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CLEANING MACHINE-STRIPPED COTTON FOR EFFICIENT GINNING AND MAXIMUM BALE "'1ALVES :>:: c.:,., -:;:).- ::;:-... r. ':,t, 26,,; c-..:>,., - ",. ~::i ~ {/) => '" -, " <~I...\ ) Technical Bulletin No. 1540 Agricultural Research Service UNITED STATES DEPARTMENT OF AGRICULTURE
CONTENTS Page A Dstract 1 Introduction.... 1 Methodology.... 2 Equip,lnent.... 2 Sampling, fiber testing, and analysis.... 3 1969 Experiment.... 3 Design..,.... 3 Results.... 3 1970 Experiments........ 7 Design.... 7 Results.... 7 1971 Experiment...,.... 10 Design.... 10 Results.... 11 1972 Experiment.... 13 Design.... 13 Results...'.... 13 Cleaning recommendations.... 16 Appendix.... 18 ILLUSTRATION Fig. 1. Recommended cleaning-machinery arrangement for machinestripped cotton... 16 TABLES 1. Range of foreign matter in machine-stripped cotton.... 2 2. Effects of seed-cotton cleaning on moisture and foreign-matter contents, cleaning efficiencies, and ginning rates, 1969.... ". 3. Effects of cleaning treatments on fiber properties, bale weights, and bale values, 1969.... 5 4. Effects of lint cleaning on moisture contents and fiber and yarn properties, 1969.... 6 5. Effects of seed-cotton cleaning on moisture contents, fiber prop erties, and foreign-matter contents of three cotton varieties, 1970... '.... 7 6. Effects of lint cleaning on moisture contents, fiber properties, waste removal, bale weights, and bale values of three cotton varieties, 1970.... 8 7. Effects of lint cleaning on fiber lengths and nep contents of three cotton varieties, 1970.... 8 8. Effects of lint cleaning on yarn quality of 'Tamcot 788', 1970.. 9 iii
Page 9. Effects of lint and seed-cotton cleaning on moisture and foreignmatter contents, nonlint contents, and ginning rates, 1971... 10 10. Effects of cleaning treatments on moisture contents, bale 'weights, fiber and yarn properties, and bale values, 1971... 11 11. Cotton-cleaning machinery used in 1972 experiment... 13 12. Effects of seed-cotton cleaning on moisture and foreign-matter contents, fiber properties, ginning rates, bale weights, and bale values, 1972... 14 13. Effects of lint cleaning on moisture contents, bale weights, fiber and yarn properties, and bale values, 1972... 15 A-I. Principal features, operating speeds, settings, and adjustments for equipment used in 1969-72 experiments... 18 A-2. Grade index values for various grades of cotton, 1969-72... 18 A-3. Results of statistical analysesfol' the 1970 experiments........ 19 The data in this publication were collected during 1969-72. The recommendations remain useful to ginners of machine-stripped cotton. Wm;hington, D.C. Issued January 1977 iv
CLEANING MACHINE-STRIPPED COTTON FOR EFFICIENT GINNING AND MAXIMUM BALE VALUES By Roy V. BAKER, EUGENE P. COLUMBUS, and J. 'WELDON LAIRD, agricltltu1"a1 enginlle1's, South Plains Ginning Research Lab01'atory, Agr'icnltm'ul Resca1'ch Service, U.S. Dcpa1 tmcnt of Ag1'iculture, L1Lbbock, Tex. ABSTRACT Experiments were conducted over a 4-year period to determine the amount of conventional seed-cotton cleaning machinery and number of lint cleaners required for machine-stripped cotton to achieve acceptable ginning performance, maximize producer returns, and insure satisfactory end-use performance of lint. Seed cotton was processed through various combinations of cleaning-machinery sequences and was subjected to one, b\'o, and three stages of lint cleaning. The combined test data indicated that machine-stripped cotton having a lint turnout of 22 percent (or more) can be satisfactorily cleaned with two extractors, two inclined cleaners, and an air-line cleaner. Cotton having a lint turnout of less than 22 percent would benefit from an additional stage of extraction. Two stages of lint cleaning were near optimum for bale value and fiber quality and produced slightly higher bale values than one stage of cleaning. Lint cleaned by three stages of lint cleaning was generally worth no more than that cleaned by two stages and often had lower fiber and yarn properties. Lint that received no lint cleaning was heavily discounted in price, and yarn made from this lint was low in appearance and high in imperfections. These results indicated that gins processing machine-stripped cotton should be equipped for two stages of lint cleaning. INTRODUCTION varying amounts of stems, branches, and leaf material are harvested during the stripping Approximately 30 percent of the U.S. cot process. Large pieces of foreign matter interton crop is harvested by mechanical strippersj fere with the operation of gin stands and have Cotton producers in the High Plains and Black to be removed from the seed cotton before ginlands of Texas use this method almost exclu ning. Smaller foreign-matter particles do not sively. Other large stripper areas are located interfere with ginning, hut they do lower the in Oklahoma and eastern New Mexico. quality of the ginned lint and reduce the unit Machine-stripped cotton requires rigorous price of the cotton. Effective cleaning systems cleaning because of high foreign-matter con must be employed to achieve economical ginning performance and to provide acceptable tent (table 1). The complete cotton boll and monetary returns to the producer. 1 Chat'ges for ginning cotton,,:osts of selected serv A series of experiments was conducted at ices incident to marketing, and related information, sem;on 1972-73. U.S. Dep. Agric., Econ. Res. Servo the South Plains Cotton Ginning Research [Rep.]ERS-2, 1 p. 1973. Laboratory, Lubbock, Tex., to determine the 1
TABLE I.-Range of fo-reign matte-r in machinest1-ipped cotton 1 Type of Range in pounds per bale 2 foreign matter Low Typical High Burs... 340 450 650 Sticks 3...... 45 115 350 Fine trash... 75 135 400 Total... 460 700 1,400 1 Data based on South Plains Ginning Research Laboratory records. 2 Based on a standard 480-pound bale of lint, net weight. 3 Includes stems, branches, and limbs. amount and arrangement of cleaning machinery required to achieve acceptable ginning performance, maximize producer returns, and insure satisfactory end-use performance of lint. These experiments were designed to evaluate conventional cleaning machinery and to formulate recommendations for the ginning industry in stripper harvesting areas. Seed-cotton-cleaning and lint-cleaning experiments 'were conducted from 1969 to 1972 at the laboratory's full-scale ginning plant. Six experiments were conducted over the 4-year period so that the combined results would be representative of the range of growing, harvesting, and ginning conditions expected over an extended period of time. Early freezes occurred during the 1969 and 1970 cotton seasons, which lowered cotton yields but had only minor effects on cotton quality. Adverse growing conditions during 1971 resulted in one of the poorest cotton seasons on record. However, the cotton used in the 1971 experiments was above average for that year and was equal.in quality to the cottons used in 1969 and 1970. Cotton produced during 1972 yielded well but was of lower quality than cotton normally produced on the Texas High Plains. The varieties of cotton selected for these experiments ranged in staple length from Hinch to 111[ inches and in Micronaire reading from 2.8 to 4.2. The varieties selected were those most popular with farmers, as \vell as those having a range of fiber characteristics. The varieties were 'Paymaster 111', 'Tamcot 788', 'Stripper 31', 'Lankart Lx571', and 'Paymaster 909'. During the period 1969-72, approximately 35 percent of the cotton land in stripper areas was planted with these five varieties. All cottons were produced within a 30-mile radius of the laboratory and were harvested by conventional brush strippers. METHODOLOGY Equipment The laboratory's full-scale ginning plant, which is equipped with modern high-capacity machinery, was used for these experiments. Special remote-control bypass valves, trash collecting devices, weighing devices, measuring instruments, and lint-sampling equipment 'were used to increase the flexibility of the ginning system and to improve the accuracy of the datu. Details on the machinery used in these experiments are given in table A-I (appendix), including equipment types, sizes, operating speeds, settings, and adjustments. Processing rates through the ginning system were controlled by a conventional automaticfeed control and an ampere controller for the gin-stand feeder. The selected processing rates provided normal loadings for the sizes of equipment used. Seed cotton was processed through cleaning, extracting, and drying equipment at rates of approximately 6 bales per hour. Ginning rates varied because of experimental treatments but were generally within the range of 3.5 to 4 bales per hour. All cotton was ginned on one high-capacity gin stand containing 178 12-inch-diameter saws. The cotton used in these experiments arrived at the gin with lint-moisture contents within the 5- to 7-percent range, which is generally accepted as optimum for ginning. Because drying was not required to satisfactorily process the cotton, unheated ambient air was used to convey the cotton through the two tower driers. DUJ"i~g these experiments, the relative humidity of the outside ambient air ranged from 25 to 55 percent. Equilibrium moisture contents of lint for this range of humidity vary from approximately 4 to 6.5 percent. Thus, in some cases the ambient air used for conveying probably dried the cotton a slight amount. However, this small drying effect was approximately equal for all treatments in D, given experiment and was assumed to have no effect on the relative ranking of the treatments. 2
Sampling, Fiber Testing, and Analysis Seed-cotton samples were taken from the wagon ~nd at the feeder apron for moisture and foreigr:-matter determinations. These data were used to ev~llnate seed-cotton cleaning performance. Moisture samples were ovendried by using standard gravimetric procedures. 2 Foreign-matter determinations were made by performing conventional seed-cotton fractionation tests. Lint samples (200 grams) were taken before and after lint cleaning for selected fiberproperty measurements. Six-pound lint samples "were taken after lint cleaning for conventional small-scale spinning tests. Standard fiberproperty measurements and spinning-test results were obtained from the USDA's Cotton Testing Laboratory at College Station, Tex., in 1969, 1970, and 1971. Texas Tech University's Textile Research Center at Lubbock performed these tests in 1972. Smith-Doxey classifications of ginned lint samples wer'e made by the USDA's Cotton Classing Office at Lubbock. Samples of seed cotton and lint "were randomly "withdrawn from the processing stream at the desired stage of cleaning. Each test sample consisted of three spec;mens collected during the processing of a test lot. Specimen results were averaged for each lot before the data were analyzed statistically by means of analysis of variance. Signjfjcant differences between treatment effects were identified by Duncan's new multiple-range test. Bale values "were calculated by using Commodity Credit Corporation loan rates and discounts that were applicable during the year each experiment was conducted. Bale weights were computed by adjusting actual lot weights to a common base. Input bur-cotton weight- was used as the base for these computations. A selected base weight for each experiment allowed the adjusted bale weights for the various treatments to fall within the normal baleweight range of 450 to 550 pounds (gross weight). ~ Shepherd, J. V. 1972. Standard procedures for foreign matter and moisture analytical tests used in cotton ginning research. U.S. Dep. Agric. Handb. No. 422, 13 pp. 1969 EXPERIMENT Design Experimental treatments were selected to (1) determine if inclined cleaners were required for cleaning machine-stripped seed cotton, (2) measure the effectiveness of a seed-cotton cleaning system using three stages of extraction, and (3) determine the effects of lint cleaning on fiber and yarn quality. The following four system combinations for seed-cotton cleaning were selected: 1. ElCLbomte.- (28 cylinders and 3 extractors ) air-line cleaner, tower drier (no heat), inclined cleaner, bur machine, tower drier (no heat), inclined cleaner, stick machine, inclined cleaner, inclined cleaner, stick machine, extractor feeder. 2. Tlfpical.- (16 cylinders and 2 extractors) air-line cleaner, tower drier (no heat), inclined cleaner, bur machine, tower drier (no heat), inclined cleaner, stick machine, extractor feeder. 3. Elabora.te-extmcting.-(3 extractors) tower drier (no heat), bur machine, tower drier (no heat), stick machine, stick machine, extractor feeder. 4. Modemte-extmcting.-(2 extractors) tower drier (no heat), bur machine, tower drier (no heat), stick machine, extractor feeder. The elaborate system contained all the machinery normally used for stripped cotton plus that normally used for machine-picked cotton. The typical system contained only the machinery normally used for stripped cotton. The elaborate-extracting system contained the same amount of extracting equipment as the elaborate system but without inclined cleaners. The moderate-extracting system differed from the typical system in a like manner. Each system for seed-cotton cleaning was tested with no lint cleaning and in combination with one, two, and three stages of lint cleaning. The 16 cleaning combinations were randomly processed within each of 3 replications. Fortyeight bales of 'Paymaster 111' cotton were ginned in one-bale lots. Results Bur cotton on the wagon averaged 32.4 percent foreign matter and 8.2 percent moisture 3
TABLE 2.-Effects of seed-cotton cleeming on moisture and fo'reign-matter contents> cleaning efficiencies, g,nd ginning rates, 1969 1 Measurement Seed-cotton cleaning treatment Level of Average of Elaborate Typical Elaborate- Moderate- signifiall levels extracting extracting cance 2 Moisture cuntent: Bur cotton, wagon Seed cotton, feeder Bur content:...pct.....pct.. Bur cotton, wagon...pct.. Seed cotton, feeder...pct.. Cleaning efficiency...pct.. Stick content: Bur cotton, wagon...pct.. Seed cotton, feeder...pct.. Cleaning efficiency...pct.. Fine trash content: Bur cotton, wagon...pct.. Seed cotton, feeder...pct.. Cleaning efficiency...pct.. Total foreign matter: Bur cotton, wagon Seed cotton, feeder...pct.....pct.. Average cleaning efficiency...pct.. Ginning rate...bales/h.. 8.6 7.6 18.3 0.6 97.8b 5.4 0.7 90.4b 8.4 2.4 79.5c 32.1 3.7 91.9c 3.89b 7.9 7.4 19.6 1.1 96.2a 5.1 1.1 84.9a 7.6 2.9 73.2b 32.3 5.0 88.9b 3.75a 8.4 7.5 19.2 0.5 98.1b 5.6 0.9 88.1ab 8.2 3.3 71.2b 32.9 4.8 89.8b 4.00b 7.8 7.5 19.2 0.9 96.6a 5.4 1.2 84.3a 7.7 3.8 64.8a 32.4 5.9 86.9a 3.90b 1 Means in a row followed by a common letter are not statistically different at the 0.05 level. 2 Asterisk indicates significant differences among seed-cotton cleaning treatments at the 0.05 level. NS indicates no significant differences at the 0.05 level. 8.2 7.5 19.1 0.8 97.1 5.4 1.0 86.9 8.0 3.1 72.2 32.4 4.9 89.4 3.89 NS NS NS.. NS.. NS.. NS.... (table 2). The average bur, stick, and fine-trash contents were 19.1, 5.4, and 8.0 percent, respectively. There were no significant differences among treatments in initial moisture or foreign-matter contents. The average fiber strength of the test cotton was 86,200 pounds per square inch, and the average micronaire reading was 4.0. The four seed-cotton cleaning systems had significantly different cleaning efficiencies and produced a range of 3.7 to 5.9 percent foreign matter after the feeder. The elaborate system did the most cleaning, and the moderate-extracting system did the least. The typical and elaborate-extracting systems had approximately equal cleaning efficiencies, which were intermediate between the high and low levels. The systems with inclined cleaners removed more fine trash than the comparable systems without inclined cleaners. Average cleaning efficiency for total foreign matter varied from a low of 86.9 percent (moderate-extracting) to a high of 91.9 percent (elaborate). Bur content of seed cotton after the feeder appeared to affect the rate of ginning. An increase in bur content from 0.5 to 1.1 percent was accompanied by a decrease in ginning rate from 4 bales per hour (elaborate-extracting) to 3.75 bales per hour (typical). The range in stick and fine-trash contents did not affect ginning rate. N onlint content a before and after two stages of lint cleaning reflected the amount of seedcotton cleaning received (table 3). However, after three stages of lint cleaning, differences in nonlint contents were not significant. The seed-cotton cleaning systems with inc1ined cleaners produced cleaner lint than the comparable systems without inclined cleaners. The typical system produced cleaner lint than the elaborate-extracting system, indicating that an additional stick machine was not equal to two a Throughout this report, "nonlint content" refers to total waste removed from lint by a Shirley analyzer. 4
... ~ TABLE 3.-Effects of cleaning treatments on fiber properties, bale weights, and bale values, 1969 1 Nonlint Staple Bale Lint or seed-cottoll content Grade Bale length weight cleaning treatment index 3 (pct) 2 value (32d inch) (lb) 4 Elaborate: No lint cleaning... 7.5d 80a 31.3a 533d $79a 1 stage... 3.7ab 9lb 31.9b 5l5c 93cde 2 stages...... 2.8a 95c 32.0b 502b 94e 3 stages... 2.8a 92bc 31.8b 499a 8tlbcde Typical: No lint cleaning... 8.0d 83a 31.6a 540d 84abc 1 stage... ~ 3.8b 92b 3l.4a 5l5c 93de 2 stages... 3.3a 93c 3l:7ab 504b 89bcde 3 stages... 3.2a ~Ob 31.9b 50la 9lbcde Elaborate-extracting: No lint cleaning... 9.lde 8la 31.5a 546e 85abcd 1 stage... 4.lc 89b 32.lb 5l7c 9lbcde 2 stages... ~... 3.5ab 9lb 31.9b 505b 92bcde 3 stages... 3.la 94c 32.0b 500a 94de Moderate-extracting: No lint cleaning... 9.7e 79a 31.5a 548e 82ab 1 stage... 5.5c 84b R2.1b 517c 86abcde 2 stages... "... 3.7ab 89b 32.lb 503b 90bcde 3 stages 3.la 93c 32.lb 498a 94de w ) Means in the same column followed by a common letter are not statistically diffel'ent at the 0.05 level. 2 Grade index values for various grades of cotton are given in table A-2 (appendix). 3 Bale weights include 21 pounds of bagging and ties. 1 Bale values based on 1969 Commodity Credit Corporation loan prices. inclined cleaners in controlling the amount of stages of lint cleaning reduced bale \veights 18 foreign matter in lint. The lowest nonlint con to 31 pounds and 11 to 14 pounds, respectively. tent (2.8 percent) was obtained with the The third stage of lint cleaning reduced bale elaborate system and three lint cleaners. The weights 3 to 5 pounds. moderate-extracting system with no lint clean Bale values,.''ls a result of the 16 cleaning ing produced the highest nonlint content (9.7 treatments, ranged from $79 to $94. Bale values percent). approaching the $94 maximum were obtained Grade index varied directly with nonlint con with all foul' seed-cotton cleaning systems. tent and ranged from 79 (Low Middling Light However, more lint cleaning was required to Spotted) to 95 (Strict Low Middling). The produce maximum bale values for the two syselaborate and typical systems required two tems without inclined cleaners than for the stages of lint cleaning to produce maximum systems with inclined cleaners. The typical grades. The elaborate-extracting and moderate system required only one lint cleaner to proextracting systems (those without inclined duce maximum bale value. Two lint cleaners cleaners) required three stages of lint clean produced maximum bale value for the elaborate ing to produce maximum grades. The third system. The elaborate-extracting and moderatestage of 1int cleaning did not improve grade extracting systems required three stages of lint index for the elaborate and typical systems. cleaning to produce maximum bale values. Bale weights were affected most by the first Bypassing all inclined cleaners, and relying and second stages of lint cleaning. Seed-cotton solely on lint cleaners to remove fine trash, cleaning affected bale weight before lint clean resulted in higher nonlint content, lower grade ing, but differences after lint cleaning were 3 index, and lower bale value. One additional pounds (or less) per bale. The first and second stage of lint cleaning was required to compen 5
TABLE 4.-Effects of lint cleaning on moist~lre contents and fiber and yarn propert'ies, 1969 1 Measurement Stage of lint cleaning 0 1 2 3 Level of significan!!e 2 Lint moisture content 3...pct.. 6.1 6.2 6.0 6.2 NS Classer's staple length..,.32d inch.. 31.5a 31.9b 31.9b >I< 32.0b 2.5-pct span length...inches.. 1.04b 1.02a 1.03ab 1.03ab >I< Length '.miformity...pct.. 45 44 44 44 NS Reflectance......R 69.3 d 71.0 71.7 72.5 Yellowness... +b.. 8.5 8.8 8.8 9.0 Picker and card waste...pet.. 10.9c 7.4b 6.5a 6.3a >I< 22s-yarn strength...lb.. 107 165 105 105 NS 44s-yarn strength...lb.. 45 43 43 43 NS Average break factor unit... ~... 2,168 2,107 2,088 :'!,098 NS Average yarn appearance index... 105b 107b 106b 102a >I< 22s-yarn imperfections...no. 20b 17a 17a 19b >I< 44s-yarn imperfections....no. 26bc 22ab 21a 24b >I< 1 Means in a row followed by a common letter are not statistically different at the 0.05 level. 2 Asterisk indicates significant differences among stages of lint cleaning at the 0.05 level. NS indicates no significant differences at the 0.05 level. :I Moisture content determined from samples taken before lint cleaning. sate for bypassing two or more inc]jned cleaners. Substituting a stick machine for two inclined cleaners resulted in slightly higher nonlint content, lower grade index, and lower bale values. Fiber- and yarn-quality measurements,,,ere made on lint samples taken after each cleaning treatment. Seed-cotton cleaning had only minor effects upon fiber and yarn properties. For this reason, data for each level of lint cleaning 'were avoraged across all four seed-cotton cleaning levels (table 4). Fiber length, determined subjectively by the classer and measured mechanically by the Digital fibrograph, showed no significant differences after one, two, and three stages of lint cleaning. Classer's staple length was shorter before than after one stage of lint cleaning, but 2.5-percent span length averaged longer before lint cleaning. This apparent discrepancy may have been due to differences in appearance of lint samples before and after lint cleaning. The lint cleaners paralleled the fibers and produced smoother samples than the uncleaned lint samples. It is possible that the uncleaned lint samples were penalized unduly because of their rough appearance and because area classers were not accustomed to classing lint that had not been processed through at least one lint cleaner. Lint cleaning increased color reflectance and yellowness vakes. With no lint cleaning, reflectance and yellowness values were 69.3 and 8.5, respectively. These values were 72.5 and 9.0 after three stages of lint cleaning. Lint cleaning decreased picker and card waste from 10.9 percent (no ]jnt cleaning) to 6.3 percent after three stages of lint cleaning. Differences between two and three stages of lint cleaning were not significant. No significant differences were found in the strength of 22s and 44s yarns or in average break factor. Yarn strengths before lint cleaning were only 2 pounds higher than after any stage of lint cleaning. The average break factor before lint cleaning was 2,168, and after three stages it was 2,098, a difference of only 70 units. Average yarn appearance was significantly affected by lint cleaning. Three stages of lint cleaning produced the lowest appearance index (l 02). One stage produced the highest appearance index (107), but this value was not significantly different from the index with no lint cleaning (105) or the index after two stages (106). Yarn imperfections were highest with no lint cleaning and after three stages of lint cleaning and were lowest after one and two 6
TABLE 5.-Effects of seed-cotton cleaning on moisture contents,!'ibe1' p1 ope1 ties, and fore'ignmatte?' contents of th1'ec cotton 'Va?-ieties, 1970 ---,--,-------------_._----------------------- Test variety Average Measurement 'Tamcot 'Paymaster 'Stripper of all 788' 111' 31' cottons Foreign-matter content: Bur cotton, wagon..,......pct.. 25.5 29.5 28.6 27.9 Seed cotton, feeder...pct.. 3.9 3.2 5.2 4.1 Moisture content: Bur cotton, wagon... "...,...pct.. 10.9 6.6 6.9 8.1 Lint, before lint cleaning...pct.. 6.9 5.8 6.2 6.3 Nonlint content, before lint cleaning...pct.. 6.4 5.2 6.7 6.1 Pressley strength...1,000 Ib/inch2.. 101 91 87 93 Fiber array, before cleaning: Upper-quartile length...inches.. 1.17 1.11 1.01 1.10 Mean length...,...inch.. 0.94 0.91 0.84 0.90 Coefficient of variation...pct.. 32.5 30.8 30.7 31.3 Short fibei's~.,...pct.. 11.0 11.0 11.5 11.2 Fibrograph length, before lint cjeaning: 2.5-pct span length...inches.. 1.08 1.00 0.93 1.00 Length uniformity...pet.. 46 47 47 47 Neps, before lint cleaning... '.No./100 inch 2 of web.. 17 15 11 14 Classification, before lint cleaning: Grade index2.... 93 89 86 89 Staple length...32d inch.. 32.5 30.8 30.0 31.1 1Ylicronaire reading.... 3.5 4.2 4.0 3.9 1 Percent of fibers shot ter than 1/2 inch. 2 Grade index values for various grades of cotton are given in table A-2 (appendix). stages. Imperfections in 22s yarn ranged f}'om 17 to 20 and in 44s yarn from 21 to 26. These data indicate that yarn spun from.lint receiving one or two stages of lint cleaning was of slightly high!>.r quality than yarn spun from lint receiving no lint cleaning or three stages. No lint cleaning produced a higher waste percentage and more imperfections than one and two stages. Three stages produced a lower appearance index and more imperfections than one and two stages. Differences in yarn quality between one and two stages were not significant. The only signi:icant difference between one and two stages was in picker and card waste percentage. A slightly lower waste percentage was obtained with two lint cleaners. 1970 EXPERIMENTS Design Three experiments were conducted in 1970 to obtain additional and more detailed data 011 the effects of lint cleaning on fiber quality and value. 'Tamcot 788', 'Paymaster 111', and 'Stripper 31' cotton varieties were subjected to identical c.leaning and ginning arrangements. Each experiment consisted of processing one of these varieties through a typical seed-cotton cleaning system and then subjecting the lint to one, two, and three stages of lint cleaning. The gin machinery sequence consisted of an air-line cleaner, inclined cleaner, bur machine, inclined cleaner, stick machine, and an extractor feeder. All cotton was conveyed through two tower driers using unheated ambient air. Six replications of each experiment were conducted with each variety of cotton. The lint cleaning treatments were selected at random within each replication. Six bales of each variety were ginned in one-third bale lots. In the 'Tamcot 788' experiment, 6-pound lint samples were taken after lint cleaning Lor small-scale spinning tests. Spinning tests were not performed on 'Paymaster 111' or 'Stripper 31' cottons. Results The three experiments were individually analyzed, and results of the analyses of vari 7
TABLE 6.-Effects of lint.cleaning on moisture contents, fiber properties, waste removal, bale weights, and bale values of three cotton varieties, 1970 Measurement Test cotton and stages of lint Moisture Nonlint Waste Bale Staple ~rade Bale cleaning contenv content removal weight 2 index length 3 value (pct) 4 (pc~) (lb) Db) (32d inch) 'Tamcot 788 : 1 stage... ~... 6;9 3.8 22 510 97 34.1 $114 2 stages... 7.0 3.3 30 502 99 33.9 116 3 stages... 6.6 3.3 32 500 99 33.9 115 'Paymaster 111': 1 stage... 6.0 3.6 16 509 98 31.2 9.5 2 stages... 5.8 2.7 23 502 99 31.5 98 3 stages... 5.8.2.5 25 500 99 31.5 98 'Stripper 31': 1 stage... 6.2 3.1 20 511 96 30.1 89 2 stages... 6.2 2.9 28 503 98 30.0 88 3 stages... 6.2 3.1 31 500 99 30.0 90 Average, all cottons: 1 stage... 6.4 3.5 19 510 97 31.8 99 2 stages... 6.3 3.0 27 502 99 31.8 101 3 stages... 6.2 3.0 29 500 99 31.8 101 1 Moisture content of lint samples taken before lint cleaning. 2 Bale weights include 21 pounds of bagging and ties. Bale weights of 'Tamcot 788', 'Paymaster 111', and 'Stripper 31' before lint cleaning.averaged 532, 525, and 531 pounds, respectively. 3 Grade index values for various grades of cotton are given in table A-2 (appendix). 4 Bale values before lint cleaning for 'Tamcot 788', 'Paymaster 111', and 'Stripper 31' were $101, $88, and $84 respectively. Bale values based on 1970 Commodity Credit Corporation loan prices. TABLE 7.-Effects of lint cleaning on fibe7' lengths andnep contents of three cotton varieties, 1970 Measurement Test cotton and Upper Co Neps stage of lint 2.5-pct Length quartile Mean Short efficient (No. per 100 cleaning span length uniformity length fibers length of variation l inch 2 of (inch) (pct) (inch) (pct) (inch) (pet).card web) 'Tamcot 788': 1 stage... 1.09 46 1.17 0.93 33.1 11.6 34 2 stages... 1.08 46 1.16.93 33.3 11.8 42 3 stages... 1.07 45 1.17.93 33.8 12.1 51 'Paymaster 111': 1 stag('.......99 47 1.11.91 30.6 10.9 13 2 stages....99 47 1.11.91 30.8 10.7 14 3 stages,.,...,. '....99 46 1.10.90 31.5 11.3 15 'Stripper 31': 1 stage....94 47 1.02.84 31.4 12.0 12 2 stages....93 47 1.01.82 32:7 13.4 13 3 stages....93 47 1.01.82 32.5 13.0 14 8 -------- Average, all cottons: 1 stage... 1.01 1.10.89 31.7 11.5 20 2 stages... 1.00 47 1.09.88 32.3 12.0 23 3 stages... 1.00.,.1" 1.09.88 32.6 12.1 27 I Percent of fibers shorter than 1/2 inch.
ance are given in table A-3 (appendix). For simplicity and ease of comparison, data from all three experiments were combined for presentation in tables 5-8. Average foreign-matter contents of the three test cottons at the wagon ranged from 25.5 to 29.5 percent (table 5), indicating that all test cottons were cleaner than the 30 to 32 percent foreign-matter content of normal stripped cotton. Moisture contents of bur cotton -at the wagon ra.nged from 6.6 to 10.9 percent. Differences in the initial average moisture and foreign-matter contents among test lots within a particular cotton variety were not significant. Seed-cotton samples taken after the feeder were analyzed for moisture and foreign-matter contents. Lint samples taken before lint cleaning were tested for nonlint, moisture, strength, length, neps, and classification. 'Tamcot 788' fibers were longer, stronger, and finer than those of 'Paymaster 111' or 'Stripper 31'. The 'Stripper 31' variety had the shortest and weakest fibers, and 'Paymaster 111' was intermediate in length and strength. 'Paymaster 111' had the lowest nonlint content and thus was the cleanest of the three cottons before lint cleaning, and 'Stripper 31' contained the most foreign matter. Grade indices before lint cleaning ranged from 86 (Low Middling) for 'Stripper 31' to 93 (Strict Low Middling) for 'Tamcot 788'. All cottons were within the premium Micronaire range of 3.5 to 4.9. 'Tamcot 788' was in the low end of this range with a reading of 3.5. Micronaire readings for 'Paymaster 111' and 'Stripper 31' were 4.2 and 4.0. One and two stages of lint cleaning reduced nonlint content in all test cottons (table 6). However, the third stage of lint cleaning had little effect on nonlint content. Bale weights were reduced an average of 19, 27, and 29 pounds, respectively, by one, two, and three stages of lint cleaning. Reductions in bale weight (as a result of foreign-matter removal) were accompanied by corresponding increases in grade index. The largest increases in grade index occurred after the first stage of lint cleaning. These increases ranged from 4 units for 'Tamcot 788' to 10 units for 'Stripper 31'. These vast improvements in grade index indicate that 50 to 100 percent of the cotton 'was increased one full grade by the first stage of lint cleaning. The second stage produced additional increases in grade index of 1 or 2 units, which is equivalent to improving the grade of approximately 10 to 20 percent of the bales. The third stage of lint cleaning did not produce further improvements in grade index for 'Tamcot 788' and 'Paymaster 111' cottons, but it did improve 'Stripper 31' by one unit. Classer's staple length tended to average longer after.lint cleaning than before. These differences were similar to those obtained in 1969 and presumably were the result of variations in appearance between uncleaned and lint-cleaned samples. Differences in staple length after one, two, and three stages of lint cleaning were not significant. Bale values were improved $5 to $13 by the first stage of Hnt cleaning. Bale-value differen ces after one, two, and three stages of lint cleaning ($1 to $3) were not statistically significant. Table 7 shows the effects of lint cleaning on TABLE 8.-Effects of lint cleaning on yarn quality of 'Tamcot 788', 1970~ Measurement Stage of lint cleaning 123 Level of significance~ Picker and card waste...pct.. 5.9 22s-yarn strength...lb.. 127b 50s-yarn strength...lb.. 45b Average break factor unit... 2514b Average yarn appearance index... 100b 22s-yarn imperfections...no. 25 50s-yarn imperfections...no. 19a 5.4 125a 44a 2463a 98b 24 18a 5.4 125a 43a 2457a 92a 25 21b 1 Means in a row followed by a common letter are not statistically different at the 0.05 level. ~ Asterisk indicates significant differences among stages of lint cleaning at the 0.05 level. NS indicates no significant differences at the 0.05 level. NS '" '" '" '" NS * 9
fiber length and nep content. Changes in fiber length and length uniformity were similar for all three cottons. Successive stages of lint cleaning generally reduced 2.5-percent span length, upper-quartile length, mean length, and length uniformity and increased coefficient of variation, short fibers, and neps. Reductions in length were small (0.01 to 0.02 inch), and increases in short fibers were generally less than 2 percentage points. N eps in 'Tamcot 788' samples increased from 17 before lint cleaning to 51 after three stages of lint cleaning. Lint cleaning did not increase neps in 'Paymaster 111' samples and produced only small nep increases in 'Stripper 31' samples. These differences in nep formation among the test cottons were likely the result of differences' in fineness and maturity. Micronaire readings, which indicate fineness and maturity, averaged 3.5 for 'Tamcot 788', 4.2 for 'Paymaster 111', and 4.0 for 'Stripper 31' (table 5). Yarn quality of 'Tamcot 788' was determined by conventional small-scale spinning (table 8). Successive stages of lint cleaning decreased strength and appearance of 22s and 50s yarns. Average break factor after one, two, and three stages of lint cleaning was 2,514, 2,463, and 2,457, respectively. The average yarn appearance index was highest (100) after one stage of lint cleaning &lld was lowest (92) after three stages. Imperfections in 22s and 50s yarns were lowest after two stages. Differences in picker and card waste were not significant. These results indicated that lint receiving one stage of lint cleaning produced slightly superior yarn. 1971 EXPERIMENT Design This experiment was designed to determine the optimum amounts of lint cleaning for cotton receiving two levels of seed-cotton cleaning. 'Lankart Lx571' cotton was subjected to two levels of seed-cotton cleaning consisting of a typical machinery sequence and a simple sequence containing about half the machinery typically used to clean stripped seed cotton. The typical sequence contained an air-line TABLE 9.-Effects of lint and seed-cotton cleaning on moisture and for'eign-matte't" con'tents, nonlint contents, and ginning rates, 1971 Seed-cotton cleaning Measurement Level of treatment. 'f' 1 -----".,-~- slgm Icance Typical Simple Moisture content: Bur cotton, wagon...pct.. 7.9 7.9 NS Seed cotton, feeder...pet.. 7.6 7.7 NS Foreign-matter content, wagon: Burs...pet.. 19.5 19.4 NS Sticks...pct.. 3.8 3.6 NS Fine trash...pet.. 6.7 7.0 NS Total...pct.. 30.0 30.0 NS Foreign-matter content, feeder: Burs...pct.. 2.3 4.6 * Sticks...pct.. 1.1 1.5 * Fine trash...pct.. 3.3 3.6 * Total...pet.. 6.7 9.7 * Nonlint content: Before lint cleaning...pet.. 7.4 9.1 * After one lint cleaner...pet.. 3.6 3.9 NS After two lint cleaners...pct.. 2.7 3.1 NS After three lint cleaners...pct.. 2.5 2.9 NS Ginning rate...bales/h.. 3.66 3.60 * 1 Asterisk indicates significant differences between seed-cotton cleaning treatments at the 0.05 level. NS' indicates no significant differences at the 0.05 level. 10
cleaner, inclined cleaner, bur machine, inclined apron averaged 6.7 percent (typical) and 9.7 cleaner, stick machine, and an extractor feed percent (simple). Differences inforeign-mater. The simple sequence contained only an in ter content (as a result of these treatments) clined cleaner, stick machine, and extractor produced significant differences in ginning feeder. All cotton was processed through two rate and nonlint content of lint before lint tower driers using unheated ambient air. Lint cleaning. The ginning rate for the simple from both seed-cotton cleaning treatments re treatment was slightly lower than for the typiceived no lint cleaning and one, two, and three cal treatment. Nonlint contents before lint stages of lint cleaning. cleaning averaged 7.4 percent (typical) and The eight cleaning combinations were repli 9.1 percent (simple). Lint cleaning reduced cated four times. Processing order was ran differences in nonlint content (as a result of domly selected for each replication. Eleven seed-cotton cleaning treatments) to nonsignifibales of cotton were ginned in lis-bale test lots. cant levels. Results Both seed-cotton cleaning treatments and each stage of lint cleaning produced signifi There were no significant differences in inicant differences in bale weight (table 10). The tial moisture or foreig-n-matter contents of the typical treatment and three stages of lint cotton, which contained 7.9 percent moisture cleaning produced the lowest bale weight (479 and 30 percent foreign matter (table 9). The pounds), and the simple treatment with no two seed-cotton cleaning treatments, typical lint cleaning produced the highest bale weight and simple, produced significant differences (524 pounds). For the typical and simple in all components of foreign matter. The treatments, one stage of lint cleaning reduced foreign-matter content of cotton at the feeder bale weights 23 and 30 pounds; two stages TABLE 10.-Effects of cleaning treatments on moistu1'e contents, bal.e ~veights, propm ties, and bctle values, 1971 1 fiber and yarn Seed-cotton cleaning treatment Level of Measurement Typical 2 Simple2 signifi 0 1 2 3 0 1 2 3 cance 3 Bale weight...lb.. 51Of 487d 481b 479a 524g 494e 488d 483c * Grade index 4... 80b 92c 93c 95c 75a 92c 94c 92c * Staple length...32d inch.. 32.3ab 32.1ab 31.5a 31.7ab 32.5b 31.8ab 31.7ab 31.6a * Micronaire reading... 3.5 3.4 3.4 3.5 3.4 3.4 3.4 3.4 NS Bale loan value 5.......... $75ab $83c $80bc $82c $73a $82c $83c $80bc * 2.5-pct span length...inches.. 1.05d 1.04c 1.03a 1.02a 1.05d 1.04c 1.03a 1.03a * Moisture content 6...pct.. 7.8 7.5 7.6 7.6 7.8 7.6 7.6 7.7 NS Length uniformity...pct.. 45 45 45 45 45 44 45 44 NS Stelometer strength...g/tex.. 19.9 19.6 20.1 19.9 19.7 19.9 20.2 20.4 NS Neps.... No./100 inch 2 of web.. 13a 14a 15ab 16b 13a 14a 14a 17b * Picker and card waste...pct.. 9.7d 6.8b 5.8a 5.8a 12.6e 7.5c 6.2a 6.0a * Characteristics of 22s yarn: Yarn strength...lb.. 101cd 100cd 98b 96a 102c 101cd 101cd 98b * Imperfections...No. 40b 35ab 32a 32a 39b 34ab 30a 30a * Characteristics of 50s yarn: Yarn strength...lb.. 35d 34c 33b 32a 35d 35d 34c 33b * Imperfections...No. 27b 26ab 25ab 26ab 24ab 24ab 21a 23ab * Average break factor... 1977c 1944bc 1906b 1846a 1997c 1971c 1958c 1900b * Average appearance index... 108b 105b 104ab 100a 106b 108b l06b l06b * 1. Means in a row followed by a common letter are not statistically different at the 0.05 level. 2 Zero, 1, 2, and 3 indicate stages of lint cleaning. 3 Asterisk indicates significant differences at the 0.05 level. NS indicates no significant differences at the 0.05 level. 4 See footnote 2 to table 3. S Bale values based on 1971 Commodity Credit Corporation loan prices. 6 Based on seed-cotton samples taken at the feeder apron. 11
reduced bale weights 29 and 36 pounds; and three stages l'educed bale weights 31 and 41 pounds. One stage of lint cleaning significantly improved grade index of lint for both seed-cotton cleaning treatments, but the second and third stages produced no furt~er improvements in grade. Average gr&.de indices before lint cleaning were 75 (Strict Good Ordinary) for the simple treatment and 80 (Low Middling) for the typical treatment. There wel'e no significant differences in grade index after one, two, and three stages of lint cleaning, and the average grade index ranged from 92 to 95 (Strict Low Middling). There was some evidence that lint cleaning reduced staple length. For the simple treatment, the staple length before lint cleaning was 32.5 thirty-seconds of an inch, and after three lint cleaners, it was significantly lower at 31.6 thirty-seconds of an inch. A similar trend occulted (though not statistically significant) with lint from the ty'pical treatment. There were no differences in staple length as a result of seed-cotton cleaning treatment. Micronaire reading was not affected by experimental treatments and averaged 3.4 or 3.5 for all test combinations. Bale values were not affected by seed-cotton cleaning treatments. One stage of lint cleaning increased bale value $8 (typical) and $9 (simpie). Bale values after two and three stages of lint cleaning were not significantly different from those produced by one stage. Fiber quality, as determined by length, strength, and nep content measurements, was not affected by seed-cotton cleaning. Lint cleaning reduced 2.5-percent span length but had little effect on length uniformity. Before lint cleaning, the 2.5-pel'cent span length of lint was 1.05 inches, and each successive stage of lint cleaning caused a reduction of about 0.01 inch. Lint cleaning also increased the number of neps per 100 square inches of card web. Before lint cleaning, the nep content of lint was 13 per 100 square inches. After three stages of lint cleaning, nep contents were significantly higher and averaged 16 and 17 per 100 square inches. Differences before lint cleaning and after one and two stages of lint cleaning were not statistically significant. Picker and card waste was highest (12.6 percent) for the simple treatment with no lint cleaning. With no lint cleaning, the typical treatment produced a waste value of 9.7 percent. The typical and simple treatments produced waste values of 6.8 and 7.5 percent after one stage of lint cleaning. There were no significant differences in picker and card waste after two or three stages of lint cleaning. As a l'esult of lint and seed-cotton treatments, yarn quality measurements on 22s and 50s yarns showed some significant differences. Increases in both seed-cotton cleaning and lint cleaning reduced yarn strength. Maximum strengths of 22s and 50s yarns were 102 and 35 pounds, the results of the simple treatment with no lint cleaning. The typical treatment with three lint cleaners produced yarns of lowest strength, averages of 96 and 32 pounds for 22s and 50s yarns. Both seed-cotton treatment and lint cleaning reduced average break factor. The simple seed-cotton treatment with no lint cleaning produced the maximum break factor (1997). Two stages of lint cleaning were required to significantly reduce break factor for lint from the typical treatment. Lint from the simple treatment required three stages of lint cleaning to significantly reduce break factor. Seed-cotton cleaning had little effect on yarn imperfections. Two and three stages of lint cleaning reduced imperfections in 22s yarn. For 50s yarn, differences in imperfections as a result of lint cleaning were not significant. Each successive stage of lint cleaning reduced average appearance index of yarn from the typical treatment, but three stages were required to produce significant differences. Appearance of yarn from the simple treatment was not affected by level of lint cleaning. The results of these data indicated that the typical treatment with one stage of lint cleaning and the simple treatment with two stages produced yarns of approximately equal quality. The yarn quality produced by these two combinations was near maximum for this test. The typical treatment with two stages of lint cleanmg also produced yarn of satisfactory quality, but yarn strength was slightly lower than for yarn produced by the two optimum combinations. Three stages of lint cleaning produced ya; n of SUbstantially lower quality 12
TABLE 1l.-Cotton-clefJ,ning machvfler'1j used in 1972 experiment 1 Machinery sequence and Machinery combination in treatment- stage of lint cleaning 1 2 3 4 5 6 --------------------------------------- X x Air-line cleaner.... Inclined cleaner.... Stick machine.... X Inclined cleaner.... X X Stick machine.... X X Inclined cleaner.... X X X X Stick machine.... X X X X Inclined cleaner... X X X X X Stick machine...... X X X X X Extractor feeder and gin... X X X X X X Stages of lint cleaning: Two stages only... X X X 0, 1, 2, and 3 stages...... X X X 1 X indicates machine was a part of the cleaning sequence. than that produced by other experimental treatments. bur cotton at the wagon ranged from 9.3 to 9.6 percent, and total foreign-matter contents ranged from 35.1 to 38.8 percent, a higher 1972 EXPERIMENT than normal range for stripped cotton. The six seed-cotton cleaning treatments pro Design duced significant differences in foreign-matter This experiment was designed to determine content of seed cotton after the feeder. The the cleaning efficiency of an air-line cleaner extractor feeder alone (treatment 1) produced and to study the effects of various levels of the highest foreign-matter content (21.6 perseed-cotton cleaning on ginning rate. Lint cent). Treatment 4 (three inclined cleaners, cleaning effects were also studied to gain more three stick machines, and a feeder) produced information on the lint cleaning requirements maximum cleaning and the lowest foreignof machine-stripped cotton. The experiment matter content (6.2 percent). Treatment 5 consisted of processing seed cotton through six (four inclined cleaners, four stick machines, machinery sequences, ranging from a mini and a feeder) produced essentially the same mum of one extractor feeder to an elaborate cleaning results as treatment 4. Treatment 3 sequence containing four inclined cleaners, (two inclined cleaners, two stick machines, four stick machines, and an extractor feeder. and a feeder) produced significantly higher No lint cleaning and one, two, and three stages foreign-matter content than treatments 4 and of lint cleaning were used with three of the 5. Treatment 6, which contained the amount sequences, and bvo stages of lint cleaning were of machinery normally used to clean stripped used with the other sequences (table 11). cotton (an air-line cleaner, two inclined clean 'Paymaster 909' cotton was subjected to ers, two stick machines, and a feeder), prothese treatments in three randomized ginning duced significantly hi g her foreign-matter replications. Data pertaining to seed-cotton contents than treatments 4 and 5 but approxicleaning were analyzed as three replications mately equal to that of treatment 3. Treatment of six cleaning sequences. The lint-cleaning 2 (one inclined cleaner, one stick machine, data were analyzed as a factorial experimr-,;t and a feeder) produced cleaning results that consisting of three seed-cotton cleaning levels were intermediate between treatments 1 and 3. and four lint cleaning levels. These results indicated that three inclined Results cleaners, three stick machines, and a feeder (treatment 4) were optimum for cleaning the There were no significant differences in ini test cotton. The use of more machinery did tial moisture or foreign-matter contents of the not improve seed-cotton cleanliness, and using test cotton (table 12). Moisture contents of less machinery resulted in significantly more 13
foreign matter, especially burs and sticks. A This equation shows the vast reduction in comparison of treatments 3 and 6 shows the ginning rate that resulted from the sticks and effect of using an air-line cleaner. The results burs that were not removed before ginning.. of this comparison indicates that the air-line The equation also indicated that sticks had' cleaner did not improve the cleaning perform about 10 times the effect of burs on ginning i ance of the seed-cotton cleaning system. rate. The effect of bur content was small, but ' Ginning rates varied from a low of 2.95 bales each percentage-point mcl'ease in stick content per hour (after treatment 1) to a high of 4.12 resulted in a 4.82-percent reduction in ginning bales per holli' (after treatment 4). This range rate. in ginning rate corresponded to the range in Grade indices of samples from treatments foreign-matt~r contents of seed cotton after the feeder. Ginning rate was correlated to bur 4 and 5 were approximately equal and were and stick content of seed cotton by means of significantlj T higher than those from the other regression analysis. The resultir.g equation was treatments (table 12). Differences in grade indices among treatments 1, 2, 3, and 6 were y=4.56-0.02b-0.22s, 1,2=0.99, not significant. All of these samples were re where y=ginning rate (bales per hour) I duced one grade because of excessive bark, but B=bur content (percent), only 45 percent of the samples from treat S=stick content (percent), ments 4 and 5 'were reduced in grade because and 1 2=coefficient of determinaton. of bark content. These data indicated that the TADLE 12.-Effects of seed-cotton cleaning on 1nOistu1'e and f01'eign-1natter contents, fiber propel ties, ginning nlies, bale weights, and bale values, 1972 1 Measurement :\Ioisture content: Bur cotton, wagon..pet.. Lint, press...pet.. Foreign-matter content at wagon: Burs... '...pet.. Sticks.......pet.. Fine trash...pet.. Seed-cotton cleaning treatment I 2 ~ 4 5 G 9.3a 6.5c 22.0a 9.1a G.Oa 9.3a 6.3bc 23.8a 8.5a 5.7a 9.3a 6.0ab 23.9a 8.8a 5.8a 9.3a 5.8a 22.6a 8.8a 5.3a 9.6a 6.lab 2l.2a 8.4a 5.5a 9.5a 6.lab 25.2a 8.4a 5.2a ----~.----------------------- Total...pet.. 37.1a 38.0a 38.5a 36.7a 35.la 38.8a Foreign-matter content after feeder: Burs...pet.. n.5d 4.8c 3.2ab l.ga 1.8ab 3.4bc Sticks...pct.. 6.2c 4.4b 3.Gb l.9a 2.4a 3.8b Fine trash..... pet.. 4.0 3.2a 2.8a 2.7a 2.5a 2.9a ------~~---.-----'"-------- Total...pet.. 2l.Gd l2.3c 9.5b G.2a 6.7a 10.Obc Ginning' rate... " bales/h,. 2.95a 3.55b 3.G3b 4.l2c 3.99c 3.67b Grade index:!...... 82a 84a 84a 9lb 9lb 83a Barky samples...pct.. loob 100b loob 45a 45a 100b Staple length....32d inch.. 3l.8a 31.7a 31.7a 31.7a 31.8a 3l.8a l\ficronaire reading.. 2.8a 2.9a 2.9a 2.8a 2.9a 2.8a Bale weight...lb.. 483b 483b 462ab 465ab 444a 475ah Bale value 3 '".... $61a $G4ab $6la $68b $65ab $63ab 1!\leans in a row followed by a common letter are not statistically different at the 0.05 level. ~ Grad.e index values for various grades of cotton are given in table A-2 (appendix). 'Bale values based on 1972 Commodity Credit Corporation loan prices.