Boll Production Research Articles

Genotypic variation in functional contributors to yield for a diverse collection of field‐grown cotton

AbstractYield improvement in cotton could be accelerated through selection for functional yield drivers such as interception of cumulative photosynthetically active radiation (∑IPAR), radiation use efficiency (RUE), and harvest index (HI). However, information on the extent to which these traits vary in cotton in the southeastern United States is limited. It was hypothesized that functional yield drivers would vary significantly within a diverse cotton collection. This study was conducted in Tifton and Athens, GA, and included a total of 4 site‐years. Lint yield, total biomass production, ∑IPAR, RUE, and HI were all affected by genotype. Biomass was more strongly correlated with RUE than ∑IPAR. Even among the highest yielding genotypes, values for functional yield drivers (biomass and harvest index) differed significantly, indicating that high yields could be achieved by differentially manipulating these underlying traits. However, when considered for all genotypes, only HI exhibited a significant positive correlation with yield. Boll production and intra‐boll yield components were also affected by genotype. When considered across upland genotypes, lint per boll, lint per seed, and lint percent were strongly associated with HI and lint yield, whereas boll mass and seed number per boll were not. We conclude that the genotypes evaluated in the current study achieve high lint production per boll and lint yields by manipulating different yield drivers. However, lint yield was primarily maximized through an increase in HI due to increases in boll production and within‐boll distribution of biomass to fiber, not due to increases in total biomass production or boll size.

Cotton boll distribution: A review

AbstractBoll distribution provides an important assessment of the response and adaptation of upland cotton (Gossypium hirsutum L.) to its environment and is strongly linked to yield and fiber quality and consequently to economic value. Several studies have measured boll distribution through end‐of‐season field or box mapping to study the spatiotemporal characteristics of bolls at both the plant and field levels, to quantify the effects of stress on cotton maturity and fiber quality, and to estimate yield as a function of the relative partitioning of resources to competing sinks. This paper discusses the environmental factors affecting boll production and distribution, reviews methods of measuring and analyzing boll distribution, and discusses the comparative advantages and drawbacks of these methods. With the advent of advanced imaging technologies, this paper also discusses the potential transition from traditional methods to machine‐based boll distribution measurements, the challenges associated with these technologies, and how continuous improvements in the baseline technologies being used in the different methods will translate to improved measurement capacities. Overall, major strides can still be made in the area of boll distribution measurement by combining the positive elements in the different studies described in this review to circumvent each of their respective limitations.

Pollen development in cotton (Gossypium hirsutum) is highly sensitive to heat exposure during the tetrad stage.

The development of gametes in plants is acutely susceptible to heatwaves as brief as a few days, adversely affecting pollen maturation and reproductive success. Pollen in cotton (Gossypium hirsutum) was differentially affected when tetrad and binucleate stages were exposed to heat, revealing new insights into the interaction between heat and pollen development. Squares were tagged and exposed to 36/25°C (day/night, moderate heat) or 40/30°C (day/night, extreme heat) for 5 days. Mature pollen grains and leaves were collected for physiological and proteomic responses. While photosynthetic competence was not compromised even at 40°C, leaf tissues became leakier. In contrast, pollen grains were markedly smaller after the tetrad stage was exposed to 40°C and boll production was reduced by 65%. Sugar levels in pollen grains were elevated after exposure to heat, eliminating carbohydrate deficits as a likely cause of poor reproductive capacity. Proteomic analysis of pure pollen samples revealed a particularly high abundance of 70-kDa heat shock (Hsp70s) and cytoskeletal proteins. While short-term bursts of heat had a minor impact on leaves, male gametophyte development was profoundly damaged. Cotton acclimates to maxima of 36°C at both the vegetative and reproductive stages but 5-days exposure to 40°C significantly impairs reproductive development.

Leaf nitrogen metabolism during reproductive phase is crucial for sustaining lint yield of densely populated cotton genotypes

AbstractPlanting density and genotype choice are important agronomic techniques to achieve high crop yields. This study explored how planting density and genotypes affect cotton (Gossypium hirsutum L.) leaf N metabolism and lint yield. Treatments included three planting densities (low, 3.00 × 104; moderate, 6.00 × 104; and high, 9.00 × 104 plants ha−1) and two genotypes (Zhongmiang16 and J‐4B). A randomized complete block design with split plot arrangement was used. Planting density of 6.00 × 104 ha−1 positively influenced leaf physio‐biochemical attributes and boll production. The high planting density reduced lint yield by suppressing leaf soluble sugar, protein, amino acid, chlorophyll a, chlorophyll b, nitrate N and nitrite N content, nitrite reductase, and nitrate reductase activity. Moderate‐density crop produced 15.9 and 10.7% more lint yield than low‐ and high‐density planting, respectively. This high yield was the result of improved leaf level functioning (e.g., increased pigmentation and N metabolism during late reproductive growth), which increased C assimilation. Favorable leaf microclimate could also have sustained activities of leaf nitrate and nitrite reductase and increased amino acid and protein contents, with better distribution of N metabolic assimilates. Late reproductive structure development closely allied with leaf physiological attributes under a short growing season. Cotton genotypes, irrespective of their architectural variation, produced higher lint yield when grown at 6 × 104 ha−1 in a short cropping season.

Amegilla sp. (Hymenoptera: Apidae) Visitors to Cotton (Gossypium hirsutum, Malvaceae) Flowers and Their Role in Crop Pollination at Djoumassi (North, Cameroon)

Aims: To evaluate the impact of a single flower visit of Amegilla sp. on the production of Gossypium hirsutum.
 Study Design: A randomized complete block design was used in a split plot scheme of 437 m2 delimited and divided into eight subplots, each measuring 8*4.5 m2.
 Place and Duration of Study: Locality of Djoumassi, Benoue Division, in the city of Garoua, the North Region of Cameroon from June through October 2018 and 2019.
 Methodology: The experiments were carried out on 540 flowers labeled at bud stage and divided in four treatments: two differentiated according to the presence or absence flowers protection regarding insect visits; the third protected and uncovered when flowers were opened, to allow Amegilla sp. visits and the fourth with the flowers protected, uncovered when they were opened, then rebagged without any visit.
 Results: Among 21 insect species recorded on G. hirsutum flowers, Amegilla sp. ranked second and harvested nectar and pollen. Throughout the pollination efficiency of a single flower visit, Amegilla sp. provoked a significant increase of the fruiting rate, the mean number of seeds per boll and the percentage of normal seeds by 14.89%, 12.93% and 7.01% respectively.
 Conclusion: The conservation and installation of Amegilla sp. nests close to G. hirsutum fields is recommended to improve its boll production and seed quality.

Time‐based remote sensing yield estimates of cotton in water‐limiting environments

AbstractThe use of high‐throughput phenotyping aids breeding programs in making more informed selections and advancements. This study's objectives were to determine which proximal remote sensing parameters (normalized difference red edge [NDRE], normalized difference vegetation index [NDVI], difference between canopy and air temperatures [∆T], and plant height) are robust estimators of cotton lint yield and to use a time‐integrated function of one parameter as a single phenotypic measurement for predicting yield. This study evaluated remote sensing parameters (NDRE, NDVI, ∆T, and plant height) measured weekly from squaring through boll production and development. Of these measurements, NDRE was most consistent in terms of r2, slope, and normality in predicting yield. From these findings, a temporal analysis was calculated as NDRE integrated over the season, namely NDRE‐days. Significant r2 values were detected for the individual remote sensing measurements, with the largest r2 occurring around peak bloom (80 d after planting). An r2 of 0.81 was identified between ∆T and lint yield in 2015, whereas in 2017 the largest r2 value with lint yield was with NDRE (r2 = .71). The temporal analysis showed a significant relationship between NDRE‐days and lint yield (P < .0001; r2 = .58 in 2015 and r2 = .68 in 2017) that was not cultivar specific. This study presents a suitable method that breeders could use to efficiently evaluate plant growth and estimate yield for variety selections while cutting resource requirements.

Information about the Effect of Climatic Factors and Soil Moisture Status on Cotton Production using Different Statistical Relations

Understanding the impacts of climatic factors on cotton production may help physiologists to determine the control mechanisms of boll retention in cotton. However, weather affects crop growth interactively, sometimes resulting in unexpected responses to prevailing conditions. Field trials, using cotton G. barbadense were carried out, to investigate the relationships between climatic factors, soil moisture status, and flower and boll production. The climatic factors considered were, i.e., daily data of maximum air temperature (°C), minimum air temperatures (°C), maximum-minimum temperature (diurnal temperature range or temperature magnitude) (°C), sunshine duration (hd-1), maximum humidity (%), minimum humidity (%) and wind speed (ms-1). It could be generally concluded that minimum humidity (water stress) and sunshine duration, were the most significant climatic factors affecting cotton flower and boll production and retention in Egyptian. Temperature appeared to be less important in the reproduction growth stage of cotton in Egypt than minimum humidity and sunshine duration. The soil moisture status showed low and insignificant correlation to flower and boll production. The positive correlation between minimum humidity value along with the negative correlation between each ofhigh maximum air temperature(temperature equalled or exceeded 37.5°C) and sunshine duration with flower and boll formation, indicate that high value of minimum humidity, short period of sunshine duration and low value of temperature would enhance flower and boll formation.

Planting Geometry Effects on the Growth and Yield of Dryland Cotton

The declining Ogallala Aquifer beneath the Southern High Plains may necessitate dryland crop production and cotton (Gossypium hirsutum L.) is a well-adapted and potentially profitable alternative crop. The limited growing season duration of the Texas Panhandle and southwestern Kansas, however, imposes significant production risk due to incomplete boll maturation. Emphasizing earlier boll production that is usually confined to sites on lower fruiting branches may reduce risk, but offsetting high planting densities are needed to maintain desirable lint yield. Our objectives were to quantify planting: 1) row width and 2) in-row spacing effects on growth, yield, and fiber quality of dryland cotton. Field tests of row widths from 0.25 to 0.76 m and plant densities with in-row spacing ranging from 0.075 to 0.15 m were conducted from 1999 to 2005 on a nearly level Pullman clay loam (fine, mixed, superactive, thermic Torrertic Paleustoll) managed in a wheat (Triticum aestivum L.), cotton, fallow (W-Ctn-F) rotation. To expand the basis of comparison, cotton growth and yields were simulated using GOSSYM and long-term (1958-2000) weather records from Bushland, TX, as input for all combinations of 0.38 or 0.76 m row widths and plant spacing of 0.075, 0.10 and 0.15 m. Experimental and computer simulated plant height and harvested boll number increased significantly with increased row spacing and, occasionally, in-row plant spacing. Modeled lint yield for 0.38 m rows decreased by approximately 50% compared with the 582 kg·ha-1 yield for conventional row spacing, which was practically duplicated by field observations in 2001 and 2004. Measured fiber quality occasionally improved with conventional row spacing over ultra-narrow rows, but was unaffected by plant spacing. Because narrow rows and frequent plant spacing did not improve lint yield or fiber quality of dryland cotton, we do not recommend this strategy to overcome a thermally limited growing season.

Cotton production and climatic factors: Studying the nature of its relationship by different statistical methods

This study investigates the statistical relationship between various climatic factors and overall flower and boll production. Also, the relationship between climatic factors and production of flowers and bolls obtained during the development periods of the flowering and boll stage. Further, predicting effects of climatic factors during different convenient intervals (in days) on cotton flower and boll production compared with daily observations. Furthermore, collects information about the nature of the relationship between various climatic factors and cotton boll development and the 15-day period both prior to and after initiation of individual bolls. And, it provides information on the effect of various climatic factors and soil moisture status during the development stage on flower and boll production in cotton. Evaporation, sunshine duration, relative humidity, surface soil temperature at 18:00 h, and maximum air temperature, are the important climatic factors that significantly affect flower and boll production. The five-day interval was found to be more adequately and sensibly related to yield parameters. Evaporation; minimum humidity, and sunshine duration were the most effective climatic factors during preceding and succeeding periods on boll production and retention. There was a negative correlation between flower and boll production and either evaporation or sunshine duration, while that correlation with minimum relative humidity was positive.

Different statistical methods to collect information about the adverse effects of climatic factors on cotton production

This study investigates the statistical relationship between various climatic factors and overall flower and boll production. Also, predicting effects of climatic factors during different convenient intervals (in days) on cotton flower and boll production compared with daily observations. Further, collects information about the nature of the relationship between various climatic factors and cotton boll development and the 15-day period both prior to and after initiation of individual bolls. And, provide information on the effect of various climatic factors and soil moisture status during the development stage on flower and boll production in cotton. Evaporation, sunshine duration, relative humidity, surface soil temperature at 1800 h, and maximum air temperature, are the important climatic factors that significantly affect flower and boll production. The five-day interval was found to be more adequately and sensibly related to yield parameters. Evaporation; minimum humidity and sunshine duration were the most effective climatic factors during preceding and succeeding periods on boll production and retention. There was a negative correlation between flower and boll production and either evaporation or sunshine duration, while that correlation with minimum relative humidity was positive.

Stress Responses of Commercial Cotton Cultivars to Reduced Irrigation at Flowering and Maximization of Yields under Sub-Optimal Subsurface Drip Irrigation

The gradual depletion of the Ogallala Aquifer in the Southern High Plains of Texas has resulted in reduced well capacities for cotton (Gossypium spp.) irrigation. This study investigated cotton cultivar responses to reduced irrigation from flowering to harvest (2013); and then evaluated season long water deficits and the impact of the timing and amount of irrigation (2014). In 2013, field-grown cotton irrigated with 5 mm per day irrigation showed relatively low stress levels as exemplified by efficiency of quantum yield values between 0.17 and 0.23. Reducing irrigation levels from 5 mm per day to 2.5 mm per day at flowering produced a range of stress levels of Fv/Fm from 0.28 to 0.54. In 2014, four of the commercial cultivars were grown in replicated plots receiving either 2.5 mm of irrigation per day or 17.5 mm of irrigation once a week. Cultivar differences in plant stress were detected for the daily and weekly irrigation strategies. Changes in plant size, boll production, and timing of cutout were observed. FM 2484B2F and Phytogen 72 exhibited no yield differences between the irrigation regimes, while All-Tex Edge and Phytogen 367 showed yield decreases (20% and 25%) under the 2.5 mm daily irrigation regime. Alteration of the timing for the limited irrigation can impact existing stress sensitivities by reducing stress levels and increasing yields.

Statistical Method to Evaluate the Relationship between Climatic Factors during the Development Periods of Flowering and Boll Formation and Cotton Production

This study investigated the relationship between climatic factors and production of flowers and bolls obtained during the development periods of the flowering and boll stage, and to determine the most representative period corresponding to the overall crop pattern. Evaporation, sunshine duration, relative humidity, surface soil temperature at 1800 h, and maximum air temperature, are the important climatic factors that significantly affect flower and boll production. There was a negative correlation between flower and boll production and either evaporation or sunshine duration, while that correlation with minimum relative humidity was positive. Higher minimum relative humidity, short period of sunshine duration, and low temperatures enhanced flower and boll formation. It could be concluded that the fourth quarter period of the production stage is the most appropriate and usable production time to collect data for determining efficient prediction equations for cotton flower and boll production, and making valuable recommendations.

Contribution of Boll Mass and Boll Number to Irrigated Cotton Yield

The production of fruit on upland cotton (Gossypium hirsutum L.) varies with environment, cultivar, and management practices, including irrigation. Yield increase in response to irrigation is a combination of additional boll production on the plant and differences in the size of individual bolls. Previous research on this subject is incomplete. The purpose of this research was to compare the effects of irrigation on boll distribution and boll size in four cotton cultivars in West Texas. Boll distribution and boll mass in response to 10 daily irrigation levels (0–6.5 mm d−1) were compared among four cultivars with varying maturities [‘Deltapine 1212 B2RF’ (DP1212), ‘Deltapine 1219 B2RF’ (DP1219), ‘FiberMax 2484 B2F’ (FM2484), and ‘FiberMax 2011 GT’ (FM2011)] from 2011 to 2013 in Lubbock, TX. Boll production and retention followed cultivar‐specific patterns in all 3 yr. Two cultivars (DP1212 and FM2011) produced fruit primarily at the bottom and middle of the plant, one had increased production high on the plant (DP1219), and one produced fruit almost exclusively in the middle of the plant (FM2484). Both boll number and boll mass contributed to lint yield, with boll number being the major determinant (on average, 90%) of lint yield, whereas boll mass accounted for 10% of lint yield on average. The contribution of boll number and boll size to yield varied among cultivars and did not appear to be wholly maturity‐related. Research studies focused on boll number should be aware that boll distribution does not account for all of the variation in yield.

Goosegrass (Eleusine indica) density effects on cotton (Gossypium hirsutum)

Goosegrass is one of the worst agricultural weeds on a worldwide basis. Understanding of its interference impact in crop field will provide useful information for weed control programs. Field experiments were conducted during 2010–2012 to determine the influence of goosegrass density on cotton growth at the weed densities of 0, 0.125, 0.25, 0.5, 1, 2, and 4 plants m−1 of row. Seed cotton yield tended to decrease with the increase in weed density, and goosegrass at a density of 4 plants m−1 of row significantly reduced cotton yields by 20 to 27%. A density of 11.6–19.2 goosegrass plant m−1 of row would result in a 50% cotton yield loss from the maximum yield according to the hyperbolic decay regression model. Boll production was not affected in the early growing season. But boll numbers per plant were reduced about 25% at the density of 4 plants m−1 of row in the late growing season. Both cotton boll weight and seed numbers per boll were significantly reduced (8%) at 4 goosegrass plants m−1 of row. Cotton plant height, stem diameter and sympodial branch number were not affected as much as cotton yields by goosegrass competition. Seed index, lint percentage and lint fiber properties were unaffected by weed competition. Intraspecific competition resulted in density-dependent effects on weed biomass per plant, 142–387 g dry weight by harvest. Goosegrass biomass m−2 tended to increase with increasing weed density as indicated by a quadratic response. The adverse impact of goosegrass on cotton yield identified in this study has indicated the need of effective goosegrass management.

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.

Fine root production and mortality in irrigated cotton, maize and sorghum sown in vertisols of northern New South Wales, Australia

Fine root (<2mm diameter) turnover (production and mortality) drives soil processes such as nutrient fluxes, carbon cycling and sequestration, activity of soil biota and structural stabilisation. Research on fine root dynamics has been focussed primarily on rainfed perennial and annual ecosystems in coarse and medium-textured soils with few studies conducted in irrigated fine-textured soils such as the vertisols. The objective of this study was to quantify the effects of tillage methods and the summer crops of cotton (Gossypium hirsutum L.), maize (Zea mays L.) and sorghum (Sorghum bicolor (L.) Moench.) on fine root number density in the non-sodic sub-surface (0.1–0.5m) and sodic subsoil (0.6–0.9m) of irrigated vertisols (average clay concentration 65g 100g−1 in the surface 1m) in northern New South Wales. It was hypothesised that fine root number density of cotton would be lower than that of maize and sorghum in the subsoil due to cotton's poor tolerance of anaerobic conditions. Fine root production, mortality and root number density of cotton, maize and sorghum, measured with a minirhizotron and a Bartz ICAP® image capture system, were evaluated for the 0.1–0.5m and 0.6–0.9m depth intervals in several irrigated experiments near Narrabri, NSW, Australia. Fine root density of cotton was low, with most occurring in the surface 0.5m. Subsoil (0.6–0.9m) root number densities of cotton were very low in continuous cotton under conventional tillage and on permanent raised beds (PRBs) but were greater with a cotton-wheat (Triticum aestivum L.) rotation sown on PRBs. Averaged over the two seasons, 2004–2005 and 2006–2007, and depth intervals, there were 3.4 roots×100mm−2 in continuous cotton sown after conventional tillage, 1.2 roots×100mm−2 in continuous cotton sown on PRBs and 6.0 roots×100mm−2 in cotton–wheat sown on PRBs. Between cotton genotypes, root number density during boll production and filling of a Bollgard®-Roundup-Ready® cotton variety was less than that of its corresponding non-Bollgard variant. Maize live root numbers did not differ significantly between continuous maize and a cotton-maize rotation but differed between depth intervals. Averaged over years and rotations, during tasselling maize had 21.5 roots×100mm−2 in the 0.1–0.5m depth interval and 5.3 roots×100mm−2 in the 0.6–0.9m depth interval. Root number density of sorghum was greater with no-tillage than with tillage in wetter seasons but generally similar or lower during a drier season. Average root numbers in the 0.1–0.5m depth interval during the “wet” seasons of 2010–2011 and 2011–2012 were 4.4 roots.100mm−2 with tillage and 9.3 roots×100mm−2 with no-tillage, and in the 0.6–0.9m depth interval were 4.5 roots×100mm−2 with tillage and 10.5 roots×100mm−2 with no-tillage. During the “dry” season of 2012–2013, however, root numbers in the 0.1–0.5m depth interval were 16.6 roots×100mm−2 with tillage and 11.8 roots×100mm−2 with no-tillage, and in the 0.6–0.9m depth interval were 13.8 roots×100mm−2 with tillage and 9.0 roots×100mm−2 with no-tillage. Fine root density of cotton was low, whereas those of sorghum and maize were high with relatively large values occurring in the deeper subsoil. Maize and sorghum were able to tolerate the waterlogged conditions in the sodic subsoils of these vertisols and may, therefore, be more suitable rotation crops for irrigated cotton farming systems than the more commonly sown wheat. These results, while relevant to other fine-textured soils that are irrigated or are periodically inundated, should not be extrapolated to medium and coarse-textured soils.

Climatic Factors: Evaporation, Sunshine, Relative Humidity, Soil and Air Temperature and Cotton Production

This study investigated the effect of climatic factors (namely, evaporation, sunshine, relative humidity, soil temperature, and air temperature) on flower and boll production and retention in cotton (Gossypium barbadense). Also, this study investigated the relationship between climatic factors and production of flowers and bolls obtained during the development periods of the flowering and boll stage, and to determine the most representative period corresponding to the overall crop pattern. Evaporation, sunshine duration, relative humidity, surface soil temperature at 1800 h, and maximum air temperature, are the important climatic factors that significantly affect flower and boll production. The least important variables were found to be surface soil temperature at 0600 h and minimum temperature. There was a negative correlation between flower and boll production and either evaporation or sunshine duration, while that correlation with minimum relative humidity was positive. Higher minimum relative humidity, short period of sunshine duration, and low temperatures enhanced flower and boll formation. Temperature appeared to be less important in the reproduction growth stage of cotton in Egypt than evaporation (water stress), sunshine duration and minimum relative humidity. These findings concur with those of other researchers except for the importance of temperature. A possible reason for that contradiction is that the effects of evaporation rate and relative humidity were not taken into consideration in the research studies conducted by other researchers in other countries. Review Article Annual Research & Review in Biology, 4(18): 2835-2855, 2014 2836

Statistical Relation Nature between Climatic Variables and Soil Moisture during the Production of Cotton (Gossypium barbadense)

The information on impact of climatic factors on cotton production is not generally available, or at least not available or at least not available in the required form. Understanding this impact may help physiologists determine a possible control of the flowering mechanism in cotton plant. Field trials, in two successive seasons using cotton G. barbadense were carried out, to investigate the relationships between climatic factors, soil moisture status, and flower and boll production. The climatic factors considered were daily maximum air temperature, minimum air temperatures, maximum-minimum temperature (diurnal temperature range), sunshine duration, maximum relative humidity, minimum relative humidity, and wind speed. Minimum relative humidity and sunshine duration were the most significant climatic factors affecting flower and boll retention and production. Temperature appeared to be less important in the reproduction growth stage of cotton in Egypt than minimum relative humidity and sunshine duration. The soil moisture status showed low and insignificant correlation to flower and boll production [1].

Statistical Study: Nature Relationship between Climatic Variables Prevailing Prior to Flowering or Subsequent to Boll Setting and Cotton Production

This study investigates the statistical relationship between climatic variables and aspects of cotton production (G. barbadense), and the effects of climatic factors prevailing prior to flowering or subsequent to boll setting on flower and boll production and retention in cotton. The effects of specific climatic factors during both pre- and post-anthesis periods on boll production and retention are mostly unknown. Thus, an understanding of these relationships may help physiologists to determine control mechanisms of production in cotton plants. Evaporation, sunshine duration, relative humidity, surface soil temperature at 1800 h, and maximum air temperature, are the important climatic factors that significantly affect flower and boll production. The least important variables were found to be surface soil temperature at 0600 h and minimum temperature. There was a negative correlation between flower and boll production and either evaporation or sunshine duration, while that correlation with minimum relative humidity was positive. Higher minimum relative humidity, short period of sunshine duration, and low temperatures enhanced flower and boll formation.

The Effect of 2,4-D Drift Rates on Cotton (Gossypium hirsutum L.) Growth and Yield

Research comparing the effects of five reduced 2,4-D rates on cotton growth, node development, and yield after herbicide exposure at the 4- to 6-leaf stage was conducted at the Texas A&amp;M Field Laboratory near College Station, Texas in 2001, 2002, and 2003. These data were used with those from previous research quantifying 2,4-D injury to correlate yield loss. Yearly environmental conditions during the three-year study had significant effects on much of the data. Plants exposed to 2,4-D rates as high as 5.3×10-4 kg a.i./ha showed no reduction in height during 2001 or 2002, but stunting was observed in 2003. The highest 2,4-D rates, 5.3×10-2 and 2.7×10-1 kg a.i./ha, had no effect on the number of plant nodes but decreased bolls on reproductive growth and increased bolls on vegetative growth during 2001 and 2003. Vegetative boll production was unaffected in 2002. Plots exposed to 2,4-D rates as high as 5.3×10-3 kg a.i./ha experienced no yield reduction. The ability to predict yield loss after early-season 2,4-D injury seems possible, with high correlations between total plant injury and yield during 2002 and 2003 (R2 = 0.82 and 0.80, respectively). The correlation between injury and yield was lower in 2001 (R2 = 0.50). Accepted for publication 16 February 2014. Published 2 June 2014.