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Cotton lint yield, seed mass, fiber quality parameters, gross return, and net return were compared for subsurface drip irrigation (SDI) lateral spacing and installation depth in a clay loam soil in western Texas for three seasons. Drip laterals were spaced either in alternate furrows (2 m) or beneath every planted bed (1 m), and installation depths were either 0.2 or 0.3 m beneath the soil surface. Net return was gross return minus fixed and variable costs. Fixed costs included the annual payment for financing the initial investment of SDI materials and installation (5.00% interest over 10 years), the annual land lease, and the annual depreciation of the SDI system. Variable costs were those associated with cotton production and were similar for the two drip lateral spacings. Lint yield, seed mass, and gross and net returns were significantly greater for the 1 m lateral spacing in the first two seasons, but these parameters were significantly greater for the 2 m lateral spacing in the third season. These parameters were consistently greater (either numerically or significantly) for the 0.3 m lateral depth in all seasons. Most fiber quality parameters were not significantly different, and no consistent trends were observed. Lint yields ranged from 640 to 1,635 kg ha-1, and net returns ranged from -$395 to $1,005 ha-1. The low lint yield and resulting net loss were due to a germination failure in the second season for the alternate furrow spaced laterals. Additional seasons of study are required before conclusions might be drawn concerning the most economic lateral spacing for cotton production in the Trans-Pecos region of Texas, but the 0.3 m lateral depth resulted in greater net returns than the 0.2 m lateral depth.

Phymatotrichum root rot, caused by the fungus Phymatotrichum omnivorum, is a serious and destructive disease that significantly reduces cotton yield and lowers lint quality. Cultural practices are commonly recommended for the control of cotton root rot, and fungicides and fumigants that may suppress the disease have also been used. Because of the high costs of these chemicals, their use may be economically feasible only when the infested portions of the field are treated. The objective of this study was to evaluate airborne multispectral imagery for detecting and mapping root rot areas in cotton fields for site-specific management of the disease. One center-pivot irrigated field and one rainfed field near Corpus Christi, Texas, were selected for this study. Airborne three-band digital imagery was taken from the two fields shortly before harvest in 2001 when the infested areas with wilted and dead plants were almost fully pronounced for the season. The imagery was georeferenced and then classified into healthy and root rot areas using unsupervised classification. Accuracy assessment on the classification maps for the two fields indicated that airborne imagery effectively and accurately identified root rot areas within the fields. Ground samples taken from the fields showed that cotton yield and some lint quality indices were significantly lower in root rot areas than in healthy areas. Buffer zones around the root rot areas were generated to account for the spread of cotton root rot on the classification maps. The mapping procedures and maps presented in this study will be useful for site-specific management of the disease.

The moisture content (MC) of cotton lint can be predicted from measurements of electrical resistance. New, automated, resistance-type moisture meters for cotton make measurements in less than 1 s using DC excitation. The sample resistance changes rapidly during the first 10 s of the measurement, making conclusions based on older measurement technology, which took several seconds, questionable. Thus, a device capable of making measurements in less than 1 s and using DC excitation was designed, built, calibrated, and tested. Data showed that the device could measure the electrical current through the samples precisely and that the current was related to the sample moisture content. Regression analysis showed that the standard error in predicting MC was 0.20% over the range 4.1% to 8.7% (wet basis). The types of plastic tested for the sample holders did not affect the resistance. A strong relationship was found between the sample resistance and the sample density over the range of 0.4 to 1.4 g/cm3.

An experiment was run to determine the optimum frequency of the rotary knife on a roller gin stand. Six treatment levels of rotary knife frequency, 150, 300, 450, 600, 750, and 900 rpm, were chosen. (The manufacturer’s specification for rotary knife frequency on the gin stand tested is 389 rpm.) The factors considered in determining the optimum rate included fiber and cottonseed quality, lint turnout, bale value, and ginning rate. There were no significant differences due to treatment with respect to fiber properties. Overall, fiber strength and elongation by the Stelometer averaged 27.8 g/tex and 6.98%, respectively; fiber span length and uniformity by the Fibrograph averaged 3.52 cm (1.38 in.) and 47.5, respectively; and fiber grade, staple, and micronaire by the USDA-AMS Classing office averaged 2.17, 46.8 32nd-in., and 38.1, respectively. These fiber properties are on samples taken from the bale and included two mill-type/air-jet lint cleaners. With the exception of linters content, there were no significant differences due to treatment on the cottonseed properties. Overall, foreign matter content of the cottonseed averaged 2.16%, and cottonseed grade averaged 114. Linters content ranged from 1.67 to 2.88% on the 300 and 900 rpm treatment, respectively. Lint turnout and bale value were not significantly different due to treatment, averaging 35.3% and $438.71 overall. Ginning rate was significantly different due to treatment; the highest rate occurred on the 300 rpm treatment and was 350 kg/m/h (1.90 bales/h). Using regression analysis, the optimum rotary knife frequency occurs at 269 rpm. At rotary knife frequencies less than 269 rpm, some of the ginning area on the roller is wasted, and roller damage is possible due to tags that cannot be cleared. At rotary knife frequencies greater than 269 rpm, compromises are made between ginning rate, seed cotton carryover, and choke-ups.

New technology to automatically engage/disengage grid bars in saw-type lint cleaners to reduce fiber waste and associated fiber damage was evaluated in five studies. The number of active grid bars in the studies varied from 0 to 10, and as the number of grid bars increased, fiber loss and damage increased. Typically for a single 5-grid bar lint cleaner, about 50% of the material that was removed was removed by the first two grid bars; for two lint cleaners, about 40% of the material was removed by the first two grid bars. Short fiber content and neps increased over 30% as grid bars increased from 2 to 10, and mill performance was degraded. Material removed from lint by saw-type lint cleaners is strongly related to variety, growing conditions and harvesting, and ranged from 6.1 to 17.5 kg (13.4 to 38.6 lb) per bale when two lint cleaners were used. In a 39,000 bale field study where lint cleaning was optimized by a computerized process control system, fiber loss from two grid bars (3.6 kg or 8 lb/bale) was about 25% of that from five grid bars (13.6 kg or 30 lb/bale).

Byproducts produced from cotton gins have commonly been referred to as trash since they were deemed to have little value. However in some areas of the cotton belt, the byproducts have been utilized successfully. Cotton gin byproducts (CGB) have been fed to livestock, used to make compost, bedding for dairy cattle, or applied back on the land to add humus to the soil. Over the years, extensive research has been performed in evaluating and creating uses for CGB. Almost without exception, all research pertaining to utilization of CGB has evaluated or measured some aspect of the product to determine a desired or needed characteristic pertaining to a specific research objective or goal. Currently, cotton gins produce various streams of byproducts due to the design and layout of the equipment used in the ginning process. In most every case, the byproducts are combined into a single waste stream and sent to a central location. The objective of this research was to characterize the various parameters of the individual waste streams prior to their being combined, to ascertain if the ginning equipment was sorting the byproducts into components that had more desirable characteristics to potential end users. Our results showed that the extractors, lower gin motes, gin stand feeder, overflow separator and lint cleaners produced a product with more desirable characteristics for livestock feeding and fuel utilization than those byproducts from the inclined cleaners and unloading system.

The fiber attachment strength of 10 different varieties of cotton were measured in samples from two growing areas in Australia. The same samples were measured in laboratory tests to obtain values for the seed index, mote content, lint fraction, and nep count. These measurements were used with standard HVI fiber values to investigate the ginnability of the different varieties, the effects of growing area on ginnability, and the effects of ginning on fiber quality. It was found that the fiber attachment strength and the mote content of the seed cotton was higher in cotton from the more northerly (lower latitude) growing area, while the lint fraction (turn out) and seed index values were similar across the cotton growing belt. The fiber attachment strength was negatively correlated with mote content but no other parameters in the data set. Regression analyses were used to develop predictive equations for the fiber attachment strength, mote content, fiber elongation, short fiber content, uniformity, and length from the measured data.

A sensor was developed to measure mass flow of lint cleaner waste (LCW) through a small-scale (one bale/h) cotton gin to provide additional information on lint cleaner performance for automated gin process control. The device consisted of a light source bank and light bar at opposite sides of the waste duct. The amount of light blocked as detected by the light bar was proportional to mass flow. Experiments were conducted to evaluate the sensor by varying the number of lint cleaners activated. Statistical correlations between sensor output and output from photodiodes configured to detect temporally varying light levels were examined. Curves were developed relating measured mass flow to sensor output, consistent with expected sensor responses. A Weibull-type function was found to best describe the sensor response as a function of experimentally measured mass flow. A re-parameterized Weibull-type function was found to be a suitable predictor of mass flow rate when runs using zero lint cleaners were included in the data. When the zero lint cleaner treatment was not included in the data set, a linear relationship best predicted mass flowrate. Total mass of particulate was best predicted by a reciprocal log model.

An experimental machine that combines the roller-ginning and lint-cleaning functions into one unit was tested. The ginning section of the machine is conventional and the cleaning section consists of a cylinder-type cleaner. Because the ginned fiber is guided directly onto the cleaning cylinder without forming a batt, a feed roll/feed bar assembly (which damages the fiber) is not required. The test consisted of comparing Pima lint cleaned with conventional mill-type/air-jet cleaners to Pima lint cleaned with the experimental machine. There were no significant differences in fiber or yarn quality between the two cleaning treatments. The experimental machine had more trash in the lint, more lint in the trash, and a lower cleaning efficiency than mill-type/air-jet cleaners, but turnout and bale value remained the same.

Seed cotton from producers from 11 major cotton producing states was ginned at either the Stoneville, Mississippi, or Mesilla Park, New Mexico, USDA, ARS cotton ginning laboratories. Particulate emissions during ginning were sampled from the exhausts of the unloader separator and the first lint cleaner and particulate captured by the unloader cyclone. Endotoxin analysis was performed on emission particulate sampled from the exhausts, and the particulate captured by the cyclone. Analysis showed that the airborne concentrations on endotoxin 100 m from the gin exhausts are below levels reported to produce respiratory health concerns.

The international cotton industry needs an inexpensive yet accurate method to determine the moisture content of cotton. Basic studies were conducted to ascertain the applicability of electrical resistance to measuring moisture content. The resistance of cotton lint samples of varying moisture content, which were loaded into a series of acrylic holders with aluminum ends and compressed to 0.3 g/cm3, was measured. The holders varied in sample thickness from 1 to 4 cm and in sample cross-sectional area from 1 to 40 cm2. The resistance was found to vary with sample thickness as expected, but the resistivity did not vary with sample cross-sectional area in the expected way. Relationships relating sample moisture content to sample resistance and sample geometry were examined. Models were found which fit the data well; the residuals varied inversely with sample moisture content and sample circumference.

The cost of drip irrigation can be reduced by using both wider lateral spacings and the same laterals for multiple years, as with subsurface placement. Multiple, low-rate fertilizer and water applications may reduce N fertilizer needs by improving efficiency and limiting the potential for leaching. The combination of these technologies may make drip irrigation of cotton profitable. Four years of continuous cotton and two years of cotton rotated with peanut were evaluated. Two subsurface drip irrigation lateral spacings (every row, 1 m, and alternate furrow, 2 m) and three sidedress-nitrogen methods (STD, single application of 112 kg/ha; INC, 112 kg/ha in five equal applications; and GOS, applications determined by GOSSYM/COMAX) were evaluated for cotton during 1991-1994. Two of the sidedressnitrogen methods (STD and GOS) were evaluated for a rainfall-only treatment. Lint yields did not differ between the lateral spacings in any year. Yields for irrigated treatments were 16 and 65% greater than rainfall-only yields in 1992 and 1993, respectively. The GOSSYM/COMAX-managed nitrogen treatment received 30% less nitrogen fertilizer than other treatments, but had similar lint yield. Several fiber physical properties were affected by irrigation and nitrogen, but these effects were small and inconsistent. For continuous cotton, or cotton rotated with peanut, the wider lateral spacing is preferred to the every-row spacing because of its lower initial cost (about 30%). The combination of lower system cost, longer system life, and lower N-fertilizer requirements could make subsurface drip irrigation of cotton profitable for southeastern Coastal Plain soils, and reduce the potential for ground water contamination.

Seed cotton from producers in Alabama, Arizona, Arkansas, California, Georgia, Mississippi, Missouri, New Mexico, South Carolina, Tennessee, and Texas was ginned at either the Stoneville or Mesilla Park USDA, ARS Cotton Ginning Laboratories. Particulate emissions during ginning were sampled from the exhausts of the unloader separator and the first lint cleaner. The gin external emission particulate sampled from both exhausts was analyzed for crop protection products/agricultural chemicals. DEF (a chemical used for defoliation of cotton plants just prior to harvest) is the only substance found routinely in gin external emissions. Exposure at the boundary line (100 m from the gin exhaust) to any of the substances detected was fractions of ppb, or in the case of DEF, an average of less than 1 ppb (1 ng/m3). The air concentrations 100 m from the gin exhaust are well below levels that would produce any health concerns. Also, none of the substances detected occurred at levels of any concern for meeting either EPA or OSHA regulations.

Seed cotton from producers in Alabama, Arizona, Arkansas, California, Mississippi, Missouri, New Mexico, South Carolina, Tennessee, and Texas was ginned at either the Stoneville or Mesilla Park USDA, ARS Cotton Ginning Laboratories. Particulate emissions during ginning were sampled from the exhausts of the unloader separator and the first lint cleaner. Proximate and X-ray fluorescence analyses were performed on the emission particulate sampled from both exhausts and the particulate captured by the unloader cyclone. Proximate analyses showed that the largest constituent of gin emissions is noncellulosic plant material (range of 43 to 66%), followed by cellulose (range of 17 to 40%), with the remainder being inorganic soil particles and water. X-ray fluorescence was used to determine the level of 19 different elements including arsenic, lead, and mercury. None of these elements occurred at levels of any concern for meeting either EPA or OSHA regulations and could be attributed primarily to native soil content of the harvested seed cotton.

Cottonseed merchants are concerned about damage to cottonseed that occurs at the cotton gin. Because of these concerns a two-year study was conducted to determine the effect of cottonseed moisture levels and seed cotton feedrates during ginning on cottonseed damage and the occurrence of seed coat fragments (SCF) in the lint. Five cottonseed moisture levels were tested the first year whereas four were used the second year. Two feedrate levels were considered each year. During the first-year experiment, the higher feedrate gave significantly higher seed damage while the SCF count only showed a higher trend. However, neither seed damage nor SCF numbers were significantly affected by the feedrates in the second-year experiment although both parameters tended to be higher for the higher feedrate. Seed damage increased with moisture content with the largest increase occurring at seed moisture levels above 12%. Seed coat fragment numbers and weights in ginned lint tended to be larger for the higher moisture contents. The study indicated cottonseed was more susceptible to damage at higher moisture contents and that high feedrates seem to accelerate the damage process.

It is desirable to predict lint cotton color in advance of processing the cotton in a gin. Improvements over the use of seed cotton color as the lone predictor are needed. Standard lint color and trash content measurements were made on 61 samples of lint and seed cotton to determine the predictability of lint color from that of seed cotton. Also, visible spectral data were collected from the seed cotton and lint samples, and from corresponding samples of fuzzy and delinted seed. Simple and multiple linear regression were conducted to determine the relationships among lint color, seed cotton color, and spectral data. Trash content data and spectral data from cotton seed were applied in addition to seed cotton data in an effort to enhance the predictability of lint color. Results from linear regression showed that seed cotton color correlated moderately (R2 ˜ 0.6) with lint color. Seed cotton and lint reflectances at individual 50-nm spectral bands correlated poorly (R2 ˜ 0.2). With trash content in the analysis, the fit was improved (R2 ˜ 0.4). Seed spectral data also improved the correlations (R2 ˜ 0.4). In addition, seed spectral data improved the correlations between seed cotton color and lint color (from R2 ˜ 0.6 to R2 ˜ 0.7). Ratios of seed spectral data were about as effective as the spectral data themselves. The inclusion of seed cotton spectral data in these models improved correlations slightly more (from R2 ˜ 0.7 to R2 ˜ 0.8). Adjusting lint and seed cotton spectral data for trash and seed reflectances was largely unsuccessful in improving correlations between lint and seed cotton spectral data. The regression methods and data relationships mentioned above are discussed in detail in the article.

A desire for improvement of the state of the art in cotton quality measurements, and for application of such measurements to the ginning process, has prompted investigation of near-infrared reflectance (NIR) as a means of measuring different cotton quality characteristics. Cotton samples from five different cotton sources covering a range of white color grades were ginned with three different lint-cleaner treatments. The lint samples then underwent a full set of High Volume Instrument quality tests at a cotton classing office. The samples were subsequently measured on an NIR spectrophotometer at 2-nm intervals from 1100 to 2500 nm. These 700 measurements were averaged into 14 bands of 100 nm in width. Ratios of the bands were calculated, and statistical model selection procedures were used to establish optimal regression models for the quality characteristics with continuous values. Correlations of the models to the quality characteristics were also calculated. Optimal models showed the following R2 values in relation to their corresponding cotton quality characteristics—0.88 for reflectance, 0.85 for yellowness, 0.60 for trash content, 0.96 for micronaire, 0.73 for strength, 0.79 for length, and 0.67 for length uniformity. The NIR ratios were also employed in discriminant analyses to establish models for classification of discrete attributes of the cotton samples. Classification accuracies were 93% for cotton source, 91% for combined source and lint-cleaner treatment, 93% for color grade, and 70% for color-grade quadrant.

Sixteen grid bar arrangements were tested to evaluate the potential benefits of adjustable grid bars for both the extracting saw and the reclaiming saw in a bur and stick extractor. Four spacing arrangements for the grid bars around the primary extraction saw were evaluated in combination with similar spacing arrangements for the grids around the reclaimer saw cylinder. In general, increases in grid spacing tended to increase both cleaning efficiency and lint wastage. Several of the grid spacing combinations produced about the same cleaning efficiency, but widely different lint wastage values. Results indicated that care should be taken in selecting a grid spacing arrangement if one wishes to maximize efficiency at a tolerable lint wastage level. Large variations were also encountered in cleaning performance and lint wastage among test cottons. These large differences in stick extractor performance illustrate the difficulty of selecting a single, grid spacing arrangement that will produce satisfactory results for a wide range of stripper-harvested cottons. One potential solution to this problem would be to develop the means for quickly adjusting the grids bars used in these types of machines, especially those grids used around the primary sling-off saw cylinder.

Data from Griffin (1974) and that of Urquhart and Williams (1924) were used to evaluate available equilibrium moisture content models at normal temperature and at elevated temperatures (up to 90° C). Models evaluated included the Henderson and Perry (1976), a simple cubic polynomial, and the BET [Brunauer, Emmett, and Teller (1938) as modified by Dent (1977)]. All three models were evaluated for lint equilibrium moisture content at normal temperature. The BET model gave the best fit, but the simpler models gave satisfactory results for engineering calculations. Only the BET model gave adequate fit for variable temperature applications. Equilibrium moisture content is important in the processes involved in lint spinning. A reasonable amount of data is available on moisture absorption, but there is a lack of data on the desorption process. Since drying lint in seed cotton samples is a desorption process, a set of equations were devised to convert from one process to the other by a simple calculation.

A three-year study was undertaken to provide additional information on important relationships between cotton gin and textile mill cleaning with respect to rotor spinning performance. Some effects of varying the aggressiveness of seed cotton cleaning, lint cleaning, and mill cleaning on fiber properties, spinning performance, and yarn quality are presented. This study also provided important insights into the effects of previous cleaning history and nonlint content on the cleaning performance of mill cleaning and carding equipment.

Adoption of the high volume instrument (HVI) classification system for the official marketing criteria for cotton coupled with the separation of color and trash into different grade components requires that ginners and producers be knowledgeable of the impact of gin equipment on color and trash. Several studies indicated that gins can increase the perceived color grade of cotton by as much as two grades and that Spotted and Light-spotted cotton could be improved to Light-spotted or White color grades. Consideration of the effect of individual equipment in a cotton gin in three recent studies indicated that the seed cotton cleaners did little to improve color but did improve trash grade. Further analysis showed that lint cleaners improved the color of cotton. In these studies, Rd (grayness or reflectance) was increased by about 4.4 units whereas +b (yellowness) was increased only about 0.5 units. Much of the improvement in color was attributable to the removal of trash from the sample. Since lint cleaners remove substantial amounts of trash, they must continue to be used to improve the color of cotton.

Equipment and techniques were developed to study cotton moisture absorption and desorption rates at temperatures ranging from 49 to 91° C (120 to 196° F). The data provided valuable insight into the moisture-time relationships for cotton lint. The moisture data was transformed and found to fit a theoretical, exponential decay function. Nonlinear regression analysis was used to fit the value of the coefficients in the theoretical equation to the experimental data. Results indicate that both temperature and air condition (dry or humid) significantly affect the “diffusivity” (rate) parameter in the nonlinear equations. As expected, higher moisture transfer rates occurred at higher temperatures and the drying rate was significantly higher than the humidification rate for cotton lint at the same temperature. When the diffusivity coefficients from this study and from the literature are plotted against temperature, the coefficients for the dry air produce an almost linear relationship with temperature. Generalized equations for moisture absorption and desorption were also developed, using historical data along with data from this study, for a temperature range of 5 to 90° C (41 to 194° F).

Literature has implied that foreign matter affects cotton reflectance and yellowness measurements made with color meters. Samples of seed cotton and lint were measured for reflectance and yellowness before and after hand cleaning of the sample faces. Results confirmed the existence of the cleaning effect on color measurements which was more pronounced with seed cotton. Because disturbance of the sample face was minimized, change in trash content appeared to be the main cause of the effect. The change in the measured area of trash in the sample face correlated well with the change in reflectance for seed cotton, but change in yellowness was less predictable. To remove the effects of trash particles on color measurements, a new method was devised in which spectrally filtered images of lint and seed cotton samples were acquired with a monochrome video camera, and a computer algorithm was written to allow color measurement on essentially lint only by not considering pixels classified as trash in the calculation of either reflectance or yellowness. Color and trash measurements were also made with a High Volume Instrument color/trash meter. Trash particles then were removed by hand from the faces of the cotton samples. Color and trash measurements were then made again with the High Volume Instrument color/trash meter. While prediction of green-red reflectance after cleaning was not improved with the new method, the blue-band reflectance of uncleaned seed cotton was more highly correlated with that of cleaned seed cotton when the new measurement technique was used. This improvement was also marginally true with lint. Additionally, prediction of blue-band reflectance of cleaned lint from that of uncleaned seed cotton was improved with the new method. Gin process-control systems requiring evaluation of seed cotton color would benefit from the use of such a technique which lessens the effects of nonlint material on color measurements.

Three irrigation scheduling methods and two microirrigation tube placements were evaluated on three cotton (Gossypium hirsutum L.) cultivars for three years on a southeastern Coastal Plain soil. Irrigation scheduling methods included two computer models, GOSSYM/COMAX and PRISM, and a method using tensiometers. Microirrigation tubing was placed on the soil surface, either adjacent to every row or in alternate furrows. Growing-season rainfall amounts ranged from 313 mm in 1990 to 544 mm in 1988. Rainfall distribution also varied widely within each year. In a similar manner, irrigation amount and frequency varied among scheduling methods and years, but no method consistently required the largest or smallest amount of irrigation. Cotton lint yields ranged from 850 to 1105 kg/ha over all years, but there were few significant differences among irrigation treatments within a year, even between the rainfall-only and irrigated treatments. Lint yields were significantly greater for the PD3 and DPL90 cultivars than for the Coker 315 cultivar during the three-year period, and the PD3 cultivar had a greater yield response to irrigation. The tensiometer-every row tube placement is the only irrigation treatment that produced cotton lint yields significantly higher than the rainfall-only treatment each year. The tensiometer scheduling method also produced significantly greater yields each year. Although yield differences occurred, they were relatively small. This fact, along with the inconsistent differences in the amount of irrigation water required, suggests that the preferred method for a particular application will probably depend more upon water or labor requirements, cost, or personal preference. Also, there was no difference in yield between the two tube placements. Because the alternate-furrow placement requires only half as much tubing, which will reduce installation costs by about 30%, it appears to be the preferred placement for this soil. Further research is needed to refine irrigation scheduling for cotton in this region.

A smooth-leaf cotton variety was subjected to three, six, and eight seed cotton cleaners and extractors and then ginned with two, one, and zero lint cleaners, respectively. The lint was made into yarn, knitted into fabric, and dyed. Tests were performed on the lint, yarn, and fabric to determine quality parameters. The treatment with one lint cleaner and six seed cotton cleaners resulted in equal or better fiber, yarn, and fabric quality than the other cleaning treatments.

Research studies were conducted during the 1980s to evaluate the relationship between harvest systems, harvest aid chemicals, and harvest environments to cotton yield and quality. Cotton yield and quality were reduced in three out of five years with once over and delayed harvesting compared to twice over harvesting. The most significant factor influencing yield and grade in these studies was rainfall occurring after the cotton was open. Rainfall totaling 50 mm or more significantly reduced yield and quality. Defoliation reduced lint yield by an average of 44 kg/ha but increased grade index. Application of Prep (ethephon) to accelerate boll opening significantly reduced yield and grade if applied at the 40% or 60% open stage, but had no detrimental effect on yield or grade if applied at the 80% open stage.

Equipment and techniques were developed to study cotton moisture absorption and desorption rates at temperatures ranging from 5 to 53° C. The equipment worked well and provided valuable insight into the moisture-time relationships for cotton lint. The moisture data was transformed and found to fit a theoretical, exponential decay function. Nonlinear regression analysis was used to fit the value of the coefficients in the theoretical equation to the experimental data. Results indicate that both temperature and air type (dry or humid) significantly affect the diffusivity (rate) and the shape parameters in the nonlinear equations. The rate of moisture transfer increased with decreasing humidity and with increasing temperature for the range of 5-41° C and then decreased for the high temperature (51-53° C) runs. The data taken at high temperatures (39-53° C) deviated from the theoretical decay function as it approached the asymptotic value.

A computer simulation model of cotton harvesting and handling system was developed. The system can consist of any number of harvesters, module builders, and boll buggies. The results from unvalidated simulation were as follows: a) initial harvest date significantly affects the lint picked and total revenue; b) one harvester is more economical than two harvesters for a 283.3-hectare farm; and c) the system without a boll buggy results in higher total return than the system with one boll buggy when harvester dumping times are short.

Field experiments were conducted in central Arizona on a sandy loam soil to evaluate the effects of irrigation uniformity on the lint yield of cotton grown with level basin irrigation. Treatments of High, Medium, and Low irrigation received seasonal water application depths of 900, 700, and 500 mm, respectively, after crop establishment. The level basin system was operated to provide a high irrigation uniformity in 1987 and a low irrigation uniformity in 1988. The measured depth of water replaced by irrigation was characterized by the low-quarter distribution uniformity which varied from 80-85% in 1987, compared to 69-82% in 1988. Under the higher irrigation uniformity in 1987, correlation between the measured yield and total depth of water replaced was not significant within either the High or Medium irrigation treatments. Under the low irrigation uniformity of 1988, yield variability within the field was more extensive, and the yield was significantly correlated with total depth of water replaced within all irrigation treatments. When expressed relative to the mean lint yield of the local farm area, yields of the High, Medium, and Low irrigation were about 6, 2, and 7% greater under high than low irrigation uniformity, respectively.

Two experiments were conducted to investigate whether saw-type lint cleaners create more fine trash in the lint than they remove. Results indicated that the lint cleaner was reasonably efficient in reducing trash levels for all size ranges investigated. The amount of cleaning accomplished, however, depended on trash particle size. The lint cleaner removed about one-half of the particles smaller than 0.25 mm (equivalent diameter) and virtually all of the particles larger than 4 mm in diameter. While these results tended to exonerate the saw-type lint cleaner of charges of creating fine trash, there was some indication that the saw gin stand increased the amount of small and medium size trash in the lint.

An automated drip irrigation system was controlled by continuously measuring cotton canopy temperature and computing 15-minute averages in a three-year field study between 1988-1990. Irrigation was applied only when average canopy temperature exceeded predetermined threshold values. Threshold temperatures were tested in 2° C increments between 26° C and 32° C. The length of irrigation cycles was shortest and amount per irrigation event was highest for all threshold temperatures during the early growth stage because canopies were small and warm bare soil contributed to measured canopy temperature. The ratio of water use to reference evapotranspiration decreased as threshold canopy temperature increased from 26° C to 32° C, but water use efficiency increased. Average canopy temperature during the period DOY 198 to 273, while net radiation exceeded 300 W m-2 and air temperature at 2 m exceeded 28° C, increased as threshold canopy temperature increased. Lint yield was highest for the 28° C threshold temperature and decreased for higher or lower threshold temperatures. Threshold temperatures = 28° C restricted water application and created increasing levels of water stress. The 28° C threshold should provide maximum lint yield where water supply and season length do not limit production. Under limited production conditions a 30° C threshold may be preferable to a 28° C threshold because lint yield is only slightly reduced but water use efficiency is higher and cotton matures more rapidly. Maximum yields were produced by 28° C and 30° C threshold canopy temperatures in which total seasonal water use ranged between 64 and 84 cm.

Three suspected categories of seed-coat-fragment contamination in cotton lint were investigated. These were chalazal chips, seed damage, and immature seed. The most important variable for the first category was the work, as estimated by a ballistic pendulum apparatus, required to remove lint from the chalazal, rounded end of the cottonseed. In the second category, the percent damage in acid-delinted samples was selected. In the third, the coefficient of variation for cottonseed diameter was the prime variable. Fabric was woven for each of the cottons and the number of seed-coat fragments on the surface of the fabrics was counted. For the group of cottons used in this study, chalazal detachment work accounted for 16% of the variability in the fragments on the fabric; percent damaged seed, 1%; and the seed size coefficient of variation, 73%. Apparently, seeds less than 3.73 mm in diameter, when present in the seed size distribution, were the major source of seed-coat-fragment contamination for this study.

Equipment and techniques were developed to study cotton moisture absorption and desorption rates. The equipment worked well and provided valuable insight into the moisture-time relationships for cotton lint. The moisture data was transformed and found to fit a theoretical, exponential decay function. Nonlinear regression analysis was used to fit the value of the coefficients in the theoretical equation. The equation can be used, with equilibrium moisture content values, to predict the time rate of change of moisture content of cotton lint. The equation applies to small samples of lint (similar in size to the lint from one lock of seed cotton) found in an air stream with a small relative velocity (0.04 m/s) at temperatures between 12 and 26° C.

Saw-type lint cleaners are excellent devices for cleaning, combing and blending cotton fibers during the ginning process. However, they adversely influence fiber properties such as length. This study considered the use of several additional, non-aggressive cleaners prior to the fiber-seed separation process (ginning) in lieu of lint cleaners after ginning. Results over a three-year period with different types of cotton (hairy- and smooth-leaf) indicated that market grade could be maintained and producer monetary retums increased by substituting three seed cotton cleaners before ginning for the second stage of lint cleaning after ginning. In addition, the fiber quality measurements of nep content, short fiber content, and length distribution were improved.

Some of the design characteristics of an experimental saw-type lint cleaner which is directly coupled to a saw-gin stand are presented along with performance data. The coupled gin stand and lint cleaner unit is designed to replace one gin stand and two stages of standard saw-type lint cleaning. Raw fiber data from both a small laboratory study and a full-scale mill study show that the coupled lint cleaner, when compared to standard lint cleaning, produces fiber that is significantly cleaner, longer, and with fewer short fibers. Spinning and weaving data also show that the coupled-lint-cleaner fiber has significantly less mill waste and a tendency to produce more uniform yam and stronger, more uniform cloth. Nep counts in the raw fiber were significantly higher for the coupled-lint-cleaner.

Nine bales of Midsouth cotton were subjected to three harvesting treatments, three levels of lint cleaning, three levels of mill opening line cleaning, and two levels of mill carding. Fiber properties after ginning were best for the normal-harvested cotton without lint cleaning, but producer returns were best for normal-harvested cotton cleaned by two lint cleaners. After the cotton was cleaned at the mill, the best fiber properties shifted from the normal-harvested cotton to the early harvested cotton. Fiber properties after mill cleaning were best for early harvested cotton ginned with one lint cleaner, cleaned at the mill opening line with a hopper, Superior Cleaner, Superior Cleaner and picker, and carded twice.

Irrigation scheduling methods using three threshold canopy temperatures (28 C, 30 C, and 32 C) were compared with soil water balance methods that replaced depleted soil moisture weekly (SWR) or at approximately two-week intervals (AUS) and a treatment that received only preplant irrigation (DRY). The largest quantity of water applied (rainfall plus irrigation) was to SWR (138 cm). The quantities for AUS (75 cm) and 28C (70 cm) treatments were similar, followed by 30C (46 cm) and 28 C (70 cm) treatments were similar, followed by 30C (46 cm), 32C (36 cm), and DRY (18 cm). Water used by these treatments was 133, 75, 78, 52, 46, and 29 cm, respectively. Volumetric soil profile moisture content of 0.28 in the SWR and AUS treatments at the end of the season showed little depletion while the 28 C, 30 C, and 32C treatments were lower at 0.24. Average canopy temperatures during the period DOY 187-274 when net radiation exceeded 200 w/m^ were 26.0, 26.8, 27.8, 24.1, 25.3, and 28.9 C, respectively, for 28 C, 30 C, 32 C, SWR, AUS, and the DRY treatments. Above 600 w/m^, the difference between canopy and air temperature increased in the 30 C, 32 C, and DRY treatments indicating water stress. Lint yield was positively related to water applied and water used, except for the SWR treatment. Rate of boll maturity was highest in the three threshold canopy temperature and DRY treatments. Cotton fiber length was decreased by water stress, micronaire value was reduced by low temperature, and fiber strength was reduced by either high water stress or low canopy temperature. Irrigation scheduled by threshold canopy temperature permits automated decision-making of both application time and amount.

Removal of foreign matter from cotton during the ginning process is a complex interaction of genetic traits, moisture differentials and machine performance parameters. Studies over a three-year period of over 30 cotton cultivars grown in Mississippi and South Carolina and processed identically at the gin, indicated that large differences occur in the initial foreign matter and in the foreign matter removal characteristics (cleanability) of cotton cultivars. Cleaning efficiencies also differ for the types of gin cleaning machinery such as seed cotton cleaners and lint cleaners. Overall cleaning efficiencies adjusted each year to a common level of foreign matter for each cultivar ranged from a low of 75.2% to 85.6%. Differences in cleaning levels occurred between years but the relative efficiencies remained similar for the cultivars.

Neps and seed-coat fragments in lint cotton cause reduced efficiency in the textile mill and detract from appearance in yam and fabric. Ginning can influence and control to some degree the level of these imperfections. Experiments were conducted to determine if these imperfections can be further reduced by production methodology. Specifically the relationships of micronaire, maturity, and fiber strength on the occurrence of neps and seed-coat fragments were investigated. The study involved 15 commercially available and experimental varieties and strains, each harvested as many as seven times to give maturity differences. The varieties were selected to give a range of fiber properties. Information obtained will aid breeders in developing varieties with a low potential for the creation of imperfections during processing

Imperfections in lint cotton, particularly neps and seed-coat fragments, reduce processing efficiency in the textile mill and detract from appearance in yam and fabric. This study identified fiber properties and varieties which are consistently associated with low nep and seed-coat fragment levels in ginned lint, yam, and fabric. Growth conditions and maturity of the cottons were considered; the level of imperfections were measured in both dyed and undyed fabric. Correlations were determined and definite trends established between many of the variables. The information obtained will aid breeders in selecting for further development those cottons which have a low potential for imperfection formation during processing.

Cotton production is an important economic base for western Texas; however, the region has erratic and limited rainfall and is dependent on limited groundwater supplies. Maximizing water use efficiency (WUE) for cotton lint yield is therefore a strategic goal in conserving limited water resources. In this study, different row spacings, planting patterns, and irrigation levels were evaluated to investigate water use efficiency for cotton under subsurface drip irrigation (SDI). An experiment with three row spacings, three planting patterns, and four water levels was conducted during three years in western Texas. The row spacing treatments were ultra–narrow (UNR), 0.76 m, and 1.02 m. The planting patterns for the 0.76–m and 1.02–m row spacings were every row planted, one planted and one skipped, and two planted and one skipped. The UNR cotton was solid–planted in 0.25–m rows in 1997 and in 0.38–m rows in 1998 and 1999. Driplines were placed beneath each planted row, except in the case of the UNR rows where the rows were planted over the 0.76–m dripline spacing. The UNR and the 0.76–m row spacings resulted in higher WUE than the 1.02–m row spacing for the highest water level in 1997, and for the lowest water level in 1998 for the every–row pattern. When the three years of data were combined for analysis, it was observed that for the lowest water treatment (0.6 mm/d in–season irrigation), the UNR spacing produced a higher WUE (0.258 kg/m3) than the 0.76–m and 1.02–m row spacings (0.198 kg/m3). The average WUE of the UNR spacing for three years of the experiment was 11.7% and 21.3% higher than the 0.76–m and 1.02–m row spacings, respectively. Although the 0.76–m and 1.02–m row spacings were not significantly different, the WUE of the 0.76–m row spacing was 10.5% higher than that of the 1.02–m row spacing. Therefore, we conclude that, under our conditions, row spacing can have a moderate impact on WUE for SDI systems. The narrower cotton spacing exhibited trends toward higher WUE. When the planting patterns were analyzed by combining three years of data, it was found that planting pattern did not have an influence on WUE for the 0.76–m and 1.02–m row spacings.

An experiment was run to determine the optimum speed of the cleaning cylinder on the Batt–Less Lint Cleaner. The Batt–Less Lint Cleaner is an experimental machine that combines the roller–ginning and lint–cleaning functions into one unit. The ginning section of the machine is a standard roller gin stand, while the lint cleaning section consists of a saw–type cleaning cylinder. Because the ginned fiber is guided directly onto the cleaning cylinder without forming a batt, a feed–roll/feed–bar assembly (which damages the fiber) is not needed. The control treatment of the experiment bypassed the cleaning cylinder of the Batt–Less Lint Cleaner and instead cleaned the fiber with mill–type/air–jet lint cleaners. The experimental treatments varied the speed of the cleaning cylinder from 300 to 1050 rpm in increments of 150 rpm. Results show that as the speed of the cleaning cylinder on the Batt–Less Lint Cleaner increased, lint trash content decreased, opening and cleaning waste (prior to carding) decreased, lint loss increased, and cleaning efficiency increased. Lint turnout and bale value were not significantly different due to treatment. With the exception of color grade, very short fibers, and 36s yarn strength, all other fiber and yarn properties were not significantly different due to treatment, and all were at acceptable levels. Based on the results of the experiment, the optimum speed of the cleaning cylinder was found to be between 750 and 900 rpm.

A computer model of a cotton (Gossypium hirsutum L.) ginning system was used to optimize producer returns. Input to the model consists of the initial grade associated with the minimum ginning sequence, cotton moisture content, maximum turnout, and cotton market prices. Output of the model consists of the operating control decisions for each stage of the ginning or drying process, final lint grade, moisture content, turnout, and producer monetary returns. Commercial application is hampered by the unavailability of sensing/controlling mechanisms for grade and moisture. In the interim, tabular optimization decisions were developed as general guidance for ginners and producers.

AN experimental cotton dust analyzer was developed for measurement of the dust-generation potential of lint cotton. High-velocity air jets are used in the analyzer for release of dust from a thin batt of lint. The dust is then sized by a 100-micrometer screen and collected on a glass fiber filter for gravimetric analysis. Laboratory results indicated that differences in dust-generation potential measured by the cotton dust analyzer were similar to those measured by experimental card room techniques. However, additional refinements and testing are needed for establishment of concrete relationships between results with the cotton dust analyzer and the potential of various types of cotton for dust generation.

THE bale tie forces exerted by modified flat bales and gin universal density bales of lint cotton were evalu-ated in separate studies. Equations were developed for the prediction of the total bale tie force as a function of lint moisture content, bale circumference, and platen sep-aration. The maximum force exerted per bale tie ranged from 4960 to 6361 N (1,115 to 1,430 lb) for modifiedflat bales and from 9475 to 11 766 N (2,130 to 2,645 lb) for gin universal density bale.

Amethod to measure the strength of adhesion of bark on cotton plants was developed as a tool for use in determining what causes bark to contaminate lint. The method measures of peak force, average force, and work to peel bark off a 1.6 mm wide by 30 mm long specimen of cotton plant material. Peak force to pull bark of specimen varied from 0.380 to 1.282 N. Average force varied from 0.134 to 0.336 N. Work to peel the bark off a 1.6 mm by 30 mm specimen varied from 0.0027 to 0.0064 J. Bark was better attached at some points than at others. The force of adhesion for individual specimens within a given sample was highly variable. Some of the preliminary results showed a large difference between dryland and irrigated cotton.

FOUR gin stand doffing brushes were tested to determine the effect of brush design on sound generation, lint doffing ability, and pneumatic conveying of lint. The sound levels produced by two experi-mental brushes were 5 to 6 dBA less in the area behind the gin stand than that produced by brushes generally used in cotton gins. An experimental brush with long bristles in closely spaced spiral rows was the most effi-cient one for doffing and for inducing an air stream for pneumatic conveying of lint, and could consequently be operated at a slower speed. Operating at a slower speed reduced the sound level in the area behind the gin stand by an additional 5 dBA. The minimum brush speed for doffing and conveying of lint under good conditions was found to be about 50 to 60 percent of the speed at which the brushes were normally operated which shows that gin stands have only a relatively small reserve of excess doffing capabilty for meeting less than optimum operating conditions. Adoption of the long bristle brush design would result in a significant reduction in the sound level produced by doffing brushes in gin stands and would aid substantially in abatement of one source of noise which cotton gin employees are ex-posed to.

TWO modules of stripper-harvested cotton, one that had been defoliated and then desiccated with arsenic acid (H3 As O4) and one that had been defoliated only, were subjected to 0 to 6 stages of lint cleaning. Standard methods were used to determine the amount of elemental arsenic (As) in samples of cottonseed, lint cleaner exhaust dust, gin room dust and lint from 0, 2, 4, and 6 stages of lint cleaning. The As content of the ginned lint and the dust samples from cotton desiccated with arsenic acid decreased as the number of lint cleaners used was increased. Only trace amounts of As were found in lint and dust from cotton not desiccated with arsenic acid.