Loftfield, V. 9., 1321. The behavior of stomata. Carne so J. 5ie Inst. Na Nariana, G., 1902. The influence of hu'nidity on the for- tion and development of stomata a. Separate from ATT. Bot. Univ. Pavia 9 ser., 5:52; Exp. Sta. Rec. / 1L0/1r /' mcCurd', J. A., (undated). Improve your hay quality with rr has7 dryin5. Pen;. State Univ., A5r. Coll. Ext. Viller, B. C., 1928. Some coserva tions on tr 1e sto mata of crop plants. Unpiblisned data. Kansas St ate Reed, Thoma VarY, H. 3., and E. Hirana, 1351. The density of sto- mata in citrus leaves, J. A5r. Res., hj:209-222. s, N. D. and G. R. hill, 1957. The continuous weasuromeris of photosynthesis, respiration, and transpiration of M1 alfa and wheat 5rowin5 under field conditf ors. Plant Physiol. 12:255-307 K. A., 195;. Hey narvestin5 methods and costs, Mich. A5r. Exit. StL. Spec Bu]. 332. USE [35";LY M'TlTlilLllllLijfllii!MWIIWIMIHJWIWS