Difference In Lint Yield Research Articles

Axant™ Flex cotton response to topramezone applied early- or mid-postemergence

Abstract The continued development of herbicide-resistant weeds, such as Palmer amaranth, represents a growing concern across the United States Cotton Belt. To mitigate this issue, BASF Corporation developed Axant™ Flex cotton, the first quadruple-stacked herbicide resistance germplasm to improve the control of troublesome weed species in cotton. Field studies were conducted in 2022 and 2023 at the Texas Tech University Research Farm near New Deal, TX, to evaluate the response of Axant Flex cotton to topramezone applied alone or in combinations when applied to 3-leaf cotton (early-postemergence (EPOST)) or to 7-leaf cotton (mid-postemergence (MPOST)). No difference in cotton stand was observed between isoxaflutole or prometryn PRE treatments compared to the nontreated control. In 2022, no EPOST treatment caused greater than 6% crop response at 7 and 14 d after application (DAA). When treatments were made to 7-leaf cotton, crop response did not exceed 18% at 7 and 14 DAA. In 2023, crop response was ≤ 2% at 28 DAA regardless of application timing. No differences in lint yield were observed following any herbicide treatment when compared to the nontreated control in either year. Additionally, fiber length and strength were not adversely affected by treatments containing topramezone EPOST or MPOST in 2022 and 2023. These results support the potential use of topramezone in Axant Flex cotton to help manage troublesome weeds without detrimental effects on yield and fiber quality.

Seed size, planting date, and seeding rate on cotton vigor and yield

AbstractCotton (Gossypium hirsutum L.) is one of the top economic crops in South Carolina, and growers make many important decisions prior to planting each year including variety selection, planting date, seed size, and seeding rate. As input costs continue to rise, greater detailed information is needed so that growers can make better informed decisions for their individual operations. The objectives of this study were to evaluate the influence of seed size, seeding rate, and planting date on the growth, development, lint yield, and fiber quality for cotton grown in South Carolina. Two seed sizes large (≤9460 seed kg−1) and small (≥12,100 seed kg−1) were planted at four seeding rates (61,775; 86,485; 111,195; and 135,905 seeds ha−1) on two different planting dates (early [late April/early May] and late [late May/early June]) in 2020, 2021, and 2022 in Florence and in 2020 and 2021 in Blackville, SC. Data collection included stand counts, biomass at multiple growth stages, plant height, lint yield, fiber quality, and overall net returns. Results showed no difference in lint yield for any of the factors in either location in 2020; however, the small‐seeded variety lint yield was 20% more than the large‐seeded variety in Florence in 2021 and 2022 and 5% higher in Blackville in 2021. In Florence, seeding rates over 100,000 seed ha−1 resulted in higher lint yield than the lower two seeding rates. In both locations, delaying planting until after May 22 increased lint yield by approximately 15% in 2021 and 2022. The large‐seeded variety consistently had greater dry biomass (12%–52% greater) than the small‐seeded variety, indicating that it produced larger, more vigorous seedlings. While seed size may not be a reliable predictor of lint yield, it has proven to be an accurate predictor of seedling vigor. Therefore, it may be beneficial to plant a high‐yielding, larger seed size variety when unfavorable planting conditions are expected.

Effects of Plant Density, Mepiquat Chloride, Early-Season Nitrogen and Water Applications on Yield and Crop Maturity of Ultra-Narrow Cotton

Research investigating row spacing in high-yielding, high-input cotton (Gossypium hirsutum L.) production systems has found higher lint yields but no maturity benefits using high plant density, 25 cm spaced ultra-narrow rows (UNR). Seven experiments comparing 38 cm UNR and conventionally spaced rows (100 cm) were conducted over three years to determine if changes in plant density or management could optimize yield and maturity in a high-input UNR cotton production system. Two of these experiments compared 25, 38 and 100 cm spaced rows under different intra-row plant density (12 to 36 plants m−2). Three experiments managed 38 cm UNR and 100 cm spaced rows separately and one had extra early application of nitrogen and water. Across the seven experiments there were no differences in lint yield or crop maturity for 38 cm UNR compared to conventionally spaced rows. The only significant response to changes in inter- or intra-row density or agronomic management was an 18% increase in handpicked lint yield in the 12 plants m−2 38 cm UNR treatment compared to the same plant density in 100 cm spaced rows in one of the two experiments. This stability of yield response across row spacings indicates that there is an opportunity to reduce seed rates whilst maintaining yields in high-input UNR systems. UNR cotton did not require any difference in mepiquat chloride or nitrogen management compared with conventionally spaced cotton, nor did extra early inputs of nitrogen or water, and we concluded that is likely that the current recommendations for mepiquat chloride or nitrogen nutrition in conventionally spaced systems are appropriate for managing high-input UNR cotton crops.

Impact of no-till, cover crop, and irrigation on Cotton yield

Water is the limiting factor for crop production within the southern US Great Plains and it has become a critical resource for multiple stakeholders. Hence, efficient irrigation and cropping systems are of paramount importance to conserve water resources. The objective of this study was to determine the effect of irrigation timing and quantity, cover crop use and tillage on cotton production in an established conservation tillage system. Evaluated tillage systems included: 1) conventional tillage (CT); 2) strip-tillage (ST); 3) no-till (NT); and 4) NT with a terminated wheat cover crop (NT-W). Irrigation treatments included 1) 5.08-6.35 mm d−1 initiated mid-season (LOW); 2) 6.35-8.38 mm d−1 initiated mid-season (MED); and 3) 5.08-6.35 mm d−1 initiated early-season (HIGH). No significant differences in lint yield or irrigation water use efficiency (IWUE) were observed between MED and HIGH. Although HIGH resulted in 12 % greater lint yields than LOW, HIGH resulted in 67 % greater irrigation water applications. LOW resulted in significantly greater IWUE than MED and HIGH. No-till systems, with and without a cover crop, had significantly greater lint yields and IWUE than CT. Furthermore, inclusion of wheat in NT increased yields and IWUE compared with ST. Applying irrigation water at a critical growth stage proved to be more water efficient than early season irrigation that was used to bank moisture in the soil profile. Delaying irrigation application until critical growth stages and using cover crops should be considered as best management approaches to conserve water resources while sustaining cotton production in the Southern Great Plains.

Spatial distribution of bolls affects yield formation in different genotypes of Bt cotton varieties

To optimize the spatial distribution of cotton bolls and to increase the yield, the relationship between yield components and boll spatial distribution was investigated among different Bt (Bacillus thuringensis) cotton varieties. A five-year field experiment was conducted to reveal the reasons for the differences in lint yield and fiber quality across three Bt cotton varieties with different yield formations from 2013 to 2017. The lint yield of Jiman 169 (the average yield from 2013–2017 was 42.2 g/plant) was the highest, i.e., 16.3 and 36.9% higher than Lumianyan 21 (L21) and Daizimian 99B (99B), respectively. And the differences in boll weight among the three cultivars were similar to the lint yield, while the others yield components were not. So the increase in lint yield was mainly attributed to the enlargement in boll weight. However, the change in fiber quality was inconsistent with the lint yield, and the quality of L21 was significantly better than that of Jimian 169 (J169) and 99B, which was caused by the diversity of boll spatial distribution. Compared with 99B, the loose-type J169 had the highest number of large bolls in inner positions; the tight-type L21 had a few large bolls and the highest number of lower and middle bolls. And approximately 80.72% of the lint yield was concentrated on the inner nodes in Jiman 169, compared with 77.44% of L21 and 66.73% of 99B during the five-year experiment. Although lint yield was significantly affected by the interannual changes, the lint yield of J169 was the highest and the most stable, as well as its yield components. These observations demonstrated the increase in lint yield was due to the increase in boll weight, and the large bolls and high fiber quality were attributed to the optimal distribution of bolls within the canopies.

Nitrogen Nutrition, Yield, and Quality of Cotton under Varying Nitrogen Application Timings and Planting Dates

Nitrogen (N) management may need to be different for cotton planted at different dates. The objective of this research was to determine the optimal N application timing for cotton under different planting dates. A field trial was conducted on the University of Tennessee West Tennessee Research and Education Center at Jackson, TN in 2011 and 2012 in a split plot randomized complete block design with four replicates. Three cotton planting dates of early planting, standard planting, and late planting and four N application timings of pre-plant, at-planting, early side-dress, and late side-dress were assigned to the whole plots and subplots, respectively. Although the interactions of planting date by N application timing, year by N application timing, and year by planting date were significant on leaf N at early bloom and late bloom; cotton plants received adequate N nutrition for optimal yield under different N application timings and varying planting dates in both years. No significant difference in lint yield was observed among the four N application timings regardless of planting date in 2011 that was wet in the early season but dry in the late season. In 2012 that was dry in the early season but wet in the late season, however, lint yield was higher with late side-dress of N than pre-plant at standard planting; the yield did not differ among the four N application timings at early planting or late planting. Higher fiber micronaire but lower fiber strength was obtained under early planting and standard planting than late planting. In 2011, the length and uniformity of fiber were not affected by the planting date. In 2012, however, the length and uniformity of fiber were greater at late planting than early planting and standard planting. The fiber length and fiber uniformity were greater with late side-dress of N than pre-plant and early side-dress of N. Overall, the effects of N application timing on cotton yield vary with planting date and year, which suggests that planting date and weather conditions need to be taken into account in deciding the N application timing.

Phenotypical Responses of Cotton and Relation to Lint Yield Under Deficit Irrigation Schemes in Semi‐Arid Environments

Adoption of regulated deficit irrigation scheme changes phenotypical responses but not lint yield. Adoption of suitable deficit irrigation scheme would result in the same lint yield as full irrigation. Morphological parameters can be used as predictors of lint yield before harvesting. Physiological parameters failed to show a consistent close relationship to lint yield under various deficit irrigation schemes. Increasing water productivity in semiarid regions is a critical sustainable production strategy to mitigate the challenges posed by depleting water resources and unpredictable climate change. Deficit irrigation has been a widely investigated practice to save water, improve water productivity, and maximize crop yield. A field experiment was conducted at the Texas AgriLife Research and Extension Center at Uvalde, TX, in 2008 and 2009 to examine the water saving potential of four traditional (fixed deficit ratios ranging from 50–80%, referred as T) and two regulated (dynamic deficit ratios of 75 and 50% overall, referred as R) deficit irrigation treatments against a full irrigation treatment. Four cultivars were assigned to the experimental field each year to test irrigation and cultivar effects on lint yield and morphological and physiological responses of cotton (Gossypium hirsutum L.). Morphological parameters showed no interaction between irrigation scheme and cultivar; however, most physiological parameters showed significant interaction between the irrigation scheme and cultivar (P < 0.05) in both years. The results also showed that: (i) two deficit irrigation treatments (80T and 70R) were found to maintain lint yield similar to the control (CTRL) in most of the cultivars; (ii) morphological parameters reflected the differences in lint yield and may be used as predictors before harvest; and (iii) physiological parameters failed to show a close consistent relationship to lint yield under various deficit irrigation schemes. Using seasonal cumulative net assimilation rate, transpiration rate, and water use efficiency may be better parameters for predicting lint yield before harvest.

Comparison of Five Tillage Systems in Coastal Plain Soils for Cotton Production

Soil compaction management in the southeastern USA typically relies heavily on the practice of annual deep tillage. Strip tillage systems have shown considerable promise for reducing energy and labor requirements, equipment costs, soil erosion, and cotton plant damage from blowing sand. Replicated field trials were conducted for three years in South Carolina, to compare the performance of three different strip tillage systems to conventional tillage and no-till methods. A second objective was to investigate whether the frequency of deep tillage can be reduced by planting cotton directly using controlled wheel traffic into the previous year’s subsoiler furrow. Tillage treatments included: conventional tillage (disk-subsoil-bed), straight shank strip-till, bent-leg shank strip-till (Paratill), bent-leg shank strip till (Terra Max), and no-till. Deep tillage was performed in all plots the first year. In years two and three, the plots were split and half received annual deep tillage and the other half were not deep tilled either year. Tillage methods were compared side by side with and without irrigation. Deep tillage reduced soil compaction and increased taproot length and cotton yields than the no-till system. There was no difference in cotton lint yield between the strip-till systems and conventional tillage in either dry land or irrigated plots. Deep tillage increased cotton lint yields compared to no-till. There was no difference in lint yield between plots which were deep-tilled in all three years with those which had tillage operation only in first year of the test. Dry matter partitioning at first bloom was reduced in plant height, total dry weight, and leaf area in strip-till and no-till production systems compared to the conventional tillage system. The results suggest that all three strip tillage systems are equally effective for cotton production and that annual deep tillage is not necessary if controlled traffic is employed.

Cotton Response and Palmer Amaranth Control with Mixtures of Glufosinate and Residual Herbicides

Recommendations to control glyphosate-resistant Palmer amaranth (Amaranthus palmeri S. Wats.) in cotton (Gossypium hirsutum L.) typically include glufosinate applied postemergence (POST) and residual herbicides applied both preemergence and POST. Residual herbicide options for POST application are limited primarily to pyrithiobac and the chloroacetamides herbicides acetochlor and S-metolachlor. Labeling for pyrithiobac warns of injury when mixed with metolachlor. No published information is available on crop or weed response to mixtures of glufosinate plus acetochlor, with or without pyrithiobac. Tolerance of WideStrike® cotton and Palmer amaranth control with glufosinate applied alone to 1- to 2-leaf cotton, glufosinate mixed with pyrithiobac or micro-encapsulated acetochlor or S-metolachlor, and three-way combinations of glufosinate plus acetochlor or S-metolachlor plus pyrithiobac were evaluated in field experiments. These treatments were followed by a second application of glufosinate and diuron plus MSMA directed at layby. Prior to the second application, glufosinate early POST alone controlled Palmer amaranth 77%. Pyrithiobac mixed with glufosinate increased control 10 to 11%, whereas acetochlor and S-metolachlor increased control 12 to 14%. Control was similar with glufosinate plus acetochlor with or without pyrithiobac, whereas combinations of glufosinate plus S-metolachlor plus pyrithiobac were 4 to 5% more effective than glufosinate plus S-metolachlor. Pyrithiobac increased cotton necrosis 3 to 4% and reduced growth 5% 7 d after application compared to glufosinate alone. Acetochlor and S-metolachlor increased necrosis 14 to 18% and reduced growth 7 to 10%. Necrosis was similar with glufosinate plus acetochlor with or without pyrithiobac. Pyrithiobac added to glufosinate plus S-metolachlor increased necrosis 3 to 4%. Injury was transient, and no differences in lint yield were noted among herbicide treatments.

Glufosinate Tolerance of Multiple WideStrike and Liberty‐Link Cotton (Gosspyium hirsutum L.) Cultivars

ABSTRACTOne option available to cotton (Gosspyium hirsutum L.) producers for control of glyphosate [N‐(phosphonomethyl)glycine]–resistant (GR) weeds is the use of glufosinate [(2RS)‐2‐amino‐4‐[hydroxy(methyl)phosphinoyl]butyric acid] (Liberty 280SL, 24.5% [w/v] glufosinate‐ammonium salt) in glufosinate‐tolerant, transgenic cotton cultivars. A field experiment conducted in 2011 and 2012 in Florence, SC, examined the effects of glufosinate on the growth, lint yield, and fiber quality of WideStrike and Liberty‐Link cotton cultivars. Five WideStrike cultivars and three Liberty‐Link cultivars were sprayed topically at the 1‐ to 3‐leaf stage and the 7‐ to 9‐leaf stage with glufosinate at 0.59 kg ha−1. Glufosinate‐ and weed‐free plots were maintained as controls for each cultivar. Reduced plant health and increased leaf injury were observed in both Liberty‐Link and WideStrike cultivars following glufosinate applications, but sprayed WideStrike cultivars displayed as much as 11% greater leaf injury than sprayed Liberty‐Link cultivars. No differences in lint yield were found between sprayed WideStrike or Liberty‐Link cultivars and their respective controls. However, averaged across all cultivars, lint yield of cotton sprayed with glufosinate was 105 kg ha−1 greater than unsprayed cotton. Yield increases of sprayed cotton appeared to be related to increased boll production at the first fruiting position and between nodes 11 and 15. Glufosinate had no effect on any fiber property evaluated. Cotton producers planting WideStrike or Liberty‐Link cotton cultivars and using glufosinate at labeled rates can adequately control GR weeds without negatively affecting lint yield or fiber quality. Cotton producers may also possibly experience slight lint yield increases as a result of glufosinate application in WideStrike and Liberty‐Link cotton cultivars.

Evaluation of Cotton Productivity by Fruiting Zone in Diverse Growing Locations

The amount and quality of cotton (Gossypium spp.) produced within a growing season is the result of many factors, but the influence of genotype is substantial. The objective of this study was to determine how growing location, fruiting behavior, and cultivars interact to produce a cotton crop. Five commercial cultivars were studied at multiple locations in Texas and Virginia. Plant height, first sympodia, and number of sympodia were measured. Plants were harvested by fruiting zone and lint yield, lint percent, seed weight, and high-volume instrumentation (HVI) fiber data were ascertained. Results indicate that cultivar had a significant effect on plant height and fruiting habit, but year also significantly affected traits measured. In addition, lint yield, lint percent, seed weight, and fiber traits were significantly affected by fruiting zone at most locations and years. It was determined that relative differences among cultivars remained constant across growing locations for plant morphology and fiber traits. Differences in lint yield per fruiting zone were not distinguishable.

Light interception and radiation use efficiency of okra and normal leaf cotton isolines

Okra-leaf cotton ( Gossypium hirsutum L.) types have been reputed to produce equal or higher amounts of lint yield than normal-leaf types, while intercepting less or similar amounts of radiation. In this field study, okra- and normal-leaf cotton isolines were compared for their efficiency to produce dry matter utilizing intercepted radiation. At three weeks after first flower, the two leaf-shape isolines produced similar amounts of dry matter, with the okra-leaf type partitioning a larger fraction to fruiting organs. However, at the end of the season no differences in lint yield, yield components and fiber-quality properties were recorded between the two isolines. Fractional light interception throughout the period of the study was greater for the normal-leaf type compared to the okra-leaf type. The okra-leaf isoline utilized intercepted radiation more efficiently to produce dry matter. Values of radiation use efficiency were estimated at 1.897 and 2.636 g MJ −1 of intercepted photosynthetically active radiation for the normal- and okra-leaf types, respectively. Growth chamber studies revealed similar single leaf carbon exchange rates, therefore radiation use efficiency differences between the leaf shape isolines could be attributed to light interception characteristics.

Variability in four diverse cotton (Gossypium hirsutum L.) germplasm populations

A broad range of cotton (Gossypium hirsutum L.) germplasm resources exist with characteristics useful for improving modern cotton cultivars. However, much of this germplasm is not well utilized. The objective of this study was to evaluate agronomic and fiber traits of four germplasm populations to determine the effectiveness of pooling germplasm for generating variability to improve traits of interest. Four populations were developed with parents chosen based on (1) dwarfing genes, (2) a combination of fiber strength and length traits, (3) glandless genes, or (4) inclusion in the G. hirsutum center-of-origin, i.e. race, germplasm group. The dwarf germplasm population had smaller bolls, a smaller lint index, a smaller seed index, lower micronaire, and shorter fibers than the other three populations. There were no significant differences in lint yield, elongation, or strength among the germplasm populations. In contrast to the general lack of significant differences among populations for agronomic and fiber traits, within population variation was observed to be high. Therefore, selections could be made within the race population to raise lint yields and within the fiber population to increase fiber length. Likewise, selections within the glandless population could be made for boll size, lint index, seed index, micronaire, and strength. These results suggest that intercrossing multiple parents in complex populations generates a large amount of variability with potential uses in crop improvement.

Effects of Genotypes and Plant Density on Yield, Yield Components and Photosynthesis in Bt Transgenic Cotton

AbstractBt (Bacillus thuringiensis) transgenic cotton (Gossypium hirsutumL.), including the introduced, indigenous Chinese non‐hybrid and hybrid cotton, is spreading very rapidly in China. Agronomic and photosynthetic performance as well as the optimum plant density for planting Bt cotton may vary with genotypes. With three types of commercial Bt cotton varieties, two field experiments were conducted to study yield performance and leaf photosynthetic rate (Pn) during 2000 and 2001, and yield interaction between variety and plant density during 2001 and 2002 in Yellow River region in northern China. The first experiment showed that the indigenous Chinese Bt cotton significantly differed from the introduced Bt cotton (IBtC) in plant growth and yield components. As a result of manipulation of boll numbers, boll weight and lint percentage, there was no significant difference in lint yield between Chinese non‐hybrid Bt cotton (CBtC) and the IBtC, but two Chinese hybrid Bt cotton (HBtC) varieties exhibited significantly higher lint yield than all other varieties in either 2000 or 2001. Hybrid cotton SCRC15 showed a one‐peak curvilinear change in diurnal course of Pn throughout the growing season, while non‐hybrid cotton 33B and SCRC16 exhibited severe mid‐day depression in Pn in squaring, flowering or boll‐setting stage. The second experiment showed that the main effect of plant population on lint yield was not significant, and yield difference among all treatments was derived from varieties and the interaction between plant density and variety. The optimal plant densities in terms of lint yield for the introduced, indigenous CBtC and HBtC genotypes were 6.0, 4.5 and 3.0 plants m−2respectively.

Pix Plus and Mepiquat Chloride Effects on Physiology, Growth, and Yield of Field-Grown Cotton

An important objective for using plant growth regulators in cotton (Gossypium hirsutum L.) is to balance vegetative and reproductive growth as well as to improve lint yield and fiber quality. Field studies were conducted at two locations (Clarkedale and Fayetteville) in Arkansas in 1997 and 1998 to determine physiologic and yield responses of cotton to foliar applications of mepiquat chloride [N,N-dimethyl-piperidinium chloride and inert ingredients] (MC) and Pix Plus [MC + Bacillus cereus]. Compared with the untreated control, application of Pix Plus and MC efficiently reduced plant height, improved leaf CO 2 -exchange rate, and increased leaf starch content. Neither Pix Plus nor MC affected photoassimilate translocation from leaves to 10- to 15-day-old bolls. Pix Plus and MC had very similar effects on plant growth and most physiologic parameters investigated in our studies. There was no difference in lint yield between Pix Plus and mepiquat chloride. However, Pix Plus increased the fraction of fruit dry matter in total dry matter.

Cotton Response to Surface Applications of Potassium Fertilizer: A 10-Year Summary

Field studies were conducted for 10 yr on a Limestone Valley soil (Dewey silt loam, a fine, kaolinitic, thermic Typic Paleudults) in north Alabama to evaluate cotton (Gossypium hirsutum L.) yield and lint quality response to long-term surface applications of K. Potassium rates were 0, 60, 120, and 180 lb K 2 O/acre for the first 3 yr of the study. Fertilizer was broadcast in the spring or split applied in fall and spring. No K fertilizer was applied during the fourth year (1990). After the fourth year, half of the treatments were left in residual and remaining treatments continued to receive annual applications of K (1991-1996). The experiment was a split plot arrangement of a randomized complete block. From 1987 to 1989, two varieties were compared, which served as whole plots. From 1991 through 1996, one variety was grown and annual vs. residual K fertilization served as whole plots. Potassium treatments were used as subplots throughout the test. From 1987 to 1989 there were no differences between 'Stoneville 825' and 'Deltapine 50'. Lint yields were increased significantly by K fertilization in 6 of 9 yr that cotton was grown on this low K soil. Potassium fertilization increased lint yields by as much as 450 lb/acre in responsive years. From 1991 through 1996, residual K produced lesser yields than where K was applied annually. There were no differences in lint yield among split (fall-spring), fall, or spring applied K. In responsive years, micronaire increased with K rate. Our results support the calibration currently used by the Auburn University Soil Testing Lab for Limestone Valley soils.

Planting and Irrigation Termination Timing Effects on the Yield of Upland and Pima Cotton

There have been conflicting results reported about the effect on cotton (Gossypium spp.) lint yield of altering planting and irrigation termination (IT) timing. The objectives of this study were to identify a planting window (PW), on a heat unit (HU) basis, and IT timing, as a function of crop growth stage, for optimum yield potential of Upland (G. hirsutum L.) and American Pima (G. babadense L.) cotton. Two PWs of Upland 'Deltapine 90' (DPL 90), Pima 'S-6', and IT treatments were included in field experiments for 11 site-years. Planting windows were defined as PW1 and PW2 for plantings prior to and following 600 HU accumulated after 1 January, respectively. Two IT treatments were imposed for each planting. Irrigation termination in the desert Southwest generally results in cessation of growth (crop termination). The first IT treatment (IT1), was imposed to ensure full development of bolls set up to cutout, and the second (IT2) was after two additional irrigations. From covariate analysis, there was no evidence of interaction between PW and IT, indicating that these treatments responded the same across the different environments for both cotton species. There were, however, differences in lint yields among treatments. For DPL 90, PW1 IT2 yielded 83 and 97 Ib/acre more than PW1 IT1 and PW2 IT2; and for Pima S-6, PW1 IT2 was 118 and 204 Ib/acre more than PW1 IT1 and PW2 IT2, respectively. Early planting is necessary for optimum yield potential of full-season cotton varieties; with the greatest yield coming from early planting and termination after the development of a second fruiting cycle (PW1 IT2). However, if a reduction in input costs and the avoidance of late-season insect pests are important considerations then cotton should be planted early (300 to 600 HU after 1 Jan) and terminated at the end of the first fruiting cycle (approximately 600 HU past cutout) to maintain the lint yield potential of full-season maturity types of Upland and Pima cotton.

Effects of Repeated Applications of Trifluralin and Pendimethalin on Cotton (Gossypium hirsutum)

The dinitroaniline herbicides, trifluralin and pendimethalin, are applied to approximately 90% of land seeded to cotton on the Texas Southern High Plains. Trifluralin and pendimethalin at 0.6 and 1.1 kg ai/ha were applied annually to plots from 1983 through 1994. Cotton stand counts, lint yield, and fiber quality varied from year-to-year due to environmental conditions. Differences in lint yield or fiber quality over the 11-yr period were not related to herbicide applications.

Comparison of Four Cotton Genotypes for Resistance to Heliothis virescens

Heliothis spp. are major pests of cotton, Gossypium hirsutum L., in many cotton‐producing countries of the world. Two strains of cotton putatively resistant to Heliothis virescens Fab., tobacco budworm, and two adapted cultivars, Deltapine 50 and DES 119, were grown in plots infested with tobacco budworm and in plots free of tobacco budworm (paired plots) for 2 yr. The difference in lint yield between each genotype grown in tobacco budworm‐infested plots and in tobacco budworm‐free plots was used as the measure of resistance. LA 850082 was significantly more resistant each year than the other three. ST 69132 was significantly more resistant each year than DES 119 and more resistant than DPL 50 1 yr. Our results confirm the Heliothis resistance of strains LA 850082 and ST 69132. LA 850082 should be a good source of resistant germplasm to use in developing cultivars that resist infestations of tobacco budworm. In terms of agronomic characteristics, LA 850082 was significantly higher in yield than the two cultivars; however, it is known to have shorter and weaker fiber. Combining the δ‐endotoxin gene from Bacillus thuringiensis with the resistance of LA 850082 is suggested as a strategy for development of cultivars with multiple mechanisms for resistance to Heliothis spp.

Prometryn Tolerance in Glanded versus Glandless Isolines of Cotton

Cotton (Gossypium hirsutum L.) cultivars normally have lysigenous glands conditioned by two dominant, independently inherited alleles, Gl2 and Gl3. Glandless (gl2gl2gl3gl3) isogenic lines are now available for a number of those cultivars. Such lines allow a decisive test for the relationship formerly proposed between accumulation of the herbicide prometryn [N,N′‐bis(1‐methylethyl)‐6‐(methylthio)‐l,3,5‐triazine‐2,4‐diamine] in the lysigenous glands and increased crop tolerance to that pesticide. Experiments were conducted in a growth chamber to compare the prometryn tolerance of glanded vs. glandless ‘Empire 61 (WR)’ and ‘Westburn M’ isolines. Two intermediately glanded Empire isolines (Gl2Gl2gl3gl3 and gl2gl2Gl3Gl3) were also available for analysis. Ratios derived from leaf chlorophyll fluorescence measurement curves established that the photosynthetic inhibition caused by prometryn in glanded cotton seedlings was of less intensity and shorter duration than in glandless plants within the same genetic background. Comparisons involving the intermediately glanded Empire isolines sugo gested that Gl2 enhances seedling tolerance more than does Gl3. Glanded vs. glandless isolines in five genetic backgrounds (i.e., Empire 61 (WR), Westburn M, ‘Delcot 277’, ‘TH 149’, and ‘Stoneville 213’) plus the two intermediate Empire isolines were also evaluated for prometryn tolerance in the field. Visual crop injury ratings and measured lint yields support the growth chamber data. The treated glanded isoline on each background displayed less injury (20–56%) and higher yield (44–60%) than the corresponding glandless isoline. Again, Gl2 showed less injury than Gl3 though differences in lint yield were not significant. Clearly, lysigenous glands enhance prometryn tolerance in cotton, and higher gland density is directly associated with higher photosynthetic rates and reduced crop injury.