A SOIL MOISTURE LOSS METHOD FOR CHARACTERIZING SIMULATED TILLAGE TREATMENTS ! r Thesis for the Degree '0‘ pk. D. 5 MICHIGAN STATE UNTVERSITY William H. Johnson 1960 THESIS m H l/Il/lllllllll @ifliji/‘f/FI W /’l// 1'. This is to certify that the thesis entitled The Basic Soil Moisture Lose Method of Characterizing Simulated Tillage Treatments. presented by ifllliam H. Johnson has been accepted towards fulfillment of the requirements for Pb.D. degree in Agricultural Engineering M [M Major professor fly /2/ ///& / Date 0-169 A SOIL MOISTURE LOSS METHOD FOR CHARACTERIZTNG SHEFLRTED TILLAGE TREATMENTS BY Uilliam.H. Johnson AN ABS? ACT Submitted to the School for Advanced Graduate Studies of Michigan State University of Agriculture and Applied Science in_partial fulfillment of the requirements for the degree of '\ DOCTOR 0F EHILOSOPHY Department of Agricultural Engineering Year 1960 Approved NILLIANiH. JCHNSON AN ABSTRACT An analysis made of past work indicated that the emergence of corn was often slow and erratic in "minimum" seedbeds. The high rate of soil moisture loSs from large-clod-size seedbeds, and there- fore rapid drying of the soil at seedlevel, was postulated as being the major contributing factor to poor emergence. The purpose of this study was to devise methods of characteriz- ing soil moisture loss from a disturbed soil layer and evaluating the effect of varying clod sizes in the tilled profile, upon soil moisture loss. Four size ranges of clods were used, varying from 0.0h6 to 0.335 inches in diameter. The control of temperature, humidity, wind flow, and radiant energy provided abasis by which multiple samples and soil treatments could be compared under common climatic conditions. Newton's equation,.%%_§_g§ - e‘Ke; plotted in the form of the moisture content ratio - time curve with slope K, provided an adequate means for characterizing the rate of soil drying after a stable dif- fusion system.was established. A parameter, P, percentage of water lost during the first 2b hour period, was used to characterize the the initial drying period. In addition to characterizing the drying rate, this method provided a basis for comparing the various soil treatments. WILLIAM H. JCHHSON AN A$TRACT The experimental results indicated that as clod size increased and compactive effort decreased, the rate of soil drying increased and the total emergence of corn was reduced. No compacted and/or stratified treatment, in which the primary soil consisted of large clods, was as effective in reducing the dry- ing rate of soil as a reduction in clod size to 0.0b6 inches. The lowest drying rate, however, occurred when the 0.0h6 inch clods were subjected to a compactive pressure treatment. A The application of 5 psi compactive pressure at seedlevel and again on the surface retarded, or at times inhibited, emergence to an undesirable extent. The stratified treatment was more satisfac- tory in that emergence was not inhibited and the fine, compacted ciod layer at seedlevel provided a highly resistant layer to the diffusion of water vapor, yet capillary movement was broken. A seedbed profile built up by separating and placing clods by size rather than subjecting a soil to a continual-size reduction process has practical potential. A SOIL MOISTURE LOSS METHOD FOR OHARACTERIZING SIMULATED TILLAGE TREATMENTS By 3" M90 William H.“ Johnson A THESIS Submitted to the School for Advanced Graduate Studies of Michigan State University of Agriculture and Applied Science in partial fulfillment of the requirement for the degree of DOCTOR OF PHILOSOPHY Department of Agricultural Engineering Year 1960 Fir Dis Hi C; if“ x! R IV 1' i _. I s U. ) I A I! v I.‘ 3 d ,1 Jr ,u . . ' ’ '0 Q Hi lliam Howard Johnson candidate for the degree of Doctor of Phi losoptw Final Examination: 8:30 AM, my 13, 1960, Room 218, Agricultural Engineering Building Dissertation: A Soil Moisture Loss Method for Characterizing Simulated Tillage Treatments Outline of Studies Major Subject: Agricultural Engineering Minor Subjects: Statistics, Applied Mechanics Biographical Items Rarn, September 3, 1922, Sidney, (hi0 Undergraduate Studies, Chic State University, who—19w Ck‘aduate Studies, Ohio State University, 1950-1958 Michigan State University, 1958-1960 Experience: U.S. Arum, Corp of Engineers, Officer, l9h3-l9li6 Instructor, Ohio Agr'l EXperiment Station, 19!:6-1953 Assistant Prof., Associate mairman of Agr'l Engineer- ing Department, Ohio Agr'l Experiment Station, 1953-1959 Associate Prof., Associate Chairman of Agr'l Engineer- ing Department, Ohio Agr'l Experiment Station, l959-Present Member of Tau Beta Pi, Phi Eta Sigma, Gamma Sigma Delta, Sigma Xi, Alpha Gainina Rho, American Society of Agricultural Engineers vi TAKE OF CONTENTS Introduction ................... StatementoftheProblem . . . . . . . . . . . . . ReviewofLiterature ............... ‘ Influences of clod size . . . . . . . . . . . Influences of soil compaction . . . . . . . . Environmental factors influencing germination and emergence . Movement of water in or through a soil . . . . Methods of characterizing the drying of soils Analysis of Possible Means of Characterizing Evaporative Hater Loss from Soil . . . . Theoretical Considerations of Newton's Equation Used as a Diffusion Equation . . EmerimentalProcedure .............. Generalprocedure .............. Screeningthesoil.............. wetting the soil . . . . . . . . . . . . . . . Placing soil in test containers . . . . . . . Determining the equilibrium moisture contents Special Equipment and Test Conditions . . . . . . . Climatic control equipment . . . . . . . . . . Soil sample test stand . . . . . . . . . . . . The 3011 C O O O O O .0 O O O O O O O O O O O O U'll-T'JI'W O\ 11 13 15 15 18 19 19 20 23 23 25 29 Di Sc Use Pose; 5433: Concl Appem vii Special Equipment and Test Conditions (cont.) Pressure application equipment . . . . . . . The standard climatic cycle The constant environmental condition . . . . Application of Newton's Equation to Soil Drying . O O O O O f O 0 Characterization of Certain Tillage Related Soil Treatments by the Drying Rate Interpretation of Results . . . . . . . . . . . . . The influence of two climatic conditions . . . The influence of compaction - no radiant energy The influence of clod size stratification, applied no radiant energy applied . . The influence of covering the soil - no radiant The influence of radiant energy energy applied The relationship of P and K to inches of water lost. The influence of soil type . . . . . . . . . . . . . The influence of soil treatment on emergence . . . . DiscussionofResults.................. Use of Newton's Equation for the Prediction of Drying Power of the Statistical Test . . . . Suggestions Concerning Future Work . Conclusions . . . . . . . . . . . . . ,Mmmmhc ... ... ... ... .. References Cited . . . . . . . . . . 0 Rates 30 30 3h 3h hl 145 AS 51 58 61 869 8 72 72 75 75 80 110 viii LIST OF TABLES Table 1 Ooniparisons of soil moisture contents from normal fallow and stratified tillage treatments . . . 2 Observed and calculated data for upper 3 inches ofsoil,sample23.............. 3 Description of the soil treatments. . . . . . . . i: Direction of water movement in samples which received radiant energy.’ . . . . . . . . . . . APPENDIX 1 Mechanicalanalysisofsoil........... 2 Aeration porosity of soil . . . . . . . . . . . . 3 to 7 Observed and calculated data for upper 3 inches Of 3011, a) data. 0 C O O O O O O O O O O O O 8 to 11 Ibserved and calculated data for upper 3 inches 12 13 1h 15 16 1? 18 ofsoil,(hiodata.............. Accumlated data, it - no radiant energy . . . . . Accumulated data, K - radiant energy. . . . . . . Accumulated data, P - no radiant energy . . . . . Accumlated data, P - radiant energy. . . . . . . Sanitary of statistical analysis . . . . . . . . . Dry weight of soil in upper 3 inches of sample, noradiant energy. . . . . . . . . . . Height of water in upper 3 inches of sample, noradiantenerw............... Page 10 36 hl 63 81 82 83 88 97 98 99 100 101 102 103 ix APPENDIX (cont. ) Table 19 20 21 22 23 Dry weight of soil in upper 3 inches of sample, withradiantenergy.. . ... .. .. . . Height of water in upper 3 inches of sample, withradiantenergy. . . . . . .. . . . . Emergence of corn planted in the sample, with noradiantenergy............. Emergence of corn planted in the sample, with radiantenerw............... Key relating sample number to treatment, with noradiantenergy............. Key relating sample number to treatmnt, with radiantenergy............... Page 1014 105 106 107 108 109 Figure \OCD‘IOVIITWN H in NO 12 13, 111 15, 16 17, 18 19, 20 21, 22 23,. 21: 25.826 28 LIST (F FIGJRES Visual comparison of clod sizes used . . . . . Sieves used in the separation of clod sizes. . A hand sprayer used to wet the layers of soil. Sample containers and covers . . . . . . . . . Exterior view of 18] environmental chamber . . Interior view of )8! environmental chamber . . The Ohio environmental chamber . . . . . . . . The BSU test stand with samples in position. . TheMSJteststand,complete......... The Ohio soil sample test stand. . . . . . . . Equipment used to compact the soil . . . . . . The relative humidity portion of the climatic cycle used . MledrYingcurVQSooooooe Sampledryingcurves....... Zones of emergence for corn. . . . standard Consolidated drying curves, no radiant Consolidated drying curves, no radiant O O O 0 energy. energy. Consolidated drying curves, radiant energy . . Consolidated drying curves, radiant energy . . . Regression of it on clod size, no radiant energy. Regression of K on clod size, radiant energy . . Page 21 21 22 - 22 2h 2h 27 27 28 28 32 33 37 39 143 116 117 118 119 52 53 xi 29 Regression of P on clod size, no radiant energy. . . 30 Regression of P on clod size, radiant energy . . . . 31 Relationship by which P can be transformed into inches of water lost. . . . . . . . . 32 Relationship by which R can.be transformed into inches of water lost, no radiant energy . . . 33 Relationship by which K can be transformed into inches of water lost, radiant energy. . . . . 3h correlative curve P vs. K . . . . . . . . . . . . . 35 Illustration of the difference that can be discovered 93% of the time . . . . . . . . . APPENDIX 1, 2 Sample drying curve. . . . . . . . . . . . . . . . . 3, h Sample drying curve. . . . . . . . . . . . . . . . . S, 6 Three drying curves resulting from supposedly identical drying conditions. . . . . . . . . 7 Nonplinear regression method of combining the three sub-sample drying curves . . . . . . . 8 Drying curve resulting from non-linear regression method of combining drying curves 9 Record of temperature and humidity resulting from the environmental chambers . . . . . . . . . 5h 55 65 67 7h 76 92 93 9h 95 95 96 xii ACKNOWLEDGMENTS In a study such as this many individuals contribute to make progress possible. Specifically those on the Michigan State Uni- versity staff: Dr. Wesley P. Buchele, Agricultural Engineering Department, major professor, continously provided gildance, counsel and encouragement. Drs. Carl H. Hall, E. A. Erickson, L. E. Halvern, and H. D. Etch respectively of the Agricultural Engineering, Soils, Applied Mechanics, and Statistics Departinents served as guidance committee members. ' Drs. B. 1. Stout and r. v. melow for making experimental equip-8 ment available. Dr. A. w. Farrell, Chairman of the Agricultural Emineering Department, made the research assistantship and project financial support available. ' Mr. James (>an and the service staff of the Agricultural Engi- neering Department for helpful assistance in the construction of apparatus. Several members on the 0110 Agricultural Experiment Station staff have also contributed: Director L. L. mmmell, w. E. Krauss, Associate Director and R. D. Harden, Chairman of the Agr' 1 Engineering Department, for provid- ing the opportunity, and incentive to pursue additional formal study. xiii Drs. D. M. Van Doren and C. R. Ueaver respectively, in the Department of Agronomy and Statistics, for their assistance in con- ducting tests and interpreting results. The mthor wishes also to express sincere gratitude to his family: Hrs. Hyoma Swift Johnson, wife, for her patience, endurance, encouragement and assistance. Larry, Cheri and Dana Johnson, children, for their patience and confidence. lHTROIlJCTION Considerable research has been conducted since the early l9h0's to minimize the number of tillage operations required to develop a suitable seedbed. This interest originates from concern for soil structural deterioration, high tillage costs, and yield remictions due to excessive tillage operations. Cook, HeColly, Robertson and Hansen (1958) define minimum tillage as being the least amount of tillage needed for quick germination and a good staid. Hillard, Taylor and Johnson (1956) summarized the re- sults of a corn tillage eiqaeriment by stating there was no advantage in working plowed land beyond that necessary to insure a good stand and that the equivalent of once-over techniques led to maximum corn yields 1h_e_n a satisfactory w a obtained. Johnson and Taylor (1958) observed the stands of corn established in minimm seedbed treatments for six years and found stands from 72 to 100 percent. The deduction from this information was that the establishment of stands was erratic and a problem when minimum seedbed preparations were used. The definition of mininum tillage in terms of stand is inadequate. In order to m the emergence of an adequate and con- sistent stand more precise specifications must be given. Research workers can use stand to evaluate a tillage operation; the farmer, however, can not. He must establish an adequate number of growing plants before a satisfactory yield can be expected. Other workers have reported a slowness of a crop to emerge follow- ing the use of minimum seedbed treatments. Richey (1959) summarized a group of technical papers on tillage by indicating that one of the prob- lems of minimum tillage mentioned in all papers was low emergence and early growth of the crop. lie further suggestci that this characteristic of minimum tillage must be overcome before full benefits can be obtain- ed. In this regard, Richele (1951;) found that the retarded growth of young seedlings not only reduced.yield and caused the crop to mature later but also affected adversely the quality of the crop produced. Taylor and Johnson (1956) suggested one fundamental characteristic of seedbeds which contributed to both stand and rate of emergence. They found significant correlations between early stands of corn and the per- centage of clods (by weight) smaller than 2 mm. in diameter. No corre- lation was found between early stands and soil moisture contents at the time of planting. Final stand was influenced by size of clods but not _ as much as early stands. These results are far reaching in that soil moisture transfer must have been more rapid and more complete as the quantity of small clods increased. A slower moisture loss from the seed zone in finer seedbeds would account for the above tendency. Farmers know from experience that soils plowed after the first of May, must be “worked“ quite soon after plowing to prevent rapid drying of the plow layer. This rapid drying makes successive tillage opera- tions more difficult and contributes to lower soil moisture contents at planting time. The hypothesis advanced in this thesis is that the coarser and less compact a seedbed is left after a tillage operation the more rapid the soil moisture loss from the seed zone and the slower the rate of emergence of the crop planted in the seedbed. Research workers in soils have found it difficult to adequately describe the size distribution of clods for optimum crop emergence and growth. Beause of this difficulty, engineers must assume sound axioms as a means of evaluating tillage treatments until more funda- mental information becomes available. One such axiom is that it is desirable to retain (or conserve) a high soil moisture content at seedlevel after a tillage and/or planting operation. many such axioms may be stated; however, this one will receive major emphasis. Basically.a tillage tool performs four functions: (a) alters clod size distribution, (b) changes location of the clods in the soil pro- file, (c) modifies the bulk density of the soil, and (d) changes loca- tion of any surface residues. Based on the hypothesis and axiom stated above, tillage treatments can be evaluated by characterizing the moist- ure loss rate as the above four functions are altered. STATEMENT’CF‘THE PROBLEM The purpose of this study was to devise methods of characterizing moisture loss from a disturbed soil layer and evaluating the effect of varying clod size, degree of compaction, and location of various clod sizes in the tilled profile, upon moisture loss. REV IEW OF LITERATURE Influences of Clod Size. Esser in 1881;,» reported by Baver (1956), studied the evaporation from a sieved soil with clod sizes ranging from 0.071 mm. to 2 mm. He found, in 2 mm.particles, the evaporation was about l/li as much as from the smaller particles. Yoder (1937) in a series of sieved soils found a clod mixture ranging from 1/8 to 1 inch to be optimum as evaluated by cotton re- sponse. He also found non-capillary pore space reduced as the clod sizes increased from l/8 to 1; inches. Emergence rate was fastest on soil ranging from 1/16 to 1/2 inch. Early emergence reflected high yield. Johnson and Twlor (1958) reported highest corn stands resulted from seedbeds in which 30 percent of the soil aggregates were smaller than 2 mm. in diameter. Stout (1959) found no significant differences in sugar beet emerg- ence as clod size varied from 0.59 to 6.35 mm.in S ranges. The soil moisture was,however, kept high through the use of covered sample boxes. Greacen (1959) reported, in wind tunnel tests, that a coarse clod system with pore sizes greater than 2 mm. lost water at a much faster rate than soils in finer tilth, for example, 3 days as compared to 30 days for a loss of 1 inch of water. He further states there must be some air convection effect but to date they had not been able to set up an effective model. Miller and Mazurak (1958) studied different growth rates of sun- flowers in sand as soil particle size varied. At field capacity the maximum growth rate was obtained from separates ranging from 9 - 13 microns. Bxlk density was highest for larger particles. Sokolovsky (1933) emphasized the importance of granulation and porosity as measures of tilth. The results indicated clods 2 - 3 mm. in diameter were best for plant growth. Pore space should be equally divided between capillary and nonpcapillary'pores. When the non-capil- lary porosityies lower than 10 percent by volume the tilth was poor. Influences of Soil Compaction. Stout (1959) found that the application of pressures above 5 psi to the soil surface decreased the emergence of sugar beet seedlings. In fact there was some evidence that the optimum pressure was below 5 psi. Hanks and Thorp (1956) found excessive compaction pressures were detrimental to wheat seedling emergence on three soil types. Hudapeth and Jones (195h) found a.hollow rubber-tired l x 10 inch seed press wheel, Spring loaded, running over the seed before they were covered, was beneficial in obtaining good cotton stands. A small harrow like device followed the press wheel. Bowen (1959) reported stands in cotton of 10, 9, 8, 7 plants out of 10 for 0, l, 3, 5 psi compaction pressure, respectively; He further noticed, however, that the moisture drying front had moved closer to the seed in uncompacted soil. Fisher (1952), French (1952), Barmington (1950), all indicated beneficial effects in sugar beet emergence from press wheels packing the soil immediately around and below the seed zone. Correlation was found between firmness of the soil, the soil moisture content in the seed zone, and emergence of the seedlings. Environmental Factors Influencing Germination and Emergence. Hunter and Dexter (1951) found only slightly better emergence was obtained by pre-soaking sugar beet seeds in water prior to planting. Dungan (192k) determined that the rapidity of water absorption was associated.with the rate of germination in corn. Seed corn harvested before complete maturity and stored at 19.2 percent moisture emerged quicker but with less vigor than corn allowed to mature on the stalk or corn stored at 12.6 percent moisture. Corn dried to 6.1 percent germi- nated slower and with less vigor. Hanks and Thorp (1957) reported that the ultimate seedling emerg- ence of wheat, grain sorghum, and soybeans was approximately the same when the soil moisture content was maintained between field capacity and wilting percentage; however,the rate of emergence was related di- rectly to moisture content. Oxygen.suppby 1imited.wheat emergence when pore space was below 16 percent in a silty clay loam and 25 per- cent in a fine sandy loam. Hunter and Erickson (1952) found corn required a kernel moisture of 30.5 percent for germination. Soil moistures which would just permit germination was 10.2 and 12.0 percent in Brookston soil. Andrew (1953) found deep planting of sweet corn followed by temperatures of 50 degrees E,caused.poor stands because of the following: 1. Delayed formation of permanent roots near the coleqptilar node. 2. Required longer first internodes and more time for emer- gence; thusgincreasing the exposure to disease. 3. Modified the balance between the time of permanent root formation and time of decay of the first internode which resulted in earlier loss of the adsorptive capacity of temporary roots. Stiles (19h8) indicated there was a different'uptake of water by seeds of corn, cotton and beans (both the total amount of water ab~ sorbed and rate of absorption) for different species and varities. Movement 25.!3E25.£§ 25 Through 3 Soil. V Rawoucos (1915) studied small cylinders of soil subjected at one end to 0° C.and the other end to 20 - h0° C. The percentage of water transferred from warm to cold increased in all different soil types with a rise in moisture content until a certain water content was reached, then it began to decrease with a further increase in moisture content. This break occurred where inter-particle voids began to fill with water. Jones and Kohnke (1952) evaluated the vapor movement in soils subjected to a temperature gradient of 2° and 32° C. For the three size ranges of sand tested «L5 to .021mm), the rate of water transfer was approximately the same. The volume of unsaturated pore space, not the pore size,appeared to determine where vapor diffusion began. Rickingham (1901;) was one of the first investigators to apply the kinetic theory of the diffusion of gases to soils. He expressed the relation of the diffusion rate to the free pore space by the following equation: D - RE2 where D is the diffusion constant, 5 is the free pore space, and k a proportionality factor or diffusion co- efficient. This expression points out that the rate of diffusion is reduced 75 percent as the free pore space is reduced 50 percent. Penman (1910) suggested a modification to Dickingham‘s equation. Instead of using.ng - S2 Penman suggests.fig - .665 where Do is the co- efficient of diffusion in air. Several other workers, as summarized by Ever (1956), have found similar values for '50? however, the equa- tion has been applied more often to soil aeration rather‘than vapor flow. Rollens, Spangler and Kirkham (195k) checked the applicability of’Hank's diffusion equation for the movement of soil moisture under a.therma1 gradient. They measured diffusion values six times greater than the calculated values. Gurr (1952), also using a diffusion equation similar to Hank's equation, measured vapor flow 3.6 times the calculated values. Taylor, Cavazza and Luigi (195h) developed an equation which 'would characterize the movement of soil moisture in response to temperature gradients. This equation was based on a moisture poten- tial gradient. Measured water vapor flow was 11 times the calculat- ed value. Hanks (1958) characterized water vapor transfer in dry soil through an equation based on vapor pressure differences. Calculated values were low with the ratio of measured.values ‘being about 1.3. calculatedivalues Penman (l9hl) characterized evaporation from fallow soil by using cylinders of soil with some radiant energy applied. Air veloc- -ity, temperature, and humidity were varied; however; nothing was re- corded about clod size though the soils were specified. No attempt was made to apply a diffusion equation but an emperical equation was evolved, E - atl/u where: E is total evaporation in inches of water, n . 3, t is time in days, and a is a.proportionality factor. Hide (195h) made observations on factors influencing the evapor- ation of soil moisture. Three waystmre suggested to reduce water loss due to evaporation. l. Decrease the amount of water which can be transported to the surface before drying occurs. 2. Decrease the temperature of the upper fringe of moist soil. ' 3. Increase the thickness of the static layer of air and thus increase the resistance to vapor diffusion. Evaporation accounted for 70 - 75 percent of the moisture loss (of total precipitation) in dry land areas. Layered trays were periodically weighed; however,only drying curves were plotted. Clod size was not indicated. Kolasew (19h1) suggested ways of suppressing evaporation of soil moisture. Wind tunnel tests were used to compare the loss of soil moisture from a soil of uniform density to one with stratified layers of compact and loose soil. Soil was wetted to field capacity and the weight loss was observed with time. Layering reduced moist- ure loss because (1) compact layers were isolated so capillary move- ment was held to a minimum, (2) compact layers did not conduct vapor because of reduced porosity. The data in Table l were presented. Table 1. Comparisons of Soil Moisture Contents From Normal Fallow and Stratified Tillage Treat- ments. Clod Size'Varied From 0 to 50 cm. Kolasew (l9hl). Treatment Date of Sampling Soil Moisture Cbntent July 15 July 31 % % Normal fallow lh.2 1h.6 Stratified (alternate loose and compacted l7.h 15.5 layers) ' Lemon (1956) was interested in reducing soil moisture loss by evaporation. The following three methods were proposed: 1. Increase the surface barrier to water vapor diffusion by increasing surface roughness (stubble, mulch, etc.). 2. Decrease capillary continuity by tillage or chemical additives. ll 3. Decrease capillary flow and moisture holding capacity of the surface layers by chemical additives of the surfact- ant type. In these tests, the soil moisture loss was characterized by plot- ting grams per hour lost vs. percentage moisture. Methods of characterizing the fling of Soils. Lewis (1921) was the first to indicate some drying systems can be characterized by the difference between the moisture con- centration in the drying body and the equilibrium moisture con- centration. In plotting this difference vs. time on semi-log- arithmic paper, a straight line resulted. Hall and Rodriguez (1958) derived an equation similar to the one by Lewis; however, it was called an'equation for the movement of moisture during the falling rate period of drying as based on Newton's equation of heating or cooling. This equation takes the form of 1é_;:_ - e'KO', where M is moisture content (dry basis), He is the equilibrium moisture, "o is the initial moisture‘content, O isatime, K is a drying constant. This equation was’used to char- acterize grain drying systems. Sherwood (1929) (1932) characterized the rate of drying daring the constant rate phase of drying. Three phases of drying were listed and were shown as grams of water lost per hour vs. percent water (dry basis): 1. Constant rate period - Evaporation takes place at the surface of the wet solid. The rate of drying is limit- ed.by the rate of diffusion of water vapor through the surface air film. 2. Falling rate period I - Generally a linear relation exp ists between rate of drying and.water content. It is characterized by a zone of decreasing wetted surface. The rate does vary with humidity and air velocity. 3. Falling rate period II - Generally the curve is concave upward. Internal diffusion of liquid controls during this period. 'Variations in humidity or air velocity do not affect drying rate. The method of Lewis, discussed above, was found to represent some systems for the second falling rate period. Geaglske and Hougen (1937) reported on the drying of differ- ent sized sands. In the second falling rate period, drying pro- ceeded by diffusion of vapor through a dried portion of solid. The drying rate was not affected by the velocity of the air mov- ing across the top of a drying layer. Drying rate increased with increased coarseness of sand and was linear according to the equation i‘gfi. aw where: w is moisture concentration in grams per gran of dry sand, it is weight of water in grams, 0- is time in hours,'A represents area in sq. cm., and a - 1 0 10.216 L + .67 L is thickness of layer in cm. .Bateman (1939) characterized the drying of wood. Moisture loss was by diffusion and was characterized by a plot of water loss in grams vs.square root of time in minutes. A straight line resulted from this plot. Fisher (1923) characterized the drying of soil by the methp ods of Sherwood for all three phases of drying. The slopes of the curves which resulted from.plotting water loss vs.percent water content were empirically determined. ANALYSIS OF POSSIBLE MEANS OF‘CHARACTERIZING EVAPORATIVE HATER 1058 FROM SOIL. A number of diffusion equations were found in the literature. Many of them were quite scholarly and eventually will provide strong mathematical tools to adequately characterize the diffusion processes. To date, the application of such equations to a soil system has a low accuracy which undoubtedly means all significant variables are not being considered. For example, none of the equap tions take into direct account the influence of clod size or the influence of eddy diffusion which results from simulated wind flow. Fer these reasons the common diffusion equations for soil were not used in this study. Chemical engineers have done much to characterize drying sys- tems; however they have concentrated on the constant rate period of drying. It was reasoned that the moisture lost after a tillage operation would be associated with the second falling rate period. Therefore methods characterizing the falling rate periods would have the most applicability. med on that had been found in the literature, the applica- tion of Newton's equation to diffusion problems as used by Hall and Rodriguez (1958) had the greatest potential for development. THEORETICAL CONSIDERATIONS (F NEWTON'S EQUATION USED AS A DIFHJSION EQUATION. The drying of a layer of soil will contirue until it is in equilibrium with the air above the surface of the soil. In at- tempting to characterize the rate of drying, the major driving force must be determined. In the application of Newton's equa- tion the driving force is asmmed to be moisture concentration. The rate of moisture loss then is proportional to the moisture concentration potential of the soil volume. The fundamental differential equation becomes: %_ '- -K (N - 1%) equation 1 where K is a proportionality constant, 0- is time, it is the moisture content of soil (dry basis) at any time, He is the soil equilibrium moisture content. W separating variables and calling the initial moisture content No, equation 1 becomes: Md" 0 - -Kd6 equation 2 j - 5 , "0 4o Then by integrating: H " Pk . e.” m Equation 3 takes the fundamental form of y - Ae'm which will equation 3 plot as a straight line on semi-logarithmic paper. The value K is the slope of this curve. Different K values will be obtained for various rates of drying. The steeper the slope of the curve the faster is the rate of drying. Hall (1957) made a similar analysis in relation to grain drying. He called the term M - i the moisture content ratio. 0 - Wang and Hall (1958) raise some question as to what extent the vapor diffusivity is actually dependent upon moisture content. Conflicting evidence is cited for hydrophilic substances. An a1- ternate equation is suggested assuming vapor pressure as the main driving force; however, the conclusion is drawn that the two equa- tions are identical when the moisture concentration is directly proportional to the vapor pressure. In order for this to be ex- actly true the temperature must be uniform throughout the medium. EXPERIMENTAL PROCEIIJRE The general procedure will be discussed first, followed by a more detailed procedure where necessary. A Rookston sandy loam soil was sieved into four clod size ranges from 0.0116 inches to 0.335 inches. The soil was rewet to about 17.5 percent moisture (dry basis) and then placed in plastic sample boxes. The samples were placed in an enviromnental-con- trol chamber and subjected to a constant air flow parallel to the surface of the soil. Some samples received radiant energy simulating sunlight. The atmosphere around the samples was conditioned to a standard climatic cycle (2).: hour cycle) some- what typical of the emergence season for corn at the middle of May. Corn was planted at the 1 1/2 - inch level and the time of emergence was noted. Periodic weights were made of the soil samples until emergence had occurred or until about 250 hours had transpired. Moisture loss in the upper three inches of soil only was used in the analysis even though the soil sample was 5 1/2 inches deep. Initial and final soil moistures were determined as well as the equlibrium moistures of the soil for the established air conditions. The moisture contents, M, at each time of weighting were calculated as follows: g! I- ") 100 . H D where U - total grams of water in upper 3 inches of soil, w - equation is grams of water lost at any time in the upper 3 inches of soil, and D - grams dry weight in the upper 3 inches of soil. The calculation of the moisture content ratios followed according to the equation H. Table 2 is a compilation of this series of calculations for each sample. These data were then plotted as a moisture content ratio - time curve, Figures 13 and 111. 17 The slope, K, of the resulting curve was determined as follows: i- this) (K) r equation 5 where Y is the vertical distance and.X is horizontal distance (as in normal slope determination procedures) measured in inches; and f is a scale factor or number which is represented from the origin on the X axisequal to the height of one logarithmic cycle on the Y axis, 5.0 in this case. The resulting slope, K, provided me means of comparing treat- ments. Percentage of the total water lost, P, in the first 2h hours from the upper three inches of soil provided a second means of comparing treatments. Clod size, compaction 0 to 5 psi, and stratification.of soil (fine clods placed and compacted in a 1-inch layer at seed level) were the major variables in samples which were subjected to cross- air-flow drying with and without radiant energy. In addition, two treatments were protected from the cross-air-flow by thin filter paper covers in an effort to provide additional thickness to the surface diffusion barrier and yet provide the standard air condi- tions around the sample. Radiant and no radiant energy were also applied to these samples. The statistical design provided for a two-way classification of clod size and soil treatment. A regression of treatments on clod size was calculated. The mean values of the treatment re- gression lines also provided a basis for comparing treatments. 18 Three sub-samples were observed for each cell of the analysis. The use and no use of radiant energy was treated as two separate analyses. In all, 11111 samples were required, 153 were observed. In addition to the statistical summary, average values for K and P were calculated based on the three sub-samples. These average values are graphically presented as a single moisture content ratio - time curve representing each treatment. The cal- culations required to accomplish this are as follows: W av. ’ (P ay.) (W ay’) ' M av. at 2h hours equation 6 D av. Urn b substitutin 14 av. at 211 hours into M " "2 the re- ’ 9 IT'S—“'74; suiting average moisture content ratio at 211 hours was obtained. The slope of the average curve was found by using K av. and Y - 1.5 inches in equation 5. Screeningfithe Soil. Air dried soil was separated into the following size ranges by the use of Anerican Standard Sieves: Sieve mening Range Sieves used inches 0.335 to 0.263 through 3/8 on #3 0.263 to 0.185 through #3 on #11 0.185 to 0.093 through #11 on #8 0.093 to 0.01:6 through #8 on #16 Figure 1 illustrates the various clod sizes. Clod size will be referred to according to the opening size of the sieve upon which they were retained, that is, 0.263, 0.185, 0.093, 0.0116 inches. 19 The sieves were shaken by hand with a gentle rotary motion to minimize additional clod size reduction." See Figure 2. Netting the Soil. The air dry soil was wetted in lots of about h pounds. Layers about l/h inch thick were sprayed with a small hand sprayer. See Figure 3. .An exact, pre-determined amount of water was added to each lot to bring the soil bulk up to 17.5 percent moisture. The wetted soil was sealed and allow- ed to stand for 2h hours. After this time the container was ro- tated to induce mixing. The soil was then transferred to and sealed in a wide-mouth glass container. No soil was used within h8 hours after wetting. ’ PléciEQLthB Soil ianest Containers. The plastic test con- tainers are shown in Figure h a, b, c. The lower portion of the container was filled with unsieved, wetted soil. The container was tapped in a more or less standard manner to induce some set- tling of the soil. This part of the sample was always left unp compacted. The upper three inches of the container was filled with soil of the various clod sizes. Where no compactive effort was used, the sample was tapped as described before to induce settling. Two fillings were used since 3 corn seeds were placed at the 1 l/2-inch level. Where the sample was subjected to compactive effort, the con- tainer was over-filled at the 1 l/2-inch level, the compactive load was applied (reducing the”level to 1 1/2 inches), 3 seeds were pressed into the soil at this level, the container was re- filled (over-filled again), and the compactive load was again applied. The final level of soil was at the container top or slightly above. In the stratified samples, the sieved clods were placed un- compacted in the 2 - 3 and 0 - 1 inch level. A compacted layer of 0.0h6 inch clods was separately formed into a Fplug" and placed at the l - 2 inch level. The “plug“ was contained by a light waxed cardboard ring, Figure hd, and.pressed twice, once at seedlevel and once on the surface. Seeds were placed in the "plug'I between the two applications of pressure. The ”plug“ was placed in the test container and surrounded with 0.0h6»inch clods. where the test container was divided, as shown in Figures 11b and c, a screen was first used as the bottom. This was later replaced with cotton gauze. A wide rubber band was used to seal the joint between sections of the test container. Determini2g_the Equilibrium Moisture contents. Soil moisture contents were determined on samples of soil which had come into equilibrium with the particular air condition. Equilibrium was determined by observing static weight conditions for the sample over several weighings. Equilibrium moistures were determined both for the radiant energy and no radiant energy condition. 2i 0.263 0.165 0.093 0.01.6 Finn‘s 1. Visual conparison of the clod sizes used. Figure 2. sieves used in the separation of clod Silos. 22 Figure 3. A hand sprmr was used to vet thin lwers of soil. Figure h. (a) The original plastic ssnple conteiner. (1)) Upper 3 in..mer oi‘ soil partitioned in l in. lmrs. (c) Oontsiner used to individually weight the upper 3 ins. and lover depth of semle. (d) cardboard ring used to contein the 1-2 in. lust of .Oii6 in. clods in the strstified swles. (e) Filter paper cover used to cover some suples not receiving rsdisnt energy. A l in. raw netsl ring tom the paper structure. (f) Filter paper cover used to cover some suples receiving radiant energy. 23 SPECIAL EQUIPMENT AND TEST CONDITIONS Climate Control Equipment. ‘Uith the objective of character- izing rates of soil drying as influenced.by soil treatment, by necessity, environmental conditions around the sample must be controlled. The fact that many samples were inyolved and the test work extended over a long period of time demanded that en- vironmental conditions must also be duplicable. Also it was de- sirable to use temperatures and humidities which were reasonable for the field emergence season of corn. Two enwironmental control chambers were used. The first chamber used a room air conditioner for temperature control and a saturated salt bath for humidity stablization. See Figures 5 and 6. llaCl was used as the salt which. according to Hall (1957) theoretically stablizes the relative humidity at about 75.5 per- cent over a temperature range of 50 to thO F. A 30 gallon plas- tic container was filled with the saturated brine and air was circulated from the chamber through the salt bath at the approxi- mate rate of 10 cfm. .As long as the heat input into the chamber was held constant and laboratory relative humidity did not drop below to percent the salt bath.permitted.the duplication of a daily’cycle of relative humidity. For heated.laboratory condi- tions much more capacity in the salt bath would be required to maintain 75.5 percent relative humidity. 2h 0' V M' Figure 5. Exterior view of the a: ewirmtal control ch-ber. Figure 6. Interior view of the rs: environmental control chamber. Saturated salt bath is below the arrow. The second climate control box was a commercialky available chamber on which the desired daily climatic cycle could be pro- grammed. A can type programmer provided a means of controlling the wet- and dry-bulb temperature. Steam was automaticalxy injected into the chamber when the control system called for humidification. Separate refrigerant coils were activated for temperature reduction and dehumidificap tion. The refrigerant coil for dehumidification was designed and placed so that the surface of the coil was well below the dew point; whereas the temperature of the surface of the coil for temperature reduction of the chamber was generally not suf- ficientky low to cause condensation. Rapid air movement was provided over this latter coil. Heating was provided for by electric resistance coils also in the circulating air flow. Figure 7 shows this chamber. This chamber provided an adequate means of control regardless of laboratory air conditions. Examples of the performance charts of both of the envir- onmental-control chambers are presented in Figure 9 of the Appendix. The soil Sample Test_stand. Two test stands were used; eadh.however provided the same function. See Figures 8, 9, and 10. Air was first drawn over the top of the samples which did not receive radiant energy. Then it proceeded across the samples receiving radiant energy after which it was discharged back into the environmental chamber. In this manner no samples were placed in the down stream air after it was slightly heated by the radi- ant lights. A glass top contained the air flow across the samples. A 75 watt radiant light source was placed outside the air stream, and so that the radiant beam was concentrated on one sample. The light source was h inches from the surface of soil which resulted in 170 Btu per hour sq. ft. being received by the soil surface. Radiant energy at the soil surface was measured with a General Electric Radiation meter. The designed air flow across the surface of the sample was to be 6 miles per hour. The'air flow was measured in a zone l/h to l 3/h inches above the soil surface with an.Alnor‘ThermoqAne- mometer and adjusted by dampering the fan outlet. multiple meas- urements at various points across the air stream showed an actual range of air flows from h75 to 550 feet per minute with an over- all average of 53h feet per minute or 6.06 miles per hour. One treatment protected the sample surface from air movement. This treatment was used both in the samples not receiving and re- ceiving radiant energy; however, there was a distinct change in method between these two conditions. Those samples receiving no radiant energy were covered with a filter-paper-surfaced ring as shown in Figures he and 8. The samples receiving radiant energy were protected from air flow with an open top filter paper ring as shown in Figure hf. In this case, the space between the sample Figure 8. The MS} soil test stand with mics in position. A glass plate top and radiant lights have been removed. Air is exhausted from the near end of the stand. Figure 9. The 160 soil ssaple test stated with glass plate and radiant limts in the fmctiening position. Figure 10. nucsicoou supine-sienna. “rises.- hmtedfruthecenterandsqleeceuldbeplscedmboth sidesod‘thefan. surface and the glass surface of the test stand was shielded from air flow; radiant energy, however, was received by the sample soil surface. The Soil. The soil was classed as a Brookston Sandy loam. A mechanical analysis was run according to a procedure developed by Rsuyoucous (1937). The following data are summarized: Sand) 50 M 6h.6% Silt‘ 50) 2“ 17.7% Clay ( 2 a 17.8% Detailed data on this analysis can be found in Table l of the Appendix. No difference in mechanical analysis for the various clod sizes could be observed from these data. The aeration porosity and field capacity for each clod size was determined for the uncompacted condition using the standard core system. Clods were placed into the core rings in a similar manner as in the test container. The cores were allowed to stap bilize at zero tension, weighed after being at 60 cm tension for h8 hours, weighed as saturated, and weighed as dried at 105° C. for 148 hours. The data in Table 2, Appendix, are summarized as follows: Clod size ins. Aeration porosity % 0.263 1411.2 0.185 . h6.0 0.093 h6.l 0.0146 h8.3 30 These data indicate the aeration porosities of the uncompacted samples were quite high and to some extent a function of clod size (1.5% is the approximate difference required for signifi— cance at the 95% level). Yoder (1937) also found that the aer- ation porosity decreased as clod size increased. An estimate of the aeration porosity at the 5 psi level of compaction was determined to be in the order of 37 percent. Pressure implication gquijment. French and Snyder (1958) devised a pneumatic ram mechanism as the means of compacting laboratory samples. This equipment was available and used as one means of compacting the 'soil after a calibration was made for the pressures desired and for the area of the pressure plate. This equipment can be seen in use in Figure 11. A flat pressure plate was used between the soil surface and point of force appli- cation from the ram. A similar method was used in Ohio except a dead weight was used as means of loading the soil. The Standargilimatic cycle. The following weather data were taken from a compilation made by Baten and Eichmier (1951) char- acterizing the period May 20 to June 1 at East Lansing, Michigan. Radiation Av. soil temperature at 1" Av. air temperature above soil Av. relative humidity at 1:30 PM 7:30 PM 7:30 AM Av. wind velocity 1385 Btu/day sq. ft.«e 53° F. 62° F. 55% 65% 78% 6.5 vii/hr. eReference indicates East Lansing is low for this period. Interpolated value of 1700 Btu/day sq. ft. is based on a smooth curve by date and is expected to be more typical of Ohio-Hi chi gan conditions . It was not possible to duplicate these values exactly nor was it demanded since the meaning of average values is questionable. Instead, a reproducable cycle close to the above values was used as follows: Radiation Av. air temperature above soil 2000 Btu/day sq. ft. 66° F. Av. relative humidity, lights on 68% Av. relative humidity, lights off 82% Av. wind velocity (1 in. above soil surface) 6 mi/hr. The cycle of relative humidity is depicted in Figure 12 and represents an overall average humidity cycle for the entire test period of July through September 1959. An actual weekly chart of temperature and relative humidity is sham in Figure 9 of the Appendix. 32 Figure 11. Equipment used to compact the soil. 90 80 70 \N «l='\n O O O 7. Relative Hunldlty N O O M ‘V‘Tj ‘T'r‘ ITII 1'61 I’Vj‘ Trina Flg. 12 - The Relative Hunldlty Portlon of the Standard Cllnatlc Cycle This same standard climatic cycle was reproduced by environ- mental control equipment used in Ohio. A chart of this cycle is also shown in Figure 9 of the Appendix. In an attempt to check the extent to which the standard cli- matic cycle was reproduced, a record was kept of the weight of water per 2h hour period which evaporated from a 14 inch diameter free water surface maintained in the air stream near the samples. The weights were quite reproducable. when a parameter, inches water lost from the free surface per day, was calculated for each sample period, the most extreme range between two samples was from 0.169 to 0.197. The Constant Climatic Condition. With the (hi0 environ- mental control equipment it was possible to hold relatively con- stant climatic conditions within the cabinet. The conditions selected for this series of tests were those equivalent to the daytime conditions of the standard cycle. These were: Dry bulb temperature 66° F. Relative humidity 68% blind velocity (1 in. above soil surface) 6 mi/hr. Radiant energy (where used) hOOO Btu/2h hrs. sq. ft. APPLICATION OF HEWON'S EQUATION T0 SOIL DRYING The possible application of Newton's equation tosoil drying has previously been pointed out. Several examples will be shown to indicate the extent to which the actual data conforms to the theoretical equation. Table 2 setsforth the observed and calculated data for one soil sample. A similar data sheet was compiled for each soil sample. Figures 13 and 1h illustrate the moisture content ratio- time curves plotted from data in or similar to that found in Table 2. After about 2h hours, a drying rate was established which conforms to the straight line relationship expressed by equation 3. Other data.and curves showing the same character- istic are presented in the Appendix as further evidence that the actual drying data conforms well to the relationship after 2h hours of drying. Based on the fact that the actual drying data conforms to»the expected relationship after 2h hours of drying, the use of Newton's equation is justifiable for this period. The fact that the data from the first 2h hours of drying did not conform to the equation caused concern. As previously indicated, the first climatic condition used was the daily stand- ard climatic cycle. The samples were always started in the earky daytime portion of the cycle. Thus, the first environmental con- dition.experienced by the soil sample was the more severe portion of the dairy cycle. This being true, a region of increased slope in the moisture content ratio-time curve could be accounted for in the first ten hours of drying. It was reasoned that if the~ increase slope of the curve was due to an abnormal environmental Table 2 - Observed and.Calculated Data for Upper 3 inches of Soil, Sample Number 23. Clod size - 0.093 inches Uncompacted No radiant energy applied Equilibrium moisture content 2.7% Dry weight - 138.8 grams Hours Total water lost Hater remaining Soil moist. Hoist. content grams grams % ratio 0 0 0 77.1 17.6 1.0 10.5 8.7 11.3 68.1 15.6 0.865 22.3 12.2 15.9 61.9 11.8 0.812 31.5 15.8 20.5 61.3 11.0 0.759 16.8 17.8 23.1 59.3 13.5 0.725 58.0 20.5 26.7 56.6 12.9 0.685 70.5 21.3 27.7 55.8 12.7 0.671 82.3 23.9 31.1 53.2 12.1 0.631 91.3 21.9 32.1 52.2 11.9 0.617 106.5 27.1 35.2 50.0 11.1 0.581 118.3 28.7 37.3 18.1 11.0 0.557 130.5 31.2 10.6 15.9 10.5 0.521 112.3 32.3 12.0 11.8 10.2 0.501 151.5 31.1 11.3 13.0 10.0 0.190 166.0 31.1 11.7 12.7 9.7 0.170 178.0 36.5 17.5 10.6 9.3 0.113 190.0 37.7 19.0 39.1 9.0 0.123 202.0 J 39.5 51.1 37.6 8.6 0.396 211.0 10.1 52.5 36.7 8.1 0.382 226.0 12.3 55.0 31:8 7.9 0.319 250.0 11.6 58.0 32.5 7.1 0.315 Moi stLre Content Rat lo -l=’ \flm’filmbc Moi stLre Content Rat lo .2 37 l { Samp e H 9' Clod Size .09) Ins.“ r__ i13032.1(? grit Energy l I 23 No Conpactlon l H i z O 25 50 75 100 I25. I50 I75 .200 225 H 8 Fl .1 -Sa |e°8rrl Curve 9 5 Stggdard 1:19am Cycle 83 le 50 Clgg Size .093 Ins. No C ctlon Radian Ener KI.§6 RY L ‘L 1 O 25 5O 75 I00 I25 I50 |75 200 225 Fig I1 Sanplgofislm Curve ° Standard Hnatlc Cycle condition, a constant climatic condition should make the early hours of drying conform to the equation. A series of samples were run under the constant climatic conditions, previously de- scribed as being equivalent to the daytime portion of the daily cycle, to check their conformity to the equation. Figures 15 and 16 represent samples dried under the constant climatic con- ditions. It can be seen that the curve during the first 21 hours of drying still does not conform to the theoretical equation. The work of Sherwood (1929) (1932) is again referred to here. The constant rate period was associated with the early drying of a saturated material. This phase did not apply to this study since the soil was not wetted to saturation. The first falling rate period was characterized by a zone of decreasing wetted surface and the second falling rate period by diffusion of water from within the body (or clod). In effect, the drying rate changed between these three phases. This information was appli- . ed in establishing the reason for the change of slope in the moisture content ratio-time curve. In the early hours of the soil drying, water evaporated from the periphery of the clods on or near the surface of the sample. As drying continued, diffusive potentials were established from the clod center to outside and from within the soil body to the surface. Once a stable diffusion system was established Newton's equation characterized the rate of drying. It took from 12 to Moisture Content Ratio i’oistu‘e Content Ratio 39 Sanpi e 0-1 Ciod Size .093 ins. gadia igfigaEnergy .2 J 5’ O O Q 25 50 75 I00 I25 I50 I75 200 225 Hours Fig. i5 Sanpie Dr E! n? Curve Constant nv romental Conditions e 0‘ ilr'm { ”"Sanpie O-iO Ciod Size" .0115 inls. __NoC “NoRad K I .i59 ' I dant Energy Ii 2' 0 25 50 75 I00 i25 I50 I75 200 225 Hours ' Fig. l6 - Sanpie Dr Curve Constant gnfiromenta i Cond it i ons 21 hours to establish a stabilized system. The ratio curves of the samples receiving radiant energy stabilized more rapidly than the non-radiant energy samples. It was apparent that the first 21 hour period of drying would have to be regarded differently than.the later period. msed on the work of Sherwood (1929) (1932), Newton's equation will not characterize the first falling rate period. This must be regarded as an unstable period since temperature changes oc- curred.when the samples were placed in the air stream or under the radiant energy source. Also the sample condition was some- what artificial in nature because the whole depth of soil was of constant moisture content which is not typical of secondary field tillage conditions. It is believed that, for a typical soil moisture condition.in.the field, Newton's equation, re- sulting in a single slope, will characterize the drying rate. meanse of the doubtful application of Newton's equation in, the instability of, and the few points upon which to base a fitted curve in, the first 21.hour period, it was decided to characterize it through the use of a single parameter rather than to completely characterize the drying rate. On this basis, percentage of water lost during the first 21 hours of drying in the upper three inches of soil was used as this parameter. Tito parameters, then, were used to characterize the drying rate: (1) Percentage of water lost during the first 21 hours of drying, P3 and (2) The slope of Newton's drying curve, ii. A definite correlation for any one treatment between P and X will be illustrated later. Once this is done the entire drying period can be estimated by determining the simle parameter P. OiARACi'BRIZATION OF CERTAIN TILLAGE REUITED SOIL TREATMENTS BY THE 5011. DRYING RATE The foregoing methods were used to characterize various soil treatments. For convenience the treatments are presented in Table 3. Table 3 - Description of the Soil Treatments ' Constant climatic conditions. 1. No compaction, sample vibrated, radiant or no radi- ant energy applied. Standard climatic cycle. 2. lio compaction, radiant or no radiant energ applied. 3. Soil pressed at seedlevel and at the surface with 1.2 psi, no radiant emery applied. 1. Soil pressed at seedlevel and at the surface with 5 psi, radiant or no radiant energy applied. 5. Soil stratified, with 0.016 inch clods pressed at 1.2 psi in l - 2 inch level; no radiant energy applied. 6. Same as 5 except 5 psi applied, both radiant and no radiant energy applied. 7. No compaction, sample covered, radiant or no radiant emery applied. In each of the seven treatments all four clod sizes were used. Triplicate sub-samples were observed for each treatment condition. See Figures 5 and 6 of the Appendix. There was question as to when and how the three sub-samples should be combined. An attempt was made to statistically fit a sec- ond degree polynomial to the points of the three sub-sample drying curves, percentage soil moisture by time, according to a multiple regression method given by mten (1915). A trial curve was fit; the degree of fit, however, was not sufficient to retain the straight line relationship in the moisture content ratio - time curve. See Figures 7 and 8 of the Appendix. Rcause of this, the method was abandoned. Instead, the data on each sub-sample were carried through in- dividually to yield a value P, percentage of water lost the first 21 hours, and K, the slope of the moisture content ratio - time curve. This method has already been illustrated. ‘ Three corn seeds were planted in the sub-sample. The time of energ ence of each of the seeds or the condition of the seed at the completion of the test was observed. A summary of these data are presented as Tables 21 and 22 of the Appendix. The time of emergence of the sprout was noted on each of the moisture content ratio - time curves. The points of emergence (or condition of the sprout or seed at the end of the test) for all sub-samples was transfered to one chart. These points were bounded with lines which identified three zones: ( 1) N11 emergence, (2) Partial emergence, and (3) No emergence These zones are represented in Figures 17 and 18. For the environ- mental conditions studied in this experiment, these charts provide a basis for evaluating the moisture content ratio - time curves. LIB .8 I '7 . :. .2 '6 "‘ ...; *‘ ;. g '5 .; E .h --Fuii Emergence ° 4.: 5 O 0 a '5 +1 «"3 Partial Emergence g I 3 '2 )i-None o 50 mo I50 200 Time - Hows IJ - Zones of Emergence for Corn Sprouts N0g Ra iant Energy Appii ed .5 . . - . ~ 0 - '- Fui i Emergence - F 33.1 . a E . 4.; 5 . “'5 Partiai Emergence 8 x 0 d) 5 x-None I +-'.2 ‘ ..‘2 E Idea—MI s x , ‘ 0 50 NO i50 200 i8 - Zones of Emergence for Corn Sprouts fielIgIant Energy Time - Hours 11 1f the curve falls outside the zone where emergence occurred it can be concluded that the soil environmental conditions were not conducive for the proper germination of the seed. Accumulated values of P and K are presented in tabular form for all sub-samples. See Tables 12 to 15 of the Appendix. As a means of visualLy checking these data, the mean value of the three sub-samples for P and K was plotted in a moisture content ratio - time curve. This gave a single curve for each treatment. These curves are shown in Figures 19 through 26 with the zones of emer- gence sketched in. Further, a method of analysis of the accumulated data was used which would characterize the influence of clod size for each treatment as well as permit a comparison between treatments. This method basically required the calculation of the regression line for each treatment; that is, the regression of the slope, K, and the percentage of water lost the first 21 hours, P, on clod size. Not all the variances of the samples were equal because P has percentage units and a check of K values indicated this also. In such a case a transformation is normalry required; however, in this case the meaning of the transformed regression values was unclear. It was most desirable to compare treatments in the actual units of K and P. Based on this fact, the fact that not all K.variances were found different; and since the percentage val- ues fall in a narrow range below 30 with a relatively large base number, it was decided not to transform the values of P and K. Rx and Anderson (1951;) cited examples where rather wide differ- ences in the variance did not greatly affect the final confidence level of the test. A trial plot of K and P values vs.clod size showed that in most cases a straight line regression characterized the data in the range studied. ‘Undoubtedly, however, over a wider range of clod size the relationship would not be maintained. Overall there was no reason to believe a quadratic regression line would contri- bute enough higher accuracy to warrant its use. A high residual was noted only in a few of the 2h regression calculations. Table 16 of the Appendix represents the mean,'5'<; regression slope, b; and the standard error of each. These data along with the arrayed confidence limits at the 95 Percent level are shown in Figures 27 to 30. INTERPRETATION OF RESULTS The Influence of Two Climatic gycles. These comparisons were drawn from columns 1 and 2 in Tables 12, 13, lb, and 15 of the Appendix and Figures 27 to 30. I The two climatic cycles, the standard cycle and the constant climatic condition, were compared primarily to check the drying characteristics of the first 2h.hours. In this regard the two climatic cycles gave essentially the same general shape of drying MoI sttre Content Rat I o MOI sture Content Rat Io b6 .0 — . _ -9—— . I I .8 ——— QQI _ .7 ._ \ I ‘ "‘ c7) e6"———" _______' .5 .II CIod Size .26 Ins. ® .5 -——No Radiant E(ner \ I VIbrated Ohlo ~\ 2 Untreated - Pressed I .2 psI Q) g) Pressed 5 psI \ .2...— StratIerd I .2 Spsl . StratIerd 5p @ 7 Covered * I00 TIme - Hours 200 Hg. ‘9 - ConsoI Idated DryIng Curves .0 09” I l 08—— L l 7 I .5 \\ (a I §\ .I-I— filogagIlzet. .I85 Ins... 0) ”K \ 92 0 an ner 2 Idxitgrated Iomgy L n rea ed .3 Pressed I .2 SpsI @\\® Pressed 5p StratIerdfi 2psI 6 StratIerd 5 ps 7 Covered l .’ I00 TIme - Hours 200 Fig. 20 - ConsoI Idated Drylng Curve Moisture Content Ratio Moi stu‘e Content Ratio h? .0 * .9L__I I I 08—— ! l .7 .6 .5 Ciod Size .095 Ins. No radiant ener Ji"'i Vibrated (Ohio 2 Untreated Pressed i.2 psi .5-—- Pressed 5 psi 4 Stratified 1.2 psi 6 Stratified 5 psi 7 Covered I J I i I 0 50 ‘ i00 I50 200 Time - Hours Fig. 2i - ConsoI Idded Drying Curves .0 * -9—' I I I .8 f ‘. . I '7 @\ "'l e . 0 \Q §~ 0’ (,— a , . \\ ‘ " Ciod Size .0 6 Ins. * , No radiant ner ‘9 lgiii=iisii!ii .h-—-I Vibrated Ohio ' 2 Untreated Pressed I.2 psi Pressed 5 psi .5-— Stratified I.2 psi 1 Stratified 5 psi 7 Covered L 0 ‘ 2 I00 200 Time - Hours Fig. 22 - Consolidated Drying Curves 148 08 A - Ciod Size .26 Ins. - Radian Ener .7“‘— II 5 I Vibrated ECHO)”- 6 §Untreated . 0' ‘_ Pressed5 psi -* -. §Stratified p5 dpsi 3-5— (,1 7Colvered ... ...: NI 4-! S 0 w 03 .—.—-—II b ...s .2 )9 on _. 4 fl , I F0 50 +915 - "(”120 200 Rag.” - ConsoI Idated Drying Curve lant Energy Applied .8 [ Ciod Si e l85 ins Radian Energy 2 . . .7 Vibrated Ohio) -— E Untreated o-6 Pressed 5 psi —I 2'. Stratifi ed 5 psi g5 . 7 Covered __ 4-1 a O a ——!'—“ a" E 2 O 50 I00 i50 00 Time - Hours Fi 21l' Consolidated Drying Curve Raglant Energy Appi lied b9 Ciod Size .095 ins. Radiant Energy lVIbrated ( Io)_ Untreated Pressed 5 psi -————- Stratified 5 psi—— \\\ 7 Covered \. (D 8 7 .6-———-—- 5 h. £3 }\\ Moisture Content Ratio 0 50 I00 I50 200 Tine - Hours 25 - Consolidated Drying Curves Ra iant Energy Applied tr' \n b\ ~a a3 Ciod Size Ins. Radiant Energy "I Vibrated ( io)—— Untreated Pressed 5 psi Stratified p5 psi 7 Covered l 0 50 i00 i50 200 Tine - Hours Fig. 26 - Consolidated Drying Curves iant Energy Applied e \N Moisture Content Ratio SO curve; therefore,the constant climatic condition was of no assistance inIproviding a single slope drying curve. Compare Figures 13, 1h to 15, 16. Where radiant energy was applied during the whole 21; hour period, in the constant climatic condition, a more rapid drying rate would be expected. The experimental evidence varified this. For the two climatic cycles, where no radiant energy was ap- plied, little difference in the overall drying curve was expect- ed. Sherwood (1929) indicated that during the second falling rate period of drying, variations in humidity or air velocity do not affect the drying rate. Therefore, even though the constant climatic condition was more severe, little influence on the re- sulting K value was expected. Also little affect was expected in P even though the initial drying occurred in the first fall- ing rate period of drying since the first 10 - 12 hours of dry- ing was under similar climatic conditions for the two climatic cycles. The data did not bear out the expected results. The values for P (,no compaction treatment and no radiant energy applied) were similar for the two climatic cycles; although there was a tendency for P to be higher for the constant climatic condition. The K values were higher for the standard climatic cycle condition (no compaction and no radiant energy applied). This was not expected and requires an explanation. A change in location of work occurred between these two series of tests. The standard climatic cycle series was run at ,Hichigan.State University and the constant climatic series in (bio. All obvious variables were controlled; however, a check of the dry weights for the samples for the two locations showed some difference. For all samples,the resulting dry sample weights were: (See Tables 17 and 19 of the Appendix). Constant climatic condition, no compactive treatment b70.79 Standard climatic cycle, no compactive treatment bh2.39 Standard climatic cycle, 1.2 psi (pressed) h93.89 These data indicate, and a review of the procedures used varify, that a.more severe vibration process was used in the sample pre- paration for the constant climatic condition.‘ Although these results indicate clod orientation was an ef- fective means of reducing the drying rate it was not an intended variable of the study. For that reason no further conclusions will be drawn other than to point out the effect and to indicate that the experimental error of the uncompacted samples could un- doubtedly be decreased by better controlling the dry weight of sub-samples. The Influence of Compaction, No Radiant Energy Applied. The data for these comparisons are from the standard climatic cycle conditions as found in columns 2, 3 and h Tables 12 and 1h of the Appendix and Figures 27 and 29. K - Slope of Drying Curve 52 I I R‘ .50 __I Vibrated (Ohio) 2 Untreated | 5 Pressed I.2 psi h.Pressed 5 psi | (, 25F5 Stratified I.2 psi ' 6 Stratified 5 psi ’35 7 Covered I , ’,% / ar‘l’a1L."’ .20 -—"‘——“=r"——' ‘9 I // s 5 , .I5 I/ / // ”” on...si 22.7 24gb .IO{ 0 .05 .i0 .I5 .20 25 Ciod Size - ins. I | ' I I I 1 69553—1fi 3 .10 .15 .20 .25 .30 ’ Arrayed Means - K (Lines over treatment numbers denote no difference) I -—-' I I I I .. .5 51—2. I I I 6 .61 .62 .63 .01. ’ Arrayed Regression Slopes Fig. 27 - Regression of K on Ciod Size MRad dlant Energy Applied 53 j I Vibrated (Ohio) 2 Untreated h Pressed 5 psi .6 __6 Stratified 5 psi 7 Covered K - Slope of Drying Curve é: 0 .05 .IO .I5 .20 Ciod Size - ins. al I I .20 .50 .50 .60 Arr: ed Means - K M. II ' L I———-I +-—— I-L_-I ‘IQ .oIo .020 .o 0.0 o .050 Arrayed egression Slopes .28 - Regression of K on Ciod Size Radiant Energy Applied N W 2h hours N O P - Percentage Water Lost First \J'i O 2 Untreated Pressed 5 Stratified Stratified 7 Covered I Vibrated (Ohio) g Pressedl .2 psi 4CD 5 O .05 .IO .I5 .20 .25 Ciod Size - inches- [ l ‘I I I § 5 2331' l l 0 65 Ar6gyed Meangs- P Eb . (Lines over treatment numbers denote no difference) , i , I z I m I II 0 .5 110 1.5 2.0 2.5 I Arrayed Regression Slope Fig. 2? - Regression of P on Ciod Size. a N0 rad nt energy applied. \N U1 \N O N U"! 20 P - Percentage Water Lost First 2h hrs. es 1:0 fiOS Arrayed Regression S opes I . I Vibrated (Ohio) I 2Untreated ® h Pressed 5 psi ~—-6 Stratified 5 psi 7 Covered \ Is— 2 /.®. I/ / |® / |® f / I 0 I //"’/;/ .z’ ___ o .05 .IO .I5 .20 .25 Ciod Size - ins. I --—-—' I I 6 < li—gfif 1 l 15 20 25 30 35 Arrayed Means - P I I I I I I (HI ‘1 2| 0 I 2.0 mg. 50 - Regression of P on Ciod Size iant Energy Appi lied The mean value (all clod sizes considered) for the percentage water lost, P, the first 2h hours was similar for all pressed treatments. There was no difference between the regression slopes for P. From the same data, the mean K values for the pressed and no treatment condition were different; however, no significant dif- ference was apparent between 1.2 and 5 psi although a trend exist- ed of a decreasing K with.pressure. Only the regression slopes, of K on clod size, of 0 and 5 psi were different. Several conclusions were drawn from these statements: 1. The application of pressure had little or no affect on reducing the percentage of water lost the first 2h hours. Also the influence of clod size was similar for all pressure treat- ments. It was observed and these data verify that a more com- plete capillary system was set up as pressure was applied. The untreated samples dried in a pronounced change of color wave which was not true in the compacted samples. The moisture which was brought to the soil surface of the pressed samples permitted drying rates equal to the drying rate of the untreated samples which dried because of high vapor diffusion rates through the soil voids. 2. The application of pressure had an affect on K; although any difference between 1.2 and 5 psi was slight and uncertain. Also as pressure was applied,the effect of clod size on K tended to reduce even though only the two extreme conditions were signi- cantly different. These results represented those expected except for the lack of effect between 1.2 and 5 psi. A smooth plate was used as a means of distributing force over the top of the soil in the pressed samples. The surface of the soil which was subjected to the plate was greatly deformed; thereby, the void opening was reduced at the surface. It was concluded.that the major barrier for diffusion for the later period of drying was a relatively ”closed" surface and it was not necessary to fully consolidate the volume of soil. Also, a more complete capillary system which transmitted water to the soil surface was establishp ed, and functioned over a longer period of time at higher pres- sures. This tended to compensate for a slightly lower vapor dif- fusion rate. 3. At no time did pressure on.the 0.263 inch clod samples give an equal effect in reducing the drying rate, either K.or P, that a decrease in clod size to 0.0h6 inches gave. The data on emergence showed the fine clod samples did not require an application of pressure to bring the treatment into the emerging zone; whereas,the large clod samples, pressure did improve the slope, K, enough to bring the curve into or near to the emerging zone. ‘At the 5 psi pressure level, evidence of de- layed emergence was observed even though the slope, K, caused the moisture content ratio - time curve to fall into the emerging zone. As the soil dried, after being subjected to the 5 psi pressure treatment, it offered considerable resistance to the JV emerging sprout. Several of the sprouts were severely curled as a result of attempting to emerge through the compacted soil layer. Not only was emergence delayed but in extreme cases the resistance was great enough to entirely prevent emergence. A summary of those sprouts which were curled is presented in Tables 21 and 22 of the Appendix. The 5 psi pressure treatment was of doubtful overall benefit, under the conditions of this experiment, because of the additional resistance to sprout penetration. Influence of Ciod Size Stratification, No Radiant Energy Applied. The data of these comparisons, for the standard climate cycle, are found in columns 2, 5, 6 of Tables 12 and lb of the Appendix and is represented in Figures 27 and 29. The mean P value (all clod sizes considered) for the per- centage of water lost during the first 2h hours for both strati- fied treatments was different from the no treatment condition. In fact the two stratified treatments were also different. Studyn ing the regression slopes for P showed no difference. From the same data the mean K.values for the stratified treatment and no treatment were significantly different; however; no significant difference was apparent between pressures in the compressed layer, although a trend existed of a decreasing K with additional pres- sure in the compressed layer. The regression slope, of.K on clod size, of the no treatment condition was different from the two stratified treatments. In comparison of the stratified treatments with the pressed treatments there was a significant difference between the mean P values. The following conclusions were based on the above data: 1. Both stratified treatments were effective in reducing the percentage of water lost during the first 2h hours of drying over the pressed and the no treatment conditions. Since the small clods, as placed at the l - 2 inch level in the stratified treat- ments, were an additional barrier to diffusion some water must be lost from below the 1 - inch level the first 2h hours in order to make the above fact true. .A check of this point revealed from 2 to 3 percent less of the total water in.the sample was lost dur- ing the first 2h.hours in the l - 3 inch level from the stratified samples as compared with the pressed or no treatment condition. The influence of clod size on P was similar for the two stratified treatments. 2. The stratified treatments had a similar effect on K as did the pressed treatments over the no treatment condition. In fact no difference was detected between the two pressed treatments and two stratified treatments. The effect of clod size on K tended to reduce even though only the extreme conditions were significantly different. i The fact that the stratified treatments were at least as de- sirable, and in some respects were more desirable from a rate of soil drying standpoint, has important ramifications. No detri- mental effects were observed on emergence characteristics from the compressed layer. Also having an uncompacted surface exp posed should provide more stability to rain drop impact and re- sistance to soil crusting conditions. The fine clod size, compacted layer provided a.barrier for vapor diffusion and intimate soil-to-seed contact without possible damaging effects of heavy applications of pressure to the entire soil‘volume. Influence of vaering the Soil, N3_Radiant EnergygApplied. The data for this comparison for the standard climatic cycle are found in columns 2 and 7 of Tables 12 and lb of the Appendix and Figures 27 and 29. As indicated before, this treatment had its value in showing the effect of increasing the thickness of the surface film barrier to diffusion and removing the possibility of eddy diffusion in the surface layer of soil. In this case,a.filter paper cover was placed one inch above the soil surface. This treatment was quite unique when comparing it to others. The percentage of water, P, lost during the first 2h hours was significantly lower than all others and P was affected by clod size to a much lesser extent. The value of K also was quite low and independent of clod size since the filter paper apparently offered a greater surface barrier to diffusion than any of the clod size surfaces. 01. In a practical sense, this treatment offers some reason as to why mulches are effective and brings up the possibility of pro- viding relatively stagnet layers of air on top of a soil which would not inhibit the emergence of a seedling. w placing a 1 inch layer of 0.263 inch or larger clods on the surface of the soil a thick, relatively stagnet air layer would be provided; yet the plant could develop as a seedling while emerging through this layer. Lower moisture losses would result; and the plant could be planted at a relatively shallow depth. The Influence of Radiant Energy. The data for these compar- isons are from Tables 13 and 15 of the Appendix and Figures 28 and 30. The application of radiant energy to the soil surface was a more realistic environment in that sunlight intensity was simula- ted. Due to the limited capacity of the environmental equipment to remove heat supplied within the chamber, fewer sample condi- tions were run. The constant climatic condition used in part of the work done in Ohio, required the use of radiant energy 2h hours per day rather than a cyclic application used in the remainder of the tests. This series of tests was run primarily to check the early portion of the moisture content ratio - time curve. On many of the 0.263 inch clod treatments, where the light intensity was high, the plant no longer emerged as a sprout but 62 as a leafed out seedling. Although this characteristic has ques- tionable desirability it provided the basis for the preceding statement that plants may develop as a seedling through a large clod soil layer. When considering the presSure and stratified treatments re- ceiving radiant energy, the effects were quite similar to those 'already discussed. The stratified treatment was low in water lost the first 2L hours, in the value of K, and was affected by clod size to a lesser extent. The minimum K value, which repre- sents the slowest rate of drying, occurred with the 0.0h6 inch clods pressed at 5 psi. This was not apparent in the samples receiving no radiant energy but is reasonable since 0.0h6 strati- fied treatment had less compacted volume than the pressed samples. In the covered treatment of this series, the radiant energy was applied directly to the surface of the soil; howeven.air flow was prevented from passing over the surface of the soil by the vertical ring of filter paper. This is a rather artificial.con- dition; however5information was gained. The heat penetration in- to these samples was different than those receiving air movement across the surface. The effect of this can be seen in Figure 28 in that the K value for the covered treatment was higher in the small clod sample as compared with the same no treatment K. In both cases the influence of eddy currents in.the surface layer of soil was minimized. In the 0.263 indh clod samples the effect of removing the eddy currents in the surface layer was greater than the effect of increased heat penetration; thus,the net effect was a reduction in the R value over the no treatment condition. In all the samples which received radiant energy, the mois- ture in the three-inch layer moved in two directions; through the surface of the soil and to deeper depths of soil. The data taken in Ohio with constant radiation provided the most complete infor- mation regarding the two directions of water movement. See Table h. From this information, 1/3 to 1/h of the total water lost after 170 hours had moved downward out of the 0 - 3 inch.layer. .Also as clod size decreased the percentage of water 10st which moved down- ward increased. The quantity of water which moved downward was al- most constant for all clod sizes. This suggests the downward move- ment was essentially independent of clod size whereas the movement ”out of the surface was not. Table h - Direction of Water Movement in the Samples Which Received Radiant Energy. (After 170 Hours of Drying). 0d Size The part of the total water, The part of the water 105 inches originally in the upper 3 ins. from the upper 3\ins. of soil.lost -- soil, lost -- Out surface To deeper depths To deeper de ths grms. grms. % 0.263 53.8 62.h 19.1 22.1 26.0 0.187 h7.5 57.h_ 20.8 25.2 30.6 0.093 h2.l 51.8 19.9 2h.5 32.1 0.0h6 38.9 50.h 19.5 25.2 33.h The Relationship of P and K to_lnches of Water Lost. A more common method of indicating evaporation rate in soil is inches of water 10st per unit time. A general method to relate the two para; meters, P and K, to inches of water lost, is presented in Figures 31, 32, and 33. Two rate periods are proposed in these charts, the first 2h hours and the period from 2h hours to 2&0 hours. Through the use of these charts any moisture content ratio — time curve can be transformed into inches of water lost per day. The relationship of P to inches of water lost during the first 2h.hours required the consideration of sample dry weight. The quantity of water present in the three-inch sample depth was a function of the quantity of soil. Compactive treatments resulted in a higher quantity of soil, and therefore water, being placed in the sample. Dry weights of all samples are recorded in Tables 17 and 19 of the Appendix. The relationship of K to inches of water lost was a function of the moisture content ratio at 2h hours as well as the dry weight of the sample. As P increased,the amount of water which remained in the sample after 2h.hours decreased, then for a common K the quantity of water lost after 2h0 hours was less. Separate curves were proposed for the radiant energy and no radiant energy environ- mental conditions since the equilibrium moisture contents were different. In order to develop these generalized relationships a common original soil moisture, 17.9%, was assumed. Knowing the original 65 53 5mg .6 8:8. 35 82835: cm :8 n. 523 3 268.33 ind: >8 ..on $3 Loam: +0 mecca. com. 8.. o gmcm oomx wEmum omm+ mega oomo 8.2m 8:. \ 8.8m cone \\ «:92; To 0.9.8 N. 8. 32 .3th 23.0mm oz 3,3 the, to 8:8. BE 3:835: em :8 v. 523 mm 388323 .. mm .m: 950: o 0p _ 628; 58 m to“. .95 ”mm 3% 333 8:8. 66 no. no. mo. .o.s\N mEMLm 0mm... h. 955 com. 955 on: . 2903 P5 288 \. m. \ \ + o m. \ \ (2% VA 3 O. c. " “NH 112 19 01193 lualuoo 91‘1le 67 .nm__aa< smaocm scm_nmm .omoo tum; .5 $65 35 “.8838: mm :8 v. 623 am 35.8223 .. R .9“. mega: 0 oh .83.. s8 m co“. s8 fig 5% tag 8:8. go. no. mo. 8.2m omm+ mega coma 25.6 03. “8.03 to £93m h o smou 112 w onea 1091000 amissow ‘0. 0°. weight of water in the sample the water remaining after 2h hours was directly calculated. The weight of water lost was related to inches of water. To relate K to inches of water lost, a moisture content ratio at 2h hours was assumed and transformed into soil moisture percentage by the equation £3—E—gg. The final moisture content was similarly calculated from a moisture content ratio at 2h0 hours found by plotting the curve for a given K according to equation 3. From the two moisture contents and the dry sample weight the quantity of moisture loss was calculated. The Influence of Soil Type. The soil used in this experi- ment was a Brookston sandy loam. The extent to which Newton's equation will characterize soils high in clay content is not known. The Influence of Soil Treatment on Emergence. Under the cli- matic conditions used in this experiment, when soil was placed in the sample container and left untreated, (uncompacted, not vibra- ted, stratified or covered) complete emergence occurred only for the 0.093 and 0.0h6 inch clod sizes when no radiant energy was applied. When the samples were subjected to radiant energy, only 70% emergence occurred for the smallest clod size. All others, larger clod sizes, were less complete in emergence or there was no emergence at all. There was a trend toward a slower rate of emergence as the soil drying rate increased. This can be seen from the Ohio data: Sprouts emerged from the 0.0h6 inch clod sample receiving no radi- ant energy in 193 hours; from the 0.093 samples in 20h hours; and sprouts were quite wilty and not through the soil in the 0.185 inch clod size at 2&0 hours when the sample was destroyed. DISCUSSION OF RESULTS Both the climatic conditions used in this experiment were severe; however, the standard climatic cycle was reasonable for emergence seasons with little or no rainfall. It is believed that the characterization of the rate of drying and the resulting emergence was a reasonable evaluation from a climatic standpoint as well as one controlled. The clod sizes used in the test were not typical of those from normal tillage operations since rather narrow clod size ranges were used. These ranges not only were a simplifying meas- ure used for experimental purposes, but also represented more nearly what was beleived to be those conditions resulting from minimum tillage operations. Overall, however, the narrow clod size ranges contributed to more severe test conditions in that small clods or particles which normally fill voids had been removed. Even though the overall test conditions were to some extent extreme, comparative results were obtained. Results indicated that as clod size increased and compactive effort decreased in a seedbed the rate of soil drying increased and total emergence was less complete (unless water was resupplied by rainfall during the emergence season). There was some evidence that vibration of the seedbed would also reduce the rate of soil drying. As indicated before, however, no compactive or stratified treatment which used the 0.263 inch clods as the primary soil was as effective in re- ducing the drying rate as a reduction in clod size. Even though the above statement is made, it is not reasonable to recommend finely prepared seedbeds based on the yield advantages of “minimum“ seedbeds as reported by many workers and the increased danger of soil crusting as the soil treatment is subjected to rain- fall. The results emphasize that a difference exists between "seed- bed” and "rootbed" and give rise to increased enthusiasm for strip preparations which can give more optimum soil conditions for both. Such a treatment must provide fine clods in a layer around the seed. Further investigation of soil stratification is Justifiable. As previously indicated, very fine clods are not desirable on the surface of the soil from the standpoint of crusting; however, a fine compact layer at seedplevel should contribute to a desirable soil-to-seed contact and also provide a diffusion barrier. The fine layer covered by large clods on the surface would reduce the risk of crusting. If it were found acceptable to permit the seedling to photosynthesize while proceeding through the large clod layer, the depth of planting can be increased at no expense to the crop and (L another effective diffusion barrier would be provided on the sur- face. The assumption is made here that the entire soil area would be subjected to the stratified treatment. From a physical view- point this seems justifiable; however, if the treatment could be restricted to a strip without horizontal diffusion movement of water being extremely significant, the treatment would have greater practical potentialities. Stratification of the soil in the seedbed requires clod sep- aration. Such a concept has several interesting ramifications. The aeration porosities resulting in these samples were quite high even in the compacted treatments. As the clod size range becomes narrow, material which normally fills the voids is removed. Re- moval of fine clods or particles provides an effective method of increasing aeration porosity and increasing its expected longevity because the material which contributes to crusting has been removed. (In concrete,a mixture of aggregate sizes is used to permit “keying" together thus forming a dense mixture). A layer of soil lifted and screened would permit placing the fine clods and individual parti- cxles of soil in a lower layer where their effects should be less damaging. Successive layers could be placed as is desirable. A seedbed profile can be built up from existing clod sizes rather than subjecting the soil to a continual mechanical clod size reduction process. 72 USE OF NEUTOH'S mUATIOII FOR THE PREDICTION OF DRYING RATES Newton's equation as used in this work can be and was used to some extent as a predictive equation. For any one treatment, a cor- relation existed between P and K which meant that for any P a defi- nite K was determined. Such a curve is presented in Figure 3h. This correlative curve, as proposed, takes into account clod size, application or no application of radiant energy, and may be inde- pendent of soil type. In order to predict the entire drying curve and judge whether emergence would occur,’only P need be determined once the correlative curve is known. Only one correlative curve is proposed since the degree to which this generalization is valid is unknown at the present time. POWER OF THE STATISTICAL TEST Concern was expressed at the start of the experiment as to the number of sub-samples which would be required to measure physical differences between treatments. Considerable time and effort was required for each sample and to go beyond three sub-samples was impractical. The intent was not to show statistical significance of any difference but to have an adequate measure of physical dif- ference which might be of practical importance. Any attempt to decide the difference which is of practical importance is largely a matter of judgment. {J In this experiment since the emergence of corn was desired, the emergence consolidation shown in Figures 17 and 18 offered the best criterian. The difference required to show practical impor- tance must be much narrower than the zone where emergence occurred. Weaver (1960) stated that about four standard deviations will equal the difference that can be discovered 95 percent of the time with any test. Applying this information to data extracted from Table l6 of the Appendix, the following differences could be de- tected 95 percent of the time: An overall estimate of 5‘; (K) - 0.005 and 5‘; (P) - 0.5 Variation in'x (K) then - 0.02 and x (P) - 2.0% Assuming an intermediate treatment condition similar to the 1.2 psi pressed treatment, 0.263 inch clod size with no radiant energy ap- plied, the range between the two moisture content ratio - time curves shown in Figure 35 represents the difference which could be detected 95 percent of the time with the variation experienced in the data of the experiment. Assuming that the sampling of P and K were simultaneously inaccurate, the range proposed in Figure 35 represents the difference required between treatments before there is assurance a true difference exists based on the 95 Percent con- fidence level. From a practical viewpoint, a decision must be made whether the treatments differ in their ability to permit full emergence. Since the emergence zone was quite large as campared to the range 7h -Untreated - no radiant energy applied ©Untreated - radiant energy applied to o Q Ir 0 K - slope of drying curve '8 lo 20 50 to P - Percent e water lost durl the fl rst afighours. ng Fig. 3h - Correlatlve curve P vs K for the one soil studied. 75 required for a true difference, it was concluded that the experi- ment had the necessary power to judge treatments within the emer- gence zone, therefore the experiment had the necessary power to measure practical differences between treatments. SUGGESTIONS CONCERNING FUTURE WORK A better method of placing the soil in the sample container would be helpful in reducing the experimental error. This would involve a standard mechanical process of dropping the soil into the sample container or of vibrating the sample. Overall, it is believed that methods similar to those used in this experiment must be used in future tillage work. Many field experiments have yielded good information; however, this information can almost never lead to an adequate mathematical characterization which will also be applicable for predictive purposes. Instead, careful laboratory study with adequate con- trol of variables is required. CONCLUSIONS (1) Newton's equation, 3.4.4113 - e’KG, plotted in the form of the moisture content rations tigi curve with slope K, provided an adequate means for characterizing the rate of soil drying after a stable diffusion system was established (normally within 2h hours after the sample was prepared.) A parameter P, percentage of water Moi stu‘e Content Rat lo 76 I If] l Assumtlons: ~90 G Water, :lh G Dry m o 25 50 W5 iOO l25 l50 l75 200 225 Time - Hours 55 - illustration of the Difference That Can Be gDiscovered 95% of the Time 77 lost during the first 2h.hour period, effectively characterized this initial drying period. (2) This method of characterizing the soil drying rate provid- ed an effective basis for comparing the influence of various soil treatments: alteration of clod size, degree of compaction, and loca- tion of various clod sizes in the tilled profile. (3) As clod size increased and compactive effort decreased, the overall rate of soil drying increased and total emergence of the corn was less complete. ‘ (h) The application of connective pressure to the soil had little or no effect on reducing P. ,(S) The application of compactive pressure tended to reduce the ' slope, K, of the moisture content ratio - time curve. A slight and uncertain difference was found between the 1.2 and 5 psi pressure tre atments . (6) The effect of clod size on K tended to reduce as the appli- cation of pressure was increased. (7) Under the climatic conditions of the experiment when no radiant energy was applied to the soil surface, complete emergence was gained in the fine clod seedbed (0.0L6 inches in diameter) with- out the application of compactive pressure. (8) The 5 psi pressure treatment delayed or inhibited emergence because a dense, dried layer was formed above the seed. Initial soil moisture content was relatively high, however. (9) Large differences were observed in K between 0 and 1.2 psi pressure treatments while small differences were found between 1.2 and 5 psi. This suggested that low compactive pressures can effec— tively reduce the drying rate. A slight vibration of the sample also reduced drying rates. (10) The stratified treatments, 0.0h6 inch clods placed and compacted in the l - 2 inch leveL-materially reduced the value of K and P over the no treatment condition. (11) The fine, compacted clod layer in the stratified treatment provided a layer of soil highly resistant to the diffusion of water vapor, yet capillary movement was broken. (12) No compacted or stratified treatment, which used the 0.263 inch clods as the primary soil, was as effective in reducing the dry- ing rate as a reduction in clod size to 0.0h6 inches. Even so, based on the possibility of soil crusting when an.entire seedbed is pre- pared of fine clods, a stratified treatment appears to be a desirable compromise treatment. (13) The lowest drying rate occurred.when the 0.0h6 inch clods were subjected to a compactive pressure treatment. (1h) Completely covering the surface of the sample with a water permeable material (the resistance of the material to vapor diffusion was inherently higher than the fine clod size) erased any effect of clod size on the rate of drying and effectively reduced the overall drying rate. - . (15) The application of radiant energy to the surface of the soil increased the rate of drying. The heat applied on the soil surface induced 1/3 to l/h of the water lost from the upper 3 inches of soil to move downward to deeper depths. The quantity of downward water movement was independent of clod size whereas the water lost from the soil surface was dependent on clod size.‘ (16) For the soil and the climatic conditions used in this ex-. periment, a definite relationship was found between P and K for any one degree of compaction. (17) Once the relationship is hnown between P and K, possibly the entire drying curve, and thus the water loss characteristics of the treatment, can be predicted by determining P. (18) The control of temperature, humidity, wind flow and radi- ant energy on or around the sample as practiced in this eXperiment provided an effective basis by which multiple samples and soil treat- ments could be compared under common environmental conditions. (19) Three sub-samples for each treatment allowed sufficient precision to measure practical differences.‘ 80 APPENDIX C Orr-.." l. 81 0.43 54..— 04...” .>< 0.6 «.02 «.3 0.00 20 4.«« 2.«0 0.2 «.3 ««0. 0 0.«0 4.2 0.2 «.00 2.« 200 «.00 0.2 0.5 ««0. « 0.6 «.3 «.02 0.00 «.« «.mm «.00 «.02 «.0: 30. a . 0.00 «.02 2.02 «.«0 0.« 04.0 «.00 0.2 «.00 000. 0 «.«0 0.2 5.: «.00 0.« «.00 0.«0 0.2 0.3 «02 0 2.00 0.02 «.2 0.00 1« «.«n «.00 «.2 0.5 002 2 33 + u a .030 a 30 u 233 .05 a: :33 0:308 Zoo 05» 0:» 300.800 .98... 050an 0300.38 .93... magnum 5 «sum .oa .30 m ..4 do; ..a no :5 008 30.50 3...: :8 .3 finance 3355»: 2 208 Table 2 - Aeration Porosity of Soil 82 Ciod size, ins. Sample .263 .185 .093 .0146 f % % Z l 1i14.8 16.0 h6.h h8.3 2 mi.8 145.7 110.0 NJ 3 113.0 145.1: h6.14 h3.3 14 10.0 146.3 h6.5 118.1 5 16.1; 116.7 115.2 16.3 Av. “1.2 116.0 h6.1 148.3 Analysis of variance SS (11' )6 F ktween means hl.39 3 13.80 23.79:“ 9028 16 C 58 Total 50. 67 19 Within groups Arrayed means I 1% level lane 116.0 ’IET 118.3 Difference for significance “1.5% Estimate of aeration porosity at the 5 psi pressure condition was determined to hem”; Table 3. Ciod size .093 inches Unconpacted No radiant energy applied 83 Sample covered Equilibrium moisture content 2.7% Observed.and Calculated Data for Upper 3 inches of soil, sample number 19. Hours Total water lost Hater remaining Soil Mbist. Heist. Content grams % grams % Ratio 0 0 0 78.8 17.6 1.0 2.0 .8 1.1 73.6 17.8 .987 6.5 2.5 3.h 71.9 17.0 .960 12.0 h.o 5.8 70.8 16.7 .980 23.5 5.9 7.9 68.5 16.2 .906 35.5 8.0 10.7 66.8 15.7 .873 h7.8 9.8 13.1 68.6 15.3 .853 60.0 11.8 15.3 63.0 18.9 .819 71.8 13.1 ' 17.6 61.3 lho5 ‘.792 83.5 11.8 19.8 59.6 18.1 .765 95.5 15.9 21.3 58.5 13.8 .785 107.5 17.3 23.2 57.1 13.5 .725 119.5 18.3 28.5 56.1 13.3 .711 132.0 19.8 26.5 5h.6 12.9 .685 1h3.3 21.6 28.9 52.8 12.5 .658 155.5 22.0 29.5 52.8 12.h .651 167.3 22.9 30.7 51.5 12.2 .638 179.5 23.9 32.0 50.5 11.9 .618 191.8 2h.8 33.2 h9.6 11.? .60h 215.5 26.3 35.2 h8.1 ll.h .58b 239.8 g7.2 36.1 87.2 11.2 .571 Table 11. Clod size .093 ‘ Compacted at 5 psi 81 Sample mmber 21 No radiant energy applied Equilibrium moisture content 2.7% Observed and Calculated Data for Upper 3 inches of Soil Hours {Iotal water lost Hater remaining Soil mist. Moist. Content grams grams S Ratio 0 0 0 96.5 17.6 1.0 2.0 6.9 7.2 89.6 16.3 .913 5.0 7.0 7.3 89.5 16.3 .913 7.0 8.1 8.1 88.1 16.1 .900 10.5 10.7 11.1 85.8 15.6 .865 22.3 11.3 11.9 82.2 15.0 .826 31.5 19.6 20.1 76.9 11.0 .759 16.3 21.6 22.5 71.9 13.7 .739 58.5 25.0 26.0 71.5 13.0 .681 70.0 26.6 27.7 69.9 12.7 .671 82.0 28.9 30.0 67.6 12.3 .615 91.0 29.9 31.1 66.6 12.1 .631 106.0 33.2 31.5 63.3 11.5 .591 118.0 31.0 35.1 62.5 11.1 .581 130.0 36.0 37.1 60.5 11.0 .557 112.0 37.9 39.1 58.6 10.7 .536 151.0 38.3 39.8 58.2 10.6 .530 178.3 11.7 13.1 51.8 10.0 .190 202.0 11.1 15.9 52.1 9.5 .156 226.0 16.1 18.3 50.1 9.1 .130 250.0 18.3 50.2 18.2 8.8 .110 85. Table 5 - Observed and Calculated Data for Upper 3 inches of Soil Sample number 30. 0104 size 0.093 Radiant energy applied 00000000020 Equilibrium moisture content 111 2.7, PM 1.7% Hours . Igz‘watefgag Hatergreafiining Soil :01 st. Moi stfiafigtent o 0 o 83.3 17.5 1.0 2.3 9.2 11.0 71.1 15.6 .880 8.0 16.0 19.2 67.3 11.1 .785 11.0 19.8 23.8 63.5 13.3 .735 23.0 21.0 ‘25.2 62.3 13.1 .703 35.0 29.3 35.2 51.0 11.3 .607 17.0 29.7 35.6 53.6 11.3 ..581 59.0 37.3 11.8 16.0 9.7 .506 71.0 37.1 11.5 16.2 9.7 .172 83.0 12.5 51.0 10.8 8.6 .136 95.0 12.6 51.1 10.7 8.5 .392 107.3 18.1 57.1 31.9 7.3 .351 119.0 18.3 56.8 35.0 7.1 .318 131.0 53.1 63.0 30.2 6.3 .291. 113.0 53.0, 61.8 30.3 6.1 .250 155.0 56.3 66.2 27.0 5.7 .253 167.3 55.5 61.9 27.8 5.8 .210 179.0 58.8 69.6 21.5 5.1 .215 191.0 58.7 67.7 21.6 5.2 .169 227.0 62.8 73.6 20.5 1.3 .165 263.3 61.6 73.9 21.7 1.6 .128 Appendix 86 Table 6 - Observed and Calculated Data for Upper 3 inches of Soil applied s Sample Number 63 Ciod size at 1-0 and 2-3 inch level 0.093 inches uncompacted Ciod size at 1-2 inch level 0.0116 inches compacted at 5 psi Radiant enerw Equilibrium moi e content-AM 2.7, PM 1.7% Hours Total water 10st Hater remaining, Soil Moist. Moist. Content grams grams 5 Ratio 0 0 0 82.6 17.2 1.0 3.3 10.0 12.1 72.6 15.2 .871 6.3 11.1 17.1 68.5 11.3 .813 10.3 17.3 20.9 65.3 13.7 .771 22.5 19.0 23.0 63.6 13.3 .731 31.0 20.1 31.9 56.2 11.7 .615 16.0 26.1 31.9 56.2 '11.7 .621 58.0 32.3 39.1 50.3 10.5 .568 70.0 32.1 39.2 50.2 10.5 .538 81.8 37.7 115.6 11.9 9.1 .1197 91.3 37.2 15.0 15.1 9.5 .169 106.0 11.8 50.6 10.8 8.5 .139 118.0 11.8 50.6 10.8 8.5 .100 130.0 16.2 55.9 36.1 7.6 .381 112.8 15.5 55.1 37.1 7.7 .315 151.0 18.2 58.3 31.1 7.2 .355 166.3 17.8 57.8 31.8 7.3 .317 190.3 19.1 59.1 33.5 7.0 .297 202.0 52.5 63.5 30.1 6.3 .297 226.0 55.6 67.3 27.0 5.6 .252 238.0 53.7 65.0 28.9 6.0 .228 f‘rrUOI‘OJO 87 Table 7 - Observed and.Calculated Data.f0r‘Upper 3 inches of Soil Sample Number 65 Cnod.size at 0-1 and 2-3 inch level 0.093 inches uncompacted Ciod size at 1-2 inch level 0.016 inches compacted at 5 psi. H0 radiant energy applied Equilibrium moisture content 2.6% Hours Wflater remaining, 8011 Moist. Hoist. Content grams % grams 5 Ratio 0 0 81.1 17.2 1.0 5.8 6.6 8.1 71.5 15.8 .903 9.8 9.0 11.1 72.1 15.3 .869 22.3 11.9 1 11.6 69.2 11.7 .828 31.0 15.1 18.6 66.0 11.0 .779 16.0 16.2 19.9 61.9 13.8 .766 58.0 19.1 23.5 62.0 13.2 .721 70.3 20.2 21.8 60.9 12.9 .703 82.3 22.2 27.3 58.9 12.5 .676 91.3 23.3 28.6 57.8 12.3 .662 118.3 21.5 30.1 56.6 12.0 .611 130.0 27.6 33.9 53.5 11.1 .600 112.0 28.0 31.1 53.1 11.3 .593 151.0 29.7 36.5 51.1 10.9 .566 166.0 31.0 38.1 50.1 10.6 .515 178.0 31.9 39.2 19.2 10.1 .531 190.0 33.0 10.6 18.1 10.2 .517 201.8 31.1 12.3 16.7 9.9 .197 211.0 31.9 12.9 16.2 9.8 .190 225.8 35.9 11.2 15.2 9.6 .176 238.0 36.7 15.1 11.1 9.1 .162 Table 8 - Observed and Calculated Data for Upper 3 inches of soil, sample number 0 - 1 Clod size - 0.093 inches ‘Uncompacted Radiant energy applied Equilibrium moisture content 1.7% Hours Total water lost Water remaining Soil Moist. moist. Content grams grams % Ratio 0 0 75.0 8 15.7 1.0 6.5 13.2 61.8 12.9 .800 22.3 23.7 51.3 10.7 .313 31.5 27.6 17.1 9.9 .586 16.8 33.8 11.2 8.6 .193 51.3 36.3 38.7 8.1 .157 70.8 39.1 35.6 7.1 .107 77.5 11.6 33.1 7.0 .378 91.3 11.3 30.7 6.1 .336 103.3 15.3 29.7 6.2 .321 118.5 18.3 26.7 5.6 .278 128.5 50.8 21.2 5.1 .213 111.0 51.6 23.1 1.9 .228 151.5 53.2 21.8 1.6 .207 198.0 59.1 15.9 3.3 .111 Appendix 89 Table 9 - Observed and Calcualted Data for Upper 3 inches of Soil Sample Number 0 - 5 Cnod size - .093 inches Uncompacted No radiant energy applied Equilibrium moisture content 2.6% Wflours Total'iater Lost ‘Hater Remaining Soil Hoist. Moist. Content grams grams 1 Ratio 0 0 82.1 17.1 1.0 6.5 7.7 71.1 15.7 .886 22.3 11.1 67.7 11.3 .791 31.5 16.7 65.1 13.8 .757 16.8 20.7 61.1 13.0 .701 51.3 22.1 59.7 12.6 .676 70.8 21.8 57.3 12.1 .613 77.5 25.6 56.5 11.9 .629 91.3 27.8 51.3 11.5 .601 103.3 28.9 53.2 11.3 .589 118.5 30.7 51.1 10.9 .561 128.5 31.0 51.1 10.8 .555 111.0 32.2 19.9 10.6 .511 151.5 33.6 18.5 10.3 .521 198.0 38.2 13.9 9.3 .153 51.4.19: IUL A 90 Table 10 - Observed and Calculated Data for'Upper 3 inches of Soil Clad size - 0.093 inches Uncompacted lo radiant energy applied Equilibrium moisture content 2.6% Sample Number 0 - 6 ‘Hours Total‘fiater Lost ‘Hater Remaining Soil Hoist. Hoist. Cbntent grams grams % Ratio 0 0 83.6 17.8 1.0 6.5 7.6 76.0 16.2 .895 22.3 11.2 69.1 11.8 .803 31.5 16.6 67.0 11.3 .770 16.8 20.6 63.0 13.5 .717 51.3 22.0 61.6 13.2 .697 70.8 23.9 59.7 12.8 .671 77.5 21.7 58.9 12.6 .658 91.3 26.2 57.1 12.3 .639 103.3 27.9 55.7 11.9 .611 118.5 29.1 51.5 11.6 .592 128.5 29.5 51. 1 11.5 .586 111.0 31.0 52.6 11.2 .566 151.5 32.1 51.2 10.9 .516 198.0 37.6 16.0 9.8 .171 Table 11 - Observed and Calculated Data for Upper 3 inches of Soil Sample Number 0 - 10 Ciod size - 0.093 inches Uncompacted No radiant enerw applied Equilibrium moisture content 2.& Hours Total Hater Lost Hater Remaining Soil lbist. Hoist. Content grams grams 5 Ratio 0 0 85.1 18.3 1.0 6.0 6.3 79.1 16.9 .911 23.0 13.7 71.7 ’ 15.1 .815 15.8 19.6 65.8 11.1 .733 53.5 21.6 68.8 13.7 .708 69.5 21.7 60.7 13.0 .663 77.8 25.9 59.5 12.7 .611 93.5 29.1 56.3 12.1 .606 102.0 29.9 55.5 11.9 .593 118.5 32.0 53.1 11.1 .661 111.8 31.5 50.9 10.9 .529 119.8 35.6 19.8 10.7 .516 169.5 37.8 ‘ 17.6 10.2 .185 212.8 12.5 12.9 9.2 .121 237.5 11.0 11.1 8.9 .101 Appendix 92 i.0 o .9 V 1'3 .8 5 .7 5 6 s |e i ‘3' gig; Sizztigirte ins. c: '5 ggRgngnt Energy overe 4?; sh K -'o'|8 “E 1 i 1 O 25 50 75 .IOO i25 8i50 i75 200 225 Fig. i - San'pie Drying va0 Standard Climatic Cycie - gag 2’3 \' é ' ,2 0 25 5O 75‘ I00 H|258 i50 i75 200 225 MoiStu-e Content Ratio {In Fl . 2 - Sanple Drying Curve 9 Standard Clinatic Cycle 1:— \n 0:403:00 Moisttre Content Ratio {N O .2 Nbflsture Content Ratio {n Appendix 93 7. 83 ie 6 Cl88 3:22. Stratified 0836M at 5 psl-—n Ke- Radiangfifinergy Z o 25 50 75 NO Hog; 150 l75200 F '9' 5 " Eigézrg'tlfiaifivsym i _C?888 Size. 816m “““‘5~<‘~‘~ Stratified, at 5 psl . .__ No Radiant Energy A K I .I5} I 2 ? l 0 25 50 75 mo l25 l50 l75 200‘ 225 Hours Fig. 1 - Sample Drying Curve Standard Cllnatlc Cycle Moisture Content Ratio Moi sttre Content Rat lo Appendix 91 .0 II .9-33 ‘85—5 lo—6K: JI 7" Sa l 0-5 10““ 7 57 0188 glszo5 .093 ins... . N0 Con'pactlon .6 N0 Radiant Energy—1 .5 , 5 K 8 J52 Jl i0 K = .159— *— 4 4‘ 0 50 l00 l50 200 Fig. 5 - Three Drying Curves Resulting From Supposedly identical Drying Conditions .9 .8 3‘ npl 0- l ‘7 Ciod mgisze 34:35 tins. '6 "— Rad i Cmpagmogyfl .5 .1 J o : - if; i9 K a .528) .2 4 l ~ 2 0 50 mo l50 200 Fig 6 - Three Dry ying Curves Resulting from r Supposedly identical ying Conditions Percentage soil moisttrem upper 5 ins. Moi stLre Content Ratio EGEmox O 0 9 8 7 .5 Appendix 95 6 Actual urve LSanme | ‘93? Quadratic Non-_1__\ Linear Regression giggle F 10m lioigtsho \®\ .... a es , éleE1-.06X-.000lxz\‘ 2 0 25 50 75 deg 388.1150 l75 200 225 Fig. 7 - Non-linear Regression Method of Conblning The Three 8 - sanpi e Dryl ng Curves \ Z 2 o 25 50 751830-1325" I75 200 225 Fig. 8 - Drying Curve Resulting From Non- 8 Linear Regres on Method of Con'bining Dryl ng Curves “,7 r... 238,5“. mu «'4th 15 l e? itmidity and tenperature record charts from the envirormental record darts ran the enviromental chanbers Top-"Ohio cranber. Botth-MSU chamber. 97 Table 12 - Accumulated Data - K values where no radiant energy was applied. (K - slope of moisture content ratio - time curve)" Column No. 1 I 2 3 l 1 5 I 6 7 Clod size Untreated Pressed Stratified Covered ins. 0 psi 0 psi 1.2 psi 5.0 psi 1.2 psi 5.0 psi 0 psi .263 .271 .350 .220 .189 .212 .238 .112 .256 .331 .290 .225 .210 .231 .120 .288 .325 .210 .203 .250 .216 .130 av. .272 .335 .250 .206 .231 .238 . 121 .185 .226 .266 .192 .161 .183 .136 .110 .218 .276 .192 .169 .208 .176 .130 .201 .220 .210 .210 .175 .169 .125 av. .215 .251 .198 .181 .189 .160 .122 .093 .152 .216 .117 .111 .160 .111 ‘ .112 .137 .208 .150 .110 .112 .111 .121 .159 .200 '.160 .160 .166 .150 .131 av. .119 .208 .152 .118 .156 .115 .121 .016 .156 .177 .137 .132 .127 .128 .127 .117 .168 .128 .113 .120 .133 .118 .119 .112 .137 .121 .135 .131 .118 av. .151 .162 .131 .132 .127 .133 .121 Note: Column 1 - Constant climatic conditions. (Ohio) Columns 2, 3, 1, 5, 6, 7 - Standard climatic cycle. Appendix 98 Table 13 - Accumulated Data - K values where radiant energy was applied. (K - slope of moisture content ratio- time curve) Column No. l l 2 1 6 7 .1211”... fifii‘bfiv'fi‘é‘fi'fi‘5tTifi—d‘53‘fifig- .263 .621 .580 .217 .302 .111 .823 .600 .120 .269 .380 .705 .530 .380 .272 .100 av. .717 .570 .319 .281 .397 .185 .689 .351 .290 .270 .360 .629 .380 ' .280 .270 .370 .629 .386 .290 .280 .350 av. .619 .372 .287 .273 .360 .093 .131 .275 .236 .266 .351 .112 .280 .210 .218 .300 .528 .290 .250 .263 .320 av. .168 .282 .212 .259 .321 .016 .392 .256 .182 .271 .2617— ' .172 .225 .188 .210 .270 .185 .271 .195 .237 .280 av. .150 .251 .188 .239 .271 Note: Column 1 - Constant climatic conditions (Ohio) Cblumns 2, 1, 6 and 7 - Standard climatic cycle. Appendix 99 Table 11 - Accumulated Data - P values Hhere no radiant energy was applied. (P - 1 water lost the first 21 hours) 33:: 2.1.2. 31.1.2 2.1.4.27 ins. 0 psi qusi 1.2 psi 5.0 psi 1.2 psi 5.0 psi 0 psi .263 23.1 21.1 20.1 21.5 20.2 18.7 5.0 23.9 26.5 26.6 26.3 21.0 19.1 6.6 22.0 23.0 23.3 21.0 20.0 19.9 6.9 av. 23.0 23.6 23.1 21.9 20.1 19.2 6.2 .185 19.7 18.1 18.1 20.6 17.1 11.7 5.1 20.5 18.3 15.9 16.2 17.0 18.0 7.5 20.6 17.3 19.9 20.7 17.9 16.5 7.2 av. 20.3 17.9 18.1 19.2 17.3 16.1 6.7 .093 18.2 18.0 16.1 15.6 16.0 13.1 6.5 17.8 17.0 18.1 20.0 17.7 13.7 5.7 16.5 16.2 16.8 19.6 16.3 11.2 8.6 av. 17.3 17.1 17.2 18.1 16.7 13.8 6.9 .016 16.9 15.1 11.1 12.6 13.0 12.2 ‘6.1 16.8 11.0 15.8 19.8 12.7 11.2 8.1 16.6 13.8 15.0 11.8 12.1 11.0 7.1 av. 16.8 11.1 15.0 11.7 12.6 13.5 7.2 Note: Column 1 - Constant climatic conditions. (Ohio) Columns 2, 3, 1, 5, 6, 7 - Standard climatic cycle. Table 15 - Accumulated Data - P values when radiant energy was "’1’ V. O“. I. 100 applied. (P - % water lost the first 2h hours) Column No. 1 l 2 h 6 7 .263 h1.0 31.6 26.3 27.1 26.5 36.h 32.0 32.7 30.h 2b.6 36.8 30.8 31.0 27.9 25.5 av. 38.1 31.5 29.3 28.5 25.5 . 185 31.0 27.0 25.6 21.1. 214.0 35.6 25.5 25.8 21.9 2h.h 32.0 26.0 26.9 2h.0 23.5 av. 3h.0 26.2 26.1 23.h 2h.0 .093 32.7 21.9 23.0 19.9 22.7 33.h 20.8 23.1 21.8 21.3 28.7 21.2 2h.0 2h.1 21.8 av. 31.6 21.3 23.h 21.9 21.9 .0h6 30.8 20.8 17.8 21.2 21.5 29.h 18.5 20.3 17.5 20.5 28.1 20.9 20.2 21.3 20.0 av. 29.1. 20.1 19.1: 20.0 20.7 —1-¥7 Note: Cb1umn l - Cbnstant climatic conditions (Ohio) Cblumns 2, h, 6, 7 - Standard climatic cycle. 101 Table 16 - Summary of the Statistical.Analysis. The treatment meanfi, regression slope b, and standard deviations are presented for each treatment. 1121311 516 7 Untreated I Pressed Stratified vaered 0 psi [ 0 psi j 1.2 psi] 5.0 psi 1.2 psilS.O psi 0 psi .1966 .2399 .1858 .1667 .1765 .1686 .1212 .003hh .005h8 .00561 .0050 .00131 .00335 .00252 .021h .0282 .0196 .0127 .0176 .0169 .0000 UV! 0‘”!!! XI .001539 .002151 .002187 .002236 .001932 .001500 .001125 k values - With radiant energy applied 32 .5710 .3687 .2665 .2632 .3380 5; .01852 .00686 .01317 .00539 .00173 b .0192 .0521 .0263 .0070 .0207 513 .008283 .003069 .005893 .002109 .002111 Percent water - No radiant energy applied 219.3833 18.2500 18.1167 19.3083 16.7500 15.7166 6.750 552 .20233 .12166 .56928 .83121 .18002 .30553 .33211 b 1.0735 1.1270 1.3136 1.5686 1.2036 .9969 .1667 5b .09019 .18992 .2516 .37308 .08051- .13661 .11868 Percent water - With radiant energy applied 2': 33.2750 21.7500 21.5583 23.1583 23.0250 55, .60018 .25155 .68199 .53778 .2157? b 1.1153 1.9537 1.6220 1.3153 .8318 5,, .26855 .11381 .30635 .21051 .09650 Appendix 102 Table 17 - Dry Height of Soil in Upper 3 inches of Sample No radiant energy applied w é 1'33 32 Pressed a 111236 CBverea ins. 0 psi 0 psi 1.2 psi 5.0 psi 1.2 psi 5.0 psi 0 psi .263 187.9 187.6 510.2 579.7 187.2 190.2 176.6 190.5 185.0 529.8 573.6 196.2 191.1 189.8 179.0 188.9 530.0 588.0 195.0 175.5 180.0 av. 185.8 187.2 523.3 580.1 192.8 185.6 182.1 .185 158.8 510.3 188.3 573.0 178.5 177.0 150.2 173.3 506.8 185.2 539.0 185.3 193.3 191.2 188.7 175.9 511.1 560.6 521.0 501.6 189.6 av. 173.6 197.7 195.9 557.5 195.9 190.6 178.0 .093 172.2 138.2 501.0 518.3 182.7 186.8 122.9 168.5 139.3 518.1 578.9 585.5 191.5 171.3 166.6 138.8 191.9 515.6 190.2 193.5 132.1 av. 169.1 138.8 503.7 557.6 186.1 190.6 112.1 .016 116.1 120.8 133.2 550.3 167.9 171.0 125.5 136.9 128.6 155.6 551.2 166.0 185.1 122.5 135.0 118.6 168.1 506.3 172.5 159.1 .150.“ av. 139.3 122.7 152.3 535.9 168.8 172.7 132.8 Note: Column 1 - Constant climatic conditions. (Ohio) Columns 2, 3, 1, 5, 6, 7 - Standard climatic cycle. Volume of upper 3 inches of sample - 515 cc. Appendix 103 Table 18 - Height of‘Hater in Upper 3 inches of Soil Sample No radiant energy applied (Column No. 1 I 2 3 17 S 1 7 Un reated Pressed Stratified covered Clod size ins. 0 psi 0 psi 1.2 psi’ 5.0 psi 1.2 psi 5.0 psi 0 psi .263 88.0 83.5 85.2 95.0 81.0 82.0 81.5 ‘ 86.0 82.1 90.6 97.7 85.0 82.6 86.3 88.0 83.9 90.0 103.8 85.0 82.1 81.0 av. 87.3 83.3 88.6 98.8 81.7 92.2 83.9 .185 88.9 86.7 87.7 100.1 82.1 82.1 81.0 86.9 86.1 83.9 91.1 83.6 86.3 81.0 82.0 82.0 91.5 97.5 92.2 87.6, 83.2 av. 85.9 81.9 87.7 96.3 86.0 85.3 82.7 .093 82.1 73.7 86.1 96.5 81.5 83.9 71.1 83.6 77.0 90.6 103.1 83.6 86.5 81.0 85.1 77.1 86.1 97.0 86.6 86.9 75.6 av. 83.7 75.91 87.6 98.9 81.9 85.8 75.9 .016 79.9 72.6 75.8 96.2 77.7 81.8 71.6 80.3 72.0 78.3 100.1 80.3 82.3 71.1 77.9 70.8 83.8 87.5 83.3 80.3 79.3 av. 79.1 71.8 79.3 91.7 80.1 81.5 75.1 Note: Column 1 - Constant climatic conditions. (Ohio) columns 2, 3, 1, 5, 6, 7 - Standard climatic cycle. Volume of upper 3 inches of sample - 515 cc. ........... Table 19 - Dry Height of Soil in Upper 3 inches of Sample. with radiant energy applied. Column No. l I 2 1 6 7 Clod size Untreated Pressed Stratified Covered in. 1—0‘p31 0 psi .0 ps .0 ps 0 ps .263 500.6 152.0 579.3 189.6 176.6 197.0 157.1 577.3 191.1 193.1 198.7 198.6 578.0 521.7 185.0 av. 198.8 169.2 578.2 501.8 185.0 .185 189.0 199.7 566.1 169.1 178.6 178.7 157.6 551.3 501.0 181.8 171.1 175.9 558.1 180.0 179.0 av. 179.7 177.7 558.7 181.1 179.8 .093 178.3 153.2 567.9 151.2 135.0 162.3 156.0 525.2 180.6 166.5 185.3 150.9 550.0 178.2 155.0 av. 175-3 153-1 517-7 171.0 152.2 .016 112.7 130.3 520.5 171.0 119.8 131.0 119.0 562.6 186.0 110.0 155.0 139.3 552-9 182.5 135-0 av. 113.9 139.5 515.3 180.8 131.6 Note: Column 1 - Constant climatic conditions. (Ohio) Columns 2, 1, 6, 7 - Standard climatic cycle. Volume of upper 3 inches of sample - 515 cc. Table 20 - Weight of water in upper 3 inches of soil sample nnyDO‘. lb 105 With radiant energy applied Column.lo. 1 I 2 1 6 7 mini?“ fit???“ %%§%7%f‘fifi-L%T‘L .263 82.0 83.2 98.9 81.3 81.5 86.0 80.2 99.7 82.6 81.6 87.5 83.0 99.5 91.8 83.0 av. 85.2 82.1 99.1 86.2 83.0 .185 78.0 85.0 90.0 79.1 72.0 78.0 78.5 91.9 77.7 80.7 83.5 83.3 98.2 78.0 80.0 av. 79.8 82.3 91.1 78.1 77.6 .093 75.0 79.8 99.2 76.1 72.2 78.5 78.9 91.1 81.3 80.7 82.5 83.9 98.3 82.6 78.0 av. 78.7 80.9 97.3 80.1 77.0 .016 71.0 75.9 91.1 80.6 73.9 71.5 78.1 97.5 81.5 77.0 77.1 77.2 96.2 83.0 75.0 av. 75.3 77.2 91.9 82.7 75.3 Note: Column 1 - Constant climatic conditions. (Ohio) Columns 2, 1, 6, 7 - Standard climatic cycle. Volume of upper 3 inches of sample - 515 cc. Appendix 106 Table 21 - Emergence of Corn Planted in the Sample. No radiant energy, lied. Column.No. 1 l 2 3 771 I 5 17 6 7 ‘Falod size Untreated Pressed Stratified Covered ins. psi Opsi 1.2 psi 5.0 pail 1.2 psi 5.5psi ps .263 l-l90i 3-3355W 1-190 2-226 3-167 2-162 3-167 2-238 1-3315 1-281c 1—186 l—D 2-190 1-330 .X X X. X X 1-210 2-3100 3-220 X X X X X X .185 3-250 X 3-263 1-238 3-167 3-179 3-202 2-2380 3-230 3-160 1-167 3-239 X 1-178 1-156 2-239 1-202 2-179 1-211 3-190 X X X 2-167 1-178 X 1:179 2-202 .093 3-198 2-30 1-178 x 1-112 3-150 3-192 1-3060 1-102 2-119 l-238C 3-198 1-151 3-191 1-211 3-238 1-112 3-166 1-225 1-238 2-166 l-22SSW 1-233C 3-213 3-166 x x 2-155 3-166 3-165 1=1_67 .016 3-168 3-190 1-166 3-161 3-119 1-155 3-161 2-178 1-167 1-179 1-168 3-161 3-226 3-238$c 3-211 x 3-113 2-198 1-212 3-166 3-191 2-179 X 3-166 3-155 2-238 1-263 * Entries indicate number of seedlings emerging and time in hours. 5 - Sprouted not through soil surface. W - Wilty. D - Seeds dried. C - curled due to compact soil. .X - Denotes samples in which seeds were not planted Note: column 1 - Constant climatic conditions. Column 2, 3, 1, 5, 6, 7 - Standard climatic cycle. (Ohio) Appendix 107 Table 22 — Energence of corn planted in samples. Radiant energy applied. Column No. 1 I 2 1 6 7 Ciod size Untreated Pressed Qtratified Covered ins. ps 0 psi 5.0 psi msi 0 psi .263 3.2009. 349% 1-166 1-113 1-955 2-2110 1-151 1-2380 3-2000 x x x 3-2000 x x, 1-215’ x 2-2150 .185 3-1900 x x 3-2620 x 3-1900 x x 3-130 x 3.2000 x x x x .093 3-1980 1-131 2-167 2-113 3-1670 1-156 1-179sc 1-2380 1-192 3-2370 x x 1-262 x 2-2620 3-1900 x x x x 7 .016 3-1980 1-287 x x 3-2870 2-2870 3-2370 1-155 1-167 x x 1-191 2-16750 1-220 3-1900 X x 1-113 X 1-167 1-211 «I Entries indicate number of seedlings emerging and time in hours. S - sprouted, not through surface W - vilty D - seeds dried (no seedling resulted) C - curled due to compact soil X - denotes samples in uhich no seeds were planted Note: Column 1 - Constant climatic conditions. (Ohio) Columns 2, 1, 6, 7 «- Standard climatic cycle. nyrvauan 108 Table 23 - Key relating sample number to treatment 110 radiant energy applied Eolumn N0. 1 I 2 3 I h 5 l 6 l 7 ing“ fig-fiiougsi 1.27:?- 72580 psi 13%ng psi Cat‘s? .263 0-20 5 18 12 31 16 2 0-21 21 0.27 0-29 0-28 52 0-16 0.26 0-33 0.65 0-18 0.66 61 0-67 .185 0.11 99 55 91 62 68 56 0-12 100 61 73 75 77 96 0-19 0-10 0-55 0-38 87 79 0-53 .093 0.5 8 60 21 32 15 7 0-6 16 93 89 66 78 59 0-10 23 0-52 0-51 88 80 15 .016 0-2 1 17 11 33 81 6 0-3 9 51 90 67 86 19 0.8 22 92 71 0-11 81 97 Rate: Column 1 - Constant climatic conditions. (Chio) Column 2, 3, 1, 5, 6, 7 - Standard climatic cycle. 0 Samples ran in Ohio Appendix 109 Table 21 - Key Relating Sample "amber to Treatment. Radiant energy applied. Cblumn No. l l 2 1 . 6 7 (nod size gntreated Pressed §trati£ied Covered ins. 0 psi 0 psi 5.0 psi 5.0 psi 0 psi .263 0-22 13 28 50 1 0-23 20 0-31 51 0-17 0-25 0-32 0-58 57 0-60 . 185 0-17 98 0.31 70 0.11 0.18 0.36 0-37 39 0-51 0-21 30 0-56 0-59 0-61 .093 0-1 82 91 19 11 0-9 0.12 0-35 69 0.13 O-lh 0bh9 0-50 63 0-62 .016 0-1 17 27 85 18 0-7 83 95 0-15 0-63 0-13 11 0-57 58 0-61 Note: Column 1 - Constant climatic conditions. Column 2, 1, 6, 7 - Standard climatic cycle. 0 samples ran in 0110 2. 9. 10. 11. 12., 13. REFERENCES CITED Andrew, R. H. The Influence of Depth of Planting and Temperature Upon Stand and Seedling Vigor of Sueet Corn Strains. Agronogy Journal 15:32-35, 1953. Barmington, R. D. The Extent of Sugar But Emergence Studies at Colorado A 8 M College. Proc. A33. _S_o__c. Sugar Beet Tech., 1950, pp. 222-2211. Barmington, R. D. Physical Factors of the Soil Affecting Beet Seedling Emergence. Proc. Am. §_o_c_. Sugar Beet Tech., 1950, pp. 228-233. mteman, Hohf, Stan). 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