Carlos J. Fernandez

Fiber Quality Response of Pima Cotton to Nitrogen and Phosphorus Deficiency

Abstract Imposing a moderate level of nutrient deficiency may be an effective management strategy to limit vegetative growth and enhance maturity of Pima cotton (Gossypium barbadense L.). Whether such deficiency affects fiber quality of American Pima cotton, however, is not well known. A field study was conducted in 1991 and 1992 to determine the fiber quality responses of Pima cotton to nitrogen and phosphorus fertilization ranging between deficient and excess. Pima cotton cv. “S‐7” was treated with nitrogen rates ranging between 0 and 269 kg ha−1 in a factorial combination with phosphorus rates ranging between 0 and 44 kg ha−1. Fiber property measurements included fiber length, strength, fineness, elongation, and color properties. Increasing rate of applied nitrogen significantly (P ≤ 0.05) increased fiber length, elongation, micronaire, and color characteristics and reduced fiber uniformity ratio in 1991. Increasing nitrogen rate significantly (P ≤ 0.10) increased fiber length, uniformity index, and yellowness in 1992, when the degree of nitrogen deficiency imposed by the lowest nitrogen rate was not as severe as the deficiency imposed by the same treatment in 1991. Phosphorus did not significantly (P ≤ 0.10) affect any of the important fiber properties—length, strength, or micronaire—in either cropping season. These results indicate moderate level of nitrogen or phosphorus deficiency does not affect Pima cotton fiber quality. Nitrogen or phosphorus deficiency severe enough to reduce fiber quality and affect marketing of Pima cotton is unlikely to be encountered under normal Pima cotton production practices.

MAPPING PHYMATOTRICHUM ROOT ROT OF COTTON USING AIRBORNE THREE-BAND DIGITAL IMAGERY

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.

Vegetative and reproductive dry weight inhibition in nitrogen‐ and phosphorus‐deficient Pima cotton 1

Abstract Whether the extent of dry weight inhibition by nitrogen (N) or phosphorus (P) deficiencies on different plant parts is the same and whether imposing moderate N and P deficiencies selectively suppress undesirable vegetative growth has not been studied in Pima cotton (Gossypium barbadense L.). The purpose of this study was to determine the extent to which dry matter accumulation in leaves, stems, and reproductive structures is inhibited by N and P deficiencies in Pima cotton. The study was conducted in 1991 and 1992 in a Uvalde silty clay loam soil (fine‐silty, mixed, hyperthermic Aridic Calciustolls). The treatments included applied rates of 0, 67, 135, 202, and 269 kg N ha‐1 in a factorial combination with 0, 15, 29, and 44 kg P ha‐1. Nitrogen deficiency (0 kg N ha‐1) significantly (P≤0.05) reduced leaf (LDW) and stem (SDW) dry weights in both years and reproductive dry weight (RDW) in 1992. Nitrogen deficiency suppressed dry weight accumulation in leaves to a greater extent than in stems. Relati...

Effects of growth environment on cotton fiber properties and motes, neps, and white speck frequency

A number of preharvest and postharvest factors alter textile quality, including cotton variety, growth environment, harvest method, lint cleaning, and combing. In this work, the impact of three planting dates in 1997 and 1999 on fiber properties, mote, neps, and white specks is monitored. Cotton is hand picked, ginned on a small laboratory gin, and processed in a mini-spinning facility. The number of motes per gram of seed cotton does not correspond to changes in nep or white speck frequency. Also, a decrease in the mean micronafis values (which corresponds to micronaire) does not correlate with increases in white speck frequency. The range of 0 values is larger for 1999 cotton than for 1997 cotton. We propose th the distribution of 0 values is important in predicting white speck potential, and that the amount of very mature fibers may be just as important as the amount of immature fibers.

Partitioning of biomass in water‐ and nitrogen‐stressed cotton during pre‐bloom stage

Abstract The partitioning of biomass between aboveground parts and roots, and between vegetative and reproductive plant parts plays a major role in determining the ability of cotton (Gossypium hirsutum L.) to produce a crop in a given environment. We evaluated the single and combined effects of water and N supply on the partitioning of biomass in cotton plants exposed to two N supply levels, 0 and 12 mM of N, and two water regimes, well irrigated and water‐stressed at an early reproductive stage. The N treatments began when the third true leaf was visible, while water deficit treatments were imposed over the N treatments when the plants were transferred into controlled‐environment chambers at a leaf area near 0.05 m2. Both water deficits and N deficits inhibited total biomass accumulation and its partitioning in cotton. Water deficit alone and N deficit alone inhibited the growth of leaves, petioles, and branches, but did not inhibit growth of the stem and enhanced the accumulation of biomass in squares. ...

Grain Sorghum Response to Hybrid, Row Spacing, and Plant Populations along the Upper Texas Gulf Coast

Grain sorghum (Sorghum bicolor L. Moench) along the upper Texas Gulf Coast is planted at different row spacings, plant populations, and hybrids according to grower preference and location. This study was conducted over a 3-year period (2001 to 2003) to determine the combination of hybrid, row spacing, and plant population on yield and net return per hectare. Below average rainfall for May and June occurred in 2002 and 2003 which resulted in lower yields than 2001. In 2001 and 2003, Dekalb (DK) 54 generally produced higher yields than Asgrow (A) 571 on the 51 cm row spacing. In 2002, no differences in grain sorghum yield were found when comparing both hybrids, plant populations, or row spacing with the exception of A 571 planted at 148,000 plants/ha on 102 cm centers which resulted in a yield reduction of at least 25%. When net returns were compared regardless of year or rainfall received, net dollar value per hectare tended to be higher for the 51 cm row spacing, especially with A 571.

Weed Control and Grain Sorghum (Sorghum bicolor) Tolerance to Pyrasulfotole plus Bromoxynil

Field studies were conducted during the 2008 and 2009 growing seasons at five locations in the Texas grain sorghum producing regions to evaluate pyrasulfotole plus bromoxynil combinations for weed control and grain sorghum response. All pyrasulfotole plus bromoxynil combinations controlled Amaranthus palmeri, Cucumis melo, and Proboscidea louisianica at least 94% while control of Urochloa texana was never better than 69%. Pyrasulfotole plus bromoxynil combinations did result in early season chlorosis and stunting; however, by the end of the growing season no visual injury or stunting differences were noted when compared to the untreated check. Early season grain sorghum chlorosis and stunting with pyrasulfotole plus bromoxynil combinations did not affect grain sorghum yields with the exception of pyrasulfotole at 0.03 kg ai/ha plus bromoxynil at 0.26 kg ai/ha plus atrazine at 0.58 kg ai/ha applied early postemergence followed by pyrasulfotole plus bromoxynil applied mid-postemergence which reduced yield at one of two locations in 2008. Grain sorghum yield increased following all pyrasulfotole plus bromoxynil treatments compared to the untreated check in 2009.

Grain Sorghum Response to Row Spacing and Plant Populations in the Texas Coastal Bend Region

Two grain sorghum (Sorghum bicolor L. Moench) studies were conducted in the Coastal Bend Region of Texas over a two-year period. In one study, sorghum growth and yield were compared when planted in a single row on beds or planted in twin rows on beds with different plant populations under dryland or irrigation. Above average rainfall occurred in May 2000 which resulted in twin rows at any plant population producing higher yields than the single row at lower plant population. In 2001, single-row plantings with either plant population (124,000–160,000 or 161,000–198,000 plants/ha) produced higher yield than twin rows planted at 161,000–198,000 plants/ha. Under irrigation, twin rows planted at 161,000–198,000 plants/ha produced higher yields than single row at the same population; however, no other yield differences were noted when row systems or plant populations were compared. In another study, 38 cm row spacings were compared with 76 cm row spacings under two plant populations. In 2000, when rains fell at an opportune time, no yield differences were noted; however, in 2001 with below average rainfall, the 76 cm plantings at 170,000–200,000 and 210,000–240,000 plants/ha produced higher yield than the 38 cm plantings at those same plant populations.

Effects of two planting patterns and plant densities on the productivity and profitability of cotton.

Aims: To evaluate the effect of two planting patterns across two plant densities on cotton growth, yield, fiber quality, and net returns. Study Design: Randomized complete block design with a 2 x 2 factorial treatment arrangement with 3 replicates was used for a total of 12 plots. Place and Duration of Study: Studies were conducted during the 2003 and 2004 growing seasons on a producer’s farm located south of Eagle Lake, Texas in Colorado County (29.49360 N, 96.34060 W). Methodology: Rows were spaced 91.4-cm apart on raised beds. Plot size was eight rows by 972 m long. The two different factors included two row planting patterns, the solid pattern with every single row planted and the skip-row pattern with a 2x1 planting pattern where 2 rows are planted and 1 row is left fallow. For the skip-row pattern, rows three and six were not planted in the 8 row plot. The second factor was seeding rate with two plant populations of 84000 and 126000 plants/ha. Original Research Article American Journal of Experimental Agriculture, 4(2): 130-141, 2014 131 Results: In neither year were any differences seen with seeding rate. In 2003, days to cutout with the skip-row pattern were 92.4d while with the solid pattern days to cut-out were 87.9d and plant height with the skip-row pattern was 100 cm while with the solid pattern, plant height was 87 cm. Lint yield was 1504 kg/ha for the solid pattern while with the skiprow pattern lint yield was 1347 kg/ha. In 2004, lint yield with the solid pattern was 27% greater than the skip-row pattern. Slight differences between the two planting patterns were observed during 2004 in days to cut-out or plant height. In both years, the solid planting pattern produced a net dollar value/ha increase over the skip-row pattern and therefore should be the row pattern used along the upper Texas Gulf Coast.

Mapping Cotton Root Rot Infestations over a 10-Year Interval with Airborne Multispectral Imagery

Cotton root rot, caused by the pathogen Phymatotrichopsis omnivora, is a very serious and destructive disease of cotton grown in the southwestern and south central U.S. Accurate information regarding temporal changes of cotton root rot infestations within fields is important for the management and control of the disease. The objective of this study was to detect the change in cotton root rot infestations within cotton fields in south Texas over a 10-year interval. An airborne three-band image and an airborne four-band image were collected from a cotton field in 2001 and 2011, respectively. The images were georeferenced, resampled to the same pixel size and then classified into root rot-infested and non-infected classes using unsupervised image classification techniques. Both images were effective to distinguish root rot-infected areas from non-infected areas. The infested areas within each field were determined and compared between the two imaging years. Preliminary results indicate that the recurring spatial patterns of the disease were similar over the 10-year interval, though there were variations in infestation patterns over the years. These results will be useful for monitoring the progression of the disease over a longer time period and for the management and control of the disease.