Nitrogen (N) is the most significant nutrient affecting crop growth and development for all types of crops, except legumes. The goal of this study was to optimize the N level for cotton grown in a semi-arid environment to enhance growth and development, determine N status, and increase seed cotton yield and biomass. Two independent field experiments each three years in duration were conducted, from 2007 to 2009 (Exp.-I) and 2018 to 2020 (Exp.-II). Experiments were laid out in a randomized complete block design with three replicates. The N treatments in Exp.-I were comprised of 0, 40, 80, 120, 160, 200 and 240 kg N/ha, while treatments in Exp.-II were comprised of 0, 70, 140, 210 and 280 kg N/ha. A wide range of data sets for cotton traits were recorded, including canopy height, leaf area index, the N status of the leaf and stem, seed cotton yield and time-series biomass data. The higher N rates 240 and 280 kg N/ha performed better for all these traits. However, the highest leaf N contents were recorded for 210 kg N/ha. Based on these results, it is suggested that under semi-arid conditions, slightly higher rates than optimum or recommended N rates could be applied as a strategy by cotton growers for a higher seed cotton yield. The findings of this study may also increase profitability in other cotton-growing areas that have similar weather conditions.

Integrated weed management practices that reduce selection for resistance on herbicides are critical to delay resistance. To quantify the reduction in selection for resistance placed on Palmer amaranth from 2,4-D applied postemergence in cotton, an experiment was conducted three times in Georgia during 2020 and 2021 evaluating the benefits of (i) a cover crop, (ii) preemergence herbicides, and (iii) timeliness of applications. When a timely total-postemergence program of glyphosate + 2,4-D was applied three times over the season in a conventionally tilled system, 281,690 glyphosate-resistant Palmer amaranth plants ha–1 were exposed to 2,4-D. Over 61,500 of these plants were exposed to multiple 2,4-D applications. Altering the production system to conservation tillage, and including a rolled-rye cover crop, reduced the total number of plants exposed to 2,4-D for the season by 72% and the number of plants exposed multiple times by 60%. Even more effective, including a mixture of residual preemergence herbicides reduced the number of plants exposed to 2,4-D at least once over 99.9%, and reduced multiple exposures over 99.3% for the season; this benefit was observed for both conventional and conservation tillage systems. Delaying the initial application of the total-postemergence program did not influence the number of Palmer amaranth plants treated at least once but increased the number of plants treated multiple times by a factor of 3.7 times. As a result of early-season weed competition, cotton height and yield reductions were also associated with both lack of preemergence residuals and delayed postemergence applications. When considering the goal of minimizing the number of Palmer amaranth treated with a postemergence application of 2,4-D in a cotton system, the preemergence was the most effective option followed by (fb) the cover crop fb making timely postemergence applications. However, the most effective approach was to utilize each of these tactics in the same growing season.

The allelopathic potentials of Hope white lupine (Lupinus albus L.) herbage and herbage extracts were evaluated. The emergence and growth of cotton (Gossypium hirsutum L. ‘Deltapine 45A’), soybean [Glycine max (L.) Merr. ‘Lee 68′], and six weed species under greenhouse conditions were measured after seeding directly into a moist, silt loam soil into which dry Hope lupine herbage, collected at second bloom, had been incorporated at rates from 500 to 8000 ppm (dry herbage/dry soil, w/w). At the lower rates, incorporated Hope white lupine stimulated the emergence of large crabgrass [Digitaria sanguinalis (L.) Scop.]; at the higher rates, cotton emergence was inhibited. Cotton and soybean fresh weights were stimulated at incorporation rates up to 2000 ppm, but were inhibited at higher concentrations. The growth of johnsongrass [Sorghum halepense (L.) Pers.] and large crabgrass was stimulated at most incorporation rates. Stimulated plants were chlorotic and had longer internodes. Emergence and growth of other species tested were not significantly affected by incorporated Hope white lupine. Equivalent concentrations of Hope white lupine herbage extracts were about 17 times more inhibitory to germination of cress (Lepidium sativum L. ‘Curlycress’) seed than to growth of sorghum [Sorghum bicolor (L.) Moench ‘AKS 663′] coleoptiles or radicles. The inhibitory principle extracted from Hope white lupine herbage was non-volatile, heat insensitive, and significantly less active in soil. Fractionation of a herbage extract suggested that neither the alkaloid nor phenolic acid content could account for herbage phytotoxicity in soil.

Conservation tillage systems for cotton production were monitored for their influence on horseweed populations. Without fall tillage, horseweed became established and was present the following spring. Disking in the fall or spring controlled horseweed for the subsequent cotton crop.

Existing long-term cotton experiments established in 1976 with minimum and intensive herbicide programs were subdivided in 1985 and 1986 to determine the longevity of fluometuron and trifluralin soil residues after discontinuing herbicide application. In monoculture cotton, seed cotton yield increased when herbicide use was discontinued in 1985 and 1986 after 9 and 10 yr of continuous use, respectively, on a Sharkey silty clay and a Dundee silt loam soil. Yield increases coincided with reductions of fluometuron and trifluralin soil residues. Fluometuron dissipated from the Dundee silt loam soil by 10 mo after the last application but was present in the Sharkey silty clay soil at 0.20 ppmw after 28 mo. Trifluralin did not totally dissipate from either soil, and low levels were present in the Dundee (0.05 ppmw) and Sharkey (0.13 ppmw) soils 30 mo after the last application. Visual injury to fall-seeded wheat and vetch decreased as herbicide residues dissipated. Fall tillage had no significant effect on the rate of fluometuron or trifluralin dissipation from either soil but reduced seed cotton yields.

A field experiment was conducted to evaluate weed control systems in a conservation tillage rotation of grain sorghum [Sorghum bicolor (L.) Moench.] – cotton (Gossypium hirsutum L.) – wheat (Triticum aestivum L.). Herbicide systems included fall and spring/summer inputs of high and low intensity. Tillage regimes were no-till (NT) and reduced-till (RT) systems; the latter included fall primary tillage followed by spring stale seedbed planting. Both tillage systems utilized controlled traffic lanes and wide, raised beds. Effective johnsongrass [Sorghum halepense (L.) Pers. # SORHA] control required intense herbicide inputs at one or both application periods, i.e., in the fall and/or spring/summer. Grain sorghum and cotton yields for the most intense weed control system, which included high inputs in both the fall and spring/summer, were not superior to systems that included high inputs in only one of the two application periods. Seedling johnsongrass emergence occurred before spring planting in RT (but not in NT) in 2 of 3 yr, and control measures were ineffective. After 3 yr, the predominant weeds were johnsongrass and browntop panicum (Panicum fasciculatum Sw. # PANFA).

Full-season interference effects of hemp sesbania [Sesbania exaltata (Raf.) Cory. # SEBEX] on cotton (Gossypium hirsutum L. 'Stoneville 213′) were investigated on a fine sandy loam soil for 3 yr at Stoneville, MS. Experimentally induced hemp sesbania populations of ≥ 3223 plants/ha significantly reduced cotton yields. Interference of hemp sesbania at 3223, 6456, 16 114, and 32 228 plants/ha, equivalent to 1, 2, 5, and 10 plants/3.3 m, reduced seed cotton yields by 19, 25, 45, and 53%, respectively. Cotton boll weights were reduced by 9% when hemp sesbania infestations were ≥ 16 114 plants/ha. Cotton plant density, seedling vigor, and initial cotton white blooms/ha at ≤75 days after planting (DAP) did not differ with varying densities of hemp sesbania. Cotton white blooms/ha were reduced by 32 228 hemp sesbania plants/ha by 77 DAP and by all weed densities by 98 DAP. Hemp sesbania height was equal to or greater than cotton height by 55 to 65 DAP. Light penetration at 1 m above the top of the cotton canopy was 36% less than in weed-free plots when hemp sesbania densities were ≤6446 plants/ha. Likewise, light penetration was reduced at the cotton canopy top and at midcanopy but was not less at the soil surface unless hemp sesbania densities were ≤ 32 223 plants/ha.

Field studies were conducted over 2 yr to evaluate rhizome johnsongrass control with tank mixtures and sequential applications of bromoxynil at 1.7 kg ai/ha and the graminicides clethodim, fluazifop-P, and quizalofop-P. When compared with the graminicide alone, bromoxynil reduced johnsongrass control 28 days after treatment (DAT) 20, 36, and 55% when applied in combination with clethodim, fluazifop-P, and quizalofop-P, respectively. Application of bromoxynil 7, 3, and 1 d before or 1, 3, and 7 d after all graminicides reduced antagonism when compared with the bromoxynil plus graminicide mixtures. Based on johnsongrass control 28 DAT, antagonism was precluded when bromoxynil was applied 3 d before clethodim and 7 d before fluazifop-P and quizalofop-P. Application of bromoxynil 3 and 7 d after quizalofop-P and 7 d after clethodim also precluded antagonism. The antagonistic tank mixtures of bromoxynil and graminicides reduced cotton yield 17% because of reduced johnsongrass control compared with graminicides alone. A 3-d or greater application interval between bromoxynil and the graminicides was necessary to maximize cotton yield.

Research was conducted from 1982 through 1984 on a Shipps clay soil (Udic chromustert) in east-central Texas to determine the density-dependent effects and critical periods of johnsongrass [Sorghum halepense (L.) Pers. # SORHA] competition with cotton (Gossypium hirsutum L.). Two experiments were conducted each year, one to assess cotton yield response to increasing johnsongrass density and the second to establish the johnsongrass-free requirement of cotton and the johnsongrass competition period. A critical minimum density of 2 plants/9.8 m of row was observed. Full-season johnsongrass competition densities exceeding 2 plants/9.8 m of row resulted in seed cotton yield reductions each year. Yield decline was most rapid as density increased from 2 to 8 plants/9.8 m of row. Yield loss averaged 1, 4, 14, 40, 65, and 70% for johnsongrass densities of 1, 2, 4, 8, 16, and 32 plants/9.8 m of row, respectively. Percent yield loss was proportional to yield potential at johnsongrass densities of 4 and 8 plants/9.8 m of row. Three to four weeks of rhizome johnsongrass competition or 6 weeks of seedling johnsongrass competition resulted in significant yield reductions. Maintaining cotton johnsongrass free for 4 weeks did not prevent significant yield reductions.

Interstate rights-of-way may serve as weed host reservoirs for the tarnished plant bug, an insect pest of cotton. Management of these rights-of-way may have an impact upon cotton pest management. In a 3-yr study, time of mowing, frequency of mowing, and sulfometuron methyl applied against overwintering rosettes influenced the cover of annual fleabane and wild carrot, which harbor tarnished plant bugs.

Hemp sesbania interference in cotton was investigated in the greenhouse and in a 2-yr field experiment at Stoneville, MS. In greenhouse experiments, cotton and hemp sesbania heights and plant dry weights (PDW) were not different in ratios of cotton to hemp sesbania of 4:0, 2:2, 1:3, and 0:4 at 3 and 5 wk after emergence (WAE). Hemp sesbania PDW were less for ratios of cotton to hemp sesbania of 3:1 when compared to hemp sesbania PDW of other ratios. Early season cotton seedling vigor and growth (0 to 28 DAP) were not affected by 32 000 hemp sesbania plants ha-1 (3 plants m of row-1). Hemp sesbania plants were hand removed 28, 42, 56, 70, and 84 d after planting (DAP). White cotton blooms and yields were reduced when hemp sesbania plants were not removed by 70 DAP. Seed cotton yields were 2590, 2570, 2460, 2030, 1610, and 1070 kg ha-1 for hemp sesbania removed at 28, 42, 46, 70 and 84 DAP or not removed, respectively. The critical period of weed control or removal of hemp sesbania in cotton is ≤62 DAP.

Nicosulfuron (50 and 100 g ai ha−1), primisulfuron (40 and 80 g ai ha−1), imazethapyr (70 and 140 g ai ha-1), and DPX-PE350 (100 and 200 g ai ha-1) injury to corn, cotton, grain sorghum, rice, and soybean was evaluated at Fayetteville, AR, during 1989-90 and 1990-91. The crops were planted 0, 1, 2, 4, 8, 14 or 16, and 52 wk after herbicide application. Visible injury to all crops declined as the time interval increased. No visible injury was observed to any crop planted at least 14 wk after nicosulfuron or primisulfuron application, or 52 wk after DPX-PE350 application. Imazethapyr injured all crops except soybean at the 52-wk interval in 1990 but not in 1989.

In order to find the most effective and economical method of incorporation, six preplant herbicides for cotton (Gossypium hirsutum L.) were incorporated with a tandem disk or field cultivator, or sprayed on unbedded soil prior to bedding with a disk bedder. These treatments were compared to incorporating sprayed beds with a rolling cultivator and no incorporation. A mixed population of pigweed (Amaranthus hybridus L. # AMACH and Amaranthus retroflexus L. # AMARE) was present each year. There was no significant difference in pigweed control among incorporation with a disk, field cultivator, or rolling cultivator. Puncturevine (Tribulus terrestris # TRBTE) and barnyardgrass [Echinochloa crus-galli (L.) Beauv. # ECHCG] were controlled best following rolling cultivator incorporation. Cotton lint yields were not affected by incorporation methods or herbicides. Economic analysis and weed control indicate that the field cultivator was the best way of incorporation.

Four-year cropping sequences of continuous cotton, cotton-soybeans-soybeans-cotton, continuous soybeans, soybeans-grain sorghum-soybeans-grain sorghum, and cotton-rice-cotton-rice were treated each year with high and low levels of herbicides to control johnsongrass. High levels of herbicide were necessary to control johnsongrass in continuous cotton, cotton-soybeans-soybeans-cotton, continuous soybeans, and the soybeans-grain sorghum rotation. Johnsongrass was not eradicated, however, after 4 years of cropping sequences with high herbicide inputs. Both low and high levels of herbicide coupled with water management required for rice production controlled johnsongrass and prevented rice yield reductions.

Field experiments were conducted to determine the effects of tank-mix and sequential postemergence (POE) applications of the insecticides carbaryl and dimethoate with sethoxydim on large crabgrass control and cotton tolerance. Large crabgrass control was similar with sethoxydim and sethoxydim-dimethoate tank mixtures. Although tank mixing carbaryl with sethoxydim reduced control, it was not reduced when carbaryl was applied 2 days before or 2 days after applying sethoxydim. Neither the insecticides nor sethoxydim applied alone or as tank mixtures injured cotton or affected lint yield, percent lint, fiber length, fiber length uniformity, fiber strength, or micronaire.

Chlorimuron applied postemergence at 2.2, 4.4, 8.8, 18, and 35 g ai/ha to cotton at either the 4-leaf, pinhead-square, first-bloom, or full-bloom growth stage was evaluated for potential as a plant growth regulator. Chlorimuron did not reduce bolls per plant at any rate or time of application, but the proportion of open to closed bolls decreased as rate increased. Seed cotton yields decreased with increasing chlorimuron rate and cotton age. The use of chlorimuron as a plant growth regulator for cotton appears limited.

Cotton and pitted morningglory emergence and dry weight decreased approximately 60 to 80% when these plants were grown under greenhouse conditions in the presence of increasing amounts (0.8 to 6.7 mg debris/g soil) of field-grown crimson clover or hairy vetch debris incorporated into the soil medium. Conversely, corn dry weight increased 20 to 75% when legume debris was placed on the soil surface; incorporated debris had very little effect on corn emergence or dry weight. Germination and seedling growth of corn, Italian ryegrass, cotton, pitted morningglory, and wild mustard decreased progressively, with species-dependent variation, when exposed to increasing concentrations (8.3 to 33.3 g debris/L) of aqueous crimson clover and hairy vetch extract. Mustard and ryegrass germination and growth were almost completely inhibited by full-strength extracts of both legumes. Bioassay species exhibited greater phytotoxic responses to hairy vetch than to crimson clover in the debris and extract studies. Emergence and growth of corn and cotton were not affected when planted into soil samples, containing root biomass and possible leaf and root exudates, collected from beneath field-grown hairy vetch and crimson clover plants. However, morningglory dry weight increased 35% in the presence of either legume root debris and accompanying soil.

Six cropping/weed control systems were evaluated from 1978 to 1980 for the control of yellow nutsedge (Cyperus esculentus L.). Supplementing cultivation of cotton (Gossypium hirsutum L. ‘Acala SJ-2′) with either preplant applications of fluridone {1 - methyl - 3 - phenyl - 5 - [3 - (trifluoromethyl)phenyl] -4(1H-pyridinone} or two hoeings for 2 yr preceding cotton treated with DSMA (disodium methanearsonate) and MSMA (monosodium methanearsonate) reduced populations of viable yellow nutsedge tubers 98 to 99% within 3 yr. Dry- or wet - fallowing plus tillage after barley (Hordeum vulgare L. ‘Kombyne’), and double cropping potatoes (Solanum tuberosum L. ‘White Rose’) treated with EPTC (S-ethyl dipropylthiocarbamate) with soybeans [Glycine max (L.) Merr. ‘Williams’] treated with alachlor [2-chloro - 2′, 6’ - diethyl - N - (methoxymethyl)acetanilide] for 2 yr preceding cotton, reduced populations of tubers 98 to 99% within 3 yr. A similar reduction of tubers (97%) was obtained by double cropping potatoes with milo [Sorghum bicolor (L.) Moench. ‘NK- 265′] for 2 yr preceding cotton.

Research was conducted to determine an effective morningglory control system for cotton grown in central Texas, Prometryn applied PRE or directed-POST applications of methazole or methazole + MSMA did not always adequately control ivyleaf, entireleaf, and seedling sharppod morningglories. However, adequate control of the above species plus pitted morningglory was achieved with a management system that used a dinitroaniline applied PPI or PRE, prometryn applied PRE (0.9 kg ai ha−1), followed by methazole (0.56 kg ha−1) or methazole + MSMA (0.56 + 1.80 kg ha−1) directed POST to cotton 10 to 15 cm high.

Field experiments were conducted to determine the effects of tank-mixing fluometuron {N,N-dimethyl-N′-[3-(trifluoromethyl)phenyl] urea} or MSMA (monosodium salt of methylarsonic acid) with sethoxydim {2-[1-(ethoxyimino)butyl]-5-[2-(ethylthio)propyl]-3-hydroxy-2-cyclohexen-1-one} or the butyl ester of fluazifop {(±)-2-[4-[[5-(trifluoromethyl)-2-pyridinyl]oxy] phenoxy] propanic acid} on cotton (Gossypium hirsutum L.) tolerance and large crabgrass [Digitaria sanguinalis (L.) Scop. # DIGSA] control. Postemergence (over-the-top) application of 1.7 kg ai/ha of fluometuron reduced cotton lint yield 17 to 23% in three of four tests. No yield reduction resulted from postemergence application of 1.1 kg ae/ha of MSMA. Tank-mixing 0.1 or 0.2 kg ai/ha of sethoxydim or 0.1 or 0.2 kg ae/ha of fluazifop with fluometuron or MSMA did not alter the effect of fluometuron or MSMA on cotton yield. Tank mixtures of 1.1 to 2.2 kg/ha of fluometuron plus sethoxydim or fluazifop were antagonistic. No antagonism was observed when fluometuron was applied 3 days before or 6 h following sethoxydim or fluazifop application. Tank-mixing 1.1 or 2.2 kg/ha of MSMA with sethoxydim or fluazifop initially reduced control of large crabgrass. Antagonism was not observed at 4 weeks after tank-mix application of MSMA plus sethoxydim, and was observed in only one of three experiments 4 weeks following tank-mix application of MSMA plus fluazifop. When antagonism was observed with tank mixtures of fluazifop plus MSMA, sequential application of MSMA 1 to 7 days before application of fluazifop did not overcome the antagonism. No antagonism occurred when MSMA was applied 6 or more hours after fluazifop application.